//-----------------------------------------------------------------------------
//
// Copyright 1993-1996 id Software
// Copyright 1994-1996 Raven Software
// Copyright 1998-1998 Chi Hoang, Lee Killough, Jim Flynn, Rand Phares, Ty Halderman
// Copyright 1999-2016 Randy Heit
// Copyright 2002-2017 Christoph Oelckers
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see http://www.gnu.org/licenses/
//
//-----------------------------------------------------------------------------
//
// DESCRIPTION:
//		Movement, collision handling.
//		Shooting and aiming.
//
//-----------------------------------------------------------------------------

/* For code that originates from ZDoom the following applies:
**
**---------------------------------------------------------------------------
**
** Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions
** are met:
**
** 1. Redistributions of source code must retain the above copyright
**    notice, this list of conditions and the following disclaimer.
** 2. Redistributions in binary form must reproduce the above copyright
**    notice, this list of conditions and the following disclaimer in the
**    documentation and/or other materials provided with the distribution.
** 3. The name of the author may not be used to endorse or promote products
**    derived from this software without specific prior written permission.
**
** THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
** IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
** OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
** IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
** NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
** THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
**---------------------------------------------------------------------------
**
*/

#include <stdlib.h>
#include <math.h>
#include <algorithm>

#include "templates.h"

#include "m_bbox.h"
#include "m_random.h"
#include "c_dispatch.h"

#include "doomdef.h"
#include "p_local.h"
#include "p_spec.h"
#include "d_player.h"
#include "p_maputl.h"
#include "p_lnspec.h"
#include "p_effect.h"
#include "p_terrain.h"
#include "p_trace.h"
#include "p_checkposition.h"
#include "p_linetracedata.h"
#include "r_utility.h"
#include "p_blockmap.h"
#include "p_3dmidtex.h"
#include "vm.h"

#include "decallib.h"

// State.

#include "a_sharedglobal.h"
#include "p_conversation.h"
#include "r_sky.h"
#include "g_levellocals.h"
#include "actorinlines.h"

CVAR(Bool, cl_bloodsplats, true, CVAR_ARCHIVE)
CVAR(Int, sv_smartaim, 0, CVAR_ARCHIVE | CVAR_SERVERINFO)
CVAR(Bool, cl_doautoaim, false, CVAR_ARCHIVE)

static void CheckForPushSpecial(line_t *line, int side, AActor *mobj, DVector2 * posforwindowcheck = NULL);
static void SpawnShootDecal(AActor *t1, AActor *defaults, const FTraceResults &trace);
static void SpawnDeepSplash(AActor *t1, const FTraceResults &trace, AActor *puff);

static FRandom pr_tracebleed("TraceBleed");
static FRandom pr_checkthing("CheckThing");
static FRandom pr_lineattack("LineAttack");
static FRandom pr_crunch("DoCrunch");

// keep track of special lines as they are hit,
// but don't process them until the move is proven valid
TArray<spechit_t> spechit;
TArray<spechit_t> portalhit;


//==========================================================================
//
// CanCollideWith
//
// Checks if an actor can collide with another one, calling virtual script functions to check.
//
//==========================================================================

bool P_CanCollideWith(AActor *tmthing, AActor *thing)
{
	static unsigned VIndex = ~0u;
	if (VIndex == ~0u)
	{
		VIndex = GetVirtualIndex(RUNTIME_CLASS(AActor), "CanCollideWith");
		assert(VIndex != ~0u);
	}

	VMValue params[3] = { tmthing, thing, false };
	VMReturn ret;
	int retval;
	ret.IntAt(&retval);

	auto clss = tmthing->GetClass();
	VMFunction *func = clss->Virtuals.Size() > VIndex ? clss->Virtuals[VIndex] : nullptr;
	if (func != nullptr)
	{
		VMCall(func, params, 3, &ret, 1);
		if (!retval) return false;
	}
	std::swap(params[0].a, params[1].a);
	params[2].i = true;

	// re-get for the other actor.
	clss = thing->GetClass();
	func = clss->Virtuals.Size() > VIndex ? clss->Virtuals[VIndex] : nullptr;
	if (func != nullptr)
	{
		VMCall(func, params, 3, &ret, 1);
		if (!retval) return false;
	}
	return true;
}

//==========================================================================
//
// FindRefPoint
//
// Finds the point on the line closest to the given coordinate
//
//==========================================================================

static DVector2 FindRefPoint(line_t *ld, const DVector2 &pos)
{
	// If there's any chance of slopes getting in the way we need to get a proper refpoint, otherwise we can save the work.
	// Slopes can get in here when:
	// - the actual sector planes are sloped
	// - there's 3D floors in this sector
	// - there's a crossable floor portal (for which the dropoff needs to be calculated within P_LineOpening, and the lower sector can easily have slopes)
	//
	// Todo: check if this bootload of checks even helps or if it adds more than it saves
	//
	if 	(ld->frontsector->floorplane.isSlope() ||
			ld->backsector->floorplane.isSlope() ||
			ld->frontsector->ceilingplane.isSlope() ||
			ld->backsector->ceilingplane. isSlope() ||
			ld->backsector->e->XFloor.ffloors.Size() != 0 ||
			ld->frontsector->e->XFloor.ffloors.Size() != 0 ||
			!ld->frontsector->PortalBlocksMovement(sector_t::ceiling) ||
			!ld->frontsector->PortalBlocksMovement(sector_t::floor))
	{

		DVector2 v1 = ld->v1->fPos();
		DVector2 d = ld->Delta();
		double r = clamp(((pos.X - v1.X) * d.X + (pos.Y - v1.Y) * d.Y) / (d.X*d.X + d.Y*d.Y), 0., 1.);
		return v1 + d*r;
	}
	return pos;
}

//==========================================================================
//
// PIT_FindFloorCeiling
//
// only3d set means to only check against 3D floors and midtexes.
//
//==========================================================================
bool ffcf_verbose;

static bool PIT_FindFloorCeiling(FMultiBlockLinesIterator &mit, FMultiBlockLinesIterator::CheckResult &cres, const FBoundingBox &box, FCheckPosition &tmf, int flags)
{
	line_t *ld = cres.line;

	if (!inRange(box, ld) || BoxOnLineSide(box, ld) != -1)
		return true;

	// A line has been hit

	if (ffcf_verbose)
	{
		Printf("Hit line %d at position %f,%f, group %d\n",
			ld->Index(), cres.Position.X, cres.Position.Y, ld->frontsector->PortalGroup);
	}

	if (!ld->backsector)
	{ // One sided line
		return true;
	}

	DVector2 refpoint = FindRefPoint(ld, cres.Position);
	FLineOpening open;

	P_LineOpening(open, tmf.thing, ld, refpoint, &cres.Position, flags);

	// adjust floor / ceiling heights
	if (!(flags & FFCF_NOCEILING))
	{
		if (open.top < tmf.ceilingz)
		{
			tmf.ceilingz = open.top;
			if (open.topsec != NULL) tmf.ceilingsector = open.topsec;
			if (ffcf_verbose) Printf("    Adjust ceilingz to %f\n", open.top);
			mit.StopUp();
		}
	}

	// If we are stepping through a portal the line's opening must be checked, regardless of the NOFLOOR flag
	if (!(flags & FFCF_NOFLOOR))
	{
		if (open.bottom > tmf.floorz)
		{
			tmf.floorz = open.bottom;
			if (open.bottomsec != NULL) tmf.floorsector = open.bottomsec;
			tmf.touchmidtex = open.touchmidtex;
			tmf.abovemidtex = open.abovemidtex;
			if (ffcf_verbose) Printf("    Adjust floorz to %f\n", open.bottom);
			if (tmf.floorz > tmf.dropoffz + tmf.thing->MaxDropOffHeight) mit.StopDown();
		}
		else if (open.bottom == tmf.floorz)
		{
			tmf.touchmidtex |= open.touchmidtex;
			tmf.abovemidtex |= open.abovemidtex;
		}

		if (open.lowfloor < tmf.dropoffz && open.lowfloor > LINEOPEN_MIN)
		{
			tmf.dropoffz = open.lowfloor;
			if (ffcf_verbose) Printf("    Adjust dropoffz to %f\n", open.bottom);
			if (tmf.floorz > tmf.dropoffz + tmf.thing->MaxDropOffHeight) mit.StopDown();
		}
	}
	return true;
}


//==========================================================================
//
// calculates the actual floor and ceiling position at a given
// coordinate. Traverses through portals unless being told not to.
//
//==========================================================================

void P_GetFloorCeilingZ(FCheckPosition &tmf, int flags)
{
	sector_t *sec = (!(flags & FFCF_SAMESECTOR) || tmf.thing->Sector == NULL)? tmf.thing->Level->PointInSector(tmf.pos) : tmf.sector;
	F3DFloor *ffc, *fff;

	tmf.ceilingz = NextHighestCeilingAt(sec, tmf.pos.X, tmf.pos.Y, tmf.pos.Z, tmf.pos.Z + tmf.thing->Height, flags, &tmf.ceilingsector, &ffc);
	tmf.floorz = tmf.dropoffz = NextLowestFloorAt(sec, tmf.pos.X, tmf.pos.Y, tmf.pos.Z, flags, tmf.thing->MaxStepHeight, &tmf.floorsector, &fff);
	tmf.dropoffisportal = tmf.floorsector != sec;

	if (fff)
	{
		tmf.floorpic = *fff->top.texture;
		tmf.floorterrain = fff->model->GetTerrain(fff->top.isceiling);
	}
	else
	{
		tmf.floorpic = tmf.floorsector->GetTexture(sector_t::floor);
		tmf.floorterrain = tmf.floorsector->GetTerrain(sector_t::floor);
	}
	tmf.ceilingpic = ffc ? *ffc->bottom.texture : tmf.ceilingsector->GetTexture(sector_t::ceiling);
	tmf.sector = sec;

}

//==========================================================================
//
// P_FindFloorCeiling
//
//==========================================================================

void P_FindFloorCeiling(AActor *actor, int flags)
{
	FCheckPosition tmf;

	tmf.thing = actor;
	tmf.pos = actor->Pos();

	if (flags & FFCF_ONLYSPAWNPOS)
	{
		flags |= FFCF_3DRESTRICT;
	}
	if (flags & FFCF_SAMESECTOR)
	{
		tmf.sector = actor->Sector;
	}
	P_GetFloorCeilingZ(tmf, flags);
	assert(tmf.thing->Sector != NULL);

	actor->floorz = tmf.floorz;
	actor->dropoffz = tmf.dropoffz;
	actor->ceilingz = tmf.ceilingz;
	actor->floorpic = tmf.floorpic;
	actor->floorterrain = tmf.floorterrain;
	actor->floorsector = tmf.floorsector;
	actor->ceilingpic = tmf.ceilingpic;
	actor->ceilingsector = tmf.ceilingsector;
	if (ffcf_verbose) Printf("Starting with ceilingz = %f, floorz = %f\n", tmf.ceilingz, tmf.floorz);

	tmf.touchmidtex = false;
	tmf.abovemidtex = false;
	validcount++;

	FPortalGroupArray grouplist;
	FMultiBlockLinesIterator mit(grouplist, actor);
	FMultiBlockLinesIterator::CheckResult cres;

	// if we already have a valid floor/ceiling sector within the current sector, 
	// we do not need to iterate through plane portals to find a floor or ceiling.
	if (actor->floorsector == actor->Sector) mit.StopDown();
	if (actor->ceilingsector == actor->Sector) mit.StopUp();

	while ((mit.Next(&cres)))
	{
		PIT_FindFloorCeiling(mit, cres, mit.Box(), tmf, flags|cres.portalflags);
	}

	if (tmf.touchmidtex) tmf.dropoffz = tmf.floorz;

	bool usetmf = !(flags & FFCF_ONLYSPAWNPOS) || (tmf.abovemidtex && (tmf.floorz <= actor->Z()));

	// when actual floor or ceiling are beyond a portal plane we also need to use the result of the blockmap iterator, regardless of the flags being specified.
	if (usetmf || tmf.floorsector->PortalGroup != actor->Sector->PortalGroup)
	{
		actor->floorz = tmf.floorz;
		actor->dropoffz = tmf.dropoffz;
		actor->floorpic = tmf.floorpic;
		actor->floorterrain = tmf.floorterrain;
		actor->floorsector = tmf.floorsector;
	}

	if (usetmf || tmf.ceilingsector->PortalGroup != actor->Sector->PortalGroup)
	{
		actor->ceilingz = tmf.ceilingz;
		actor->ceilingpic = tmf.ceilingpic;
		actor->ceilingsector = tmf.ceilingsector;
	}
}


// Debug CCMD for checking errors in the MultiBlockLinesIterator (needs to be removed when this code is complete)
CCMD(ffcf)
{
	ffcf_verbose = true;
	P_FindFloorCeiling(players[0].mo, 0);
	ffcf_verbose = false;
}
//==========================================================================
//
// TELEPORT MOVE
// 

//
// P_TeleportMove
//
// [RH] Added telefrag parameter: When true, anything in the spawn spot
//		will always be telefragged, and the move will be successful.
//		Added z parameter. Originally, the thing's z was set *after* the
//		move was made, so the height checking I added for 1.13 could
//		potentially erroneously indicate the move was okay if the thing
//		was being teleported between two non-overlapping height ranges.
//
//==========================================================================

bool	P_TeleportMove(AActor* thing, const DVector3 &pos, bool telefrag, bool modifyactor) 
{
	FCheckPosition tmf;
	sector_t *oldsec = thing->Sector;

	// kill anything occupying the position


	// The base floor/ceiling is from the subsector that contains the point.
	// Any contacted lines the step closer together will adjust them.
	tmf.thing = thing;
	tmf.pos = pos;
	tmf.touchmidtex = false;
	tmf.abovemidtex = false;
	P_GetFloorCeilingZ(tmf, 0);

	spechit.Clear();	// this is needed so that no more specials get activated after crossing a teleporter.

	bool StompAlwaysFrags = ((thing->flags2 & MF2_TELESTOMP) || (thing->Level->flags & LEVEL_MONSTERSTELEFRAG) || telefrag) && !(thing->flags7 & MF7_NOTELESTOMP);

	// P_LineOpening requires the thing's z to be the destination z in order to work.
	double savedz = thing->Z();
	thing->SetZ(pos.Z);
	sector_t *sector = thing->Level->PointInSector(pos);

	FPortalGroupArray grouplist;
	FMultiBlockLinesIterator mit(grouplist, thing->Level, pos.X, pos.Y, pos.Z, thing->Height, thing->radius, sector);
	FMultiBlockLinesIterator::CheckResult cres;

	while (mit.Next(&cres))
	{
		PIT_FindFloorCeiling(mit, cres, mit.Box(), tmf, 0);
	}
	thing->SetZ(savedz);

	if (tmf.touchmidtex) tmf.dropoffz = tmf.floorz;

	FMultiBlockThingsIterator mit2(grouplist, thing->Level, pos.X, pos.Y, pos.Z, thing->Height, thing->radius, false, sector);
	FMultiBlockThingsIterator::CheckResult cres2;

	while (mit2.Next(&cres2))
	{
		AActor *th = cres2.thing;

		if (!(th->flags & MF_SHOOTABLE))
			continue;

		// don't clip against self
		if (th == thing)
			continue;

		if ((th->flags2 | tmf.thing->flags2) & MF2_THRUACTORS)
			continue;

		if ((th->ThruBits & tmf.thing->ThruBits) && ((th->flags8 | tmf.thing->flags8) & MF8_ALLOWTHRUBITS))
			continue;

		double blockdist = th->radius + tmf.thing->radius;
		if (fabs(th->X() - cres2.Position.X) >= blockdist || fabs(th->Y() - cres2.Position.Y) >= blockdist)
			continue;

		if (tmf.thing->flags6 & MF6_THRUSPECIES && tmf.thing->GetSpecies() == th->GetSpecies())
			continue;

		// [RH] Z-Check
		// But not if not MF2_PASSMOBJ or MF3_DONTOVERLAP are set!
		// Otherwise those things would get stuck inside each other.
		if ((thing->flags2 & MF2_PASSMOBJ || th->flags4 & MF4_ACTLIKEBRIDGE) && !(thing->Level->i_compatflags & COMPATF_NO_PASSMOBJ))
		{
			if (!(th->flags3 & thing->flags3 & MF3_DONTOVERLAP))
			{
				if (pos.Z > th->Top() ||	// overhead
					pos.Z + thing->Height < th->Z())	// underneath
					continue;
			}
		}

		if (!P_CanCollideWith(tmf.thing, th))
			continue;

		// Don't let players and monsters block item teleports (all other actor types will still block.)
		if ((thing->IsKindOf(NAME_Inventory) || (thing->flags2 & MF2_TELESTOMP)) && !(thing->flags & MF_SOLID) && ((th->flags3 & MF3_ISMONSTER) || th->player != nullptr))
			continue;

		// monsters don't stomp things except on boss level
		// [RH] Some Heretic/Hexen monsters can telestomp
		// ... and some items can never be telefragged while others will be telefragged by everything that teleports upon them.
		if ((StompAlwaysFrags && !(th->flags6 & MF6_NOTELEFRAG)) || (th->flags7 & MF7_ALWAYSTELEFRAG))
		{
			// Don't actually damage if predicting a teleport
			if (thing->player == NULL || !(thing->player->cheats & CF_PREDICTING))
				P_DamageMobj(th, thing, thing, TELEFRAG_DAMAGE, NAME_Telefrag, DMG_THRUSTLESS);
			continue;
		}
		return false;
	}

	if (modifyactor)
	{
		// the move is ok, so link the thing into its new position
		thing->SetOrigin(pos, false);
		thing->floorz = tmf.floorz;
		thing->ceilingz = tmf.ceilingz;
		thing->floorsector = tmf.floorsector;
		thing->floorpic = tmf.floorpic;
		thing->floorterrain = tmf.floorterrain;
		thing->ceilingsector = tmf.ceilingsector;
		thing->ceilingpic = tmf.ceilingpic;
		thing->dropoffz = tmf.dropoffz;        // killough 11/98
		thing->BlockingLine = NULL;

		if (thing->flags2 & MF2_FLOORCLIP)
		{
			thing->AdjustFloorClip();
		}

		thing->renderflags |= RF_NOINTERPOLATEVIEW;

		// If this teleport was caused by a move, P_TryMove() will handle the
		// sector transition messages better than we can here.
		// This needs to be compatibility optioned because some older maps exploited this missing feature.
		if (!(thing->flags6 & MF6_INTRYMOVE) && !(thing->Level->i_compatflags2 & COMPATF2_TELEPORT))
		{
			thing->CheckSectorTransition(oldsec);
		}
	}

	return true;
}

//==========================================================================
//
// [RH] P_PlayerStartStomp
//
// Like P_TeleportMove, but it doesn't move anything, and only monsters and other
// players get telefragged.
//
//==========================================================================

void P_PlayerStartStomp(AActor *actor, bool mononly)
{
	FPortalGroupArray grouplist;
	FMultiBlockThingsIterator mit(grouplist, actor);
	FMultiBlockThingsIterator::CheckResult cres;

	while ((mit.Next(&cres)))
	{
		AActor *th = cres.thing;

		if (!(th->flags & MF_SHOOTABLE))
			continue;

		// don't clip against self, and don't kill your own voodoo dolls
		if (th == actor || (th->player == actor->player && th->player != NULL))
			continue;

		double blockdist = th->radius + actor->radius;
		if (fabs(th->X() - cres.Position.X) >= blockdist || fabs(th->Y() - cres.Position.Y) >= blockdist)
			continue;

		// only kill monsters and other players
		if (th->player == NULL && !(th->flags3 & MF3_ISMONSTER))
			continue;

		if ((th->flags6 & MF6_NOTELEFRAG) && !(th->flags7 & MF7_ALWAYSTELEFRAG))
			continue;

		if (th->player != NULL && mononly)
			continue;

		if (actor->Z() > th->Top())
			continue;        // overhead
		if (actor->Top() < th->Z())
			continue;        // underneath

		P_DamageMobj(th, actor, actor, TELEFRAG_DAMAGE, NAME_Telefrag);
	}
}

//==========================================================================
//
// killough 8/28/98:
//
// P_GetFriction()
//
// Returns the friction associated with a particular mobj.
//
//==========================================================================

double P_GetFriction(const AActor *mo, double *frictionfactor)
{
	double friction = ORIG_FRICTION;
	double movefactor = ORIG_FRICTION_FACTOR;
	double newfriction;
	double newmf;

	const msecnode_t *m;
	sector_t *sec;

	if (mo->IsNoClip2())
	{
		// The default values are fine for noclip2 mode
	}
	else if (mo->flags2 & MF2_FLY && mo->flags & MF_NOGRAVITY)
	{
		friction = FRICTION_FLY;
	}
	else if ((!(mo->flags & MF_NOGRAVITY) && mo->waterlevel > 1) ||
		(mo->waterlevel == 1 && mo->Z() > mo->floorz+ 6))
	{
		friction = mo->Sector->GetFriction(sector_t::floor, &movefactor);
		movefactor *= 0.5;

		// Check 3D floors -- might be the source of the waterlevel
		for (unsigned i = 0; i < mo->Sector->e->XFloor.ffloors.Size(); i++)
		{
			F3DFloor *rover = mo->Sector->e->XFloor.ffloors[i];
			if (!(rover->flags & FF_EXISTS)) continue;
			if (!(rover->flags & FF_SWIMMABLE)) continue;

			if (mo->Z() > rover->top.plane->ZatPoint(mo) ||
				mo->Z() < rover->bottom.plane->ZatPoint(mo))
				continue;

			newfriction = rover->model->GetFriction(rover->top.isceiling, &newmf);
			if (newfriction < friction || friction == ORIG_FRICTION)
			{
				friction = newfriction;
				movefactor = newmf * 0.5;
			}
		}
	}
	else if (var_friction && !(mo->flags & (MF_NOCLIP | MF_NOGRAVITY)))
	{	// When the object is straddling sectors with the same
		// floor height that have different frictions, use the lowest
		// friction value (muddy has precedence over icy).

		for (m = mo->touching_sectorlist; m; m = m->m_tnext)
		{
			sec = m->m_sector;
			DVector3 pos = mo->PosRelative(sec);

			// 3D floors must be checked, too
			for (unsigned i = 0; i < sec->e->XFloor.ffloors.Size(); i++)
			{
				F3DFloor *rover = sec->e->XFloor.ffloors[i];
				if (!(rover->flags & FF_EXISTS)) continue;

				if (rover->flags & FF_SOLID)
				{
					// Must be standing on a solid floor
					if (!mo->isAtZ(rover->top.plane->ZatPoint(pos))) continue;
				}
				else if (rover->flags & FF_SWIMMABLE)
				{
					// Or on or inside a swimmable floor (e.g. in shallow water)
					if (mo->Z() > rover->top.plane->ZatPoint(pos) ||
						(mo->Top()) < rover->bottom.plane->ZatPoint(pos))
						continue;
				}
				else
					continue;

				newfriction = rover->model->GetFriction(rover->top.isceiling, &newmf);
				if (newfriction < friction || friction == ORIG_FRICTION)
				{
					friction = newfriction;
					movefactor = newmf;
				}
			}

			if (!(sec->Flags & SECF_FRICTION) &&
				Terrains[sec->GetTerrain(sector_t::floor)].Friction == 0)
			{
				continue;
			}
			newfriction = sec->GetFriction(sector_t::floor, &newmf);
			if ((newfriction < friction || friction == ORIG_FRICTION) &&
				(mo->Z() <= sec->floorplane.ZatPoint(pos) ||
				(sec->GetHeightSec() != NULL &&
				mo->Z() <= sec->heightsec->floorplane.ZatPoint(pos))))
			{
				friction = newfriction;
				movefactor = newmf;
			}
		}
	}

	if (mo->Friction != 1)
	{
		friction = clamp((friction * mo->Friction), 0., 1.);
		movefactor = FrictionToMoveFactor(friction);
	}

	if (frictionfactor)
		*frictionfactor = movefactor;

	return friction;
}

//==========================================================================
//
// phares 3/19/98
// P_GetMoveFactor() returns the value by which the x,y
// movements are multiplied to add to player movement.
//
// killough 8/28/98: rewritten
//
//==========================================================================

double P_GetMoveFactor(const AActor *mo, double *frictionp)
{
	double movefactor, friction;

	// If the floor is icy or muddy, it's harder to get moving. This is where
	// the different friction factors are applied to 'trying to move'. In
	// p_mobj.c, the friction factors are applied as you coast and slow down.

	if ((friction = P_GetFriction(mo, &movefactor)) < ORIG_FRICTION)
	{
		// phares 3/11/98: you start off slowly, then increase as
		// you get better footing

		double velocity = mo->VelXYToSpeed();

		if (velocity > MORE_FRICTION_VELOCITY * 4)
			movefactor *= 8;
		else if (velocity > MORE_FRICTION_VELOCITY * 2)
			movefactor *= 4;
		else if (velocity > MORE_FRICTION_VELOCITY)
			movefactor *= 2;
	}

	if (frictionp)
		*frictionp = friction;

	return movefactor;
}

//==========================================================================
//
// Checks if the line intersects with the actor
// returns 
// - 1 when above/below
// - 0 when intersecting
// - -1 when outside the portal
//
// Note that this check is done from the 'other' side of the portal
// so plane names seem to be inverted.
//
//==========================================================================

static int LineIsAbove(line_t *line, AActor *actor)
{
	if (line->frontsector->PortalBlocksMovement(sector_t::floor)) return -1;
	return line->frontsector->GetPortalPlaneZ(sector_t::floor) >= actor->Top();
}

static int LineIsBelow(line_t *line, AActor *actor)
{
	if (line->frontsector->PortalBlocksMovement(sector_t::ceiling)) return -1;
	return line->frontsector->GetPortalPlaneZ(sector_t::ceiling) <= actor->Z();
}

//
// MOVEMENT ITERATOR FUNCTIONS
//

//==========================================================================
//
//
// PIT_CheckLine
// Adjusts tmfloorz and tmceilingz as lines are contacted
//
//
//==========================================================================

static // killough 3/26/98: make static
bool PIT_CheckLine(FMultiBlockLinesIterator &mit, FMultiBlockLinesIterator::CheckResult &cres, const FBoundingBox &box, FCheckPosition &tm, const bool wasfit)
{
	line_t *ld = cres.line;
	bool rail = false;

	if (!inRange(box, ld) || BoxOnLineSide(box, ld) != -1)
		return true;

	// A line has been hit
	/*
	=
	= The moving thing's destination position will cross the given line.
	= If this should not be allowed, return false.
	= If the line is special, keep track of it to process later if the move
	=       is proven ok.  NOTE: specials are NOT sorted by order, so two special lines
	=       that are only 8 pixels apart could be crossed in either order.
	*/

	if (!ld->backsector)
	{ // One sided line

		// Needed for polyobject portals.
		if (cres.line->isLinePortal() && (cres.line->sidedef[0]->Flags & WALLF_POLYOBJ))
		{
			spechit_t spec;
			spec.line = ld;
			spec.Refpos = cres.Position;
			spec.Oldrefpos = tm.thing->PosRelative(ld);
			portalhit.Push(spec);
			return true;
		}

		if (((cres.portalflags & FFCF_NOFLOOR) && LineIsAbove(cres.line, tm.thing) != 0) ||
			((cres.portalflags & FFCF_NOCEILING) && LineIsBelow(cres.line, tm.thing) != 0))
		{
			// this blocking line is in a different vertical layer and does not intersect with the actor that is being checked.
			// Since a one-sided line does not have an opening there's nothing left to do about it.
			return true;
		}

		// check if the actor can step through the ceiling portal. In this case one-sided lines in the current area should not block
		// Use the same rules for stepping through a portal as for non-portal case.
		bool ismissile = (tm.thing->flags & MF_MISSILE) && !(tm.thing->flags6 & MF6_STEPMISSILE) && !(tm.thing->flags3 & MF3_FLOORHUGGER);
		if (!ismissile && !cres.line->frontsector->PortalBlocksMovement(sector_t::ceiling))
		{
			double portz = cres.line->frontsector->GetPortalPlaneZ(sector_t::ceiling);
			if (tm.thing->Z() < portz && tm.thing->Z() + tm.thing->MaxStepHeight >= portz && tm.floorz < portz)
			{
				if (wasfit)
				{
					tm.floorz = portz;
					tm.floorsector = cres.line->frontsector;
					tm.floorpic = cres.line->sidedef[0]->GetTexture(side_t::mid);
					tm.floorterrain = 0;
					tm.portalstep = true;
					tm.portalgroup = cres.line->frontsector->GetOppositePortalGroup(sector_t::ceiling);
				}
				return true;
			}
		}

		if (tm.thing->flags2 & MF2_BLASTED)
		{
			P_DamageMobj(tm.thing, NULL, NULL, tm.thing->Mass >> 5, NAME_Melee);
		}
		if (wasfit)
		{
			tm.thing->BlockingLine = ld;
		}
		CheckForPushSpecial(ld, 0, tm.thing);
		return false;
	}

