// d_sprite.c: software top-level rasterization driver module for drawing
// sprites

#include "quakedef.h"
#include "d_local.h"

static int sprite_height;
static int minindex, maxindex;
static sspan_t *sprite_spans;

/*
=====================
D_SpriteDrawSpans
=====================
*/
void D_SpriteDrawSpans(sspan_t * pspan)
{
    int count, spancount, izistep;
    int izi;
    byte *pbase, *pdest;
    fixed16_t s, t, snext, tnext, sstep, tstep;
    float sdivz, tdivz, zi, z, du, dv, spancountminus1;
    float sdivz8stepu, tdivz8stepu, zi8stepu;
    byte btemp;
    short *pz;

    sstep = 0;			// keep compiler happy
    tstep = 0;			// ditto

    pbase = cacheblock;

    sdivz8stepu = d_sdivzstepu * 8;
    tdivz8stepu = d_tdivzstepu * 8;
    zi8stepu = d_zistepu * 8;

// we count on FP exceptions being turned off to avoid range problems
    izistep = (int) (d_zistepu * 0x8000 * 0x10000);

    do {
	pdest =
	    (byte *) d_viewbuffer + (screenwidth * pspan->v) + pspan->u;
	pz = d_pzbuffer + (d_zwidth * pspan->v) + pspan->u;

	count = pspan->count;

	if (count <= 0)
	    goto NextSpan;

	// calculate the initial s/z, t/z, 1/z, s, and t and clamp
	du = (float) pspan->u;
	dv = (float) pspan->v;

	sdivz = d_sdivzorigin + dv * d_sdivzstepv + du * d_sdivzstepu;
	tdivz = d_tdivzorigin + dv * d_tdivzstepv + du * d_tdivzstepu;
	zi = d_ziorigin + dv * d_zistepv + du * d_zistepu;
	z = (float) 0x10000 / zi;	// prescale to 16.16 fixed-point
	// we count on FP exceptions being turned off to avoid range problems
	izi = (int) (zi * 0x8000 * 0x10000);

	s = (int) (sdivz * z) + sadjust;
	if (s > bbextents)
	    s = bbextents;
	else if (s < 0)
	    s = 0;

	t = (int) (tdivz * z) + tadjust;
	if (t > bbextentt)
	    t = bbextentt;
	else if (t < 0)
	    t = 0;

	do {
	    // calculate s and t at the far end of the span
	    if (count >= 8)
		spancount = 8;
	    else
		spancount = count;

	    count -= spancount;

	    if (count) {
		// calculate s/z, t/z, zi->fixed s and t at far end of span,
		// calculate s and t steps across span by shifting
		sdivz += sdivz8stepu;
		tdivz += tdivz8stepu;
		zi += zi8stepu;
		z = (float) 0x10000 / zi;	// prescale to 16.16 fixed-point

		snext = (int) (sdivz * z) + sadjust;
		if (snext > bbextents)
		    snext = bbextents;
		else if (snext < 8)
		    snext = 8;	// prevent round-off error on <0 steps from
		//  from causing overstepping & running off the
		//  edge of the texture

		tnext = (int) (tdivz * z) + tadjust;
		if (tnext > bbextentt)
		    tnext = bbextentt;
		else if (tnext < 8)
		    tnext = 8;	// guard against round-off error on <0 steps

		sstep = (snext - s) >> 3;
		tstep = (tnext - t) >> 3;
	    } else {
		// calculate s/z, t/z, zi->fixed s and t at last pixel in span (so
		// can't step off polygon), clamp, calculate s and t steps across
		// span by division, biasing steps low so we don't run off the
		// texture
		spancountminus1 = (float) (spancount - 1);
		sdivz += d_sdivzstepu * spancountminus1;
		tdivz += d_tdivzstepu * spancountminus1;
		zi += d_zistepu * spancountminus1;
		z = (float) 0x10000 / zi;	// prescale to 16.16 fixed-point
		snext = (int) (sdivz * z) + sadjust;
		if (snext > bbextents)
		    snext = bbextents;
		else if (snext < 8)
		    snext = 8;	// prevent round-off error on <0 steps from
		//  from causing overstepping & running off the
		//  edge of the texture