	// MBF bouncers are treated as missiles here.
	bool Projectile = (tm.thing->flags & MF_MISSILE || tm.thing->BounceFlags & BOUNCE_MBF);

	uint32_t ProjectileBlocking = ML_BLOCKEVERYTHING | ML_BLOCKPROJECTILE;
	if ( tm.thing->flags8 & MF8_BLOCKASPLAYER ) ProjectileBlocking |= ML_BLOCK_PLAYERS | ML_BLOCKING;

	if (!(Projectile) || (ld->flags & ProjectileBlocking) )
	{
		if (ld->flags & ML_RAILING)
		{
			rail = true;
		}
		else if (P_IsBlockedByLine(tm.thing, ld) ||
			((Projectile) && (ld->flags & ML_BLOCKPROJECTILE)))
		{
			if (cres.portalflags & FFCF_NOFLOOR)
			{
				int state = LineIsAbove(cres.line, tm.thing);
				if (state == -1) return true;
				if (state == 1)
				{
					if (wasfit)
					{
						// the line should not block but we should set the ceilingz to the portal boundary so that we can't float up into that line.
						double portalz = cres.line->frontsector->GetPortalPlaneZ(sector_t::floor);
						if (portalz < tm.ceilingz)
						{
							tm.ceilingz = portalz;
							tm.ceilingsector = cres.line->frontsector;
						}
					}
					return true;
				}
			}
			else if (cres.portalflags & FFCF_NOCEILING)
			{
				// same, but for downward portals
				int state = LineIsBelow(cres.line, tm.thing);
				if (state == -1) return true;
				if (state == 1)
				{
					if (wasfit)
					{
						double portalz = cres.line->frontsector->GetPortalPlaneZ(sector_t::ceiling);
						if (portalz > tm.floorz)
						{
							tm.floorz = portalz;
							tm.floorsector = cres.line->frontsector;
							tm.floorterrain = 0;
						}
					}
					return true;
				}
			}
			else
			{
				if (tm.thing->flags2 & MF2_BLASTED)
				{
					P_DamageMobj(tm.thing, NULL, NULL, tm.thing->Mass >> 5, NAME_Melee);
				}
				if (wasfit)
				{
					tm.thing->BlockingLine = ld;
				}
				// Calculate line side based on the actor's original position, not the new one.
				CheckForPushSpecial(ld, P_PointOnLineSide(cres.Position, ld), tm.thing);
				return false;
			}
		}
	}
	DVector2 ref = FindRefPoint(ld, cres.Position);
	FLineOpening open;

	P_LineOpening(open, tm.thing, ld, ref, &cres.Position, cres.portalflags);
	// Use the same rules for stepping through a portal as for non-portal case.
	bool ismissile = (tm.thing->flags & MF_MISSILE) && !(tm.thing->flags6 & MF6_STEPMISSILE) && !(tm.thing->flags3 & MF3_FLOORHUGGER);
	if (!ismissile && !tm.thing->Sector->PortalBlocksMovement(sector_t::ceiling))
	{
		sector_t *oppsec = cres.line->frontsector == tm.thing->Sector ? cres.line->backsector : cres.line->frontsector;
		if (oppsec->PortalBlocksMovement(sector_t::ceiling))
		{
			double portz = tm.thing->Sector->GetPortalPlaneZ(sector_t::ceiling);
			if (tm.thing->Z() < portz && tm.thing->Z() + tm.thing->MaxStepHeight >= portz && tm.floorz < portz)
			{
				if (wasfit)
				{
					// Actor is stepping through a portal.
					tm.portalstep = true;
					tm.portalgroup = tm.thing->Sector->GetOppositePortalGroup(sector_t::ceiling);
				}
				return true;
			}
		}
	}

	// [RH] Steep sectors count as dropoffs, if the actor touches the boundary between a steep slope and something else
	if (!(tm.thing->flags & MF_DROPOFF) &&
		!(tm.thing->flags & (MF_NOGRAVITY | MF_NOCLIP)))
	{
		if ((open.frontfloorplane.fC() < tm.thing->MaxSlopeSteepness) != (open.backfloorplane.fC() < tm.thing->MaxSlopeSteepness))
		{
			// on the boundary of a steep slope
			return false;
		}
	}

	// If the floor planes on both sides match we should recalculate open.bottom at the actual position we are checking
	// This is to avoid bumpy movement when crossing a linedef with the same slope on both sides.
	// This should never narrow down the opening, though, only widen it.
	if (open.frontfloorplane == open.backfloorplane && open.bottom > LINEOPEN_MIN)
	{
		auto newopen = open.frontfloorplane.ZatPoint(cres.Position);
		if (newopen < open.bottom) open.bottom = newopen;
	}

	if (rail &&
		// Eww! Gross! This check means the rail only exists if you stand on the
		// high side of the rail. So if you're walking on the low side of the rail,
		// it's possible to get stuck in the rail until you jump out. Unfortunately,
		// there is an area on Strife MAP04 that requires this behavior. Still, it's
		// better than Strife's handling of rails, which lets you jump into rails
		// from either side. How long until somebody reports this as a bug and I'm
		// forced to say, "It's not a bug. It's a feature?" Ugh.
		(!(tm.thing->Level->i_compatflags2 & COMPATF2_RAILING) ||
		open.bottom == tm.thing->Sector->floorplane.ZatPoint(ref)))
	{
		open.bottom += 32;
	}

	if (wasfit)
	{
		// adjust floor / ceiling heights
		if (!(cres.portalflags & FFCF_NOCEILING))
		{
			if (open.top < tm.ceilingz)
			{
				tm.ceilingz = open.top;
				tm.ceilingsector = open.topsec;
				tm.ceilingpic = open.ceilingpic;
				tm.ceilingline = ld;
				tm.thing->BlockingLine = ld;
				if (open.topffloor)
					tm.thing->Blocking3DFloor = open.topffloor->model;
			}
		}

		// If we are stepping through a portal the line's opening must be checked, regardless of the NOFLOOR flag
		if (!(cres.portalflags & FFCF_NOFLOOR) || (tm.portalstep && open.bottomsec->PortalGroup == tm.portalgroup))
		{
			if (open.bottom > tm.floorz)
			{
				tm.floorz = open.bottom;
				tm.floorsector = open.bottomsec;
				tm.floorpic = open.floorpic;
				tm.floorterrain = open.floorterrain;
				tm.touchmidtex = open.touchmidtex;
				tm.abovemidtex = open.abovemidtex;
				tm.thing->BlockingLine = ld;
				if (open.bottomffloor)
					tm.thing->Blocking3DFloor = open.bottomffloor->model;
			}
			else if (open.bottom == tm.floorz)
			{
				tm.touchmidtex |= open.touchmidtex;
				tm.abovemidtex |= open.abovemidtex;
			}

			if (open.lowfloor < tm.dropoffz)
			{
				// Do not alter the dropoff if the previous portal layer got it solely from its own data.
				if (!(cres.portalflags & FFCF_NOCEILING) || tm.dropoffisportal)
				{
					tm.dropoffz = open.lowfloor;
					tm.dropoffisportal = open.lowfloorthroughportal;
				}
			}
		}
	}

	// if contacted a special line, add it to the list
	spechit_t spec;
	if (ld->special)
	{
		spec.line = ld;
		spec.Refpos = cres.Position;
		spec.Oldrefpos = tm.thing->PosRelative(ld);
		spechit.Push(spec);
	}
	if (ld->isLinePortal())
	{
		spec.line = ld;
		spec.Refpos = cres.Position;
		spec.Oldrefpos = tm.thing->PosRelative(ld);
		portalhit.Push(spec);
	}

	return true;
}

//==========================================================================
//
//
// PIT_CheckPortal
// This checks the destination side of a non-static line portal
// We cannot run a full P_CheckPosition there because it'd set 
// multiple fields to values that can cause problems in other
// parts of the code
// 
// What this does is starting a separate BlockLinesIterator
// and only taking the absolutely necessary information
// (i.e. floor and ceiling height plus terrain)
// 
//
//==========================================================================

static bool PIT_CheckPortal(FMultiBlockLinesIterator &mit, FMultiBlockLinesIterator::CheckResult cres, const FBoundingBox &box, FCheckPosition &tm)
{
	// if in another vertical section let's just ignore it.
	if (cres.portalflags & (FFCF_NOCEILING | FFCF_NOFLOOR)) return false;

	if (!inRange(box, cres.line) || BoxOnLineSide(box, cres.line) != -1)
		return false;

	line_t *lp = cres.line->getPortalDestination();
	double zofs = 0;

	P_TranslatePortalXY(cres.line, cres.Position.X, cres.Position.Y);
	P_TranslatePortalZ(cres.line, zofs);

	// fudge a bit with the portal line so that this gets included in the checks that normally only get run on two-sided lines
	sector_t *sec = lp->backsector;
	if (lp->backsector == NULL) lp->backsector = lp->frontsector;
	tm.thing->AddZ(zofs);

	FBoundingBox pbox(cres.Position.X, cres.Position.Y, tm.thing->radius);
	FBlockLinesIterator it(tm.thing->Level, pbox);
	bool ret = false;
	line_t *ld;

	// Check all lines at the destination
	while ((ld = it.Next()))
	{
		if (!inRange(pbox, ld) || BoxOnLineSide(pbox, ld) != -1)
			continue;

		if (ld->backsector == NULL) 
			continue;

		DVector2 ref = FindRefPoint(ld, cres.Position);
		FLineOpening open;

		P_LineOpening(open, tm.thing, ld, ref, &cres.Position, 0);

		// adjust floor / ceiling heights
		if (open.top - zofs < tm.ceilingz)
		{
			tm.ceilingz = open.top - zofs;
			tm.ceilingpic = open.ceilingpic;
			/*
			tm.ceilingsector = open.topsec;
			tm.ceilingline = ld;
			tm.thing->BlockingLine = ld;
			*/
			ret = true;
		}

		if (open.bottom - zofs > tm.floorz)
		{
			tm.floorz = open.bottom - zofs;
			tm.floorpic = open.floorpic;
			tm.floorterrain = open.floorterrain;
			/*
			tm.floorsector = open.bottomsec;
			tm.touchmidtex = open.touchmidtex;
			tm.abovemidtex = open.abovemidtex;
			tm.thing->BlockingLine = ld;
			*/
			ret = true;
		}

		if (open.lowfloor - zofs < tm.dropoffz)
			tm.dropoffz = open.lowfloor - zofs;
	}
	tm.thing->AddZ(-zofs);
	lp->backsector = sec;

	return ret;
}


//==========================================================================
//
// Isolated to keep the code readable and fix the logic
//
//==========================================================================

static bool CheckRipLevel(AActor *victim, AActor *projectile)
{
	if (victim->RipLevelMin > 0 && projectile->RipperLevel < victim->RipLevelMin) return false;
	if (victim->RipLevelMax > 0 && projectile->RipperLevel > victim->RipLevelMax) return false;
	return true;
}


//==========================================================================
//
// Isolated to keep the code readable and allow reuse in other attacks
//
//==========================================================================

static bool P_ProjectileImmune(AActor* target, AActor* source)
{
	// This one's directly taken from DSDA.
	auto targetgroup = target->GetClass()->ActorInfo()->projectile_group;
	auto sourcegroup = source->GetClass()->ActorInfo()->projectile_group;

	return
		( // PG_GROUPLESS means no immunity, even to own species
			targetgroup != -1/*PG_GROUPLESS*/ ||
			target == source
			) &&
		(
			( // target type has default behaviour, and things are the same type
				targetgroup == 0/*PG_DEFAULT*/ &&
				(source->GetSpecies() == target->GetSpecies() && !(target->flags6 & MF6_DOHARMSPECIES))
				) ||
			( // target type has special behaviour, and things have the same group
				targetgroup != 0/*PG_DEFAULT*/ &&
				targetgroup == sourcegroup
				)
			);
}

static bool CanAttackHurt(AActor *victim, AActor *shooter)
{
	// players are never subject to infighting settings and are always allowed
	// to harm / be harmed by anything.
	if (!victim->player && !shooter->player)
	{
		int infight = victim->Level->GetInfighting();
		if (infight < 0 && (victim->flags7 & MF7_FORCEINFIGHTING)) infight = 0;	// This must override the 'no infight' setting to take effect.

		if (infight < 0)
		{
			// -1: Monsters cannot hurt each other, but make exceptions for
			//     friendliness and hate status.
			if (shooter->flags & MF_SHOOTABLE)
			{
				// Question: Should monsters be allowed to shoot barrels in this mode?
				// The old code does not.
				if (victim->flags3 & MF3_ISMONSTER)
				{
					// Monsters that are clearly hostile can always hurt each other
					if (!victim->IsHostile(shooter))
					{
						// The same if the shooter hates the target
						if (victim->tid == 0 || shooter->TIDtoHate != victim->tid)
						{
							return false;
						}
					}
				}
			}
		}
		else if (infight == 0)
		{
			//  0: Monsters cannot hurt same species except 
			//     cases where they are clearly supposed to do that
			if (victim->IsFriend(shooter))
			{
				// Friends never harm each other, unless the shooter has the HARMFRIENDS set.
				if (!(shooter->flags7 & MF7_HARMFRIENDS)) return false;
			}
			else
			{
				if (victim->TIDtoHate != 0 && victim->TIDtoHate == shooter->TIDtoHate)
				{
					// [RH] Don't hurt monsters that hate the same victim as you do
					return false;
				}

				if (P_ProjectileImmune(victim, shooter))
				{
					// Don't hurt same species or any relative -
					// but only if the target isn't one's hostile.
					if (!victim->IsHostile(shooter))
					{
						// Allow hurting monsters the shooter hates.
						if (victim->tid == 0 || shooter->TIDtoHate != victim->tid)
						{
							return false;
						}
					}
				}
			}
		}
		// else if (infight==1) every shot hurts anything - no further tests needed
	}
	return true;
}

//==========================================================================
//
// P_DoMissileDamage
// Handle damaging/poisoning enemies from missiles.
// target is the target to be dealt damage to.
// inflictor is the actor dealing the damage.
//
//==========================================================================

void P_DoMissileDamage(AActor* inflictor, AActor* target)
{
	// Do poisoning (if using new style poison)
	if (inflictor->PoisonDamage > 0 && inflictor->PoisonDuration != INT_MIN)
	{
		P_PoisonMobj(target, inflictor, inflictor->target, inflictor->PoisonDamage, inflictor->PoisonDuration, inflictor->PoisonPeriod, inflictor->PoisonDamageType);
	}

	// Do damage
	int damage = inflictor->GetMissileDamage((inflictor->flags4 & MF4_STRIFEDAMAGE) ? 3 : 7, 1);
	if ((damage > 0) || (inflictor->flags6 & MF6_FORCEPAIN) || (inflictor->flags7 & MF7_CAUSEPAIN))
	{
		int newdam = P_DamageMobj(target, inflictor, inflictor->target, damage, inflictor->DamageType);
		if (damage > 0)
		{
			if ((inflictor->flags5 & MF5_BLOODSPLATTER) &&
				!(target->flags & MF_NOBLOOD) &&
				!(target->flags2 & MF2_REFLECTIVE) &&
				!(target->flags2 & (MF2_INVULNERABLE | MF2_DORMANT)) &&
				!(inflictor->flags3 & MF3_BLOODLESSIMPACT) &&
				(pr_checkthing() < 192))
			{
				P_BloodSplatter(inflictor->Pos(), target, inflictor->AngleTo(target));
			}
			if (!(inflictor->flags3 & MF3_BLOODLESSIMPACT))
			{
				P_TraceBleed(newdam > 0 ? newdam : damage, target, inflictor);
			}
		}
	}
	else
	{
		P_GiveBody(target, -damage);
	}
}
DEFINE_ACTION_FUNCTION(AActor, DoMissileDamage)
{
	PARAM_SELF_PROLOGUE(AActor);
	PARAM_OBJECT_NOT_NULL(target, AActor);
	P_DoMissileDamage(self, target);
	return 0;
}
//==========================================================================
//
// PIT_CheckThing
//
//==========================================================================

bool PIT_CheckThing(FMultiBlockThingsIterator &it, FMultiBlockThingsIterator::CheckResult &cres, const FBoundingBox &box, FCheckPosition &tm)
{
	AActor *thing = cres.thing;
	double topz;
	bool 	solid;
	int 	damage;

	// don't clip against self
	if (thing == tm.thing)
		return true;

	if ((thing->flags2 | tm.thing->flags2) & MF2_THRUACTORS)
		return true;

	if ((thing->ThruBits & tm.thing->ThruBits) && ((thing->flags8 | tm.thing->flags8) & MF8_ALLOWTHRUBITS))
		return true;

	if (!((thing->flags & (MF_SOLID | MF_SPECIAL | MF_SHOOTABLE)) || thing->flags6 & MF6_TOUCHY))
		return true;	// can't hit thing

	double blockdist = thing->radius + tm.thing->radius;
	if (fabs(thing->X() - cres.Position.X) >= blockdist || fabs(thing->Y() - cres.Position.Y) >= blockdist)
		return true;

	if ((tm.thing->flags6 & MF6_THRUSPECIES) && (tm.thing->GetSpecies() == thing->GetSpecies()))
		return true;

	tm.thing->BlockingMobj = thing;
	topz = thing->Top();

	// Both things overlap in x or y direction
	bool unblocking = false;

	// walking on other actors and unblocking is too messy through restricted portal types so disable it.
	if (!(cres.portalflags & FFCF_RESTRICTEDPORTAL))
	{
		if (!(thing->Level->i_compatflags & COMPATF_NO_PASSMOBJ) && !(tm.thing->flags & (MF_FLOAT | MF_MISSILE | MF_SKULLFLY | MF_NOGRAVITY)) &&
			(thing->flags & MF_SOLID) && (thing->flags4 & MF4_ACTLIKEBRIDGE))
		{
			// [RH] Let monsters walk on actors as well as floors
			if ((tm.thing->flags3 & MF3_ISMONSTER) &&
				topz >= tm.floorz && topz <= tm.thing->Z() + tm.thing->MaxStepHeight)
			{
				// The commented-out if is an attempt to prevent monsters from walking off a
				// thing further than they would walk off a ledge. I can't think of an easy
				// way to do this, so I restrict them to only walking on bridges instead.
				// Uncommenting the if here makes it almost impossible for them to walk on
				// anything, bridge or otherwise.
				//			if (abs(thing->x - tmx) <= thing->radius &&
				//				abs(thing->y - tmy) <= thing->radius)
				{
					tm.stepthing = thing;
					tm.floorz = topz;
				}
			}
		}

		if (((tm.FromPMove || tm.thing->player != NULL) && thing->flags&MF_SOLID))
		{
			DVector3 oldpos = tm.thing->PosRelative(thing);
			// Both actors already overlap. To prevent them from remaining stuck allow the move if it
			// takes them further apart or the move does not change the position (when called from P_ChangeSector.)
			if (tm.pos.X == tm.thing->X() && tm.pos.Y == tm.thing->Y())
			{
				unblocking = true;
			}
			else if (fabs(thing->X() - oldpos.X) < (thing->radius + tm.thing->radius) &&
				fabs(thing->Y() - oldpos.Y) < (thing->radius + tm.thing->radius))

			{
				double newdist = thing->Distance2D(cres.Position.X, cres.Position.Y);
				double olddist = thing->Distance2D(oldpos.X, oldpos.Y);

				if (newdist > olddist)
				{
					// unblock only if there's already a vertical overlap (or both actors are flagged not to overlap)
					unblocking = (tm.thing->Top() > thing->Z() && tm.thing->Z() < topz) || (tm.thing->flags3 & thing->flags3 & MF3_DONTOVERLAP);
				}
			}
		}
	}

	// [RH] If the other thing is a bridge, then treat the moving thing as if it had MF2_PASSMOBJ, so
	// you can use a scrolling floor to move scenery items underneath a bridge.
	if ((tm.thing->flags2 & MF2_PASSMOBJ || thing->flags4 & MF4_ACTLIKEBRIDGE) && !(tm.thing->Level->i_compatflags & COMPATF_NO_PASSMOBJ))
	{ // check if a mobj passed over/under another object
		if (!(tm.thing->flags & MF_MISSILE) ||
			!(tm.thing->flags2 & MF2_RIP) ||
			(thing->flags5 & MF5_DONTRIP) ||
			((tm.thing->flags6 & MF6_NOBOSSRIP) && (thing->flags2 & MF2_BOSS)))
		{
			if (thing->flags & MF_SPECIAL)
			{
				// Vanilla condition, i.e. without equality, for item pickups
				if ((tm.thing->Z() > topz) || (tm.thing->Top() < thing->Z()))
					return true;
			}
			// Some things prefer not to overlap each other, if possible (Q: Is this even needed anymore? It was just for dealing with some deficiencies in the code below in Heretic.)
			else if (!(tm.thing->flags3 & thing->flags3 & MF3_DONTOVERLAP))
			{
				if ((tm.thing->Z() >= topz) || (tm.thing->Top() <= thing->Z()))
					return true;
			}
			else return unblocking;	// This may not really make sense, but Heretic depends on the broken implementation.
		}
	}

	// Call the script callback. This must be done before any other checks that perform some actual action or may already return a 'block'.
	// The checks here are to do this only for conditions that would later result in an action, calling this for everything would be too much of a drag if
	// too many scripted overrides were being used, as PIT_CheckThing is even called for touching all the monster corpses lying around.
	if (((thing->flags & MF_SOLID) || (thing->flags6 & (MF6_TOUCHY | MF6_BUMPSPECIAL))) && 
		((tm.thing->flags & (MF_SOLID|MF_MISSILE)) || (tm.thing->flags2 & MF2_BLASTED) || (tm.thing->flags6 & MF6_BLOCKEDBYSOLIDACTORS) || (tm.thing->BounceFlags & BOUNCE_MBF)))
	{
		if (!P_CanCollideWith(tm.thing, thing)) return true;
	}


	if (tm.thing->player == NULL || !(tm.thing->player->cheats & CF_PREDICTING))
	{
		// touchy object is alive, toucher is solid
		if (thing->flags6 & MF6_TOUCHY && tm.thing->flags & MF_SOLID && thing->health > 0 &&
			// Thing is an armed mine or a sentient thing
			(thing->flags6 & MF6_ARMED || thing->IsSentient()) &&
			// either different classes or players
			(thing->player || thing->GetClass() != tm.thing->GetClass()) &&
			// or different species if DONTHARMSPECIES
			(!(thing->flags6 & MF6_DONTHARMSPECIES) || thing->GetSpecies() != tm.thing->GetSpecies()) &&
			// touches vertically
			topz >= tm.thing->Z() && tm.thing->Top() >= thing->Z() &&
			// prevents lost souls from exploding when fired by pain elementals
			(thing->master != tm.thing && tm.thing->master != thing))
			// Difference with MBF: MBF hardcodes the LS/PE check and lets actors of the same species
			// but different classes trigger the touchiness, but that seems less straightforwards.
		{
			thing->flags6 &= ~MF6_ARMED; // Disarm
			P_DamageMobj(thing, NULL, NULL, thing->health, NAME_None, DMG_FORCED);  // kill object
			return true;
		}

		// Check for MF6_BUMPSPECIAL
		// By default, only players can activate things by bumping into them
		if ((thing->flags6 & MF6_BUMPSPECIAL) && ((tm.thing->player != NULL)
			|| ((thing->activationtype & THINGSPEC_MonsterTrigger) && (tm.thing->flags3 & MF3_ISMONSTER))
			|| ((thing->activationtype & THINGSPEC_MissileTrigger) && (tm.thing->flags & MF_MISSILE))
			) && (thing->Level->maptime > thing->lastbump)) // Leave the bumper enough time to go away
		{
			if (P_ActivateThingSpecial(thing, tm.thing))
				thing->lastbump = thing->Level->maptime + TICRATE;
		}
	}

	// Check for skulls slamming into things
	if (tm.thing->flags & MF_SKULLFLY)
	{
		bool res = tm.thing->CallSlam(tm.thing->BlockingMobj);
		tm.thing->BlockingMobj = NULL;
		return res;
	}

	// [ED850] Player Prediction ends here. There is nothing else they could/should do.
	if (tm.thing->player != NULL && (tm.thing->player->cheats & CF_PREDICTING))
	{
		solid = (thing->flags & MF_SOLID) &&
			!(thing->flags & MF_NOCLIP) &&
			((tm.thing->flags & MF_SOLID) || (tm.thing->flags6 & MF6_BLOCKEDBYSOLIDACTORS));

		return !solid || unblocking;
	}

	// Check for blasted thing running into another
	if ((tm.thing->flags2 & MF2_BLASTED) && (thing->flags & MF_SHOOTABLE))
	{
		if (!(thing->flags2 & MF2_BOSS) && (thing->flags3 & MF3_ISMONSTER) && !(thing->flags3 & MF3_DONTBLAST))
		{
			// ideally this should take the mass factor into account
			thing->Vel += tm.thing->Vel.XY();
			if (fabs(thing->Vel.X) + fabs(thing->Vel.Y) > 3.)
			{
				int newdam;
				damage = (tm.thing->Mass / 100) + 1;
				newdam = P_DamageMobj(thing, tm.thing, tm.thing, damage, tm.thing->DamageType);
				P_TraceBleed(newdam > 0 ? newdam : damage, thing, tm.thing);
				damage = (thing->Mass / 100) + 1;
				newdam = P_DamageMobj(tm.thing, thing, thing, damage >> 2, tm.thing->DamageType);
				P_TraceBleed(newdam > 0 ? newdam : damage, tm.thing, thing);
			}
			return false;
		}
	}
	// Check for missile or non-solid MBF bouncer
	if (tm.thing->flags & MF_MISSILE || ((tm.thing->BounceFlags & BOUNCE_MBF) && !(tm.thing->flags & MF_SOLID)))
	{
		// Check for a non-shootable mobj
		if (thing->flags2 & MF2_NONSHOOTABLE)
		{
			return true;
		}
		// Check for passing through a ghost
		if ((thing->flags3 & MF3_GHOST) && (tm.thing->flags2 & MF2_THRUGHOST))
		{
			return true;
		}

		if ((tm.thing->flags6 & MF6_MTHRUSPECIES)
			&& tm.thing->target // NULL pointer check
			&& (tm.thing->target->GetSpecies() == thing->GetSpecies()))
			return true;

		// Check for rippers passing through corpses
		if ((thing->flags & MF_CORPSE) && (tm.thing->flags2 & MF2_RIP) && !(thing->flags & MF_SHOOTABLE))
		{
			return true;
		}

		double clipheight;

		if (thing->projectilepassheight > 0)
		{
			clipheight = thing->projectilepassheight;
		}
		else if (thing->projectilepassheight < 0 && (thing->Level->i_compatflags & COMPATF_MISSILECLIP))
		{
			clipheight = -thing->projectilepassheight;
		}
		else
		{
			clipheight = thing->Height;
		}

		// Check if it went over / under
		if (tm.thing->Z() > thing->Z() + clipheight)
		{ // Over thing
			return true;
		}
		if (tm.thing->Top() < thing->Z())
		{ // Under thing
			return true;
		}

		// [RH] What is the point of this check, again? In Hexen, it is unconditional,
		// but here we only do it if the missile's damage is 0.
		// MBF bouncer might have a non-0 damage value, but they must not deal damage on impact either.
		if ((tm.thing->BounceFlags & BOUNCE_Actors) && (tm.thing->IsZeroDamage() || !(tm.thing->flags & MF_MISSILE)))
		{
			return (((tm.thing->target == thing && !(tm.thing->flags8 & MF8_HITOWNER)) || !(thing->flags & MF_SOLID)) && 
				(tm.thing->SpecialMissileHit(thing) != 0));
		}

		switch (tm.thing->SpecialMissileHit(thing))
		{
		case 0:		return false;
		case 1:		return true;
		default:	break;
		}

		// [RH] Extend DeHacked infighting to allow for monsters
		// to never fight each other

		if (tm.thing->target != NULL)
		{
			if (thing == tm.thing->target && !(tm.thing->flags8 & MF8_HITOWNER))
			{ // Don't missile self -- [MK] unless explicitly allowed
				return true;
			}

			if (!CanAttackHurt(thing, tm.thing->target))
			{
				return false;
			}
		}
		if (!(thing->flags & MF_SHOOTABLE))
		{ // Didn't do any damage
			return !(thing->flags & MF_SOLID);
		}
		if ((thing->flags4 & MF4_SPECTRAL) && !(tm.thing->flags4 & MF4_SPECTRAL))
		{
			return true;
		}

		if ((tm.DoRipping && !(thing->flags5 & MF5_DONTRIP)) && CheckRipLevel(thing, tm.thing))
		{
			if (!(tm.thing->flags6 & MF6_NOBOSSRIP) || !(thing->flags2 & MF2_BOSS))
			{
				bool *check = tm.LastRipped.CheckKey(thing);
				if (check == NULL || !*check)
				{
					tm.LastRipped[thing] = true;
					if (!(thing->flags & MF_NOBLOOD) &&
						!(thing->flags2 & MF2_REFLECTIVE) &&
						!(tm.thing->flags3 & MF3_BLOODLESSIMPACT) &&
						!(thing->flags2 & (MF2_INVULNERABLE | MF2_DORMANT)))
					{ // Ok to spawn blood
						P_RipperBlood(tm.thing, thing);
					}
					S_Sound(tm.thing, CHAN_BODY, 0, tm.thing->SoundVar(NAME_RipSound), 1, ATTN_IDLE);

					// Do poisoning (if using new style poison)
					if (tm.thing->PoisonDamage > 0 && tm.thing->PoisonDuration != INT_MIN)
					{
						P_PoisonMobj(thing, tm.thing, tm.thing->target, tm.thing->PoisonDamage, tm.thing->PoisonDuration, tm.thing->PoisonPeriod, tm.thing->PoisonDamageType);
					}

					damage = tm.thing->GetMissileDamage(3, 2);
					int newdam = P_DamageMobj(thing, tm.thing, tm.thing->target, damage, tm.thing->DamageType);
					if (!(tm.thing->flags3 & MF3_BLOODLESSIMPACT))
					{
						P_TraceBleed(newdam > 0 ? newdam : damage, thing, tm.thing);
					}
					if (thing->flags2 & MF2_PUSHABLE
						&& !(tm.thing->flags2 & MF2_CANNOTPUSH))
					{ // Push thing
						if (thing->lastpush != tm.PushTime)
						{
							thing->Vel += tm.thing->Vel.XY() * thing->pushfactor;
							thing->lastpush = tm.PushTime;
						}
					}
				}
				spechit.Clear();
				return true;
			}
		}

		P_DoMissileDamage(tm.thing, thing);

		if ((thing->flags7 & MF7_THRUREFLECT) && (thing->flags2 & MF2_REFLECTIVE) && (tm.thing->flags & MF_MISSILE))
		{
			if (tm.thing->flags2 & MF2_SEEKERMISSILE)
			{
				tm.thing->tracer = tm.thing->target;
			}
			tm.thing->target = thing;
			return true;
		}
		return false;		// don't traverse any more
	}
	if (thing->flags2 & MF2_PUSHABLE && !(tm.thing->flags2 & MF2_CANNOTPUSH))
	{ // Push thing
		if (thing->lastpush != tm.PushTime)
		{
			thing->Vel += tm.thing->Vel.XY() * thing->pushfactor;
			thing->lastpush = tm.PushTime;
		}
	}
	solid = (thing->flags & MF_SOLID) &&
		!(thing->flags & MF_NOCLIP) &&
		((tm.thing->flags & MF_SOLID) || (tm.thing->flags6 & MF6_BLOCKEDBYSOLIDACTORS));

	// Check for special pickup
	if ((thing->flags & MF_SPECIAL) && (tm.thing->flags & MF_PICKUP)
		// [RH] The next condition is to compensate for the extra height
		// that gets added by P_CheckPosition() so that you cannot pick
		// up things that are above your true height.
		&& thing->Z() < tm.thing->Top() - tm.thing->MaxStepHeight)
	{ // Can be picked up by tmthing
		P_TouchSpecialThing(thing, tm.thing);	// can remove thing
	}

	// killough 3/16/98: Allow non-solid moving objects to move through solid
	// ones, by allowing the moving thing (tmthing) to move if it's non-solid,
	// despite another solid thing being in the way.
	// killough 4/11/98: Treat no-clipping things as not blocking

	return !solid || unblocking;

	// return !(thing->flags & MF_SOLID);	// old code -- killough
}



/*
===============================================================================

MOVEMENT CLIPPING

===============================================================================
*/

//==========================================================================
//
// P_CheckPosition
// This is purely informative, nothing is modified
// (except things picked up and missile damage applied).
// 
// in:
//	a AActor (can be valid or invalid)
//	a position to be checked
//	 (doesn't need to be related to the AActor->x,y)
//
// during:
//	special things are touched if MF_PICKUP
//	early out on solid lines?
//
// out:
//	newsubsec
//	floorz
//	ceilingz
//	tmdropoffz = the lowest point contacted (monsters won't move to a dropoff)
//	speciallines[]
//	numspeciallines
//  AActor *BlockingMobj = pointer to thing that blocked position (NULL if not
//   blocked, or blocked by a line).
//
//==========================================================================

bool P_CheckPosition(AActor *thing, const DVector2 &pos, FCheckPosition &tm, bool actorsonly)
{
	sector_t *newsec;
	AActor *thingblocker;
	double realHeight = thing->Height;

	tm.thing = thing;

	tm.pos.X = pos.X;
	tm.pos.Y = pos.Y;
	tm.pos.Z = thing->Z();

	newsec = tm.sector = thing->Level->PointInSector(pos);
	tm.ceilingline = thing->BlockingLine = NULL;

	// Retrieve the base floor / ceiling from the target location.
	// Any contacted lines the step closer together will adjust them.
	if (!thing->IsNoClip2())
	{
		if (!newsec->PortalBlocksMovement(sector_t::ceiling) || !newsec->PortalBlocksMovement(sector_t::floor))
		{
			// Use P_GetFloorCeilingZ only if there's portals to consider. Its logic is subtly different than what is needed here for 3D floors.
			P_GetFloorCeilingZ(tm, FFCF_SAMESECTOR);
		}
		else
		{
			tm.floorz = tm.dropoffz = newsec->floorplane.ZatPoint(pos);
			tm.dropoffisportal = false;
			tm.floorpic = newsec->GetTexture(sector_t::floor);
			tm.ceilingz = newsec->ceilingplane.ZatPoint(pos);
			tm.ceilingpic = newsec->GetTexture(sector_t::ceiling);
			tm.floorsector = tm.ceilingsector = newsec;
			tm.floorterrain = newsec->GetTerrain(sector_t::floor);
		}

		F3DFloor*  rover;
		double thingtop = thing->Height > 0 ? thing->Top() : thing->Z() + 1;

		for (unsigned i = 0; i<newsec->e->XFloor.ffloors.Size(); i++)
		{
			rover = newsec->e->XFloor.ffloors[i];
			if (!(rover->flags & FF_SOLID) || !(rover->flags & FF_EXISTS)) continue;

			double ff_bottom = rover->bottom.plane->ZatPoint(pos);
			double ff_top = rover->top.plane->ZatPoint(pos);

			double delta1 = thing->Z() - (ff_bottom + ((ff_top - ff_bottom) / 2));
			double delta2 = thingtop - (ff_bottom + ((ff_top - ff_bottom) / 2));

			if (ff_top > tm.floorz && fabs(delta1) < fabs(delta2))
			{
				tm.floorz = tm.dropoffz = ff_top;
				tm.dropoffisportal = false;
				tm.floorpic = *rover->top.texture;
				tm.floorterrain = rover->model->GetTerrain(rover->top.isceiling);
			}
			if (ff_bottom < tm.ceilingz && fabs(delta1) >= fabs(delta2))
			{
				tm.ceilingz = ff_bottom;
				tm.ceilingpic = *rover->bottom.texture;
			}
		}
	}
	else
	{
		// With noclip2, we must ignore 3D floors and go right to the uppermost ceiling and lowermost floor.
		tm.floorz = tm.dropoffz = LowestFloorAt(newsec, pos.X, pos.Y, &tm.floorsector);
		tm.ceilingz = HighestCeilingAt(newsec, pos.X, pos.Y, &tm.ceilingsector);
		tm.floorpic = tm.floorsector->GetTexture(sector_t::floor);
		tm.floorterrain = tm.floorsector->GetTerrain(sector_t::floor);
		tm.ceilingpic = tm.ceilingsector->GetTexture(sector_t::ceiling);
	}

	tm.touchmidtex = false;
	tm.abovemidtex = false;
	validcount++;

	// Remove all old entries before returning.
	spechit.Clear();
	portalhit.Clear();

	if ((thing->flags & MF_NOCLIP) && !(thing->flags & MF_SKULLFLY))
		return true;

	// Check things first, possibly picking things up.
	thing->BlockingMobj = NULL;
	thingblocker = NULL;
	if (thing->player)
	{ // [RH] Fake taller height to catch stepping up into things.
		thing->Height = realHeight + thing->MaxStepHeight;
	}

	tm.stepthing = NULL;
	FBoundingBox box(pos.X, pos.Y, thing->radius);

	FPortalGroupArray pcheck;
	FMultiBlockThingsIterator it2(pcheck, thing->Level, pos.X, pos.Y, thing->Z(), thing->Height, thing->radius, false, newsec);
	FMultiBlockThingsIterator::CheckResult tcres;

	if (!(thing->flags2 & MF2_THRUACTORS))
	while ((it2.Next(&tcres)))
	{
		if (!PIT_CheckThing(it2, tcres, it2.Box(), tm))
		{ // [RH] If a thing can be stepped up on, we need to continue checking
			// other things in the blocks and see if we hit something that is
			// definitely blocking. Otherwise, we need to check the lines, or we
			// could end up stuck inside a wall.
			AActor *BlockingMobj = thing->BlockingMobj;

			// If this blocks through a restricted line portal, it will always completely block.
			if (BlockingMobj == NULL || (thing->Level->i_compatflags & COMPATF_NO_PASSMOBJ) || (tcres.portalflags & FFCF_RESTRICTEDPORTAL))
			{ // Thing slammed into something; don't let it move now.
				thing->Height = realHeight;
				return false;
			}
			else if (!BlockingMobj->player && !(thing->flags & (MF_FLOAT | MF_MISSILE | MF_SKULLFLY)) &&
				BlockingMobj->Top() - thing->Z() <= thing->MaxStepHeight)
			{
				if (thingblocker == NULL ||
					BlockingMobj->Z() > thingblocker->Z())
				{
					thingblocker = BlockingMobj;
				}
				thing->BlockingMobj = NULL;
			}
			else if (thing->player &&
				thing->Top() - BlockingMobj->Z() <= thing->MaxStepHeight)
			{
				if (thingblocker)
				{ // There is something to step up on. Return this thing as
					// the blocker so that we don't step up.
					thing->Height = realHeight;
					return false;
				}
				// Nothing is blocking us, but this actor potentially could
				// if there is something else to step on.
				thing->BlockingMobj = NULL;
			}
			else
			{ // Definitely blocking
				thing->Height = realHeight;
				return false;
			}
		}
	}

	// check lines

	// [RH] We need to increment validcount again, because a function above may
	// have already set some lines to equal the current validcount.
	//
	// Specifically, when DehackedPickup spawns a new item in its TryPickup()
	// function, that new actor will set the lines around it to match validcount
	// when it links itself into the world. If we just leave validcount alone,
	// that will give the player the freedom to walk through walls at will near
	// a pickup they cannot get, because their validcount will prevent them from
	// being considered for collision with the player.
	validcount++;

	// Clear out any residual garbage left behind by PIT_CheckThing induced recursions etc.
	spechit.Clear();
	portalhit.Clear();

	thing->BlockingMobj = NULL;
	thing->Height = realHeight;
	if (actorsonly || (thing->flags & MF_NOCLIP))
		return (thing->BlockingMobj = thingblocker) == NULL;


	FMultiBlockLinesIterator it(pcheck, thing->Level, pos.X, pos.Y, thing->Z(), thing->Height, thing->radius, newsec);
	FMultiBlockLinesIterator::CheckResult lcres;

	double thingdropoffz = tm.floorz;
	//bool onthing = (thingdropoffz != tmdropoffz);
	tm.floorz = tm.dropoffz;

	bool good = true;

	while (it.Next(&lcres))
	{
		bool thisresult = PIT_CheckLine(it, lcres, it.Box(), tm, good);
		good &= thisresult;
		if (thisresult)
		{
			FLinePortal *port = lcres.line->getPortal();
			if (port != NULL && port->mFlags & PORTF_PASSABLE && port->mType != PORTT_LINKED)
			{
				// Checking the other side of the portal completely is too costly,
				// but checking the portal's destination line is necessary to 
				// retrieve the proper sector heights on the other side.
				if (PIT_CheckPortal(it, lcres, it.Box(), tm))
				{
					tm.thing->BlockingLine = lcres.line;
				}
			}
		}
	}
	if (!good)
	{
		return false;
	}
	if (tm.ceilingz - tm.floorz < thing->Height)
	{
		return false;
	}
	if (tm.touchmidtex)
	{
		tm.dropoffz = tm.floorz;
	}
	else if (tm.stepthing != NULL)
	{
		tm.dropoffz = thingdropoffz;
	}

	return (thing->BlockingMobj = thingblocker) == NULL;
}

bool P_CheckPosition(AActor *thing, const DVector2 &pos, bool actorsonly)
{
	FCheckPosition tm;
	return P_CheckPosition(thing, pos, tm, actorsonly);
}


//----------------------------------------------------------------------------
//
// FUNC P_TestMobjLocation
//
// Returns true if the mobj is not blocked by anything at its current
// location, otherwise returns false.
//
//----------------------------------------------------------------------------

int P_TestMobjLocation(AActor *mobj)
{
	ActorFlags flags;

	flags = mobj->flags;
	mobj->flags &= ~MF_PICKUP;
	if (P_CheckPosition(mobj, mobj->Pos()))
	{ // XY is ok, now check Z
		mobj->flags = flags;
		if ((mobj->Z() < mobj->floorz) || (mobj->Top() > mobj->ceilingz))
		{ // Bad Z
			return false;
		}
		return true;
	}
	mobj->flags = flags;
	return false;
}

//=============================================================================
//
// P_CheckOnmobj(AActor *thing)
//
//				Checks if the new Z position is legal
//=============================================================================

AActor *P_CheckOnmobj(AActor *thing)
{
	double oldz;
	int good;
	AActor *onmobj;

	oldz = thing->Z();
	P_FakeZMovement(thing);
	good = P_TestMobjZ(thing, false, &onmobj);
	thing->SetZ(oldz);

	return good ? NULL : onmobj;
}

//=============================================================================
//
// P_TestMobjZ
//
//=============================================================================

int P_TestMobjZ(AActor *actor, bool quick, AActor **pOnmobj)
{
	AActor *onmobj = nullptr;
	if (pOnmobj) *pOnmobj = nullptr;
	if (actor->flags & MF_NOCLIP)
	{
		return true;
	}

	FPortalGroupArray check;
	FMultiBlockThingsIterator it(check, actor, -1, true);
	FMultiBlockThingsIterator::CheckResult cres;

	while (it.Next(&cres))
	{
		AActor *thing = cres.thing;

		double blockdist = thing->radius + actor->radius;
		if (fabs(thing->X() - cres.Position.X) >= blockdist || fabs(thing->Y() - cres.Position.Y) >= blockdist)
		{
			continue;
		}
		if ((actor->flags2 | thing->flags2) & MF2_THRUACTORS)
		{
			continue;
		}
		if ((actor->ThruBits & thing->ThruBits) && ((actor->flags8 | thing->flags8) & MF8_ALLOWTHRUBITS))
		{
			continue;
		}
		if ((actor->flags6 & MF6_THRUSPECIES) && (thing->GetSpecies() == actor->GetSpecies()))
		{
			continue;
		}
		if (!(thing->flags & MF_SOLID))
		{ // Can't hit thing
			continue;
		}
		if (thing->flags & (MF_SPECIAL | MF_NOCLIP))
		{ // [RH] Specials and noclippers don't block moves
			continue;
		}
		if (thing->flags & (MF_CORPSE))
		{ // Corpses need a few more checks
			if (!(actor->flags & MF_ICECORPSE))
				continue;
		}
		if (!(thing->flags4 & MF4_ACTLIKEBRIDGE) && (actor->flags & MF_SPECIAL))
		{ // [RH] Only bridges block pickup items
			continue;
		}
		if (thing == actor)
		{ // Don't clip against self
			continue;
		}
		if ((actor->flags & MF_MISSILE) && (thing == actor->target))
		{ // Don't clip against whoever shot the missile.
			continue;
		}
		if (actor->Z() > thing->Top())
		{ // over thing
			continue;
		}
		else if (actor->Top() <= thing->Z())
		{ // under thing
			continue;
		}
		else if (!quick && onmobj != NULL && thing->Top() < onmobj->Top())
		{ // something higher is in the way
			continue;
		}
		else if (!P_CanCollideWith(actor, thing))
		{ // If they cannot collide, they cannot block each other.
			continue;
		}


		onmobj = thing;
		if (quick) break;
	}

	if (pOnmobj) *pOnmobj = onmobj;
	return onmobj == NULL;
}


//=============================================================================
//
// P_FakeZMovement
//
//				Fake the zmovement so that we can check if a move is legal
//=============================================================================

void P_FakeZMovement(AActor *mo)
{
	//
	// adjust height
	//
	mo->AddZ(mo->Vel.Z);
	if ((mo->flags&MF_FLOAT) && mo->target)
	{ // float down towards target if too close
		if (!(mo->flags & MF_SKULLFLY) && !(mo->flags & MF_INFLOAT))
		{
			double dist = mo->Distance2D(mo->target);
			double delta = mo->target->Center() - mo->Z();
			if (delta < 0 && dist < -(delta * 3))
				mo->AddZ(-mo->FloatSpeed);
			else if (delta > 0 && dist < (delta * 3))
				mo->AddZ(mo->FloatSpeed);
		}
	}
	if (mo->player && mo->flags&MF_NOGRAVITY && (mo->Z() > mo->floorz) && !mo->IsNoClip2())
	{
		mo->AddZ(DAngle(4.5 * mo->Level->maptime).Sin());
	}

	//
	// clip movement
	//
	if (mo->Z() <= mo->floorz)
	{ // hit the floor
		mo->SetZ(mo->floorz);
	}

	if (mo->Top() > mo->ceilingz)
	{ // hit the ceiling
		mo->SetZ(mo->ceilingz - mo->Height);
	}
}

//===========================================================================
//
// CheckForPushSpecial
//
//===========================================================================

static void CheckForPushSpecial(line_t *line, int side, AActor *mobj, DVector2 *posforwindowcheck)
{
	if (line->special && !(mobj->flags6 & MF6_NOTRIGGER))
	{
		if (posforwindowcheck && !(mobj->Level->i_compatflags2 & COMPATF2_PUSHWINDOW) && line->backsector != NULL)
		{ // Make sure this line actually blocks us and is not a window
			// or similar construct we are standing inside of.
			DVector3 pos = mobj->PosRelative(line);
			double fzt = line->frontsector->ceilingplane.ZatPoint(*posforwindowcheck);
			double fzb = line->frontsector->floorplane.ZatPoint(*posforwindowcheck);
			double bzt = line->backsector->ceilingplane.ZatPoint(*posforwindowcheck);
			double bzb = line->backsector->floorplane.ZatPoint(*posforwindowcheck);
			if (fzt >= mobj->Top() && bzt >= mobj->Top() &&
				fzb <= mobj->Z() && bzb <= mobj->Z())
			{
				if (line->flags & ML_3DMIDTEX)
				{
					double top, bot;
					P_GetMidTexturePosition(line, side, &top, &bot);
					if (bot < mobj->Top() && top > mobj->Z())
					{
						goto isblocking;
					}
				}
				// we must also check if some 3D floor in the backsector may be blocking
				for (auto rover : line->backsector->e->XFloor.ffloors)
				{
					if (!(rover->flags & FF_SOLID) || !(rover->flags & FF_EXISTS)) continue;

					double ff_bottom = rover->bottom.plane->ZatPoint(*posforwindowcheck);
					double ff_top = rover->top.plane->ZatPoint(*posforwindowcheck);

					if (ff_bottom < mobj->Top() && ff_top > mobj->Z())
					{
						goto isblocking;
					}
				}
				return;
			}
		}
	isblocking:
		if (mobj->flags2 & MF2_PUSHWALL)
		{
			P_ActivateLine(line, mobj, side, SPAC_Push);
		}
		else if (mobj->flags2 & MF2_IMPACT)
		{
			if ((mobj->Level->flags2 & LEVEL2_MISSILESACTIVATEIMPACT) ||
				!(mobj->flags & MF_MISSILE) ||
				(mobj->target == NULL))
			{
				P_ActivateLine(line, mobj, side, SPAC_Impact);
			}
			else
			{
				P_ActivateLine(line, mobj->target, side, SPAC_Impact);
			}
		}
	}
}

//==========================================================================
//
// P_TryMove
// Attempt to move to a new position,
// crossing special lines unless MF_TELEPORT is set.
//
//==========================================================================

bool P_TryMove(AActor *thing, const DVector2 &pos,
	int dropoff, // killough 3/15/98: allow dropoff as option
	const secplane_t *onfloor, // [RH] Let P_TryMove keep the thing on the floor
	FCheckPosition &tm,
	bool missileCheck)	// [GZ] Fired missiles ignore the drop-off test
{
	sector_t	*oldsector;
	double		oldz;
	int 		side;
	int 		oldside;
	sector_t*	oldsec = thing->Sector;	// [RH] for sector actions
	sector_t*	newsec;

	tm.floatok = false;
	tm.portalstep = false;
	oldz = thing->Z();
	if (onfloor)
	{
		thing->SetZ(onfloor->ZatPoint(pos));
	}
	thing->flags6 |= MF6_INTRYMOVE;
	if (!P_CheckPosition(thing, pos, tm))
	{
		AActor *BlockingMobj = thing->BlockingMobj;
		// Solid wall or thing
		if (!BlockingMobj || BlockingMobj->player || !thing->player)
		{
			goto pushline;
		}
		else
		{
			if (BlockingMobj->player || !thing->player)
			{
				goto pushline;
			}
			else if (BlockingMobj->Top() - thing->Z() > thing->MaxStepHeight
				|| ((BlockingMobj->Sector->ceilingplane.ZatPoint(pos) - (BlockingMobj->Top()) < thing->Height) && BlockingMobj->Sector->PortalBlocksMovement(sector_t::ceiling))
				|| (tm.ceilingz - (BlockingMobj->Top()) < thing->Height))
			{
				goto pushline;
			}
		}
		if (!(tm.thing->flags2 & MF2_PASSMOBJ) || (tm.thing->Level->i_compatflags & COMPATF_NO_PASSMOBJ))
		{
			thing->SetZ(oldz);
			thing->flags6 &= ~MF6_INTRYMOVE;
			return false;
		}
	}

	if (thing->flags3 & MF3_FLOORHUGGER)
	{
		thing->SetZ(tm.floorz);
	}
	else if (thing->flags3 & MF3_CEILINGHUGGER)
	{
		thing->SetZ(tm.ceilingz - thing->Height);
	}

	if (onfloor && tm.floorsector == thing->floorsector)
	{
		thing->SetZ(tm.floorz);
	}
	if (!(thing->flags & MF_NOCLIP))
	{
		if (tm.ceilingz - tm.floorz < thing->Height)
		{
			goto pushline;		// doesn't fit
		}

		tm.floatok = true;

		if (!(thing->flags & MF_TELEPORT)
			&& tm.ceilingz < thing->Top()
			&& !(thing->flags3 & MF3_CEILINGHUGGER)
			&& (!(thing->flags2 & MF2_FLY) || !(thing->flags & MF_NOGRAVITY)))
		{
			goto pushline;		// mobj must lower itself to fit
		}
		if (thing->flags2 & MF2_FLY && thing->flags & MF_NOGRAVITY)
		{
#if 1
			if (thing->Top() > tm.ceilingz)
				goto pushline;
#else
			// When flying, slide up or down blocking lines until the actor
			// is not blocked.
			if (thing->Top() > tm.ceilingz)
			{
				thing->Vel.Z = -8;
				goto pushline;
			}
			else if (thing->Z() < tm.floorz && tm.floorz - tm.dropoffz > thing->MaxDropOffHeight)
			{
				thing->Vel.Z = 8;
				goto pushline;
			}
#endif
		}
		if (!(thing->flags & MF_TELEPORT) && (!(thing->flags3 & MF3_FLOORHUGGER) || thing->flags5 & MF5_NODROPOFF))
		{
			if ((thing->flags & MF_MISSILE) && !(thing->flags6 & MF6_STEPMISSILE) && tm.floorz > thing->Z() && !(thing->flags3 & MF3_FLOORHUGGER))
			{ // [RH] Don't let normal missiles climb steps
				goto pushline;
			}
			if (tm.floorz - thing->Z() > thing->MaxStepHeight)
			{ // too big a step up
				goto pushline;
			}
			else if (thing->Z() < tm.floorz)
			{ // [RH] Check to make sure there's nothing in the way for the step up
				double savedz = thing->Z();
				thing->SetZ(tm.floorz);
				auto good = P_TestMobjZ(thing);
				thing->SetZ(savedz);
				if (!good)
				{
					goto pushline;
				}
				if (thing->flags6 & MF6_STEPMISSILE)
				{
					thing->SetZ(tm.floorz);
					// If moving down, cancel vertical component of the velocity
					if (thing->Vel.Z < 0)
					{
						// If it's a bouncer, let it bounce off its new floor, too.
						if (thing->BounceFlags & BOUNCE_Floors)
						{
							thing->FloorBounceMissile(tm.floorsector->floorplane);
						}
						else
						{
							thing->Vel.Z = 0;
						}
					}
				}
			}
		}

		// compatibility check: Doom originally did not allow monsters to cross dropoffs at all.
		// If the compatibility flag is on, only allow this when the velocity comes from a scroller
		if ((thing->Level->i_compatflags & COMPATF_CROSSDROPOFF) && !(thing->flags4 & MF4_SCROLLMOVE))
		{
			dropoff = false;
		}

		if (dropoff == 2 &&  // large jump down (e.g. dogs)
			(tm.floorz - tm.dropoffz > 128. || thing->target == NULL || thing->target->Z() >tm.dropoffz))
		{
			dropoff = false;
		}


		// killough 3/15/98: Allow certain objects to drop off
		if ((!dropoff && !(thing->flags & (MF_DROPOFF | MF_FLOAT | MF_MISSILE))) || (thing->flags5&MF5_NODROPOFF))
		{
			if (!(thing->flags5&MF5_AVOIDINGDROPOFF))
			{
				double floorz = tm.floorz;
				// [RH] If the thing is standing on something, use its current z as the floorz.
				// This is so that it does not walk off of things onto a drop off.
				if (thing->flags2 & MF2_ONMOBJ)
				{
					floorz = MAX(thing->Z(), tm.floorz);
				}

				if (floorz - tm.dropoffz > thing->MaxDropOffHeight &&
					!(thing->flags2 & MF2_BLASTED) && !missileCheck)
				{ // Can't move over a dropoff unless it's been blasted
					// [GZ] Or missile-spawned
					thing->SetZ(oldz);
					thing->flags6 &= ~MF6_INTRYMOVE;
					return false;
				}
			}
			else
			{
				// special logic to move a monster off a dropoff
				// this intentionally does not check for standing on things.
				if (thing->floorz - tm.floorz > thing->MaxDropOffHeight ||
					thing->dropoffz - tm.dropoffz > thing->MaxDropOffHeight)
				{
					thing->flags6 &= ~MF6_INTRYMOVE;
					return false;
				}
			}
		}
		if (thing->flags2 & MF2_CANTLEAVEFLOORPIC
			&& (tm.floorpic != thing->floorpic
			|| tm.floorz - thing->Z() != 0))
		{ // must stay within a sector of a certain floor type
			thing->SetZ(oldz);
			thing->flags6 &= ~MF6_INTRYMOVE;
			return false;
		}

		//Added by MC: To prevent bot from getting into dangerous sectors.
		if (thing->player && thing->player->Bot != NULL && thing->flags & MF_SHOOTABLE)
		{
			if (tm.sector != thing->Sector
				&& thing->Level->BotInfo.IsDangerous(tm.sector))
			{
				thing->player->Bot->prev = thing->player->Bot->dest;
				thing->player->Bot->dest = nullptr;
				thing->Vel.X = thing->Vel.Y = 0;
				thing->SetZ(oldz);
				thing->flags6 &= ~MF6_INTRYMOVE;
				return false;
			}
		}
	}

	// [RH] Check status of eyes against fake floor/ceiling in case
	// it slopes or the player's eyes are bobbing in and out.

	bool oldAboveFakeFloor, oldAboveFakeCeiling;
	double viewheight;
	// pacify GCC
	viewheight = thing->player ? thing->player->viewheight : thing->Height / 2;
	oldAboveFakeFloor = oldAboveFakeCeiling = false;

	if (oldsec->heightsec)
	{
		double eyez = oldz + viewheight;

		oldAboveFakeFloor = eyez > oldsec->heightsec->floorplane.ZatPoint(thing);
		oldAboveFakeCeiling = eyez > oldsec->heightsec->ceilingplane.ZatPoint(thing);
	}

	// Borrowed from MBF: 
	if (thing->BounceFlags & BOUNCE_MBF &&  // killough 8/13/98
		!(thing->flags & (MF_MISSILE | MF_NOGRAVITY)) &&
		!thing->IsSentient() && tm.floorz - thing->Z() > 16)
	{ // too big a step up for MBF bouncers under gravity
		thing->flags6 &= ~MF6_INTRYMOVE;
		return false;
	}


	// Check for crossed portals
	bool portalcrossed;
	portalcrossed = false;

	while (true)
	{
		double bestfrac = 1.1;
		spechit_t besthit;
		int besthitnum;
		// find the portal nearest to the crossing actor
		for (unsigned i = 0; i < portalhit.Size();i++)
		{
			auto &spec = portalhit[i];

			line_t *ld = spec.line;
			if (ld->frontsector->PortalGroup != thing->Sector->PortalGroup) continue;	// must be in the same group to be considered valid.