		tnext = (int) (tdivz * z) + tadjust;
		if (tnext > bbextentt)
		    tnext = bbextentt;
		else if (tnext < 8)
		    tnext = 8;	// guard against round-off error on <0 steps

		if (spancount > 1) {
		    sstep = (snext - s) / (spancount - 1);
		    tstep = (tnext - t) / (spancount - 1);
		}
	    }

	    do {
		btemp = *(pbase + (s >> 16) + (t >> 16) * cachewidth);
		if (btemp != 255) {
		    if (*pz <= (izi >> 16)) {
			*pz = izi >> 16;
			*pdest = btemp;
		    }
		}

		izi += izistep;
		pdest++;
		pz++;
		s += sstep;
		t += tstep;
	    } while (--spancount > 0);

	    s = snext;
	    t = tnext;

	} while (count > 0);

      NextSpan:
	pspan++;

    } while (pspan->count != DS_SPAN_LIST_END);
}

/*
=====================
D_SpriteScanLeftEdge
=====================
*/
void D_SpriteScanLeftEdge(void)
{
    int i, v, itop, ibottom, lmaxindex;
    emitpoint_t *pvert, *pnext;
    sspan_t *pspan;
    float du, dv, vtop, vbottom, slope;
    fixed16_t u, u_step;

    pspan = sprite_spans;
    i = minindex;
    if (i == 0)
	i = r_spritedesc.nump;

    lmaxindex = maxindex;
    if (lmaxindex == 0)
	lmaxindex = r_spritedesc.nump;

    vtop = ceil(r_spritedesc.pverts[i].v);

    do {
	pvert = &r_spritedesc.pverts[i];
	pnext = pvert - 1;

	vbottom = ceil(pnext->v);

	if (vtop < vbottom) {
	    du = pnext->u - pvert->u;
	    dv = pnext->v - pvert->v;
	    slope = du / dv;
	    u_step = (int) (slope * 0x10000);
	    // adjust u to ceil the integer portion
	    u = (int) ((pvert->u +
			(slope * (vtop - pvert->v))) * 0x10000) +
		(0x10000 - 1);
	    itop = (int) vtop;
	    ibottom = (int) vbottom;

	    for (v = itop; v < ibottom; v++) {
		pspan->u = u >> 16;
		pspan->v = v;
		u += u_step;
		pspan++;
	    }
	}

	vtop = vbottom;

	i--;
	if (i == 0)
	    i = r_spritedesc.nump;

    } while (i != lmaxindex);
}


/*
=====================
D_SpriteScanRightEdge
=====================
*/
void D_SpriteScanRightEdge(void)
{
    int i, v, itop, ibottom;
    emitpoint_t *pvert, *pnext;
    sspan_t *pspan;
    float du, dv, vtop, vbottom, slope, uvert, unext, vvert, vnext;
    fixed16_t u, u_step;

    pspan = sprite_spans;
    i = minindex;

    vvert = r_spritedesc.pverts[i].v;
    if (vvert < r_refdef.fvrecty_adj)
	vvert = r_refdef.fvrecty_adj;
    if (vvert > r_refdef.fvrectbottom_adj)
	vvert = r_refdef.fvrectbottom_adj;

    vtop = ceil(vvert);

    do {
	pvert = &r_spritedesc.pverts[i];
	pnext = pvert + 1;

	vnext = pnext->v;
	if (vnext < r_refdef.fvrecty_adj)
	    vnext = r_refdef.fvrecty_adj;
	if (vnext > r_refdef.fvrectbottom_adj)
	    vnext = r_refdef.fvrectbottom_adj;

	vbottom = ceil(vnext);

	if (vtop < vbottom) {
	    uvert = pvert->u;
	    if (uvert < r_refdef.fvrectx_adj)
		uvert = r_refdef.fvrectx_adj;
	    if (uvert > r_refdef.fvrectright_adj)
		uvert = r_refdef.fvrectright_adj;

	    unext = pnext->u;
	    if (unext < r_refdef.fvrectx_adj)
		unext = r_refdef.fvrectx_adj;
	    if (unext > r_refdef.fvrectright_adj)
		unext = r_refdef.fvrectright_adj;

	    du = unext - uvert;
	    dv = vnext - vvert;
	    slope = du / dv;
	    u_step = (int) (slope * 0x10000);
	    // adjust u to ceil the integer portion
	    u = (int) ((uvert + (slope * (vtop - vvert))) * 0x10000) +
		(0x10000 - 1);
	    itop = (int) vtop;
	    ibottom = (int) vbottom;

	    for (v = itop; v < ibottom; v++) {
		pspan->count = (u >> 16) - pspan->u;
		u += u_step;
		pspan++;
	    }
	}

	vtop = vbottom;
	vvert = vnext;

	i++;
	if (i == r_spritedesc.nump)
	    i = 0;