			// see if the line was crossed
			oldside = P_PointOnLineSide(spec.Oldrefpos, ld);
			side = P_PointOnLineSide(spec.Refpos, ld);
			if (oldside == 0 && side == 1)
			{
				divline_t dl2 = { ld->v1->fX(), ld->v1->fY(), ld->Delta().X, ld->Delta().Y };
				divline_t dl1 = { spec.Oldrefpos.X, spec.Oldrefpos.Y, spec.Refpos.X - spec.Oldrefpos.X, spec.Refpos.Y - spec.Oldrefpos.Y };
				double frac = P_InterceptVector(&dl1, &dl2);
				if (frac < bestfrac)
				{
					besthit = spec;
					bestfrac = frac;
					besthitnum = i;
				}
			}
		}

		if (bestfrac < 1.1)
		{
			portalhit.Delete(besthitnum);
			line_t *ld = besthit.line;
			FLinePortal *port = ld->getPortal();
			if (port->mType == PORTT_LINKED)
			{
				FLinkContext ctx;
				thing->UnlinkFromWorld(&ctx);
				thing->SetXY(tm.pos + port->mDisplacement);
				thing->Prev += port->mDisplacement;
				thing->LinkToWorld(&ctx);
				P_FindFloorCeiling(thing);
				portalcrossed = true;
				tm.portalstep = false;
				tm.pos += port->mDisplacement;
			}
			else if (!portalcrossed)
			{
				DVector3 pos(tm.pos, thing->Z());
				DVector3 oldthingpos = thing->Pos();
				DVector2 thingpos = oldthingpos;
				
				P_TranslatePortalXY(ld, pos.X, pos.Y);
				P_TranslatePortalXY(ld, thingpos.X, thingpos.Y);
				P_TranslatePortalZ(ld, pos.Z);
				thing->SetXYZ(thingpos.X, thingpos.Y, pos.Z);
				if (!P_CheckPosition(thing, pos, true))	// check if some actor blocks us on the other side. (No line checks, because of the mess that'd create.)
				{
					thing->SetXYZ(oldthingpos);
					thing->flags6 &= ~MF6_INTRYMOVE;
					return false;
				}
				FLinkContext ctx;
				thing->UnlinkFromWorld(&ctx);
				thing->SetXYZ(pos);
				P_TranslatePortalVXVY(ld, thing->Vel.X, thing->Vel.Y);
				P_TranslatePortalAngle(ld, thing->Angles.Yaw);
				thing->LinkToWorld(&ctx);
				P_FindFloorCeiling(thing);
				thing->ClearInterpolation();
				portalcrossed = true;
				tm.portalstep = false;
			}
			// if this is the current camera we need to store the point where the portal was crossed and the exit
			// so that the renderer can properly calculate an interpolated position along the movement path.
			if (thing->Level->isCamera(thing))
			{
				divline_t dl1 = { besthit.Oldrefpos.X,besthit.Oldrefpos.Y, besthit.Refpos.X - besthit.Oldrefpos.X, besthit.Refpos.Y - besthit.Oldrefpos.Y };
				DVector3a hit = { {dl1.x + dl1.dx * bestfrac, dl1.y + dl1.dy * bestfrac, 0.},0. };

				R_AddInterpolationPoint(hit);
				if (port->mType == PORTT_LINKED)
				{
					hit.pos.X += port->mDisplacement.X;
					hit.pos.Y += port->mDisplacement.Y;
				}
				else
				{
					P_TranslatePortalXY(ld, hit.pos.X, hit.pos.Y);
					P_TranslatePortalZ(ld, hit.pos.Z);
					auto p = thing->Level->GetConsolePlayer();
					if (p) p->viewz += hit.pos.Z;	// needs to be done here because otherwise the renderer will not catch the change.
					P_TranslatePortalAngle(ld, hit.angle);
				}
				R_AddInterpolationPoint(hit);
			}
			if (port->mType == PORTT_LINKED)
			{
				continue;
		}
		}
		break;
	}



	if (!portalcrossed)
	{
		// the move is ok, so link the thing into its new position
		FLinkContext ctx;
		thing->UnlinkFromWorld(&ctx);

		oldsector = thing->Sector;
		thing->floorz = tm.floorz;
		thing->ceilingz= tm.ceilingz;
		thing->dropoffz = tm.dropoffz;		// killough 11/98: keep track of dropoffs
		thing->floorpic = tm.floorpic;
		thing->floorterrain = tm.floorterrain;
		thing->floorsector = tm.floorsector;
		thing->ceilingpic = tm.ceilingpic;
		thing->ceilingsector = tm.ceilingsector;
		thing->SetXY(pos);

		thing->LinkToWorld(&ctx);
	}

	if (thing->flags2 & MF2_FLOORCLIP)
	{
		thing->AdjustFloorClip();
	}

	// if any special lines were hit, do the effect
	if (!(thing->flags & (MF_TELEPORT | MF_NOCLIP)))
	{
		spechit_t spec;
		DVector2 lastpos = thing->Pos();
		while (spechit.Pop(spec))
		{
			line_t *ld = spec.line;
			// see if the line was crossed

			side = P_PointOnLineSide(spec.Refpos, ld);
			oldside = P_PointOnLineSide(spec.Oldrefpos, ld);
			if (side != oldside && ld->special && !(thing->flags6 & MF6_NOTRIGGER))
			{
				if (thing->player && (thing->player->cheats & CF_PREDICTING))
				{
					P_PredictLine(ld, thing, oldside, SPAC_Cross);
				}
				else if (thing->player)
				{
					P_ActivateLine(ld, thing, oldside, SPAC_Cross);
				}
				else if (thing->flags2 & MF2_MCROSS)
				{
					P_ActivateLine(ld, thing, oldside, SPAC_MCross);
				}
				else if (thing->flags2 & MF2_PCROSS)
				{
					P_ActivateLine(ld, thing, oldside, SPAC_PCross);
				}
				else if ((ld->special == Teleport ||
					ld->special == Teleport_NoFog ||
					ld->special == Teleport_Line))
				{	// [RH] Just a little hack for BOOM compatibility
					P_ActivateLine(ld, thing, oldside, SPAC_MCross);
				}
				else
				{
					P_ActivateLine(ld, thing, oldside, SPAC_AnyCross);
				}
			}
		}
	}

	// [RH] Don't activate anything if just predicting
	if (thing->player && (thing->player->cheats & CF_PREDICTING))
	{
		thing->flags6 &= ~MF6_INTRYMOVE;
		return true;
	}

	// [RH] Check for crossing fake floor/ceiling
	newsec = thing->Sector;
	if (newsec->heightsec && oldsec->heightsec && newsec->SecActTarget)
	{
		const sector_t *hs = newsec->heightsec;
		double eyez = thing->Z() + viewheight;
		double fakez = hs->floorplane.ZatPoint(pos);

		if (!oldAboveFakeFloor && eyez > fakez)
		{ // View went above fake floor
			newsec->TriggerSectorActions(thing, SECSPAC_EyesSurface);
		}
		else if (oldAboveFakeFloor && eyez <= fakez)
		{ // View went below fake floor
			newsec->TriggerSectorActions(thing, SECSPAC_EyesDive);
		}

		if (!(hs->MoreFlags & SECMF_FAKEFLOORONLY))
		{
			fakez = hs->ceilingplane.ZatPoint(pos);
			if (!oldAboveFakeCeiling && eyez > fakez)
			{ // View went above fake ceiling
				newsec->TriggerSectorActions(thing, SECSPAC_EyesAboveC);
			}
			else if (oldAboveFakeCeiling && eyez <= fakez)
			{ // View went below fake ceiling
				newsec->TriggerSectorActions(thing, SECSPAC_EyesBelowC);
			}
		}
	}

	// If the actor stepped through a ceiling portal we need to reacquire the actual position info after the transition
	if (tm.portalstep)
	{
		FLinkContext ctx;
		DVector3 oldpos = thing->Pos();
		thing->UnlinkFromWorld(&ctx);
		thing->SetXYZ(thing->PosRelative(tm.portalgroup));
		thing->Prev += thing->Pos() - oldpos;
		thing->Sector = thing->Level->PointInSector(thing->Pos());
		thing->PrevPortalGroup = thing->Sector->PortalGroup;
		thing->LinkToWorld(&ctx);

		P_FindFloorCeiling(thing);
	}

	// [RH] If changing sectors, trigger transitions
	thing->CheckSectorTransition(oldsec);
	thing->flags6 &= ~MF6_INTRYMOVE;
	return true;

pushline:
	thing->flags6 &= ~MF6_INTRYMOVE;

	// [RH] Don't activate anything if just predicting
	if (thing->player && (thing->player->cheats & CF_PREDICTING))
	{
		return false;
	}

	thing->SetZ(oldz);
	if (!(thing->flags&(MF_TELEPORT | MF_NOCLIP)))
	{
		int numSpecHitTemp;

		if (tm.thing->flags2 & MF2_BLASTED)
		{
			P_DamageMobj(tm.thing, NULL, NULL, tm.thing->Mass >> 5, NAME_Melee);
		}
		numSpecHitTemp = (int)spechit.Size();
		while (numSpecHitTemp > 0)
		{
			// see which lines were pushed
			spechit_t &spec = spechit[--numSpecHitTemp];
			side = P_PointOnLineSide(spec.Refpos, spec.line);
			CheckForPushSpecial(spec.line, side, thing, &spec.Refpos);
		}
	}
	return false;
}

bool P_TryMove(AActor *thing, const DVector2 &pos,
	int dropoff, // killough 3/15/98: allow dropoff as option
	const secplane_t *onfloor, bool missilecheck) // [RH] Let P_TryMove keep the thing on the floor
{
	FCheckPosition tm;
	return P_TryMove(thing, pos, dropoff, onfloor, tm, missilecheck);
}


//==========================================================================
//
// P_CheckMove
// Similar to P_TryMove but doesn't actually move the actor. Used for polyobject crushing
//
//==========================================================================

bool P_CheckMove(AActor *thing, const DVector2 &pos, FCheckPosition& tm, int flags)
{
	double		newz = thing->Z();

	auto f1 = thing->flags & MF_PICKUP;
	thing->flags &= ~MF_PICKUP;
	auto res = P_CheckPosition(thing, pos, tm);
	thing->flags |= f1;
	if (!res)
	{
		// Ignore PCM_DROPOFF. Not necessary here: a little later it is.
		if (!flags || (!(flags & PCM_NOACTORS) && !(flags & PCM_NOLINES)))
		{
			return false;
		}
		if (!(flags & PCM_NOACTORS) && thing->BlockingMobj)
		{
			return false;
		}
		if (!(flags & PCM_NOLINES) && thing->BlockingLine)
		{
			return false;
		}
	}

	if (thing->flags3 & MF3_FLOORHUGGER)
	{
		newz = tm.floorz;
	}
	else if (thing->flags3 & MF3_CEILINGHUGGER)
	{
		newz = tm.ceilingz - thing->Height;
	}

	if (!(thing->flags & MF_NOCLIP))
	{
		if (tm.ceilingz - tm.floorz < thing->Height)
		{
			return false;
		}

		if (!(thing->flags & MF_TELEPORT)
			&& tm.ceilingz - newz < thing->Height
			&& !(thing->flags3 & MF3_CEILINGHUGGER)
			&& (!(thing->flags2 & MF2_FLY) || !(thing->flags & MF_NOGRAVITY)))
		{
			return false;
		}
		if (thing->flags2 & MF2_FLY && thing->flags & MF_NOGRAVITY)
		{
			if (thing->Top() > tm.ceilingz)
				return false;
		}
		if (!(thing->flags & MF_TELEPORT) && (!(thing->flags3 & MF3_FLOORHUGGER) || thing->flags5 & MF5_NODROPOFF))
		{
			if (tm.floorz - newz > thing->MaxStepHeight)
			{ // too big a step up
				return false;
			}
			else if ((thing->flags & MF_MISSILE) && !(thing->flags6 & MF6_STEPMISSILE) && tm.floorz > newz && !(thing->flags3 & MF3_FLOORHUGGER))
			{ // [RH] Don't let normal missiles climb steps
				return false;
			}
			else if (newz < tm.floorz)
			{ // [RH] Check to make sure there's nothing in the way for the step up
				double savedz = thing->Z();
				thing->SetZ(newz = tm.floorz);
				int good = P_TestMobjZ(thing);
				thing->SetZ(savedz);
				if (!good)
				{
					return false;
				}
			}
			else if ((flags & PCM_DROPOFF) && !(thing->flags & (MF_FLOAT|MF_DROPOFF)))
			{
				if (newz - tm.dropoffz > thing->MaxDropOffHeight)
				{
					return false;
				}
			}
		}

		if (thing->flags2 & MF2_CANTLEAVEFLOORPIC
			&& (tm.floorpic != thing->floorpic
			|| tm.floorz - newz != 0))
		{ // must stay within a sector of a certain floor type
			return false;
		}
	}

	return true;
}

bool P_CheckMove(AActor *thing, const DVector2 &pos, int flags)
{
	FCheckPosition tm;
	return P_CheckMove(thing, pos, tm, flags);
}


//==========================================================================
//
// SLIDE MOVE
// Allows the player to slide along any angled walls.
//
//==========================================================================

struct FSlide
{
	double 			bestSlidefrac;
	double 			secondSlidefrac;

	line_t* 		bestslideline;
	line_t* 		secondslideline;

	AActor* 		slidemo;

	DVector2		tmmove;

	void HitSlideLine(line_t *ld);
	void SlideTraverse(const DVector2 &start, const DVector2 &end);
	void SlideMove(AActor *mo, DVector2 tryp, int numsteps);

	// The bouncing code uses the same data structure
	bool BounceTraverse(const DVector2 &start, const DVector2 &end);
	bool BounceWall(AActor *mo);
};

//==========================================================================
//
// P_HitSlideLine
// Adjusts the xmove / ymove
// so that the next move will slide along the wall.
// If the floor is icy, then you can bounce off a wall.				// phares
//
//==========================================================================

void FSlide::HitSlideLine(line_t* ld)
{
	int 	side;

	DAngle lineangle;
	DAngle moveangle;
	DAngle deltaangle;

	double movelen;
	bool	icyfloor;	// is floor icy?							// phares
	//   |
	// Under icy conditions, if the angle of approach to the wall	//   V
	// is more than 45 degrees, then you'll bounce and lose half
	// your velocity. If less than 45 degrees, you'll slide along
	// the wall. 45 is arbitrary and is believable.

	// Check for the special cases of horz or vert walls.

	// killough 10/98: only bounce if hit hard (prevents wobbling)
	icyfloor =
		!(slidemo->flags8 & MF8_NOFRICTIONBOUNCE) &&
		tmmove.LengthSquared() > 4*4 &&
		var_friction &&  // killough 8/28/98: calc friction on demand
		slidemo->Z() <= slidemo->floorz &&
		P_GetFriction(slidemo, NULL) > ORIG_FRICTION;

	if (ld->Delta().X == 0)
	{ // ST_VERTICAL
		if (icyfloor && (fabs(tmmove.X) > fabs(tmmove.Y)))
		{
			tmmove.X = -tmmove.X / 2;
			tmmove.Y /= 2; // absorb half the velocity
			if (slidemo->player && slidemo->health > 0 && !(slidemo->player->cheats & CF_PREDICTING))
			{
				S_Sound(slidemo, CHAN_VOICE, 0, "*grunt", 1, ATTN_IDLE); // oooff!//   ^
			}
		}																		//   |
		else																	// phares
			tmmove.X = 0; // no more movement in the X direction
		return;
	}

	if (ld->Delta().Y == 0)
	{ // ST_HORIZONTAL
		if (icyfloor && (fabs(tmmove.Y) > fabs(tmmove.X)))
		{
			tmmove.X /= 2; // absorb half the velocity
			tmmove.Y = -tmmove.Y / 2;
			if (slidemo->player && slidemo->health > 0 && !(slidemo->player->cheats & CF_PREDICTING))
			{
				S_Sound(slidemo, CHAN_VOICE, 0, "*grunt", 1, ATTN_IDLE); // oooff!
			}
		}
		else
			tmmove.Y = 0; // no more movement in the Y direction
		return;
	}

	// The wall is angled. Bounce if the angle of approach is		// phares
	// less than 45 degrees.										// phares

	DVector3 pos = slidemo->PosRelative(ld);
	side = P_PointOnLineSide(pos, ld);

	lineangle = ld->Delta().Angle();

	if (side == 1)
		lineangle += 180.;

	moveangle = tmmove.Angle();

	// prevents sudden path reversal due to rounding error |	// phares
	moveangle += 3600/65536.*65536.;		// Boom added 10 to the angle here.
	
	deltaangle = ::deltaangle(lineangle, moveangle);								//   V
	movelen = tmmove.Length();
	if (icyfloor && (deltaangle > 45) && (deltaangle < 135))
	{
		moveangle = ::deltaangle(deltaangle, lineangle);
		movelen /= 2; // absorb
		if (slidemo->player && slidemo->health > 0 && !(slidemo->player->cheats & CF_PREDICTING))
		{
			S_Sound(slidemo, CHAN_VOICE, 0, "*grunt", 1, ATTN_IDLE); // oooff!
		}
		tmmove = moveangle.ToVector(movelen);
	}	
	else
	{	
		// The compatibility option that used to be here had to be removed because
		// with floating point math it was no longer possible to reproduce.

#if 0
		// with full precision this should work now. Needs some testing
		if (deltaangle < 0)	deltaangle += 180.;
		tmmove = lineangle.ToVector(movelen * deltaangle.Cos());
#else
		divline_t dll, dlv;
		double inter1, inter2, inter3;

		P_MakeDivline(ld, &dll);

		dlv.x = pos.X;
		dlv.y = pos.Y;
		dlv.dx = dll.dy;
		dlv.dy = -dll.dx;

		inter1 = P_InterceptVector(&dll, &dlv);

		dlv.dx = tmmove.X;
		dlv.dy = tmmove.Y;
		inter2 = P_InterceptVector(&dll, &dlv);
		inter3 = P_InterceptVector(&dlv, &dll);

		if (inter3 != 0)
		{
			tmmove.X = (inter2 - inter1) * dll.dx / inter3;
			tmmove.Y = (inter2 - inter1) * dll.dy / inter3;
		}
		else
		{
			tmmove.Zero();
		}
#endif
	}																// phares
}


//==========================================================================
//
// PTR_SlideTraverse
//
//==========================================================================

void FSlide::SlideTraverse(const DVector2 &start, const DVector2 &end)
{
	FLineOpening open;
	FPathTraverse it(slidemo->Level, start.X, start.Y, end.X, end.Y, PT_ADDLINES);
	intercept_t *in;

	while ((in = it.Next()))
	{
		line_t* 	li;

		if (!in->isaline)
		{
			// should never happen
			Printf("PTR_SlideTraverse: not a line?\n");
			continue;
		}

		li = in->d.line;

		if (!(li->flags & ML_TWOSIDED) || !li->backsector)
		{
			DVector3 pos = slidemo->PosRelative(li);
			if (P_PointOnLineSide(pos, li))
			{
				// don't hit the back side
				continue;
			}
			goto isblocking;
		}
		if (P_IsBlockedByLine(slidemo, li)) goto isblocking;

		// set openrange, opentop, openbottom
		P_LineOpening(open, slidemo, li, it.InterceptPoint(in));

		if (open.range < slidemo->Height)
			goto isblocking;				// doesn't fit

		if (open.top < slidemo->Top())
			goto isblocking;				// mobj is too high

		if (open.bottom - slidemo->Z() > slidemo->MaxStepHeight)
		{
			goto isblocking;				// too big a step up
		}
		else if (slidemo->Z() < open.bottom)
		{ // [RH] Check to make sure there's nothing in the way for the step up
			double savedz = slidemo->Z();
			slidemo->SetZ(open.bottom);
			int good = P_TestMobjZ(slidemo);
			slidemo->SetZ(savedz);
			if (!good)
			{
				goto isblocking;
			}
		}

		// this line doesn't block movement
		continue;

		// the line does block movement,
		// see if it is closer than best so far
	isblocking:
		if (in->frac < bestSlidefrac)
		{
			secondSlidefrac = bestSlidefrac;
			secondslideline = bestslideline;
			bestSlidefrac = in->frac;
			bestslideline = li;
		}

		return;		// stop
	}
}



//==========================================================================
//
// P_SlideMove
//
// The vel.x / vel.y move is bad, so try to slide along a wall.
//
// Find the first line hit, move flush to it, and slide along it
//
// This is a kludgy mess.
//
//==========================================================================

void FSlide::SlideMove(AActor *mo, DVector2 tryp, int numsteps)
{
	DVector2 lead;
	DVector2 trail;
	DVector2 newpos;
	DVector2 move;
	const secplane_t * walkplane;
	int hitcount;

	hitcount = 3;
	slidemo = mo;

	if (mo->player && mo->player->mo == mo && mo->reactiontime > 0)
		return;	// player coming right out of a teleporter.

retry:
	if (!--hitcount)
		goto stairstep; 		// don't loop forever

	// trace along the three leading corners
	if (tryp.X > 0)
	{
		lead.X = mo->X() + mo->radius;
		trail.X = mo->X() - mo->radius;
	}
	else
	{
		lead.X = mo->X() - mo->radius;
		trail.X = mo->X() + mo->radius;
	}

	if (tryp.Y > 0)
	{
		lead.Y = mo->Y() + mo->radius;
		trail.Y = mo->Y() - mo->radius;
	}
	else
	{
		lead.Y = mo->Y() - mo->radius;
		trail.Y = mo->Y() + mo->radius;
	}

	bestSlidefrac = 1.01;

	SlideTraverse(lead, lead + tryp);
	SlideTraverse(DVector2(trail.X, lead.Y), tryp + DVector2(trail.X, lead.Y));
	SlideTraverse(DVector2(lead.X, trail.Y), tryp + DVector2(lead.X, trail.Y));

	// move up to the wall
	if (bestSlidefrac > 1)
	{
		// the move must have hit the middle, so stairstep
	stairstep:
		// killough 3/15/98: Allow objects to drop off ledges
		move = { 0, tryp.Y };
		walkplane = P_CheckSlopeWalk(mo, move);
		if (!P_TryMove(mo, mo->Pos() + move, true, walkplane))
		{
			move = { tryp.X, 0 };
			walkplane = P_CheckSlopeWalk(mo, move);
			P_TryMove(mo, mo->Pos() + move, true, walkplane);
		}
		return;
	}

	// fudge a bit to make sure it doesn't hit
	bestSlidefrac -= 1. / 32;
	if (bestSlidefrac > 0)
	{
		newpos = tryp * bestSlidefrac;

		// [BL] We need to abandon this function if we end up going through a teleporter
		const DVector2 startvel = mo->Vel.XY();

		// killough 3/15/98: Allow objects to drop off ledges
		if (!P_TryMove(mo, mo->Pos() + newpos, true))
			goto stairstep;

		if (mo->Vel.XY() != startvel)
			return;
	}

	// Now continue along the wall.
	bestSlidefrac = 1. - (bestSlidefrac + 1. / 32);	// remainder
	if (bestSlidefrac > 1)
		bestSlidefrac = 1;
	else if (bestSlidefrac <= 0)
		return;

	tryp = tmmove = tryp*bestSlidefrac;

	HitSlideLine(bestslideline); 	// clip the moves

	mo->Vel.X = tmmove.X * numsteps;
	mo->Vel.Y = tmmove.Y * numsteps;

	// killough 10/98: affect the bobbing the same way (but not voodoo dolls)
	if (mo->player && mo->player->mo == mo)
	{
		if (fabs(mo->player->Vel.X) > fabs(mo->Vel.X))
			mo->player->Vel.X = mo->Vel.X;
		if (fabs(mo->player->Vel.Y) > fabs(mo->Vel.Y))
			mo->player->Vel.Y = mo->Vel.Y;
	}

	walkplane = P_CheckSlopeWalk(mo, tmmove);

	// killough 3/15/98: Allow objects to drop off ledges
	if (!P_TryMove(mo, mo->Pos() + tmmove, true, walkplane))
	{
		goto retry;
	}
}

void P_SlideMove(AActor *mo, const DVector2 &pos, int numsteps)
{
	FSlide slide;
	slide.SlideMove(mo, pos, numsteps);
}

//============================================================================
//
// P_CheckSlopeWalk
//
//============================================================================

const secplane_t * P_CheckSlopeWalk(AActor *actor, DVector2 &move)
{
	static secplane_t copyplane;
	if (actor->flags & MF_NOGRAVITY)
	{
		return NULL;
	}

	DVector3 pos = actor->PosRelative(actor->floorsector);
	const secplane_t *plane = &actor->floorsector->floorplane;
	double planezhere = plane->ZatPoint(pos);

	for (auto rover : actor->floorsector->e->XFloor.ffloors)
	{
		if (!(rover->flags & FF_SOLID) || !(rover->flags & FF_EXISTS)) continue;

		double thisplanez = rover->top.plane->ZatPoint(pos);

		if (thisplanez > planezhere && thisplanez <= actor->Z() + actor->MaxStepHeight)
		{
			copyplane = *rover->top.plane;
			if (copyplane.fC() < 0) copyplane.FlipVert();
			plane = &copyplane;
			planezhere = thisplanez;
		}
	}

	if (actor->floorsector != actor->Sector)
	{
		for (auto rover : actor->Sector->e->XFloor.ffloors)
		{
			if (!(rover->flags & FF_SOLID) || !(rover->flags & FF_EXISTS)) continue;

			double thisplanez = rover->top.plane->ZatPoint(actor);

			if (thisplanez > planezhere && thisplanez <= actor->Z() + actor->MaxStepHeight)
			{
				copyplane = *rover->top.plane;
				if (copyplane.fC() < 0) copyplane.FlipVert();
				plane = &copyplane;
				planezhere = thisplanez;
			}
		}
	}

	if (actor->floorsector != actor->Sector)
	{
		// this additional check prevents sliding on sloped dropoffs
		if (planezhere>actor->floorz + 4)
			return NULL;
	}

	if (actor->Z() - planezhere > 1)
	{ // not on floor
		return NULL;
	}

	if (plane->isSlope())
	{
		DVector2 dest;
		double t;

		dest = actor->Pos() + move;
		t = (plane->Normal() | DVector3(dest, actor->Z())) + plane->fD();
		if (t < 0)
		{ // Desired location is behind (below) the plane
			// (i.e. Walking up the plane)
			if (plane->fC() < actor->MaxSlopeSteepness)
			{ // Can't climb up slopes of ~45 degrees or more
				if (actor->flags & MF_NOCLIP)
				{
					return (actor->floorsector == actor->Sector) ? plane : NULL;
				}
				else
				{
					const msecnode_t *node;
					bool dopush = true;

					if (plane->fC() > actor->MaxSlopeSteepness * 2 / 3)
					{
						for (node = actor->touching_sectorlist; node; node = node->m_tnext)
						{
							sector_t *sec = node->m_sector;
							if (sec->floorplane.fC() >= actor->MaxSlopeSteepness)
							{
								DVector3 pos = actor->PosRelative(sec) +move;

								if (sec->floorplane.ZatPoint(pos) >= actor->Z() - actor->MaxStepHeight)
								{
									dopush = false;
									break;
								}
							}
						}
					}
					if (dopush)
					{
						move = plane->Normal() * 2;
						actor->Vel.X = move.X;
						actor->Vel.Y = move.Y;
					}
					return (actor->floorsector == actor->Sector) ? plane : NULL;
				}
			}
			// Slide the desired location along the plane's normal
			// so that it lies on the plane's surface
			dest -= plane->Normal() * t;
			move = dest - actor->Pos().XY();
			return (actor->floorsector == actor->Sector) ? plane : NULL;
		}
		else if (t > 0)
		{ // Desired location is in front of (above) the plane
			if (actor->isAtZ(planezhere))	// it is very important not to be too precise here.
			{ 
				// Actor's current spot is on/in the plane, so walk down it
				// Same principle as walking up, except reversed
				dest += plane->Normal() * t;
				move = dest - actor->Pos().XY();
				return (actor->floorsector == actor->Sector) ? plane : NULL;
			}
		}
	}
	return NULL;
}

//============================================================================
//
// PTR_BounceTraverse
//
//============================================================================

bool FSlide::BounceTraverse(const DVector2 &start, const DVector2 &end)
{
	FLineOpening open;
	FPathTraverse it(slidemo->Level, start.X, start.Y, end.X, end.Y, PT_ADDLINES);
	intercept_t *in;

	while ((in = it.Next()))
	{

		line_t  *li;

		if (!in->isaline)
		{
			Printf("PTR_BounceTraverse: not a line?\n");
			continue;
		}

		li = in->d.line;
		if (li->flags & ML_BLOCKEVERYTHING)
		{
			goto bounceblocking;
		}
		if (!(li->flags&ML_TWOSIDED) || !li->backsector)
		{
			if (P_PointOnLineSide(slidemo->Pos(), li))
				continue;			// don't hit the back side
			goto bounceblocking;
		}


		P_LineOpening(open, slidemo, li, it.InterceptPoint(in));	// set openrange, opentop, openbottom
		if (open.range < slidemo->Height)
			goto bounceblocking;				// doesn't fit

		if (open.top < slidemo->Top())
			goto bounceblocking;				// mobj is too high

		if (open.bottom > slidemo->Z())
			goto bounceblocking;				// mobj is too low

		continue;			// this line doesn't block movement

		// the line does block movement, see if it is closer than best so far
	bounceblocking:
		if (in->frac < bestSlidefrac)
		{
			secondSlidefrac = bestSlidefrac;
			secondslideline = bestslideline;
			bestSlidefrac = in->frac;
			bestslideline = li;
		}
		return false;   // stop
	}
	return true;
}

//============================================================================
//
// P_BounceWall
//
//============================================================================

bool FSlide::BounceWall(AActor *mo)
{
	DVector2         lead;
	int             side;
	DAngle         lineangle, moveangle, deltaangle;
	double         movelen;
	line_t			*line;

	if (!(mo->BounceFlags & BOUNCE_Walls))
	{
		return false;
	}

	slidemo = mo;
	//
	// trace along the three leading corners
	//
	if (mo->Vel.X > 0)
	{
		lead.X = mo->X() + mo->radius;
	}
	else
	{
		lead.X = mo->X() - mo->radius;
	}
	if (mo->Vel.Y > 0)
	{
		lead.Y = mo->Y() + mo->radius;
	}
	else
	{
		lead.Y = mo->Y() - mo->radius;
	}
	bestSlidefrac = 1.01;
	bestslideline = mo->BlockingLine;
	if (BounceTraverse(lead, lead+mo->Vel.XY()) && mo->BlockingLine == NULL)
	{ // Could not find a wall, so bounce off the floor/ceiling instead.
		double floordist = mo->Z() - mo->floorz;
		double ceildist = mo->ceilingz - mo->Z();
		if (floordist <= ceildist)
		{
			mo->FloorBounceMissile(mo->Sector->floorplane);
			return true;
		}
		else
		{
			mo->FloorBounceMissile(mo->Sector->ceilingplane);
			return true;
		}
	}
	line = bestslideline;

	if (line->special == Line_Horizon || ((mo->BounceFlags & BOUNCE_NotOnSky) && line->hitSkyWall(mo)))
	{
		mo->SeeSound = mo->BounceSound = 0;	// it might make a sound otherwise
		mo->Destroy();
		return true;
	}

	// [ZZ] if bouncing missile hits a damageable linedef, it dies
	if (P_ProjectileHitLinedef(mo, line) && mo->bouncecount > 0)
	{
		mo->Vel.Zero();
		mo->Speed = 0;
		mo->bouncecount = 0;
		if (mo->flags & MF_MISSILE)
			P_ExplodeMissile(mo, line, nullptr);
		else mo->CallDie(nullptr, nullptr);
		return true;
	}

	// The amount of bounces is limited
	if (mo->bouncecount>0 && --mo->bouncecount == 0)
	{
		if (mo->flags & MF_MISSILE)
			P_ExplodeMissile(mo, line, NULL);
		else
			mo->CallDie(NULL, NULL);
		return true;
	}

	side = P_PointOnLineSide(mo->Pos(), line);
	lineangle = line->Delta().Angle();
	if (side == 1)
	{
		lineangle += 180;
	}
	moveangle = mo->Vel.Angle();
	deltaangle = (lineangle * 2) - moveangle;
	mo->Angles.Yaw = deltaangle;

	movelen = mo->Vel.XY().Length() * GetWallBounceFactor(mo);

	FBoundingBox box(mo->X(), mo->Y(), mo->radius);
	if (BoxOnLineSide(box, line) == -1)
	{
		DVector2 ofs = deltaangle.ToVector(mo->radius);
		DVector3 pos = mo->Vec3Offset(ofs.X, ofs.Y, 0.);
		mo->SetOrigin(pos, true);

	}
	if (movelen < 1)
	{
		movelen = 2;
	}
	DVector2 vel = deltaangle.ToVector(movelen);
	mo->Vel.X = vel.X;
	mo->Vel.Y = vel.Y;
	if (mo->BounceFlags & BOUNCE_UseBounceState)
	{
		FState *bouncestate = mo->FindState(NAME_Bounce, NAME_Wall);
		if (bouncestate != NULL)
		{
			mo->SetState(bouncestate);
		}
	}
	return true;
}

bool P_BounceWall(AActor *mo)
{
	FSlide slide;
	return slide.BounceWall(mo);
}

//==========================================================================
//
//
//
//==========================================================================

extern FRandom pr_bounce;
bool P_BounceActor(AActor *mo, AActor *BlockingMobj, bool ontop)
{
	if (mo && (mo->flags & MF_MISSILE) && BlockingMobj)
	{
		switch (mo->SpecialMissileHit(BlockingMobj))
		{
			case 1:		return true;
			case 0:		return false;
			default:	break;
		}
	}

	//Don't go through all of this if the actor is reflective and wants things to pass through them.
	if (BlockingMobj && ((BlockingMobj->flags2 & MF2_REFLECTIVE) && (BlockingMobj->flags7 & MF7_THRUREFLECT)))	return true;
	if (mo && BlockingMobj && ((mo->BounceFlags & BOUNCE_AllActors)
		|| ((mo->flags & MF_MISSILE) && (!(mo->flags2 & MF2_RIP) 
		|| (BlockingMobj->flags5 & MF5_DONTRIP) 
		|| ((mo->flags6 & MF6_NOBOSSRIP) && (BlockingMobj->flags2 & MF2_BOSS))) && (BlockingMobj->flags2 & MF2_REFLECTIVE))
		|| ((BlockingMobj->player == NULL) && (!(BlockingMobj->flags3 & MF3_ISMONSTER)))))
	{
		// Rippers should not bounce off shootable actors, since they rip through them.
		if ((mo->flags & MF_MISSILE) && (mo->flags2 & MF2_RIP) && BlockingMobj->flags & MF_SHOOTABLE
			&& !(mo->BounceFlags & BOUNCE_BounceOnUnrips && BlockingMobj->flags5 & MF5_DONTRIP))
			return true;

		if (BlockingMobj->flags & MF_SHOOTABLE && mo->BounceFlags & BOUNCE_NotOnShootables)
		{
			mo->bouncecount = 1;	// let it explode now.
		}

		if (mo->bouncecount>0 && --mo->bouncecount == 0)
		{
			if (mo->flags & MF_MISSILE)
				P_ExplodeMissile(mo, nullptr, BlockingMobj);
			else
				mo->CallDie(BlockingMobj, nullptr);
			return true;
		}

		if (mo->flags7 & MF7_HITTARGET)	mo->target = BlockingMobj;
		if (mo->flags7 & MF7_HITMASTER)	mo->master = BlockingMobj;
		if (mo->flags7 & MF7_HITTRACER)	mo->tracer = BlockingMobj;

		if (!ontop)
		{
			DAngle angle = BlockingMobj->AngleTo(mo) + ((pr_bounce() % 16) - 8);
			double speed = mo->VelXYToSpeed() * GetWallBounceFactor(mo); // [GZ] was 0.75, using wallbouncefactor seems more consistent
			if (fabs(speed) < EQUAL_EPSILON) speed = 0;
			mo->Angles.Yaw = angle;
			mo->VelFromAngle(speed);
			mo->PlayBounceSound(true);
		}
		else
		{
			double dot = mo->Vel.Z;

			if (mo->BounceFlags & (BOUNCE_HereticType | BOUNCE_MBF))
			{
				mo->Vel.Z -= 2. * dot;
				if (!(mo->BounceFlags & BOUNCE_MBF)) // Heretic projectiles die, MBF projectiles don't.
				{
					mo->flags |= MF_INBOUNCE;
					mo->SetState(mo->FindState(NAME_Death));
					mo->flags &= ~MF_INBOUNCE;
					return false;
				}
				else
				{
					mo->Vel.Z *= GetMBFBounceFactor(mo);
				}
			}
			else // Don't run through this for MBF-style bounces
			{
				// The reflected velocity keeps only about 70% of its original speed
				mo->Vel.Z = (mo->Vel.Z - 2. * dot) * mo->bouncefactor;
			}

			mo->PlayBounceSound(true);
			if (mo->BounceFlags & BOUNCE_MBF) // Bring it to rest below a certain speed
			{
				if (fabs(mo->Vel.Z) < mo->Mass * mo->GetGravity() / 64)
					mo->Vel.Z = 0;
			}
			else if (mo->BounceFlags & (BOUNCE_AutoOff | BOUNCE_AutoOffFloorOnly))
			{
				if (!(mo->flags & MF_NOGRAVITY) && (mo->Vel.Z < 3.))
					mo->BounceFlags &= ~BOUNCE_TypeMask;
			}
		}
		if (mo->BounceFlags & BOUNCE_UseBounceState)
		{
			FName names[] = { NAME_Bounce, NAME_Actor, NAME_Creature };
			FState *bouncestate;
			int count = 2;
 			if ((BlockingMobj->flags & MF_SHOOTABLE) && !(BlockingMobj->flags & MF_NOBLOOD))
			{
				count = 3;
			}
			bouncestate = mo->FindState(count, names);
			if (bouncestate != NULL)
			{
				mo->SetState(bouncestate);
			}
		}
		return true;
	}
	return false;
}

//============================================================================
//
// Aiming
//
//============================================================================

CVAR(Bool, aimdebug, false, 0)

struct AimTarget : public FTranslatedLineTarget
{
	DAngle pitch;
	double frac;

	void Clear()
	{
		memset(this, 0, sizeof(*this));
		frac = FLT_MAX;
	}
};

struct aim_t
{
	enum
	{
		aim_up = 1,
		aim_down = 2
	};

	DAngle			aimpitch;
	double			attackrange;
	double			shootz;			// Height if not aiming up or down
	double			limitz;			// height limit for portals to avoid bad setups
	AActor*			shootthing;
	AActor*			friender;		// actor to check friendliness again
	AActor*			aimtarget;		// if we want to aim at precisely this target.

	DAngle			toppitch, bottompitch;
	AimTarget		linetarget;
	AimTarget		thing_friend, thing_other;

	int				flags;
	sector_t *		lastsector;
	secplane_t *	lastfloorplane;
	secplane_t *	lastceilingplane;

	int				aimdir;
	DVector3		startpos;
	DVector2		aimtrace;
	double			startfrac;

	bool			crossedffloors;
	bool			unlinked;

	// Creates a clone of this structure with the basic info copied.
	aim_t Clone()
	{
		aim_t cloned;

		cloned.aimtrace = aimtrace;
		cloned.aimpitch = aimpitch;
		cloned.aimtarget = aimtarget;
		cloned.attackrange = attackrange;
		cloned.shootthing = shootthing;
		cloned.friender = friender;
		cloned.shootz = shootz;
		cloned.unlinked = unlinked;
		cloned.flags = flags;
		return cloned;
	}

	//============================================================================
	//
	// SetResult
	//
	//============================================================================

	void SetResult(AimTarget &res, double frac, AActor *th, DAngle pitch)
	{
		if (res.frac > frac)
		{
			res.linetarget = th;
			res.pitch = pitch;
			res.angleFromSource = (th->Pos() - startpos).Angle();
			res.attackAngleFromSource = res.angleFromSource;	// at this point we do not have an attack angle so it's the same as the actual angle between actors.
			res.unlinked = unlinked;
			res.frac = frac;
		}
	}

	void SetResult(AimTarget &res, AimTarget &set)
	{
		if (res.frac > set.frac)
		{
			res = set;
		}
	}

	//============================================================================
	//
	// Result
	//
	//============================================================================

	AimTarget *Result()
	{
		AimTarget *result = &linetarget;
		if (result->linetarget == NULL)
		{
			if (thing_other.linetarget != NULL)
			{
				result = &thing_other;
			}
			else if (thing_friend.linetarget != NULL)
			{
				result = &thing_friend;
			}
		}
		return result;
	}


	//============================================================================
	//
	// AimTraverse3DFloors
	//
	//============================================================================

	bool AimTraverse3DFloors(const divline_t &trace, intercept_t * in, int frontflag, int *planestocheck)
	{
		sector_t * nextsector;
		secplane_t * nexttopplane, *nextbottomplane;
		line_t * li = in->d.line;

		nextsector = NULL;
		nexttopplane = nextbottomplane = NULL;
		*planestocheck = aimdir;

		if (li->backsector == NULL) return true;	// shouldn't really happen but crashed once for me...
		if (li->frontsector->e->XFloor.ffloors.Size() || li->backsector->e->XFloor.ffloors.Size())
		{
			F3DFloor* rover;
			DAngle highpitch, lowpitch;

			double trX = trace.x + trace.dx * in->frac;
			double trY = trace.y + trace.dy * in->frac;
			double dist = attackrange * in->frac;

			// 3D floor check. This is not 100% accurate but normally sufficient when
			// combined with a final sight check
			for (int i = 1; i <= 2; i++)
			{
				sector_t * s = i == 1 ? li->frontsector : li->backsector;

				for (unsigned k = 0; k < s->e->XFloor.ffloors.Size(); k++)
				{
					crossedffloors = true;
					rover = s->e->XFloor.ffloors[k];

					if ((rover->flags & FF_SHOOTTHROUGH) || !(rover->flags & FF_EXISTS)) continue;

					double ff_bottom = rover->bottom.plane->ZatPoint(trX, trY);
					double ff_top = rover->top.plane->ZatPoint(trX, trY);


					highpitch = -VecToAngle(dist, ff_top - shootz);
					lowpitch = -VecToAngle(dist, ff_bottom - shootz);

					if (highpitch <= toppitch)
					{
						// blocks completely
						if (lowpitch >= bottompitch) return false;
						// blocks upper edge of view
						if (lowpitch > toppitch)
						{
							toppitch = lowpitch;
							if (frontflag != i - 1)
							{
								nexttopplane = rover->bottom.plane;
								*planestocheck &= ~aim_up;
							}
						}
					}
					else if (lowpitch >= bottompitch)
					{
						// blocks lower edge of view
						if (highpitch < bottompitch)
						{
							bottompitch = highpitch;
							if (frontflag != i - 1)
							{
								nextbottomplane = rover->top.plane;
								*planestocheck &= ~aim_down;
							}
						}
					}
					// trace is leaving a sector with a 3d-floor

					if (frontflag == i - 1)
					{
						if (s == lastsector)
						{
							// upper slope intersects with this 3d-floor
							if (rover->bottom.plane == lastceilingplane && lowpitch > toppitch)
							{
								toppitch = lowpitch;
							}
							// lower slope intersects with this 3d-floor
							if (rover->top.plane == lastfloorplane && highpitch < bottompitch)
							{
								bottompitch = highpitch;
							}
						}
					}
					if (toppitch >= bottompitch) return false;		// stop
				}
			}
		}

		lastsector = nextsector;
		lastceilingplane = nexttopplane;
		lastfloorplane = nextbottomplane;
		return true;
	}

	//============================================================================
	//
	// traverses a sector portal
	//
	//============================================================================

	void EnterSectorPortal(int position, double frac, sector_t *entersec, DAngle newtoppitch, DAngle newbottompitch)
	{
		double portalz = entersec->GetPortalPlaneZ(position);

		if (position == sector_t::ceiling && portalz < limitz) return;
		else if (position == sector_t::floor && portalz > limitz) return;
		aim_t newtrace = Clone();


		newtrace.toppitch = newtoppitch;
		newtrace.bottompitch = newbottompitch;
		newtrace.aimdir = position == sector_t::ceiling? aim_t::aim_up : aim_t::aim_down;
		newtrace.startpos = startpos + entersec->GetPortalDisplacement(position);
		newtrace.startfrac = frac + 1. / attackrange;	// this is to skip the transition line to the portal which would produce a bogus opening
		newtrace.lastsector = entersec->Level->PointInSector(newtrace.startpos + aimtrace * newtrace.startfrac);
		newtrace.limitz = portalz;
		if (aimdebug)
			Printf("-----Entering %s portal from sector %d to sector %d\n", position ? "ceiling" : "floor", lastsector->sectornum, newtrace.lastsector->sectornum);
		newtrace.AimTraverse();
		SetResult(linetarget, newtrace.linetarget);
		SetResult(thing_friend, newtrace.thing_friend);
		SetResult(thing_other, newtrace.thing_other);
		if (aimdebug)
			Printf("-----Exiting %s portal\n", position ? "ceiling" : "floor");
	}

	//============================================================================
	//
	// traverses a line portal
	//
	//============================================================================

	void EnterLinePortal(line_t *li, double frac)
	{
		aim_t newtrace = Clone();

		FLinePortal *port = li->getPortal();
		if (port->mType != PORTT_LINKED && (flags & ALF_PORTALRESTRICT)) return;

		newtrace.toppitch = toppitch;
		newtrace.bottompitch = bottompitch;
		newtrace.aimdir = aimdir;
		newtrace.unlinked = (port->mType != PORTT_LINKED);
		newtrace.startpos = startpos;
		newtrace.aimtrace = aimtrace;
		P_TranslatePortalXY(li, newtrace.startpos.X, newtrace.startpos.Y);
		P_TranslatePortalZ(li, newtrace.startpos.Z);
		P_TranslatePortalVXVY(li, newtrace.aimtrace.X, newtrace.aimtrace.Y);

		newtrace.startfrac = frac + 1 / attackrange;	// this is to skip the transition line to the portal which would produce a bogus opening

		DVector2 pos = newtrace.startpos + newtrace.aimtrace * newtrace.startfrac;

		newtrace.lastsector = li->GetLevel()->PointInSector(pos);
		P_TranslatePortalZ(li, limitz);
		if (aimdebug)
			Printf("-----Entering line portal from sector %d to sector %d\n", lastsector->sectornum, newtrace.lastsector->sectornum);
		newtrace.AimTraverse();
		SetResult(linetarget, newtrace.linetarget);
		SetResult(thing_friend, newtrace.thing_friend);
		SetResult(thing_other, newtrace.thing_other);
	}

	//============================================================================
	//
	// Finds where the trace exits an actor to check for hits from above/below 
	//
	//============================================================================

	double ExitPoint(AActor *thing)
	{
		// The added check at the exit point only has some value if a 3D distance check is involved
		if (!(flags & ALF_CHECK3D)) return -1;

		divline_t trace = { startpos.X, startpos.Y, aimtrace.X, aimtrace.Y };
		divline_t line;

		for (int i = 0; i < 4; ++i)
		{
			switch (i)
			{
			case 0:		// Top edge
				line.y = thing->Y() + thing->radius;
				if (trace.y > line.y) continue;
				line.x = thing->X() + thing->radius;
				line.dx = -thing->radius * 2;
				line.dy = 0;
				break;

			case 1:		// Right edge
				line.x = thing->X() + thing->radius;
				if (trace.x > line.x) continue;
				line.y = thing->Y() - thing->radius;
				line.dx = 0;
				line.dy = thing->radius * 2;
				break;

			case 2:		// Bottom edge
				line.y = thing->Y() - thing->radius;
				if (trace.y < line.y) continue;
				line.x = thing->X() - thing->radius;
				line.dx = thing->radius * 2;
				line.dy = 0;
				break;

			case 3:		// Left edge
				line.x = thing->X() - thing->radius;
				if (trace.x < line.x) continue;
				line.y = thing->Y() + thing->radius;
				line.dx = 0;
				line.dy = thing->radius * -2;
				break;
			}

			// If it is, see if the trace crosses it
			if (P_PointOnDivlineSide(line.x, line.y, &trace) !=
				P_PointOnDivlineSide(line.x + line.dx, line.y + line.dy, &trace))
			{
				// It's a hit
				double frac = P_InterceptVector(&trace, &line);
				if (frac > 1.) frac = 1.;
				return frac;
			}
		}

		return -1.;
	}

	//============================================================================
	//
	// PTR_AimTraverse
	// Sets linetaget and aimpitch when a target is aimed at.
	//
	//============================================================================

	void AimTraverse()
	{
		// for smart aiming
		linetarget.Clear();
		thing_friend.Clear();
		thing_other.Clear();
		crossedffloors = lastsector->e->XFloor.ffloors.Size() != 0;
		lastfloorplane = lastceilingplane = NULL;

		// check the initial sector for 3D-floors and portals
		bool ceilingportalstate = (aimdir & aim_t::aim_up) && toppitch < 0 && !lastsector->PortalBlocksMovement(sector_t::ceiling);
		bool floorportalstate = (aimdir & aim_t::aim_down) && bottompitch > 0 && !lastsector->PortalBlocksMovement(sector_t::floor);

		for (auto rover : lastsector->e->XFloor.ffloors)
		{
			if ((rover->flags & FF_SHOOTTHROUGH) || !(rover->flags & FF_EXISTS)) continue;

			double bottomz = rover->bottom.plane->ZatPoint(startpos);

			if (bottomz >= startpos.Z + shootthing->Height)
			{
				lastceilingplane = rover->bottom.plane;
				// no ceiling portal if below a 3D floor
				ceilingportalstate = false;
			}

			bottomz = rover->top.plane->ZatPoint(startpos);
			if (bottomz <= startpos.Z)
			{
				lastfloorplane = rover->top.plane;
				// no floor portal if above a 3D floor
				floorportalstate = false;
			}
		}
		if (ceilingportalstate) EnterSectorPortal(sector_t::ceiling, 0, lastsector, toppitch, MIN<DAngle>(0., bottompitch));
		if (floorportalstate) EnterSectorPortal(sector_t::floor, 0, lastsector, MAX<DAngle>(0., toppitch), bottompitch);

		FPathTraverse it(lastsector->Level, startpos.X, startpos.Y, aimtrace.X, aimtrace.Y, PT_ADDLINES | PT_ADDTHINGS | PT_COMPATIBLE | PT_DELTA, startfrac);
		intercept_t *in;

		if (aimdebug)
			Printf("Start AimTraverse, start = %f,%f,%f, vect = %f,%f\n", startpos.X, startpos.Y, startpos.Z, aimtrace.X, aimtrace.Y);
		
		while ((in = it.Next()))
		{
			line_t* 			li;
			AActor* 			th;
			DAngle	 			pitch;
			DAngle				thingtoppitch;
			DAngle 				thingbottompitch;
			double 				dist;
			DAngle				thingpitch;

			if (linetarget.linetarget != NULL && in->frac > linetarget.frac) return;	// we already found something better in another portal section.

			if (in->isaline)
			{
				li = in->d.line;
				int frontflag = P_PointOnLineSidePrecise(startpos, li);

				if (aimdebug)
					Printf("Found line %d: toppitch = %f, bottompitch = %f\n", li->Index(), toppitch.Degrees, bottompitch.Degrees);

				if (li->isLinePortal() && frontflag == 0)
				{
					EnterLinePortal(li, in->frac);
					return;
				}


				if (!(li->flags & ML_TWOSIDED) || (li->flags & ML_BLOCKEVERYTHING))
					return;				// stop

				// Crosses a two sided line.
				// A two sided line will restrict the possible target ranges.
				FLineOpening open;
				P_LineOpening(open, NULL, li, it.InterceptPoint(in), (DVector2*)nullptr, FFCF_NODROPOFF);

				// The following code assumes that portals on the front of the line have already been processed.

				if (open.range <= 0 || open.bottom >= open.top)
					return;
					
				dist = attackrange * in->frac;

				if (open.bottom != LINEOPEN_MIN)
				{
					pitch = -VecToAngle(dist, open.bottom - shootz);
					if (pitch < bottompitch) bottompitch = pitch;
				}

				if (open.top != LINEOPEN_MAX)
				{
					pitch = -VecToAngle(dist, open.top - shootz);
					if (pitch > toppitch) toppitch = pitch;
				}

				if (toppitch >= bottompitch)
					return;

				int planestocheck;
				if (!AimTraverse3DFloors(it.Trace(), in, frontflag, &planestocheck))
					return;

				if (aimdebug)
					Printf("After line %d: toppitch = %f, bottompitch = %f, planestocheck = %d\n", li->Index(), toppitch.Degrees, bottompitch.Degrees, planestocheck);

				sector_t *entersec = frontflag ? li->frontsector : li->backsector;
				sector_t *exitsec = frontflag ? li->backsector : li->frontsector;
				lastsector = entersec;
				// check portal in backsector when aiming up/downward is possible, the line doesn't have portals on both sides and there's actually a portal in the backsector
				if ((planestocheck & aim_up) && toppitch < 0 && open.top != LINEOPEN_MAX && !entersec->PortalBlocksMovement(sector_t::ceiling))
				{
					EnterSectorPortal(sector_t::ceiling, in->frac, entersec, toppitch, MIN<DAngle>(0., bottompitch));
				}
				if ((planestocheck & aim_down) && bottompitch > 0 && open.bottom != LINEOPEN_MIN && !entersec->PortalBlocksMovement(sector_t::floor))
				{
					EnterSectorPortal(sector_t::floor, in->frac, entersec, MAX<DAngle>(0., toppitch), bottompitch);
				}
				continue;					// shot continues
			}

			// shoot a thing
			th = in->d.thing;
			if (th == shootthing)
				continue;					// can't shoot self

			if (aimtarget != NULL && th != aimtarget)
				continue;					// only care about target, and you're not it

			// If we want to start a conversation anything that has one should be
			// found, regardless of other settings.
			if (!(flags & ALF_CHECKCONVERSATION) || th->Conversation == NULL)
			{
				if (!(flags & ALF_CHECKNONSHOOTABLE))			// For info CCMD, ignore stuff about GHOST and SHOOTABLE flags
				{
					if (!(th->flags&MF_SHOOTABLE))
						continue;					// corpse or something

					// check for physical attacks on a ghost
					if ((th->flags3 & MF3_GHOST) &&
						shootthing->player &&	// [RH] Be sure shootthing is a player
						shootthing->player->ReadyWeapon &&
						(shootthing->player->ReadyWeapon->flags2 & MF2_THRUGHOST))
					{
						continue;
					}
				}
			}
			dist = attackrange * in->frac;

			// Don't autoaim certain special actors
			if (!cl_doautoaim && th->flags6 & MF6_NOTAUTOAIMED)
			{
				continue;
			}

			// we must do one last check whether the trace has crossed a 3D floor
			if (lastsector == th->Sector && th->Sector->e->XFloor.ffloors.Size())
			{
				if (lastceilingplane)
				{
					double ff_top = lastceilingplane->ZatPoint(th);
					DAngle pitch = -VecToAngle(dist, ff_top - shootz);
					// upper slope intersects with this 3d-floor
					if (pitch > toppitch)
					{
						toppitch = pitch;
					}
				}
				if (lastfloorplane)
				{
					double ff_bottom = lastfloorplane->ZatPoint(th);
					DAngle pitch = -VecToAngle(dist, ff_bottom - shootz);
					// lower slope intersects with this 3d-floor
					if (pitch < bottompitch)
					{
						bottompitch = pitch;
					}
				}
			}

			// check angles to see if the thing can be aimed at

			thingtoppitch = -VecToAngle(dist, th->Top() - shootz);

			if (thingtoppitch > bottompitch)
			{
				// Check for a hit from above
				if (shootz > th->Top())
				{
					double exitfrac = ExitPoint(th);
					if (exitfrac > 0.)
					{
						double exitdist = attackrange * exitfrac;
						thingtoppitch = -VecToAngle(exitdist, th->Top() - shootz);
						if (thingtoppitch > bottompitch) continue;
					}
					else continue;					// shot over the thing
				}
				else continue;					// shot over the thing
			}

			thingbottompitch = -VecToAngle(dist, th->Z() - shootz);

			if (thingbottompitch < toppitch)
			{
				// Check for a hit from below
				if (shootz < th->Z())
				{
					double exitfrac = ExitPoint(th);
					if (exitfrac > 0.)
					{
						double exitdist = attackrange * exitfrac;
						thingbottompitch = -VecToAngle(exitdist, th->Z() - shootz);
						if (thingbottompitch < toppitch) continue;
					}
					else continue;					// shot over the thing
				}
				continue;					// shot under the thing
			}

			if (crossedffloors)
			{
				// if 3D floors were in the way do an extra visibility check for safety
				if (!unlinked && !P_CheckSight(shootthing, th, SF_IGNOREVISIBILITY | SF_IGNOREWATERBOUNDARY))
				{
					// the thing can't be seen so we can safely exclude its range from our aiming field
					if (thingtoppitch < toppitch)
					{
						if (thingbottompitch > toppitch) toppitch = thingbottompitch;
					}
					else if (thingbottompitch>bottompitch)
					{
						if (thingtoppitch < bottompitch) bottompitch = thingtoppitch;
					}
					if (toppitch < bottompitch) continue;
					else return;
				}
			}

			// this thing can be hit!
			if (thingtoppitch < toppitch)
				thingtoppitch = toppitch;

			if (thingbottompitch > bottompitch)
				thingbottompitch = bottompitch;

			thingpitch = thingtoppitch / 2 + thingbottompitch / 2;

			if (flags & ALF_CHECK3D)
			{
				// We need to do a 3D distance check here because this is nearly always used in
				// combination with P_LineAttack. P_LineAttack uses 3D distance but FPathTraverse
				// only 2D. This causes some problems with Hexen's weapons that use different
				// attack modes based on distance to target
				double cosine = thingpitch.Cos();
				if (cosine != 0)
				{
					double tracelen = DVector2(it.Trace().dx, it.Trace().dy).Length();
					double d3 = tracelen * in->frac / cosine;
					if (d3 > attackrange)
					{
						return;
					}
				}
			}

			if ((flags & ALF_NOFRIENDS) && th->IsFriend(friender) && aimtarget == NULL)
			{
				continue;
			}
			else if (sv_smartaim != 0 && !(flags & ALF_FORCENOSMART) && aimtarget == NULL)
			{
				// try to be a little smarter about what to aim at!
				// In particular avoid autoaiming at friends and barrels.
				if (th->IsFriend(friender))
				{
					if (sv_smartaim < 2)
					{
						// friends don't aim at friends (except players), at least not first
						if (aimdebug)
							Printf("Hit friend %s at %f,%f,%f\n", th->GetClass()->TypeName.GetChars(), th->X(), th->Y(), th->Z());
						SetResult(thing_friend, in->frac, th, thingpitch);
					}
				}
				else if (!(th->flags3 & MF3_ISMONSTER) && th->player == NULL)
				{
					if (sv_smartaim < 3)
					{
						// don't autoaim at barrels and other shootable stuff unless no monsters have been found
						if (aimdebug)
							Printf("Hit other %s at %f,%f,%f\n", th->GetClass()->TypeName.GetChars(), th->X(), th->Y(), th->Z());
						SetResult(thing_other, in->frac, th, thingpitch);
					}
				}
				else
				{
					if (aimdebug)
						Printf("Hit target %s at %f,%f,%f\n", th->GetClass()->TypeName.GetChars(), th->X(), th->Y(), th->Z());
					SetResult(linetarget, in->frac, th, thingpitch);
					return;
				}
			}
			else
			{
				if (aimdebug)
					Printf("Hit target %s at %f,%f,%f\n", th->GetClass()->TypeName.GetChars(), th->X(), th->Y(), th->Z());
				SetResult(linetarget, in->frac, th, thingpitch);
				return;
			}
		}
	}
};

//============================================================================
//
// P_AimLineAttack
//
//============================================================================

DAngle P_AimLineAttack(AActor *t1, DAngle angle, double distance, FTranslatedLineTarget *pLineTarget, DAngle vrange,
	int flags, AActor *target, AActor *friender)
{
	double shootz = t1->Center() - t1->Floorclip + t1->AttackOffset();

	// can't shoot outside view angles
	if (vrange == 0)
	{
		if (t1->player == NULL || !t1->Level->IsFreelookAllowed())
		{
			vrange = 35.;
		}
		else
		{
			// [BB] Disable autoaim on weapons with WIF_NOAUTOAIM.
			auto weapon = t1->player->ReadyWeapon;
			if ((weapon && (weapon->IntVar(NAME_WeaponFlags) & WIF_NOAUTOAIM)) && !(flags & ALF_NOWEAPONCHECK))
			{
				vrange = 0.5;
			}
			else
			{
				// 35 degrees is approximately what Doom used. You cannot have a
				// vrange of 0 degrees, because then toppitch and bottompitch will
				// be equal, and PTR_AimTraverse will never find anything to shoot at
				// if it crosses a line.
				vrange = clamp(t1->player->userinfo.GetAimDist(), 0.5, 35.);
			}
		}
	}

	aim_t aim;

	aim.flags = flags;
	aim.shootthing = t1;
	aim.friender = (friender == NULL) ? t1 : friender;
	aim.aimdir = aim_t::aim_up | aim_t::aim_down;
	aim.startpos = t1->Pos();
	aim.aimtrace = angle.ToVector(distance);
	aim.limitz = aim.shootz = shootz;
	aim.toppitch = t1->Angles.Pitch - vrange;
	aim.bottompitch = t1->Angles.Pitch + vrange;
	aim.attackrange = distance;
	aim.aimpitch = t1->Angles.Pitch;
	aim.lastsector = t1->Sector;
	aim.startfrac = 0;
	aim.unlinked = false;
	aim.aimtarget = target;

	aim.AimTraverse();

	AimTarget *result = aim.Result();

	if (pLineTarget)
	{
		*pLineTarget = *result;
	}
	return result->linetarget ? result->pitch : t1->Angles.Pitch;
}

//==========================================================================
//
// Helper stuff for P_LineAttack
//
//==========================================================================

struct Origin
{
	AActor *Caller;
	FName PuffSpecies;
	bool hitGhosts;
	bool MThruSpecies;
	bool ThruSpecies;
	bool ThruActors;
	bool UseThruBits;
	bool Spectral;
	uint32_t ThruBits;
};

static ETraceStatus CheckForActor(FTraceResults &res, void *userdata)
{
	if (res.HitType != TRACE_HitActor)
	{
		return TRACE_Stop;
	}

	Origin *data = (Origin *)userdata;

	// Skip actors if the puff has:
	// 1. THRUACTORS 
	// 2. SPECTRAL (unless the puff has SPECTRAL)
	// 3. MTHRUSPECIES on puff and the shooter has same species as the hit actor
	// 4. THRUSPECIES on puff and the puff has same species as the hit actor
	// 5. THRUGHOST on puff and the GHOST flag on the hit actor

	if ((data->ThruActors) || 
		(!(data->Spectral) && res.Actor->flags4 & MF4_SPECTRAL) ||
		(data->MThruSpecies && res.Actor->GetSpecies() == data->Caller->GetSpecies()) ||
		(data->ThruSpecies && res.Actor->GetSpecies() == data->PuffSpecies) ||
		(data->hitGhosts && res.Actor->flags3 & MF3_GHOST))
	{
		return TRACE_Skip;
	}

	if (data->UseThruBits && (data->ThruBits & res.Actor->ThruBits))
		return TRACE_Skip;

	return TRACE_Stop;
}

//==========================================================================
//
// P_LineAttack
//
// if damage == 0, it is just a test trace that will leave linetarget set
//
//==========================================================================

AActor *P_LineAttack(AActor *t1, DAngle angle, double distance,
	DAngle pitch, int damage, FName damageType, PClassActor *pufftype, int flags, FTranslatedLineTarget*victim, int *actualdamage, 
	double sz, double offsetforward, double offsetside)
{
	bool nointeract = !!(flags & LAF_NOINTERACT);
	DVector3 direction;
	double shootz;
	FTraceResults trace;
	Origin TData;
	TData.Caller = t1;
	bool killPuff = false;
	AActor *puff = NULL;
	int pflag = 0;
	int puffFlags = (flags & LAF_ISMELEEATTACK) ? PF_MELEERANGE : 0;
	bool spawnSky = false;
	if (flags & LAF_NORANDOMPUFFZ)
		puffFlags |= PF_NORANDOMZ;

	if (victim != NULL)
	{
		memset(victim, 0, sizeof(*victim));
	}
	if (actualdamage != NULL)
	{
		*actualdamage = 0;
	}

	double pc = pitch.Cos();

	direction = { pc * angle.Cos(), pc * angle.Sin(), -pitch.Sin() };
	shootz = t1->Center() - t1->Floorclip + t1->AttackOffset();

	if (t1->player != NULL)
	{
		// this is coming from a weapon attack function which needs to transfer information to the obituary code,
		// We need to preserve this info from the damage type because the actual damage type can get overridden by the puff
		pflag = DMG_PLAYERATTACK;
	}

	// [MC] If overriding, set it to the base of the actor.
	// Offset by the amount specified.
	if (flags & LAF_OVERRIDEZ)
		shootz = t1->Z();
	shootz += sz;

	// We need to check the defaults of the replacement here
	AActor *puffDefaults = GetDefaultByType(pufftype->GetReplacement(t1->Level));
	
	TData.hitGhosts = (t1->player != NULL &&
		t1->player->ReadyWeapon != NULL &&
		(t1->player->ReadyWeapon->flags2 & MF2_THRUGHOST)) ||
		(puffDefaults && (puffDefaults->flags2 & MF2_THRUGHOST));
	
	spawnSky = (puffDefaults && (puffDefaults->flags3 & MF3_SKYEXPLODE));
	TData.MThruSpecies = (puffDefaults && (puffDefaults->flags6 & MF6_MTHRUSPECIES));
	TData.PuffSpecies = NAME_None;
	TData.Spectral = (puffDefaults && (puffDefaults->flags4 & MF4_SPECTRAL));

	// [MC] To prevent possible mod breakage, this flag is pretty much necessary.
	// Somewhere, someone is relying on these to spawn on actors and move through them.

	if ((puffDefaults->flags7 & MF7_ALLOWTHRUFLAGS))
	{
		TData.ThruSpecies = (puffDefaults && (puffDefaults->flags6 & MF6_THRUSPECIES));
		TData.ThruActors = (puffDefaults && (puffDefaults->flags2 & MF2_THRUACTORS));
		
		// [MC] Because this is a one-hit trace event, we need to spawn the puff, get the species
		// and destroy it. Assume there is no species unless tempuff isn't NULL. We cannot get
		// a proper species the same way as puffDefaults flags it appears...