    } while (i != maxindex);

    pspan->count = DS_SPAN_LIST_END;	// mark the end of the span list 
}


/*
=====================
D_SpriteCalculateGradients
=====================
*/
void D_SpriteCalculateGradients(void)
{
    vec3_t p_normal, p_saxis, p_taxis, p_temp1;
    float distinv;

    TransformVector(r_spritedesc.vpn, p_normal);
    TransformVector(r_spritedesc.vright, p_saxis);
    TransformVector(r_spritedesc.vup, p_taxis);
    VectorInverse(p_taxis);

    distinv = 1.0 / (-DotProduct(modelorg, r_spritedesc.vpn));

    d_sdivzstepu = p_saxis[0] * xscaleinv;
    d_tdivzstepu = p_taxis[0] * xscaleinv;

    d_sdivzstepv = -p_saxis[1] * yscaleinv;
    d_tdivzstepv = -p_taxis[1] * yscaleinv;

    d_zistepu = p_normal[0] * xscaleinv * distinv;
    d_zistepv = -p_normal[1] * yscaleinv * distinv;

    d_sdivzorigin = p_saxis[2] - xcenter * d_sdivzstepu -
	ycenter * d_sdivzstepv;
    d_tdivzorigin = p_taxis[2] - xcenter * d_tdivzstepu -
	ycenter * d_tdivzstepv;
    d_ziorigin = p_normal[2] * distinv - xcenter * d_zistepu -
	ycenter * d_zistepv;

    TransformVector(modelorg, p_temp1);

    sadjust =
	((fixed16_t) (DotProduct(p_temp1, p_saxis) * 0x10000 + 0.5)) -
	(-(cachewidth >> 1) << 16);
    tadjust =
	((fixed16_t) (DotProduct(p_temp1, p_taxis) * 0x10000 + 0.5)) -
	(-(sprite_height >> 1) << 16);

// -1 (-epsilon) so we never wander off the edge of the texture
    bbextents = (cachewidth << 16) - 1;
    bbextentt = (sprite_height << 16) - 1;
}


/*
=====================
D_DrawSprite
=====================
*/
void D_DrawSprite(void)
{
    int i, nump;
    float ymin, ymax;
    emitpoint_t *pverts;
    sspan_t spans[MAXHEIGHT + 1];

#ifdef __alpha__
    static int first = 0;
    if (!first++)
	Con_Printf("Warning- Alpha/Linux sprites broken\n");
    return;
#endif

    sprite_spans = spans;

// find the top and bottom vertices, and make sure there's at least one scan to
// draw
    ymin = 999999.9;
    ymax = -999999.9;
    pverts = r_spritedesc.pverts;

    for (i = 0; i < r_spritedesc.nump; i++) {
	if (pverts->v < ymin) {
	    ymin = pverts->v;
	    minindex = i;
	}

	if (pverts->v > ymax) {
	    ymax = pverts->v;
	    maxindex = i;
	}

	pverts++;
    }

    ymin = ceil(ymin);
    ymax = ceil(ymax);

    if (ymin >= ymax)
	return;			// doesn't cross any scans at all

    cachewidth = r_spritedesc.pspriteframe->width;
    sprite_height = r_spritedesc.pspriteframe->height;
    cacheblock = (byte *) & r_spritedesc.pspriteframe->pixels[0];

// copy the first vertex to the last vertex, so we don't have to deal with
// wrapping
    nump = r_spritedesc.nump;
    pverts = r_spritedesc.pverts;
    pverts[nump] = pverts[0];

    D_SpriteCalculateGradients();
    D_SpriteScanLeftEdge();
    D_SpriteScanRightEdge();
    D_SpriteDrawSpans(sprite_spans);
}