		AActor *tempuff = NULL;
		if (pufftype != NULL)
			tempuff = Spawn(t1->Level, pufftype, t1->Pos(), ALLOW_REPLACE);
		if (tempuff != NULL)
		{
			TData.PuffSpecies = tempuff->GetSpecies();
			TData.UseThruBits = tempuff->flags8 & MF8_ALLOWTHRUBITS;
			TData.ThruBits = tempuff->ThruBits;
			tempuff->Destroy();
		}
	}
	else
	{
		TData.ThruSpecies = false;
		TData.ThruActors = false;
		TData.UseThruBits = false;
	}
	// if the puff uses a non-standard damage type, this will override default, hitscan and melee damage type.
	// All other explicitly passed damage types (currenty only MDK) will be preserved.
	if ((damageType == NAME_None || damageType == NAME_Melee || damageType == NAME_Hitscan) &&
		puffDefaults != NULL && puffDefaults->DamageType != NAME_None)
	{
		damageType = puffDefaults->DamageType;
	}

	uint32_t tflags = TRACE_NoSky | TRACE_Impact;
	if (nointeract || (puffDefaults && puffDefaults->flags6 & MF6_NOTRIGGER)) tflags &= ~TRACE_Impact;
	if (spawnSky)
	{
		tflags &= ~TRACE_NoSky;
		tflags |= TRACE_HitSky;
	}

	// [MC] Check the flags and set the position according to what is desired.
	// LAF_ABSPOSITION: Treat the offset parameters as direct coordinates.
	// LAF_ABSOFFSET: Ignore the angle.

	DVector3 tempos;

	if (flags & LAF_ABSPOSITION)
	{
		tempos = DVector3(offsetforward, offsetside, sz);
	}
	else if (flags & LAF_ABSOFFSET)
	{
		tempos = t1->Vec2OffsetZ(offsetforward, offsetside, shootz);
	}
	else if (0.0 == offsetforward && 0.0 == offsetside)
	{
		// Default case so exact comparison is enough
		tempos = t1->PosAtZ(shootz);
	}
	else
	{
		const double s = angle.Sin();
		const double c = angle.Cos();
		tempos = t1->Vec2OffsetZ(offsetforward * c + offsetside * s, offsetforward * s - offsetside * c, shootz);
	}

	// Perform the trace.
	if (!Trace(tempos, t1->Sector, direction, distance, MF_SHOOTABLE, 
		ML_BLOCKEVERYTHING | ML_BLOCKHITSCAN, t1, trace, tflags, CheckForActor, &TData))
	{ // hit nothing
		if (!nointeract && puffDefaults && puffDefaults->ActiveSound)
		{ // Play miss sound
			S_Sound(t1, CHAN_WEAPON, 0, puffDefaults->ActiveSound, 1, ATTN_NORM);
		}

		// [MC] LAF_NOINTERACT guarantees puff spawning and returns it directly to the calling function.
		// No damage caused, no sounds played, no blood splatters.

		if (nointeract || (puffDefaults && puffDefaults->flags3 & MF3_ALWAYSPUFF))
		{ // Spawn the puff anyway
			puff = P_SpawnPuff(t1, pufftype, trace.HitPos, trace.SrcAngleFromTarget, trace.SrcAngleFromTarget, 2, puffFlags);

			if (nointeract)
			{
				return puff;
			}
		}
		else
		{
			return nullptr;
		}
	}
	else
	{
		if (trace.HitType != TRACE_HitActor)
		{

			if (trace.HitType == TRACE_HasHitSky || (trace.HitType == TRACE_HitWall
				&& trace.Line->special == Line_Horizon && spawnSky))
			{
				puffFlags |= PF_HITSKY;
			}

			P_GeometryLineAttack(trace, t1, damage, damageType);
			if (victim != NULL) victim->unlinked = trace.unlinked;

			// position a bit closer for puffs
			if (nointeract || trace.HitType != TRACE_HitWall || ((trace.Line->special != Line_Horizon) || spawnSky))
			{
				DVector2 pos = t1->Level->GetPortalOffsetPosition(trace.HitPos.X, trace.HitPos.Y, -trace.HitVector.X * 4, -trace.HitVector.Y * 4);
				puff = P_SpawnPuff(t1, pufftype, DVector3(pos, trace.HitPos.Z - trace.HitVector.Z * 4), trace.SrcAngleFromTarget,
					trace.SrcAngleFromTarget - 90, 0, puffFlags);
				puff->radius = 1/65536.;

				if (nointeract)
				{
					return puff;
				}
			}

			// [RH] Spawn a decal
			if (trace.HitType == TRACE_HitWall && trace.Line->special != Line_Horizon && !trace.Line->isVisualPortal() && !(flags & LAF_NOIMPACTDECAL) && !(puffDefaults->flags7 & MF7_NODECAL))
			{
				// [TN] If the actor or weapon has a decal defined, use that one.
				if (t1->DecalGenerator != NULL ||
					(t1->player != NULL && t1->player->ReadyWeapon != NULL && t1->player->ReadyWeapon->DecalGenerator != NULL))
				{
					// [ZK] If puff has FORCEDECAL set, do not use the weapon's decal
					if (puffDefaults->flags7 & MF7_FORCEDECAL && puff != NULL && puff->DecalGenerator)
						SpawnShootDecal(puff,  puff, trace);
					else
						SpawnShootDecal(t1, t1, trace);
				}

				// Else, look if the bulletpuff has a decal defined.
				else if (puff != NULL && puff->DecalGenerator)
				{
					SpawnShootDecal(puff, puff, trace);
				}

				else
				{
					SpawnShootDecal(t1, t1, trace);
				}
			}
			else if (puff != NULL &&
				trace.CrossedWater == NULL &&
				trace.Sector->heightsec == NULL &&
				trace.HitType == TRACE_HitFloor)
			{
				P_HitWater(puff, trace.Sector, trace.HitPos);
			}
		}
		else
		{
			// Hit a thing, so it could be either a puff or blood
			DVector3 bleedpos = trace.HitPos;
			// position a bit closer for puffs/blood if using compatibility mode.
			if (trace.Actor->Level->i_compatflags & COMPATF_HITSCAN)
			{
				DVector2 ofs = t1->Level->GetPortalOffsetPosition(bleedpos.X, bleedpos.Y, -10 * trace.HitVector.X, -10 * trace.HitVector.Y);
				bleedpos.X = ofs.X;
				bleedpos.Y = ofs.Y;
				bleedpos.Z -= -10 * trace.HitVector.Z;
			}

			// Spawn bullet puffs or blood spots, depending on target type.
			if (nointeract || (puffDefaults && puffDefaults->flags3 & MF3_PUFFONACTORS) ||
				(trace.Actor->flags & MF_NOBLOOD) ||
				(trace.Actor->flags2 & (MF2_INVULNERABLE | MF2_DORMANT)))
			{
				if (!(trace.Actor->flags & MF_NOBLOOD))
					puffFlags |= PF_HITTHINGBLEED;

				// We must pass the unreplaced puff type here 
				puff = P_SpawnPuff(t1, pufftype, bleedpos, trace.SrcAngleFromTarget, trace.SrcAngleFromTarget - 90, 2, puffFlags | PF_HITTHING, trace.Actor);
			}
			if (victim != NULL)
			{
				victim->linetarget = trace.Actor;
				victim->attackAngleFromSource = trace.SrcAngleFromTarget;
				// With arbitrary portals this cannot be calculated so using the actual attack angle is the only option.
				victim->angleFromSource = trace.unlinked ? victim->attackAngleFromSource : t1->AngleTo(trace.Actor);
				victim->unlinked = trace.unlinked;
			}
			if (nointeract)
			{
				return puff;
			}

			// Allow puffs to inflict poison damage, so that hitscans can poison, too.
			if (puffDefaults != NULL && puffDefaults->PoisonDamage > 0 && puffDefaults->PoisonDuration != INT_MIN)
			{
				P_PoisonMobj(trace.Actor, puff ? puff : t1, t1, puffDefaults->PoisonDamage, puffDefaults->PoisonDuration, puffDefaults->PoisonPeriod, puffDefaults->PoisonDamageType);
			}

			// [GZ] If MF6_FORCEPAIN is set, we need to call P_DamageMobj even if damage is 0!
			// Note: The puff may not yet be spawned here so we must check the class defaults, not the actor.
			int newdam = damage;
			if (damage || (puffDefaults != NULL && ((puffDefaults->flags6 & MF6_FORCEPAIN) || (puffDefaults->flags7 & MF7_CAUSEPAIN))))
			{
				int dmgflags = DMG_INFLICTOR_IS_PUFF | pflag;
				// Allow MF5_PIERCEARMOR on a weapon as well.
				if (t1->player != NULL && (dmgflags & DMG_PLAYERATTACK) && t1->player->ReadyWeapon != NULL &&
					t1->player->ReadyWeapon->flags5 & MF5_PIERCEARMOR)
				{
					dmgflags |= DMG_NO_ARMOR;
				}
				
				if (puff == NULL)
				{
					// Since the puff is the damage inflictor we need it here 
					// regardless of whether it is displayed or not.
					puff = P_SpawnPuff(t1, pufftype, bleedpos, 0., 0., 2, puffFlags | PF_HITTHING | PF_TEMPORARY);
					killPuff = true;
				}
				auto src = t1;
				if ((flags & LAF_TARGETISSOURCE) && t1 && t1->target) src = t1->target;
				newdam = P_DamageMobj(trace.Actor, puff ? puff : t1, src, damage, damageType, dmgflags|DMG_USEANGLE, trace.SrcAngleFromTarget);
				if (actualdamage != NULL)
				{
					*actualdamage = newdam;
				}
			}
			if (!(puffDefaults != NULL && puffDefaults->flags3&MF3_BLOODLESSIMPACT))
			{
				IFVIRTUALPTR(trace.Actor, AActor, SpawnLineAttackBlood)
				{
					VMValue params[] = { trace.Actor, t1, bleedpos.X, bleedpos.Y, bleedpos.Z, trace.SrcAngleFromTarget.Degrees, damage, newdam };
					VMCall(func, params, countof(params), nullptr, 0);
				}
				if (damage)
				{
					// [RH] Stick blood to walls
					P_TraceBleed(newdam > 0 ? newdam : damage, trace.HitPos, trace.Actor, trace.SrcAngleFromTarget, pitch);
				}
			}
			
		}
		if (trace.Crossed3DWater || trace.CrossedWater)
		{
			if (puff == NULL)
			{ // Spawn puff just to get a mass for the splash
				puff = P_SpawnPuff(t1, pufftype, trace.HitPos, 0., 0., 2, puffFlags | PF_HITTHING | PF_TEMPORARY);
				killPuff = true;
			}
			SpawnDeepSplash(t1, trace, puff);
		}
	}
	if (killPuff && puff != NULL)
	{
		puff->Destroy();
		puff = NULL;
	}
	return puff;
}

AActor *P_LineAttack(AActor *t1, DAngle angle, double distance,
	DAngle pitch, int damage, FName damageType, FName pufftype, int flags, FTranslatedLineTarget *victim, int *actualdamage, 
	double sz, double offsetforward, double offsetside)
{
	PClassActor *type = PClass::FindActor(pufftype);
	if (type == NULL)
	{
		if (victim != NULL)
		{
			memset(victim, 0, sizeof(*victim));
		}
		Printf("Attempt to spawn unknown actor type '%s'\n", pufftype.GetChars());
		return NULL;
	}
	else
	{
		return P_LineAttack(t1, angle, distance, pitch, damage, damageType, type, flags, victim, actualdamage, sz, offsetforward, offsetside);
	}
}

//==========================================================================
//
// P_LineTrace
//
//==========================================================================
struct CheckLineData
{
	AActor *Caller;
	bool ThruSpecies;
	bool ThruActors;
	int NumPortals;
};

static ETraceStatus CheckLineTrace(FTraceResults &res, void *userdata)
{
	CheckLineData *TData = (CheckLineData *)userdata;
	if ( res.HitType == TRACE_CrossingPortal )
	{
		TData->NumPortals++;
		return TRACE_Skip;
	}
	if ( res.HitType != TRACE_HitActor )
	{
		return TRACE_Stop;
	}
	if ( (TData->ThruActors) || (TData->ThruSpecies && res.Actor->GetSpecies() == TData->Caller->GetSpecies()) )
	{
		return TRACE_Skip;
	}
	return TRACE_Stop;
}

int P_LineTrace(AActor *t1, DAngle angle, double distance,
	DAngle pitch, int flags, double sz, double offsetforward,
	double offsetside, FLineTraceData *outdata)
{
	FTraceResults trace;
	CheckLineData TData;
	TData.Caller = t1;
	TData.ThruSpecies = !!(flags & TRF_THRUSPECIES);
	TData.ThruActors = !!(flags & TRF_THRUACTORS);
	TData.NumPortals = 0;
	DVector3 direction;
	double pc = pitch.Cos();
	direction = { pc * angle.Cos(), pc * angle.Sin(), -pitch.Sin() };
	DVector3 startpos;
	double startz = t1->Z() - t1->Floorclip;
	startz += sz;
	if ( flags & TRF_ABSPOSITION )
	{
		startpos = DVector3(offsetforward, offsetside, sz);
	}
	else if ( flags & TRF_ABSOFFSET )
	{
		startpos = t1->Vec2OffsetZ(offsetforward, offsetside, startz);
	}
	else if ( (offsetforward == 0.0) && (offsetside == 0.0) )
	{
		startpos = t1->PosAtZ(startz);
	}
	else
	{
		const double s = angle.Sin();
		const double c = angle.Cos();
		startpos = t1->Vec2OffsetZ(offsetforward * c + offsetside * s, offsetforward * s - offsetside * c, startz);
	}

	ActorFlags aflags = (flags & TRF_ALLACTORS) ? ActorFlags::FromInt(0xFFFFFFFF) : MF_SHOOTABLE;
	if ( flags & TRF_SOLIDACTORS ) aflags |= MF_SOLID;
	int lflags = ML_BLOCKEVERYTHING|ML_BLOCKHITSCAN;
	if ( flags & TRF_BLOCKUSE ) lflags |= ML_BLOCKUSE;
	if ( flags & TRF_BLOCKSELF )
	{
		bool Projectile = ( (t1->flags&MF_MISSILE) || (t1->BounceFlags&BOUNCE_MBF) );
		bool NotBlocked = ( (t1->flags3&MF3_NOBLOCKMONST) || ( (t1->Level->i_compatflags&COMPATF_NOBLOCKFRIENDS) && (t1->flags&MF_FRIENDLY) ) );
		if ( Projectile ) lflags |= ML_BLOCKPROJECTILE;
		if ( !Projectile || (t1->flags8&MF8_BLOCKASPLAYER) ) lflags |= ML_BLOCKING;
		if ( !NotBlocked ) lflags |= ML_BLOCKMONSTERS;
		if ( t1->player || (t1->flags8&MF8_BLOCKASPLAYER) ) lflags |= ML_BLOCKING|ML_BLOCK_PLAYERS;
		if ( t1->flags&MF_FLOAT ) lflags |= ML_BLOCK_FLOATERS;
	}
	if ( flags & TRF_THRUBLOCK ) lflags &= ~ML_BLOCKEVERYTHING;
	if ( flags & TRF_THRUHITSCAN ) lflags &= ~ML_BLOCKHITSCAN;
	int tflags = TRACE_ReportPortals;
	if ( flags & TRF_NOSKY ) tflags |= TRACE_NoSky;

	// Do trace
	bool ret = Trace(startpos, t1->Level->PointInSector(startpos), direction, distance, aflags, lflags, t1, trace, tflags, CheckLineTrace, &TData);
	if ( outdata )
	{
		memset(outdata,0,sizeof(*outdata));
		outdata->HitActor = trace.Actor;
		outdata->HitLine = trace.Line;
		outdata->HitSector = trace.Sector;
		outdata->Hit3DFloor = trace.ffloor;
		outdata->SectorPlane = (trace.HitType == TRACE_HitCeiling) ? 1 : 0;
		if ( trace.HitType == TRACE_HitWall )
		{
			outdata->LineSide = trace.Side;
			int txpart;
			switch ( trace.Tier )
			{
			case TIER_Middle:
				outdata->LinePart = 1;
				outdata->HitTexture = trace.Line->sidedef[trace.Side]->textures[1].texture;
				break;
			case TIER_Upper:
				outdata->LinePart = 0;
				outdata->HitTexture = trace.Line->sidedef[trace.Side]->textures[0].texture;
				break;
			case TIER_Lower:
				outdata->LinePart = 2;
				outdata->HitTexture = trace.Line->sidedef[trace.Side]->textures[2].texture;
				break;
			case TIER_FFloor:
				outdata->LinePart = 1;	// act as if middle was hit
				txpart = (trace.ffloor->flags & FF_UPPERTEXTURE) ? 0 : (trace.ffloor->flags & FF_LOWERTEXTURE) ? 2 : 1;
				outdata->HitTexture = trace.ffloor->master->sidedef[0]->textures[txpart].texture;
				break;
			}
		}
		else outdata->HitTexture = trace.HitTexture;
		outdata->HitLocation = trace.HitPos;
		outdata->HitDir = trace.HitVector;
		outdata->Distance = trace.Distance;
		// [MK] Subtract two "bogus" portal crossings used internally by trace code
		outdata->NumPortals = TData.NumPortals-2;
		outdata->HitType = trace.HitType;
	}
	return ret;
}

//==========================================================================
//
// P_LinePickActor
//
//==========================================================================

AActor *P_LinePickActor(AActor *t1, DAngle angle, double distance, DAngle pitch, ActorFlags actorMask, uint32_t wallMask) 
{
	DVector3 direction;
	double shootz;

	double pc = pitch.Cos();
	direction = { pc * angle.Cos(), pc * angle.Sin(), -pitch.Sin() };
	shootz = t1->Center() - t1->Floorclip + t1->AttackOffset();

	FTraceResults trace;
	Origin TData;
	
	TData.Caller = t1;
	TData.hitGhosts = true;
	TData.MThruSpecies = false;
	TData.ThruActors = false;
	TData.ThruSpecies = false;
	TData.PuffSpecies = NAME_None;
	
	if (Trace(t1->PosAtZ(shootz), t1->Sector, direction, distance,
		actorMask, wallMask, t1, trace, TRACE_NoSky | TRACE_PortalRestrict, CheckForActor, &TData))
	{
		if (trace.HitType == TRACE_HitActor)
		{
			return trace.Actor;
		}
	}

	return NULL;
}

//==========================================================================
//
//
//
//==========================================================================

void P_TraceBleed(int damage, const DVector3 &pos, AActor *actor, DAngle angle, DAngle pitch)
{
	if (!cl_bloodsplats)
		return;

	const char *bloodType = "BloodSplat";
	int count;
	double noise;


	if ((actor->flags & MF_NOBLOOD) ||
		(actor->flags5 & MF5_NOBLOODDECALS) ||
		(actor->flags2 & (MF2_INVULNERABLE | MF2_DORMANT)) ||
		(actor->player && actor->player->cheats & CF_GODMODE))
	{
		return;
	}

	if (damage < 15)
	{	// For low damages, there is a chance to not spray blood at all
		if (damage <= 10)
		{
			if (pr_tracebleed() < 160)
			{
				return;
			}
		}
		count = 1;
		noise = 11.25 / 256.;
	}
	else if (damage < 25)
	{
		count = 2;
		noise = 22.5 / 256.;
	}
	else
	{	// For high damages, there is a chance to spray just one big glob of blood
		if (pr_tracebleed() < 24)
		{
			bloodType = "BloodSmear";
			count = 1;
			noise = 45. / 256.;
		}
		else
		{
			count = 3;
			noise = 45. / 256.;
		}
	}

	for (; count; --count)
	{
		FTraceResults bleedtrace;

		DAngle bleedang = angle + (pr_tracebleed() - 128) * noise;
		DAngle bleedpitch = pitch + (pr_tracebleed() - 128) * noise;
		double cosp = bleedpitch.Cos();
		DVector3 vdir = DVector3(cosp * bleedang.Cos(), cosp * bleedang.Sin(), -bleedpitch.Sin());

		if (Trace(pos, actor->Sector, vdir, 172, 0, ML_BLOCKEVERYTHING, actor, bleedtrace, TRACE_NoSky))
		{
			if (bleedtrace.HitType == TRACE_HitWall)
			{
				PalEntry bloodcolor = actor->BloodColor;
				if (bloodcolor != 0)
				{
					bloodcolor.r >>= 1;	// the full color is too bright for blood decals
					bloodcolor.g >>= 1;
					bloodcolor.b >>= 1;
					bloodcolor.a = 1;
				}

				uint32_t bloodTrans = (bloodcolor != 0 ? actor->BloodTranslation : 0);

				DImpactDecal::StaticCreate(actor->Level, bloodType, bleedtrace.HitPos,
					bleedtrace.Line->sidedef[bleedtrace.Side], bleedtrace.ffloor, bloodcolor, bloodTrans);
			}
		}
	}
}

void P_TraceBleed(int damage, AActor *target, DAngle angle, DAngle pitch)
{
	P_TraceBleed(damage, target->PosPlusZ(target->Height/2), target, angle, pitch);
}


//==========================================================================
//
//
//
//==========================================================================

void P_TraceBleed(int damage, AActor *target, AActor *missile)
{
	DAngle pitch;

	if (target == NULL || missile->flags3 & MF3_BLOODLESSIMPACT)
	{
		return;
	}

	if (missile->Vel.Z != 0)
	{
		double aim;

		aim = g_atan(missile->Vel.Z / target->Distance2D(missile));
		pitch = -DAngle::ToDegrees(aim);
	}
	else
	{
		pitch = 0.;
	}
	P_TraceBleed(damage, target->PosPlusZ(target->Height/2), target, missile->AngleTo(target), pitch);
}

//==========================================================================
//
//
//
//==========================================================================

void P_TraceBleed(int damage, FTranslatedLineTarget *t, AActor *puff)
{
	if (t->linetarget == NULL || puff->flags3 & MF3_BLOODLESSIMPACT)
	{
		return;
	}

	DAngle pitch = (pr_tracebleed() - 128) * (360 / 65536.);
	P_TraceBleed(damage, t->linetarget->PosPlusZ(t->linetarget->Height/2), t->linetarget, t->angleFromSource, pitch);
}


//==========================================================================
//
//
//
//==========================================================================

void P_TraceBleed(int damage, AActor *target)
{
	if (target != NULL)
	{
		DAngle angle = pr_tracebleed() * (360 / 256.);
		DAngle pitch = (pr_tracebleed() - 128) * (360 / 65536.);
		P_TraceBleed(damage, target->PosPlusZ(target->Height / 2), target, angle, pitch);
	}
}

//==========================================================================
//
// [RH] Rail gun stuffage
//
//==========================================================================

struct SRailHit
{
	AActor *HitActor;
	DVector3 HitPos;
	DAngle HitAngle;
};
struct RailData
{
	AActor *Caller;
	TArray<SRailHit> RailHits;
	TArray<SPortalHit> PortalHits;
	FName PuffSpecies;
	bool StopAtOne;
	bool StopAtInvul;
	bool ThruGhosts;
	bool ThruSpecies;
	bool MThruSpecies;
	bool ThruActors;
	bool UseThruBits;
	uint32_t ThruBits;
	int limit;
	int count;
};

static ETraceStatus ProcessRailHit(FTraceResults &res, void *userdata)
{
	RailData *data = (RailData *)userdata;
	if (res.HitType == TRACE_CrossingPortal)
	{
		SPortalHit newhit;
		newhit.HitPos = res.HitPos;
		newhit.ContPos = res.SrcFromTarget;
		newhit.OutDir = res.HitVector;
		data->PortalHits.Push(newhit);
		return TRACE_Continue;
	}

	if (res.HitType != TRACE_HitActor)
	{
		return TRACE_Stop;
	}

	// Skip actors if the puff has:
	// 1. THRUACTORS (This one did NOT include a check for spectral)
	// 2. MTHRUSPECIES on puff and the shooter has same species as the hit actor
	// 3. THRUSPECIES on puff and the puff has same species as the hit actor
	// 4. THRUGHOST on puff and the GHOST flag on the hit actor

	if ((data->ThruActors) ||
		(data->UseThruBits && (data->ThruBits & res.Actor->ThruBits)) ||
		(data->MThruSpecies && res.Actor->GetSpecies() == data->Caller->GetSpecies()) ||
		(data->ThruSpecies && res.Actor->GetSpecies() == data->PuffSpecies) ||
		(data->ThruGhosts && res.Actor->flags3 & MF3_GHOST))
	{
		return TRACE_Skip;
	}

	// Invulnerable things completely block the shot
	if (data->StopAtInvul && res.Actor->flags2 & MF2_INVULNERABLE)
	{
		return TRACE_Stop;
	}

	// Save this thing for damaging later, and continue the trace
	SRailHit newhit;
	newhit.HitActor = res.Actor;
	newhit.HitPos = res.HitPos;
	newhit.HitAngle = res.SrcAngleFromTarget;
	if (res.Actor->Level->i_compatflags & COMPATF_HITSCAN)
	{
		DVector2 ofs = res.Actor->Level->GetPortalOffsetPosition(newhit.HitPos.X, newhit.HitPos.Y, -10 * res.HitVector.X, -10 * res.HitVector.Y);
		newhit.HitPos.X = ofs.X;
		newhit.HitPos.Y = ofs.Y;
		newhit.HitPos.Z -= -10 * res.HitVector.Z;
	}
	data->RailHits.Push(newhit);

	if (data->limit)
	{
		data->count++;
	}
	return (data->StopAtOne || (data->limit && (data->count >= data->limit)) || (res.Actor->flags8 & MF8_STOPRAILS)) 
			? TRACE_Stop : TRACE_Continue;
}

//==========================================================================
//
//
//
//==========================================================================
void P_RailAttack(FRailParams *p)
{
	DVector3 start;
	FTraceResults trace;

	PClassActor *puffclass = p->puff;
	if (puffclass == NULL)
	{
		puffclass = PClass::FindActor(NAME_BulletPuff);
	}

	AActor *source = p->source;
	DAngle pitch = source->Angles.Pitch + p->pitchoffset;
	DAngle angle = source->Angles.Yaw + p->angleoffset;

	DVector3 vec(DRotator(-pitch, angle, angle));
	double shootz = source->Center() - source->FloatSpeed + p->offset_z - source->Floorclip;

	if (!(p->flags & RAF_CENTERZ))
	{
		shootz += source->AttackOffset();
	}

	int puffflags = 0;
	if (p->flags & RAF_NORANDOMPUFFZ)
	{
		puffflags |= PF_NORANDOMZ;
	}

	DVector2 xy = source->Vec2Angle(p->offset_xy, angle - 90.);

	RailData rail_data;
	rail_data.Caller = source;
	rail_data.limit = p->limit;
	rail_data.count = 0;
	rail_data.StopAtOne = !!(p->flags & RAF_NOPIERCE);
	start.X = xy.X;
	start.Y = xy.Y;
	start.Z = shootz;

	int flags;

	assert(puffclass != NULL);		// Because we set it to a default above
	AActor *puffDefaults = GetDefaultByType(puffclass->GetReplacement(source->Level)); //Contains all the flags such as FOILINVUL, etc.

	// disabled because not complete yet.
	flags = (puffDefaults->flags6 & MF6_NOTRIGGER) ? TRACE_ReportPortals : TRACE_PCross | TRACE_Impact | TRACE_ReportPortals;
	rail_data.StopAtInvul = (puffDefaults->flags3 & MF3_FOILINVUL) ? false : true;
	rail_data.MThruSpecies = ((puffDefaults->flags6 & MF6_MTHRUSPECIES)) ? true : false;
	
	// Prevent mod breakage as somewhere, someone is relying on these to spawn on an actor 
	// and move through them...
	if ((puffDefaults->flags7 & MF7_ALLOWTHRUFLAGS))
	{
		rail_data.ThruGhosts = !!(puffDefaults->flags2 & MF2_THRUGHOST);
		rail_data.ThruSpecies = !!(puffDefaults->flags6 & MF6_THRUSPECIES);
		rail_data.ThruActors = !!(puffDefaults->flags2 & MF2_THRUACTORS);
		rail_data.UseThruBits = true;
	}
	else
	{
		rail_data.ThruGhosts = false;
		rail_data.MThruSpecies = false;
		rail_data.ThruActors = false;
		rail_data.UseThruBits = false;
	}
	// used as damage inflictor
	AActor *thepuff = NULL;
	
	if (puffclass != NULL) thepuff = Spawn(source->Level, puffclass, source->Pos(), ALLOW_REPLACE);
		rail_data.PuffSpecies = (thepuff != NULL) ? thepuff->GetSpecies() : NAME_None;

	if (thepuff)
	{
		rail_data.ThruBits = thepuff->ThruBits;
		if (rail_data.UseThruBits)
			rail_data.UseThruBits = !!(thepuff->flags8 & MF8_ALLOWTHRUBITS);
	}

	Trace(start, source->Sector, vec, p->distance, MF_SHOOTABLE, ML_BLOCKEVERYTHING, source, trace,	flags, ProcessRailHit, &rail_data);

	// Hurt anything the trace hit
	unsigned int i;
	FName damagetype = (puffDefaults == NULL || puffDefaults->DamageType == NAME_None) ? FName(NAME_Railgun) : puffDefaults->DamageType;

	for (i = 0; i < rail_data.RailHits.Size(); i++)
	{
		bool spawnpuff;
		bool bleed = false;

		int actorpuffflags = puffflags | PF_HITTHING;
		AActor *hitactor = rail_data.RailHits[i].HitActor;
		DVector3 &hitpos = rail_data.RailHits[i].HitPos;
		DAngle hitangle = rail_data.RailHits[i].HitAngle;

		if ((hitactor->flags & MF_NOBLOOD) ||
			(hitactor->flags2 & MF2_DORMANT || ((hitactor->flags2 & MF2_INVULNERABLE) && !(puffDefaults->flags3 & MF3_FOILINVUL))))
		{
			spawnpuff = (puffclass != NULL);
		}
		else
		{
			spawnpuff = (puffclass != NULL && puffDefaults->flags3 & MF3_ALWAYSPUFF);
			actorpuffflags |= PF_HITTHINGBLEED; // [XA] Allow for puffs to jump to XDeath state.
			if (!(puffDefaults->flags3 & MF3_BLOODLESSIMPACT))
			{
				bleed = true;
			}
		}
		if (spawnpuff)
		{
			P_SpawnPuff(source, puffclass, hitpos, hitangle, hitangle - 90, 1, actorpuffflags, hitactor);
		}
		
		int dmgFlagPass = DMG_INFLICTOR_IS_PUFF;
		if (puffDefaults != NULL)	// is this even possible?
		{
			if (puffDefaults->PoisonDamage > 0 && puffDefaults->PoisonDuration != INT_MIN)
			{
				P_PoisonMobj(hitactor, thepuff ? thepuff : source, source, puffDefaults->PoisonDamage, puffDefaults->PoisonDuration, puffDefaults->PoisonPeriod, puffDefaults->PoisonDamageType);
			}
			if (puffDefaults->flags3 & MF3_FOILINVUL) dmgFlagPass |= DMG_FOILINVUL;
			if (puffDefaults->flags7 & MF7_FOILBUDDHA) dmgFlagPass |= DMG_FOILBUDDHA;
		}
		// [RK] If the attack source is a player, send the DMG_PLAYERATTACK flag.
		int newdam = P_DamageMobj(hitactor, thepuff ? thepuff : source, source, p->damage, damagetype, dmgFlagPass | DMG_USEANGLE | (source->player ? DMG_PLAYERATTACK : 0), hitangle);

		if (bleed)
		{
			P_SpawnBlood(hitpos, hitangle, newdam > 0 ? newdam : p->damage, hitactor);
			P_TraceBleed(newdam > 0 ? newdam : p->damage, hitpos, hitactor, hitangle, pitch);
		}
	}

	P_GeometryLineAttack(trace, p->source, p->damage, damagetype);

	// Spawn a decal or puff at the point where the trace ended.
	if (trace.HitType == TRACE_HitWall)
	{
		AActor* puff = NULL;

		if (puffclass != NULL && puffDefaults->flags3 & MF3_ALWAYSPUFF)
		{
			puff = P_SpawnPuff(source, puffclass, trace.HitPos, trace.SrcAngleFromTarget, trace.SrcAngleFromTarget - 90, 1, puffflags);
			if (puff && (trace.Line != NULL) && (trace.Line->special == Line_Horizon) && !(puff->flags3 & MF3_SKYEXPLODE))
				puff->Destroy();
		}
		if (puffDefaults != nullptr && puffDefaults->flags7 & MF7_FORCEDECAL && puffDefaults->DecalGenerator)
			SpawnShootDecal(source, puffDefaults, trace);
		else
			SpawnShootDecal(source, source, trace);

	}
	if (trace.HitType == TRACE_HitFloor || trace.HitType == TRACE_HitCeiling)
	{
		AActor* puff = NULL;
		if (puffclass != NULL && puffDefaults->flags3 & MF3_ALWAYSPUFF)
		{
			puff = P_SpawnPuff(source, puffclass, trace.HitPos, trace.SrcAngleFromTarget, trace.SrcAngleFromTarget - 90, 1, puffflags);
			if (puff && !(puff->flags3 & MF3_SKYEXPLODE) &&
				(((trace.HitType == TRACE_HitFloor) && (puff->floorpic == skyflatnum)) ||
				((trace.HitType == TRACE_HitCeiling) && (puff->ceilingpic == skyflatnum))))
			{
				puff->Destroy();
			}
		}
	}
	if (thepuff != NULL)
	{
		if (trace.Crossed3DWater || trace.CrossedWater)
		{
			SpawnDeepSplash(source, trace, thepuff);
		}
		else if (trace.HitType == TRACE_HitFloor && trace.Sector->heightsec == NULL)
		{
			P_HitWater(thepuff, trace.Sector, trace.HitPos);
		}
		thepuff->Destroy();
	}

	// Draw the slug's trail.
	P_DrawRailTrail(source, rail_data.PortalHits, p->color1, p->color2, p->maxdiff, p->flags, p->spawnclass, angle, p->duration, p->sparsity, p->drift, p->SpiralOffset, pitch);
}

//==========================================================================
//
// [RH] P_AimCamera
//
//==========================================================================

CVAR(Float, chase_height, -8.f, CVAR_ARCHIVE | CVAR_GLOBALCONFIG)
CVAR(Float, chase_dist, 90.f, CVAR_ARCHIVE | CVAR_GLOBALCONFIG)

void P_AimCamera(AActor *t1, DVector3 &campos, DAngle &camangle, sector_t *&CameraSector, bool &unlinked)
{
	double distance = clamp<double>(chase_dist, 0, 30000);
	DAngle angle = t1->Angles.Yaw - 180;
	DAngle pitch = t1->Angles.Pitch;
	FTraceResults trace;
	DVector3 vvec;
	double sz;

	double pc = pitch.Cos();

	vvec = { pc * angle.Cos(), pc * angle.Sin(), pitch.Sin() };
	sz = t1->Top() - t1->Floorclip + clamp<double>(chase_height, -1000, 1000);

	if (Trace(t1->PosAtZ(sz), t1->Sector, vvec, distance, 0, 0, NULL, trace) &&
		trace.Distance > 10)
	{
		// Position camera slightly in front of hit thing
		campos = t1->PosAtZ(sz) + vvec *(trace.Distance - 5);
	}
	else
	{
		campos = trace.HitPos - trace.HitVector * 1/256.;
	}
	CameraSector = trace.Sector;
	unlinked = trace.unlinked;
	camangle = trace.SrcAngleFromTarget - 180.;
}


//==========================================================================
//
// P_TalkFacing
//
// Looks for something within 5.625 degrees left or right of the player
// to talk to.
//
//==========================================================================

bool P_TalkFacing(AActor *player)
{
	static const double angleofs[] = { 0, 90./16, -90./16 };
	FTranslatedLineTarget t;

	for (double angle : angleofs)
	{
		P_AimLineAttack(player, player->Angles.Yaw + angle, TALKRANGE, &t, 35., ALF_FORCENOSMART | ALF_CHECKCONVERSATION | ALF_PORTALRESTRICT);
		if (t.linetarget != NULL)
		{
			if (t.linetarget->health > 0 && // Dead things can't talk.
				!(t.linetarget->flags4 & MF4_INCOMBAT) && // Fighting things don't talk either.
				t.linetarget->Conversation != NULL)
			{
				// Give the NPC a chance to play a brief animation
				t.linetarget->ConversationAnimation(0);
				P_StartConversation(t.linetarget, player, true, true);
				return true;
			}
			return false;
		}
	}
	return false;
}

//==========================================================================
//
// USE LINES
//
//==========================================================================

bool P_UseTraverse(AActor *usething, const DVector2 &start, const DVector2 &end, bool &foundline)
{
	FPathTraverse it(usething->Level, start.X, start.Y, end.X, end.Y, PT_ADDLINES | PT_ADDTHINGS);
	intercept_t *in;
	DVector3 xpos = { start.X, start.Y, usething->Z() };

	while ((in = it.Next()))
	{
		// [RH] Check for things to talk with or use a puzzle item on
		if (!in->isaline)
		{
			AActor * const mobj = in->d.thing;

			if (mobj == usething)
				continue;
			// Check thing

			// Check for puzzle item use or USESPECIAL flag
			// Extended to use the same activationtype mechanism as BUMPSPECIAL does
			if (mobj->flags5 & MF5_USESPECIAL || mobj->special == UsePuzzleItem)
			{
				if (P_ActivateThingSpecial(mobj, usething))
					return true;
			}
			IFVIRTUALPTR(mobj, AActor, Used)
			{
				VMValue params[] = { mobj, usething };
				int ret;
				VMReturn vret(&ret);
				VMCall(func, params, 2, &vret, 1);
				if (ret) return true;
			}
			continue;
		}

		if (it.PortalRelocate(in, PT_ADDLINES | PT_ADDTHINGS, &xpos))
		{
			continue;
		}

		FLineOpening open;
		if (in->d.line->special == 0 || !(in->d.line->activation & (SPAC_Use | SPAC_UseThrough | SPAC_UseBack)))
		{
		blocked:
			if (in->d.line->flags & (ML_BLOCKEVERYTHING | ML_BLOCKUSE))
			{
				open.range = 0;
			}
			else
			{
				P_LineOpening(open, NULL, in->d.line, it.InterceptPoint(in));
			}
			if (open.range <= 0 ||
				(in->d.line->special != 0 && (usething->Level->i_compatflags & COMPATF_USEBLOCKING)))
			{
				// [RH] Give sector a chance to intercept the use

				sector_t * sec;

				sec = usething->Sector;

				if (sec->SecActTarget && sec->TriggerSectorActions(usething, SECSPAC_Use))
				{
					return true;
				}

				sec = P_PointOnLineSide(xpos, in->d.line) == 0 ?
					in->d.line->frontsector : in->d.line->backsector;

				if (sec != NULL && sec->SecActTarget &&
					sec->TriggerSectorActions(usething, SECSPAC_UseWall))
				{
					return true;
				}

				if (usething->player)
				{
					S_Sound(usething, CHAN_VOICE, 0, "*usefail", 1, ATTN_IDLE);
				}
				return true;		// can't use through a wall
			}
			foundline = true;
			continue;			// not a special line, but keep checking
		}

		if (P_PointOnLineSide(xpos, in->d.line) == 1)
		{
			if (!(in->d.line->activation & SPAC_UseBack))
			{
				// [RH] continue traversal for two-sided lines
				//return in->d.line->backsector != NULL;		// don't use back side
				goto blocked;	// do a proper check for back sides of triggers
			}
			else
			{
				P_ActivateLine(in->d.line, usething, 1, SPAC_UseBack, &xpos);
				return true;
			}
		}
		else
		{
			if ((in->d.line->activation & (SPAC_Use | SPAC_UseThrough | SPAC_UseBack)) == SPAC_UseBack)
			{
				goto blocked; // Line cannot be used from front side so treat it as a non-trigger line
			}

			P_ActivateLine(in->d.line, usething, 0, SPAC_Use, &xpos);

			//WAS can't use more than one special line in a row
			//jff 3/21/98 NOW multiple use allowed with enabling line flag
			//[RH] And now I've changed it again. If the line is of type
			//	   SPAC_USE, then it eats the use. Everything else passes
			//	   it through, including SPAC_USETHROUGH.
			if (usething->Level->i_compatflags & COMPATF_USEBLOCKING)
			{
				if (in->d.line->activation & SPAC_UseThrough) continue;
				else return true;
			}
			else
			{
				if (!(in->d.line->activation & SPAC_Use)) continue;
				else return true;
			}

		}

	}
	return false;
}

//==========================================================================
//
// Returns false if a "oof" sound should be made because of a blocking
// linedef. Makes 2s middles which are impassable, as well as 2s uppers
// and lowers which block the player, cause the sound effect when the
// player tries to activate them. Specials are excluded, although it is
// assumed that all special linedefs within reach have been considered
// and rejected already (see P_UseLines).
//
// by Lee Killough
//
//==========================================================================

bool P_NoWayTraverse(AActor *usething, const DVector2 &start, const DVector2 &end)
{
	FPathTraverse it(usething->Level, start.X, start.Y, end.X, end.Y, PT_ADDLINES);
	intercept_t *in;

	while ((in = it.Next()))
	{
		line_t *ld = in->d.line;
		FLineOpening open;

		// [GrafZahl] de-obfuscated. Was I the only one who was unable to make sense out of
		// this convoluted mess?
		if (ld->special) continue;
		if (ld->isLinePortal()) return false;
		if (ld->flags&(ML_BLOCKING | ML_BLOCKEVERYTHING | ML_BLOCK_PLAYERS)) return true;
		P_LineOpening(open, NULL, ld, it.InterceptPoint(in));
		if (open.range <= 0 ||
			open.bottom > usething->Z() + usething->MaxStepHeight ||
			open.top < usething->Top()) return true;
	}
	return false;
}

//==========================================================================
//
// P_UseLines
//
// Looks for special lines in front of the player to activate
//
//==========================================================================

void P_UseLines(player_t *player)
{
	bool foundline = false;

	// If the player is transitioning a portal, use the group that is at its vertical center.
	DVector2 start = player->mo->GetPortalTransition(player->mo->Height / 2);
	// [NS] Now queries the Player's UseRange.
	DVector2 end = start + player->mo->Angles.Yaw.ToVector(player->mo->FloatVar(NAME_UseRange));

	// old code:
	// This added test makes the "oof" sound work on 2s lines -- killough:

	if (!P_UseTraverse(player->mo, start, end, foundline))
	{ // [RH] Give sector a chance to eat the use
		sector_t *sec = player->mo->Sector;
		int spac = SECSPAC_Use;
		if (foundline) spac |= SECSPAC_UseWall;
		if ((!sec->SecActTarget || !sec->TriggerSectorActions(player->mo, spac)) &&
			P_NoWayTraverse(player->mo, start, end))
		{
			S_Sound(player->mo, CHAN_VOICE, 0, "*usefail", 1, ATTN_IDLE);
		}
	}
}

//==========================================================================
//
// P_UsePuzzleItem
//
// Returns true if the puzzle item was used on a line or a thing.
//
//==========================================================================

int P_UsePuzzleItem(AActor *PuzzleItemUser, int PuzzleItemType)
{
	DVector2 start;
	DVector2 end;
	double usedist;

	// [NS] If it's a Player, get their UseRange.
	if (PuzzleItemUser->player)
		usedist = PuzzleItemUser->player->mo->FloatVar(NAME_UseRange);
	else
		usedist = USERANGE;

	start = PuzzleItemUser->GetPortalTransition(PuzzleItemUser->Height / 2);
	end = PuzzleItemUser->Angles.Yaw.ToVector(usedist);

	FPathTraverse it(PuzzleItemUser->Level, start.X, start.Y, end.X, end.Y, PT_DELTA | PT_ADDLINES | PT_ADDTHINGS);
	intercept_t *in;

	while ((in = it.Next()))
	{
		AActor *mobj;
		FLineOpening open;

		if (in->isaline)
		{ // Check line
			if (in->d.line->special != UsePuzzleItem)
			{
				P_LineOpening(open, NULL, in->d.line, it.InterceptPoint(in));
				if (open.range <= 0)
				{
					return false; // can't use through a wall
				}
				continue;
			}
			if (P_PointOnLineSide(PuzzleItemUser->Pos(), in->d.line) == 1)
			{ // Don't use back sides
				return false;
			}
			if (PuzzleItemType != in->d.line->args[0])
			{ // Item type doesn't match
				return false;
			}
			int args[3] = { in->d.line->args[2], in->d.line->args[3], in->d.line->args[4] };
			P_StartScript(PuzzleItemUser->Level, PuzzleItemUser, in->d.line, in->d.line->args[1], NULL, args, 3, ACS_ALWAYS);
			in->d.line->special = 0;
			return true;
		}
		// Check thing
		mobj = in->d.thing;
		if (mobj->special != UsePuzzleItem)
		{ // Wrong special
			continue;
		}
		if (PuzzleItemType != mobj->args[0])
		{ // Item type doesn't match
			continue;
		}
		int args[3] = { mobj->args[2], mobj->args[3], mobj->args[4] };
		P_StartScript(PuzzleItemUser->Level, PuzzleItemUser, NULL, mobj->args[1], NULL, args, 3, ACS_ALWAYS);
		mobj->special = 0;
		return true;
	}
	return false;
}

//==========================================================================
//
// RADIUS ATTACK
//
//
//==========================================================================


// [RH] Damage scale to apply to thing that shot the missile.
static float selfthrustscale;

CUSTOM_CVAR(Float, splashfactor, 1.f, CVAR_SERVERINFO)
{
	if (self <= 0.f)
		self = 1.f;
	else
		selfthrustscale = 1.f / self;
}

//==========================================================================
//
// P_GetRadiusDamage
// 
// Part of P_RadiusAttack, separated so the GetRadiusAttack function can
// exist without needing to maintain more than one function.
// 
// Used by anything without OLDRADIUSDMG flag
//==========================================================================

static double GetRadiusDamage(bool fromaction, AActor *bombspot, AActor *thing, int bombdamage, int bombdistance, int fulldamagedistance, bool thingbombsource)
{
	// [RH] New code. The bounding box only covers the
	// height of the thing and not the height of the map.
	double points;
	double len;
	double dx, dy;
	double boxradius;

	double bombdistancefloat = 1. / (double)(bombdistance - fulldamagedistance);
	double bombdamagefloat = (double)bombdamage;

	DVector2 vec = bombspot->Vec2To(thing);
	dx = fabs(vec.X);
	dy = fabs(vec.Y);
	boxradius = thing->radius;

	// The damage pattern is square, not circular.
	len = double(dx > dy ? dx : dy);

	if (bombspot->Z() < thing->Z() || bombspot->Z() >= thing->Top())
	{
		double dz;

		if (bombspot->Z() > thing->Z())
		{
			dz = double(bombspot->Z() - thing->Top());
		}
		else
		{
			dz = double(thing->Z() - bombspot->Z());
		}
		if (len <= boxradius)
		{
			len = dz;
		}
		else
		{
			len -= boxradius;
			len = g_sqrt(len*len + dz*dz);
		}
	}
	else
	{
		len -= boxradius;
		if (len < 0.f)
			len = 0.f;
	}
	len = clamp<double>(len - (double)fulldamagedistance, 0, len);
	points = bombdamagefloat * (1. - len * bombdistancefloat);

	// Calculate the splash and radius damage factor if called by P_RadiusAttack.
	// Otherwise, just get the raw damage. This allows modders to manipulate it
	// however they want.
	if (!fromaction)
	{
		if (thingbombsource) //thing is bomb source
		{
			points = points * splashfactor;
		}
		points *= thing->RadiusDamageFactor;
	}

	return points;
}

//==========================================================================
//
// P_GetOldRadiusDamage
// 
// Part of P_RadiusAttack, separated so the GetRadiusAttack function can
// exist without needing to maintain more than one function.
// 
// Used by barrels (OLDRADIUSDMG flag). Returns calculated damage 
// based on XY distance.
//==========================================================================

static int GetOldRadiusDamage(bool fromaction, AActor *bombspot, AActor *thing, int bombdamage, int bombdistance, int fulldamagedistance)
{
	const int ret = fromaction ? 0 : -1; // -1 is specifically for P_RadiusAttack; continue onto another actor.
	double dx, dy, dist;

	DVector2 vec = bombspot->Vec2To(thing);
	dx = fabs(vec.X);
	dy = fabs(vec.Y);

	dist = dx>dy ? dx : dy;
	dist -= thing->radius;

	if (dist < 0)
		dist = 0;

	if (dist >= bombdistance)
		return ret;  // out of range

	// When called from the action function, ignore the sight check.
	if (fromaction || P_CheckSight(thing, bombspot, SF_IGNOREVISIBILITY | SF_IGNOREWATERBOUNDARY))
	{
		dist = clamp<double>(dist - fulldamagedistance, 0, dist);
		int damage = Scale(bombdamage, bombdistance - int(dist), bombdistance);

		if (!fromaction)
		{
			double factor = splashfactor * thing->RadiusDamageFactor;
			damage = int(damage * factor);
		}

		return damage;
	}

	return ret;	// Not in sight.
}

//==========================================================================
//
// GetRadiusDamage
//
// Returns the falloff damage from an A_Explode attack without doing any
// damage and not taking into account any damage reduction.
//==========================================================================

int P_GetRadiusDamage(AActor *self, AActor *thing, int damage, int distance, int fulldmgdistance, bool oldradiusdmg)
{

	if (!thing)
	{
		return 0;
	}
	else if (thing == self)
	{	// No point in calculating falloff in this case since it is the bomb spot.
		return damage;
	}

	fulldmgdistance = clamp<int>(fulldmgdistance, 0, distance - 1);

	// Mirroring A_Explode's behavior.
	if (distance <= 0)
		distance = damage;

	const int newdam = oldradiusdmg
		? GetOldRadiusDamage(true, self, thing, damage, distance, fulldmgdistance)
		: int(GetRadiusDamage(true, self, thing, damage, distance, fulldmgdistance, false));

	return newdam;
}

//==========================================================================
//
// P_RadiusAttack
// Source is the creature that caused the explosion at spot.
//
//==========================================================================

int P_RadiusAttack(AActor *bombspot, AActor *bombsource, int bombdamage, int bombdistance, FName bombmod,
	int flags, int fulldamagedistance, FName species)
{
	if (bombdistance <= 0)
		return 0;
	fulldamagedistance = clamp<int>(fulldamagedistance, 0, bombdistance - 1);

	FPortalGroupArray grouplist(FPortalGroupArray::PGA_Full3d);
	FMultiBlockThingsIterator it(grouplist, bombspot->Level, bombspot->X(), bombspot->Y(), bombspot->Z() - bombdistance, bombspot->Height + bombdistance*2, bombdistance, false, bombspot->Sector);
	FMultiBlockThingsIterator::CheckResult cres;

	if (flags & RADF_SOURCEISSPOT)
	{ // The source is actually the same as the spot, even if that wasn't what we received.
		bombsource = bombspot;
	}

	P_GeometryRadiusAttack(bombspot, bombsource, bombdamage, bombdistance, bombmod, fulldamagedistance);

	TArray<AActor*> targets;
	int count = 0;
	while ((it.Next(&cres)))
	{
		AActor *thing = cres.thing;
		// Vulnerable actors can be damaged by radius attacks even if not shootable
		// Used to emulate MBF's vulnerability of non-missile bouncers to explosions.
		if (!((thing->flags & MF_SHOOTABLE) || (thing->flags6 & MF6_VULNERABLE)))
			continue;

		// Boss spider and cyborg and Heretic's ep >= 2 bosses
		// take no damage from concussion.
		if (thing->flags3 & MF3_NORADIUSDMG && !(bombspot->flags4 & MF4_FORCERADIUSDMG))
			continue;

		if (!(flags & RADF_HURTSOURCE) && (thing == bombsource || thing == bombspot))
		{ // don't damage the source of the explosion
			continue;
		}

		// MBF21
		auto targetgroup = thing->GetClass()->ActorInfo()->splash_group;
		auto sourcegroup = bombspot->GetClass()->ActorInfo()->splash_group;
		if (targetgroup != 0 && targetgroup == sourcegroup) continue;

		// a much needed option: monsters that fire explosive projectiles cannot 
		// be hurt by projectiles fired by a monster of the same type.
		// Controlled by the DONTHARMCLASS and DONTHARMSPECIES flags.
		if ((bombsource && !thing->player) // code common to both checks
			&& ( // Class check first
			((bombsource->flags4 & MF4_DONTHARMCLASS) && (thing->GetClass() == bombsource->GetClass()))
			|| // Nigh-identical species check second
			((bombsource->flags6 & MF6_DONTHARMSPECIES) && (thing->GetSpecies() == bombsource->GetSpecies()))
			)
			)	continue;

		if((species != NAME_None) && (thing->Species != species))
		{
			continue;
		}

		targets.Push(thing);
	}

	for (AActor *thing : targets)
	{
		// Barrels always use the original code, since this makes
		// them far too "active." BossBrains also use the old code
		// because some user levels require they have a height of 16,
		// which can make them near impossible to hit with the new code.
		if ((flags & RADF_NODAMAGE) || (!((bombspot->flags5 | thing->flags5) & MF5_OLDRADIUSDMG) && 
			!(flags & RADF_OLDRADIUSDAMAGE) && !(thing->Level->i_compatflags2 & COMPATF2_EXPLODE2)))
		{
			double points = GetRadiusDamage(false, bombspot, thing, bombdamage, bombdistance, fulldamagedistance, bombsource == thing);
			double check = int(points) * bombdamage;
			// points and bombdamage should be the same sign (the double cast of 'points' is needed to prevent overflows and incorrect values slipping through.)
			if ((check > 0 || (check == 0 && bombspot->flags7 & MF7_FORCEZERORADIUSDMG)) && P_CheckSight(thing, bombspot, SF_IGNOREVISIBILITY | SF_IGNOREWATERBOUNDARY))
			{ // OK to damage; target is in direct path
				double vz;
				double thrust;
				int damage = abs((int)points);
				int newdam = damage;

				if (!(flags & RADF_NODAMAGE))
				{
					//[MC] Don't count actors saved by buddha if already at 1 health.
					int prehealth = thing->health;
					newdam = P_DamageMobj(thing, bombspot, bombsource, damage, bombmod, DMG_EXPLOSION);
					if (thing->health < prehealth)	count++;
				}
				else if (thing->player == NULL && (!(flags & RADF_NOIMPACTDAMAGE) && !(thing->flags7 & MF7_DONTTHRUST)))
					thing->flags2 |= MF2_BLASTED;

				if (!(thing->flags & MF_ICECORPSE))
				{
					if (!(flags & RADF_NODAMAGE) && !(bombspot->flags3 & MF3_BLOODLESSIMPACT))
						P_TraceBleed(newdam > 0 ? newdam : damage, thing, bombspot);

					if ((flags & RADF_NODAMAGE) || !(bombspot->flags2 & MF2_NODMGTHRUST))
					{
						if (bombsource == NULL || !(bombsource->flags2 & MF2_NODMGTHRUST))
						{
							if (!(thing->flags7 & MF7_DONTTHRUST))
							{
							
								thrust = points * 0.5 / (double)thing->Mass;
								if (bombsource == thing)
								{
									thrust *= selfthrustscale;
								}
								vz = (thing->Center() - bombspot->Z()) * thrust;
								if (bombsource != thing)
								{
									vz *= 0.5;
								}
								else
								{
									vz *= 0.8;
								}
								thing->Thrust(bombspot->AngleTo(thing), thrust);
								if (!(flags & RADF_NODAMAGE) || (flags & RADF_THRUSTZ))
								{
									if (!(thing->Level->i_compatflags2 & COMPATF2_EXPLODE1) || (flags & RADF_THRUSTZ))
										thing->Vel.Z += vz;	// this really doesn't work well
								}
							}
						}
					}
				}
			}
		}
		else
		{
			// [RH] Old code just for barrels
			int damage = GetOldRadiusDamage(false, bombspot, thing, bombdamage, bombdistance, fulldamagedistance);

			if (damage < 0)
				continue;		// Sight check failed.
			else if (damage > 0 || (bombspot->flags7 & MF7_FORCEZERORADIUSDMG))
			{ // OK to damage; target is in direct path
				//[MC] Don't count actors saved by buddha if already at 1 health.
				int prehealth = thing->health;
				int newdam = P_DamageMobj(thing, bombspot, bombsource, damage, bombmod, DMG_EXPLOSION);
				P_TraceBleed(newdam > 0 ? newdam : damage, thing, bombspot);
				if (thing->health < prehealth)	count++;
			}
		}
	}
	return count;
}

//==========================================================================
//
// SECTOR HEIGHT CHANGING
// After modifying a sector's floor or ceiling height,
// call this routine to adjust the positions
// of all things that touch the sector.
//
// If anything doesn't fit anymore, true will be returned.
//
// [RH] If crushchange is non-negative, they will take the
//		specified amount of damage as they are being crushed.
//		If crushchange is negative, you should set the sector
//		height back the way it was and call P_ChangeSector()
//		again to undo the changes.
//		Note that this is very different from the original
//		true/false usage of crushchange! If you want regular
//		DOOM crushing behavior set crushchange to 10 or -1
//		if no crushing is desired.
//
//==========================================================================


struct FChangePosition
{
	sector_t *sector;
	double moveamt;
	int crushchange;
	bool nofit;
	bool movemidtex;
	bool instant;
};

TArray<AActor *> intersectors;

EXTERN_CVAR(Int, cl_bloodtype)

//=============================================================================
//
// P_AdjustFloorCeil
//
//=============================================================================

bool P_AdjustFloorCeil(AActor *thing, FChangePosition *cpos)
{
	ActorFlags2 flags2 = thing->flags2 & MF2_PASSMOBJ;
	FCheckPosition tm;

	if ((thing->flags2 & MF2_PASSMOBJ) && (thing->flags3 & MF3_ISMONSTER))
	{
		tm.FromPMove = true;
	}

	if (cpos->movemidtex)
	{
		// From Eternity:
		// ALL things must be treated as PASSMOBJ when moving
		// 3DMidTex lines, otherwise you get stuck in them.
		thing->flags2 |= MF2_PASSMOBJ;
	}

	bool isgood = P_CheckPosition(thing, thing->Pos(), tm);
	if (!(thing->flags4 & MF4_ACTLIKEBRIDGE))
	{
		thing->floorz = tm.floorz;
		thing->ceilingz = tm.ceilingz;
		thing->dropoffz = tm.dropoffz;		// killough 11/98: remember dropoffs
		thing->floorpic = tm.floorpic;
		thing->floorterrain = tm.floorterrain;
		thing->floorsector = tm.floorsector;
		thing->ceilingpic = tm.ceilingpic;
		thing->ceilingsector = tm.ceilingsector;
	}
	else
	{
		// Bridges only keep the info at their spawn position
		// This is necessary to prevent moving sectors from altering the bridge's z-position.
		// The bridge should remain at its current z, even if the sector change would cause
		// floorz or ceilingz to be changed in a way that would make P_ZMovement adjust the bridge.
		P_FindFloorCeiling(thing, FFCF_ONLYSPAWNPOS);
	}

	// restore the PASSMOBJ flag but leave the other flags alone.
	thing->flags2 = (thing->flags2 & ~MF2_PASSMOBJ) | flags2;

	return isgood;
}

//=============================================================================
//
// P_FindAboveIntersectors
//
//=============================================================================

void P_FindAboveIntersectors(AActor *actor)
{
	if (actor->flags & MF_NOCLIP)
		return;

	if (!(actor->flags & MF_SOLID))
		return;

	FPortalGroupArray check;
	FMultiBlockThingsIterator it(check, actor);
	FMultiBlockThingsIterator::CheckResult cres;
	while (it.Next(&cres))
	{
		AActor *thing = cres.thing;
		double blockdist = actor->radius + thing->radius;
		if (fabs(thing->X() - cres.Position.X) >= blockdist || fabs(thing->Y() - cres.Position.Y) >= blockdist)
			continue;

		if (!(thing->flags & MF_SOLID))
		{ // Can't hit thing
			continue;
		}
		if (thing->flags & (MF_SPECIAL))
		{ // [RH] Corpses and specials don't block moves
			continue;
		}
		if (thing->flags & (MF_CORPSE))
		{ // Corpses need a few more checks
			if (!(actor->flags & MF_ICECORPSE))
				continue;
		}
		if (thing == actor)
		{ // Don't clip against self
			continue;
		}
		if (!((thing->flags2 | actor->flags2) & MF2_PASSMOBJ) && !((thing->flags3 | actor->flags3) & MF3_ISMONSTER))
		{
			// Don't bother if both things don't have MF2_PASSMOBJ set and aren't monsters.
			// These things would always block each other which in nearly every situation is 
			// not what is wanted here.
			continue;
		}
		if (thing->Z() > actor->Z() &&
			thing->Z() <= actor->Top())
		{ // Thing intersects above the base
			intersectors.Push(thing);
		}
	}
}

//=============================================================================
//
// P_FindBelowIntersectors
//
//=============================================================================

void P_FindBelowIntersectors(AActor *actor)
{
	if (actor->flags & MF_NOCLIP)
		return;

	if (!(actor->flags & MF_SOLID))
		return;

	FPortalGroupArray check;
	FMultiBlockThingsIterator it(check, actor);
	FMultiBlockThingsIterator::CheckResult cres;
	while (it.Next(&cres))
	{
		AActor *thing = cres.thing;
		double blockdist = actor->radius + thing->radius;
		if (fabs(thing->X() - cres.Position.X) >= blockdist || fabs(thing->Y() - cres.Position.Y) >= blockdist)
			continue;

		if (!(thing->flags & MF_SOLID))
		{ // Can't hit thing
			continue;
		}
		if (thing->flags & (MF_SPECIAL))
		{ // [RH] Corpses and specials don't block moves
			continue;
		}
		if (thing->flags & (MF_CORPSE))
		{ // Corpses need a few more checks
			if (!(actor->flags & MF_ICECORPSE))
				continue;
		}
		if (thing == actor)
		{ // Don't clip against self
			continue;
		}
		if (!((thing->flags2 | actor->flags2) & MF2_PASSMOBJ) && !((thing->flags3 | actor->flags3) & MF3_ISMONSTER))
		{
			// Don't bother if both things don't have MF2_PASSMOBJ set and aren't monsters.
			// These things would always block each other which in nearly every situation is 
			// not what is wanted here.
			continue;
		}
		if (thing->Top() <= actor->Top() &&
			thing->Top() > actor->Z())
		{ // Thing intersects below the base
			intersectors.Push(thing);
		}
	}
}

//=============================================================================
//
// P_DoCrunch
//
//=============================================================================

void P_DoCrunch(AActor *thing, FChangePosition *cpos)
{
	if (!(thing && thing->CallGrind(true) && cpos)) return;
	cpos->nofit = true;

	if ((cpos->crushchange > 0) && !(thing->Level->maptime & 3))
	{
		int newdam = P_DamageMobj(thing, NULL, NULL, cpos->crushchange, NAME_Crush);

		// spray blood in a random direction
		if (!(thing->flags2&(MF2_INVULNERABLE | MF2_DORMANT)))
		{
			if (!(thing->flags&MF_NOBLOOD))
			{
				PClassActor *bloodcls = thing->GetBloodType();
				
				P_TraceBleed (newdam > 0 ? newdam : cpos->crushchange, thing);
				if (bloodcls != NULL)
				{
					AActor *mo;

					mo = Spawn(thing->Level, bloodcls, thing->PosPlusZ(thing->Height / 2), ALLOW_REPLACE);

					mo->Vel.X = pr_crunch.Random2() / 16.;
					mo->Vel.Y = pr_crunch.Random2() / 16.;
					if (thing->BloodTranslation != 0 && !(mo->flags2 & MF2_DONTTRANSLATE))
					{
						mo->Translation = thing->BloodTranslation;
					}

					if (mo->flags5 & MF5_PUFFGETSOWNER)
					{
						mo->target = thing;
					}

					if (!(cl_bloodtype <= 1)) mo->renderflags |= RF_INVISIBLE;
				}

				DAngle an = (M_Random() - 128) * (360./256);
				if (cl_bloodtype >= 1)
				{
					P_DrawSplash2(thing->Level, 32,  thing->PosPlusZ(thing->Height/2), an, 2, thing->BloodColor);
				}
			}
			if (thing->CrushPainSound != 0 && !S_GetSoundPlayingInfo(thing, thing->CrushPainSound))
			{
				S_Sound(thing, CHAN_VOICE, 0, thing->CrushPainSound, 1.f, ATTN_NORM);
			}
		}
	}

	// keep checking (crush other things)
	return;
}

//=============================================================================
//
// P_PushUp
//
// Returns 0 if thing fits, 1 if ceiling got in the way, or 2 if something
// above it didn't fit.
//=============================================================================

int P_PushUp(AActor *thing, FChangePosition *cpos)
{
	unsigned int firstintersect = intersectors.Size();
	unsigned int lastintersect;
	int mymass = thing->Mass;

	if (thing->Top() > thing->ceilingz)
	{
		return 1;
	}
	// [GZ] Skip thing intersect test for THRUACTORS things.
	if (thing->flags2 & MF2_THRUACTORS)
		return 0;
	P_FindAboveIntersectors(thing);
	lastintersect = intersectors.Size();
	for (; firstintersect < lastintersect; firstintersect++)
	{
		AActor *intersect = intersectors[firstintersect];
		// [GZ] Skip this iteration for THRUSPECIES things
		// Should there be MF2_THRUGHOST / MF3_GHOST checks there too for consistency?
		// Or would that risk breaking established behavior? THRUGHOST, like MTHRUSPECIES,
		// is normally for projectiles which would have exploded by now anyway...
		if (thing->flags6 & MF6_THRUSPECIES && thing->GetSpecies() == intersect->GetSpecies())
			continue;
		if ((thing->flags & MF_MISSILE) && (intersect->flags2 & MF2_REFLECTIVE) && (intersect->flags7 & MF7_THRUREFLECT))
			continue;
		if (!P_CanCollideWith(thing, intersect))
			continue;

		if (!(intersect->flags2 & MF2_PASSMOBJ) ||
			(!(intersect->flags3 & MF3_ISMONSTER) && intersect->Mass > mymass) ||
			(intersect->flags4 & MF4_ACTLIKEBRIDGE)
			)
		{
			// Can't push bridges or things more massive than ourself
			return 2;
		}
		double oldz = intersect->Z();
		P_AdjustFloorCeil(intersect, cpos);
		intersect->SetZ(thing->Top() + 1/65536.);
		if (P_PushUp(intersect, cpos))
		{ // Move blocked
			P_DoCrunch(intersect, cpos);
			intersect->SetZ(oldz);
			return 2;
		}
		if (cpos->instant)
		{
			intersect->Prev.Z += intersect->Z() - oldz;
			intersect->renderflags |= RF_NOINTERPOLATEVIEW;
		}

		intersect->UpdateRenderSectorList();
	}
	thing->CheckPortalTransition(true);
	return 0;
}

//=============================================================================
//
// P_PushDown
//
// Returns 0 if thing fits, 1 if floor got in the way, or 2 if something
// below it didn't fit.
//=============================================================================

int P_PushDown(AActor *thing, FChangePosition *cpos)
{
	unsigned int firstintersect = intersectors.Size();
	unsigned int lastintersect;
	int mymass = thing->Mass;

	if (thing->Z() <= thing->floorz)
	{
		return 1;
	}
	P_FindBelowIntersectors(thing);
	lastintersect = intersectors.Size();
	for (; firstintersect < lastintersect; firstintersect++)
	{
		AActor *intersect = intersectors[firstintersect];

		// [GZ] Skip this iteration for THRUSPECIES things
		// Should there be MF2_THRUGHOST / MF3_GHOST checks there too for consistency?
		// Or would that risk breaking established behavior? THRUGHOST, like MTHRUSPECIES,
		// is normally for projectiles which would have exploded by now anyway...
		if (thing->flags6 & MF6_THRUSPECIES && thing->GetSpecies() == intersect->GetSpecies())
			continue;
		if ((thing->flags & MF_MISSILE) && (intersect->flags2 & MF2_REFLECTIVE) && (intersect->flags7 & MF7_THRUREFLECT))
			continue;
		if (!P_CanCollideWith(thing, intersect))
			continue;

		if (!(intersect->flags2 & MF2_PASSMOBJ) ||
			(!(intersect->flags3 & MF3_ISMONSTER) && intersect->Mass > mymass) ||
			(intersect->flags4 & MF4_ACTLIKEBRIDGE)
			)
		{
			// Can't push bridges or things more massive than ourself
			return 2;
		}
		double oldz = intersect->Z();
		P_AdjustFloorCeil(intersect, cpos);
		if (oldz > thing->Z() - intersect->Height)
		{ // Only push things down, not up.
			intersect->SetZ(thing->Z() - intersect->Height);
			if (P_PushDown(intersect, cpos))
			{ // Move blocked
				P_DoCrunch(intersect, cpos);
				intersect->SetZ(oldz);
				return 2;
			}
			intersect->UpdateRenderSectorList();
		}
	}
	thing->CheckPortalTransition(true);
	return 0;
}

//=============================================================================
//
// PIT_FloorDrop
//
//=============================================================================

void PIT_FloorDrop(AActor *thing, FChangePosition *cpos)
{
	double oldfloorz = thing->floorz;
	double oldz = thing->Z();

	P_AdjustFloorCeil(thing, cpos);

	if (oldfloorz == thing->floorz) return;
	if (thing->flags4 & MF4_ACTLIKEBRIDGE) return; // do not move bridge things

	if (thing->Vel.Z == 0 &&
		(!(thing->flags & MF_NOGRAVITY) ||
		(thing->Z() == oldfloorz && !(thing->flags & MF_NOLIFTDROP))))
	{
		if ((thing->flags & MF_NOGRAVITY) || (thing->flags5 & MF5_MOVEWITHSECTOR) ||
			(((cpos->sector->Flags & SECF_FLOORDROP) || cpos->moveamt < 9)
			&& thing->Z() - thing->floorz <= cpos->moveamt))
		{
			if (cpos->instant)
			{
				thing->Prev.Z += thing->floorz - oldz;
				thing->renderflags |= RF_NOINTERPOLATEVIEW;
			}
			thing->SetZ(thing->floorz);
			P_CheckFakeFloorTriggers(thing, oldz);
			thing->UpdateRenderSectorList();
		}
	}
	else if ((thing->Z() != oldfloorz && !(thing->flags & MF_NOLIFTDROP)))
	{
		if ((thing->flags & MF_NOGRAVITY) && (thing->flags6 & MF6_RELATIVETOFLOOR))
		{
			if (cpos->instant)
			{
				thing->Prev.Z += -oldfloorz + thing->floorz;
				thing->renderflags |= RF_NOINTERPOLATEVIEW;
			}
			thing->AddZ(-oldfloorz + thing->floorz);
			P_CheckFakeFloorTriggers(thing, oldz);
			thing->UpdateRenderSectorList();
		}
	}
	if (thing->player && thing->player->mo == thing)
	{
		thing->player->viewz += thing->Z() - oldz;
	}
}

//=============================================================================
//
// PIT_FloorRaise
//
//=============================================================================

void PIT_FloorRaise(AActor *thing, FChangePosition *cpos)
{
	double oldfloorz = thing->floorz;
	double oldz = thing->Z();

	P_AdjustFloorCeil(thing, cpos);

	if (oldfloorz == thing->floorz) return;

	// Move things intersecting the floor up
	if (thing->Z() <= thing->floorz)
	{
		if (thing->flags4 & MF4_ACTLIKEBRIDGE)
		{
			cpos->nofit = true;
			return; // do not move bridge things
		}
		intersectors.Clear();
		if (cpos->instant)
		{
			thing->Prev.Z += thing->floorz - thing->Z();
			thing->renderflags |= RF_NOINTERPOLATEVIEW;
		}

		thing->SetZ(thing->floorz);
	}
	else
	{
		if ((thing->flags & MF_NOGRAVITY) && (thing->flags6 & MF6_RELATIVETOFLOOR))
		{
			intersectors.Clear();
			thing->AddZ(-oldfloorz + thing->floorz);
			if (cpos->instant)
			{
				thing->Prev.Z += -oldfloorz + thing->floorz;
				thing->renderflags |= RF_NOINTERPOLATEVIEW;
			}
		}
		else return;
	}
	switch (P_PushUp(thing, cpos))
	{
	default:
		P_CheckFakeFloorTriggers(thing, oldz);
		thing->UpdateRenderSectorList();
		break;
	case 1:
		P_DoCrunch(thing, cpos);
		P_CheckFakeFloorTriggers(thing, oldz);
		thing->UpdateRenderSectorList();
		break;
	case 2:
		P_DoCrunch(thing, cpos);
		thing->SetZ(oldz);
		break;
	}
	if (thing->player && thing->player->mo == thing)
	{
		thing->player->viewz += thing->Z() - oldz;
	}
}

//=============================================================================
//
// PIT_CeilingLower
//
//=============================================================================

void PIT_CeilingLower(AActor *thing, FChangePosition *cpos)
{
	bool onfloor;
	double oldz = thing->Z();

	onfloor = thing->Z() <= thing->floorz;
	P_AdjustFloorCeil(thing, cpos);

	if (thing->Top() > thing->ceilingz)
	{
		if (thing->flags4 & MF4_ACTLIKEBRIDGE)
		{
			cpos->nofit = true;
			return; // do not move bridge things
		}
		intersectors.Clear();
		if (thing->ceilingz - thing->Height >= thing->floorz)
		{
			thing->SetZ(thing->ceilingz - thing->Height);
		}
		else
		{
			thing->SetZ(thing->floorz);
		}
		thing->UpdateRenderSectorList();
		switch (P_PushDown(thing, cpos))
		{
		case 2:
			// intentional fall-through
		case 1:
			if (onfloor)
				thing->SetZ(thing->floorz);
			P_DoCrunch(thing, cpos);
			P_CheckFakeFloorTriggers(thing, oldz);
			thing->UpdateRenderSectorList();
			break;
		default:
			P_CheckFakeFloorTriggers(thing, oldz);
			thing->UpdateRenderSectorList();
			break;
		}
	}
	if (thing->player && thing->player->mo == thing)
	{
		thing->player->viewz += thing->Z() - oldz;
	}
}

//=============================================================================
//
// PIT_CeilingRaise
//
//=============================================================================

void PIT_CeilingRaise(AActor *thing, FChangePosition *cpos)
{
	bool isgood = P_AdjustFloorCeil(thing, cpos);
	double oldz = thing->Z();

	if (thing->flags4 & MF4_ACTLIKEBRIDGE) return; // do not move bridge things

	// For DOOM compatibility, only move things that are inside the floor.
	// (or something else?) Things marked as hanging from the ceiling will
	// stay where they are.
	if (thing->Z() < thing->floorz &&
		thing->Top() >= thing->ceilingz - cpos->moveamt &&
		!(thing->flags & MF_NOLIFTDROP))
	{
		thing->SetZ(thing->floorz);
		if (thing->Top() > thing->ceilingz)
		{
			thing->SetZ(thing->ceilingz - thing->Height);
		}
		P_CheckFakeFloorTriggers(thing, oldz);
		thing->UpdateRenderSectorList();
	}
	else if ((thing->flags2 & MF2_PASSMOBJ) && !isgood && thing->Top() < thing->ceilingz)
	{
		AActor *onmobj;
		if (!P_TestMobjZ(thing, true, &onmobj) && onmobj->Z() <= thing->Z())
		{
			thing->SetZ(MIN(thing->ceilingz - thing->Height, onmobj->Top()));
			thing->UpdateRenderSectorList();
		}
	}
	if (thing->player && thing->player->mo == thing)
	{
		thing->player->viewz += thing->Z() - oldz;
	}
}

//=============================================================================
//
// P_ChangeSector	[RH] Was P_CheckSector in BOOM
//
// jff 3/19/98 added to just check monsters on the periphery
// of a moving sector instead of all in bounding box of the
// sector. Both more accurate and faster.
//
//=============================================================================

bool P_ChangeSector(sector_t *sector, int crunch, double amt, int floorOrCeil, bool isreset, bool instant)
{
	FChangePosition cpos;
	void(*iterator)(AActor *, FChangePosition *);
	void(*iterator2)(AActor *, FChangePosition *) = NULL;
	msecnode_t *n;

	cpos.nofit = false;
	cpos.crushchange = crunch;
	cpos.moveamt = fabs(amt);
	cpos.movemidtex = false;
	cpos.sector = sector;
	cpos.instant = instant;

	// Also process all sectors that have 3D floors transferred from the
	// changed sector.
	if (sector->e->XFloor.attached.Size() && floorOrCeil != 2)
	{
		unsigned       i;
		sector_t*      sec;


		// Use different functions for the four different types of sector movement.
		// for 3D-floors the meaning of floor and ceiling is inverted!!!
		if (floorOrCeil == 1)
		{
			iterator = (amt >= 0) ? PIT_FloorRaise : PIT_FloorDrop;
		}
		else
		{
			iterator = (amt >= 0) ? PIT_CeilingRaise : PIT_CeilingLower;
		}

		for (i = 0; i < sector->e->XFloor.attached.Size(); i++)
		{
			sec = sector->e->XFloor.attached[i];
			P_Recalculate3DFloors(sec);	// Must recalculate the 3d floor and light lists

			// no thing checks for attached sectors because of heightsec
			if (sec->heightsec == sector) continue;

			for (n = sec->touching_thinglist; n; n = n->m_snext) n->visited = false;
			do
			{
				for (n = sec->touching_thinglist; n; n = n->m_snext)
				{
					if (!n->visited)
					{
						n->visited = true;
						if (!(n->m_thing->flags & MF_NOBLOCKMAP) ||	//jff 4/7/98 don't do these
							(n->m_thing->flags5 & MF5_MOVEWITHSECTOR))
						{
							iterator(n->m_thing, &cpos);
						}
						break;
					}
				}
			} while (n);
			sec->CheckPortalPlane(!floorOrCeil);
		}
	}
	P_Recalculate3DFloors(sector);			// Must recalculate the 3d floor and light lists

	// [RH] Use different functions for the four different types of sector
	// movement.
	switch (floorOrCeil)
	{
	case 0:
		// floor
		iterator = (amt < 0) ? PIT_FloorDrop : PIT_FloorRaise;
		break;

	case 1:
		// ceiling
		iterator = (amt < 0) ? PIT_CeilingLower : PIT_CeilingRaise;
		break;

	case 2:
		// 3dmidtex
		// This must check both floor and ceiling 
		iterator = (amt < 0) ? PIT_FloorDrop : PIT_FloorRaise;
		iterator2 = (amt < 0) ? PIT_CeilingLower : PIT_CeilingRaise;
		cpos.movemidtex = true;
		break;

	default:
		// invalid
		assert(floorOrCeil > 0 && floorOrCeil < 2);
		return false;
	}

	// killough 4/4/98: scan list front-to-back until empty or exhausted,
	// restarting from beginning after each thing is processed. Avoids
	// crashes, and is sure to examine all things in the sector, and only
	// the things which are in the sector, until a steady-state is reached.
	// Things can arbitrarily be inserted and removed and it won't mess up.
	//
	// killough 4/7/98: simplified to avoid using complicated counter

	// Mark all things invalid

	for (n = sector->touching_thinglist; n; n = n->m_snext)
		n->visited = false;

	do
	{
		for (n = sector->touching_thinglist; n; n = n->m_snext)	// go through list
		{
			if (!n->visited)								// unprocessed thing found
			{
				n->visited = true; 							// mark thing as processed
				if (!(n->m_thing->flags & MF_NOBLOCKMAP) ||	//jff 4/7/98 don't do these
					(n->m_thing->flags5 & MF5_MOVEWITHSECTOR))
				{
					iterator(n->m_thing, &cpos);		 			// process it
					if (iterator2 != NULL) iterator2(n->m_thing, &cpos);
				}
				break;										// exit and start over
			}
		}
	} while (n);	// repeat from scratch until all things left are marked valid

	if (floorOrCeil != 2) sector->CheckPortalPlane(floorOrCeil);	// check for portal obstructions after everything is done.

	if (!cpos.nofit && !isreset /* && sector->MoreFlags & (SECMF_UNDERWATERMASK)*/)
	{
		// If this is a control sector for a deep water transfer, all actors in affected
		// sectors need to have their waterlevel information updated and if applicable,
		// execute appropriate sector actions.
		// Only check if the sector move was successful.
		TArray<sector_t *> & secs = sector->e->FakeFloor.Sectors;
		for (unsigned i = 0; i < secs.Size(); i++)
		{
			sector_t * s = secs[i];

			for (n = s->touching_thinglist; n; n = n->m_snext)
				n->visited = false;

			do
			{
				for (n = s->touching_thinglist; n; n = n->m_snext)	// go through list
				{
					if (!n->visited && n->m_thing->Sector == s)		// unprocessed thing found
					{
						n->visited = true; 							// mark thing as processed

						n->m_thing->UpdateWaterLevel(false);
						P_CheckFakeFloorTriggers(n->m_thing, n->m_thing->Z() - amt);
					}
				}
			} while (n);	// repeat from scratch until all things left are marked valid
		}

	}

	return cpos.nofit;
}

//==========================================================================
//
//
//
//==========================================================================

void SpawnShootDecal(AActor *t1, AActor *defaults, const FTraceResults &trace)
{
	FDecalBase *decalbase = nullptr;

	if (defaults->player != nullptr && defaults->player->ReadyWeapon != nullptr)
	{
		decalbase = defaults->player->ReadyWeapon->DecalGenerator;
	}
	else
	{
		decalbase = defaults->DecalGenerator;
	}
	if (decalbase != nullptr)
	{
		DImpactDecal::StaticCreate(t1->Level, decalbase->GetDecal(),
			trace.HitPos, trace.Line->sidedef[trace.Side], trace.ffloor);
	}
}

//==========================================================================
//
//
//
//==========================================================================

static void SpawnDeepSplash(AActor *t1, const FTraceResults &trace, AActor *puff)
{
	const DVector3 *hitpos;
	if (trace.Crossed3DWater)
	{
		hitpos = &trace.Crossed3DWaterPos;
	}
	else if (trace.CrossedWater && trace.CrossedWater->heightsec)
	{
		hitpos = &trace.CrossedWaterPos;
	}
	else return;

	P_HitWater(puff != NULL ? puff : t1, t1->Level->PointInSector(*hitpos), *hitpos);
}

//=============================================================================
//
// P_ActivateThingSpecial
//
// Handles the code for things activated by death, USESPECIAL or BUMPSPECIAL
//
//=============================================================================

bool P_ActivateThingSpecial(AActor * thing, AActor * trigger, bool death)
{
	bool res = false;

	// Target switching mechanism
	if (thing->activationtype & THINGSPEC_ThingTargets)		thing->target = trigger;
	if (thing->activationtype & THINGSPEC_TriggerTargets)	trigger->target = thing;

	// State change mechanism. The thing needs to be not dead and to have at least one of the relevant flags
	if (!death && (thing->activationtype & (THINGSPEC_Activate | THINGSPEC_Deactivate | THINGSPEC_Switch)))
	{
		// If a switchable thing does not know whether it should be activated
		// or deactivated, the default is to activate it.
		if ((thing->activationtype & THINGSPEC_Switch)
			&& !(thing->activationtype & (THINGSPEC_Activate | THINGSPEC_Deactivate)))
		{
			thing->activationtype |= THINGSPEC_Activate;
		}
		// Can it be activated?
		if (thing->activationtype & THINGSPEC_Activate)
		{
			thing->activationtype &= ~THINGSPEC_Activate; // Clear flag
			if (thing->activationtype & THINGSPEC_Switch) // Set other flag if switching
				thing->activationtype |= THINGSPEC_Deactivate;
			thing->CallActivate(trigger);
			res = true;
		}
		// If not, can it be deactivated?
		else if (thing->activationtype & THINGSPEC_Deactivate)
		{
			thing->activationtype &= ~THINGSPEC_Deactivate; // Clear flag
			if (thing->activationtype & THINGSPEC_Switch)	// Set other flag if switching
				thing->activationtype |= THINGSPEC_Activate;
			thing->CallDeactivate(trigger);
			res = true;
		}
	}

	// Run the special, if any
	if (thing->special)
	{
		res = !!P_ExecuteSpecial(thing->Level, thing->special, NULL,
			// TriggerActs overrides the level flag, which only concerns thing activated by death
			(((death && thing->Level->flags & LEVEL_ACTOWNSPECIAL && !(thing->activationtype & THINGSPEC_TriggerActs))
			|| (thing->activationtype & THINGSPEC_ThingActs)) // Who triggers?
			? thing : trigger),
			false, thing->args[0], thing->args[1], thing->args[2], thing->args[3], thing->args[4]);

		// Clears the special if it was run on thing's death or if flag is set.
		// Note that Hexen originally did not clear the special which some original maps depend on (e.g. the bell in HEXDD.)
		if ((death && !(thing->Level->flags2 & LEVEL2_HEXENHACK)) || (thing->activationtype & THINGSPEC_ClearSpecial && res)) thing->special = 0;
	}

	// Returns the result
	return res;
}
