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/** Implementation of the LimitBoneWeightsProcess post processing step */


#include "LimitBoneWeightsProcess.h"
#include "StringUtils.h"
#include <assimp/postprocess.h>
#include <assimp/DefaultLogger.hpp>
#include <assimp/scene.h>
#include <stdio.h>

using namespace Assimp;


// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
LimitBoneWeightsProcess::LimitBoneWeightsProcess()
{
    mMaxWeights = AI_LMW_MAX_WEIGHTS;
}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
LimitBoneWeightsProcess::~LimitBoneWeightsProcess()
{
    // nothing to do here
}

// ------------------------------------------------------------------------------------------------
// Returns whether the processing step is present in the given flag field.
bool LimitBoneWeightsProcess::IsActive( unsigned int pFlags) const
{
    return (pFlags & aiProcess_LimitBoneWeights) != 0;
}

// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void LimitBoneWeightsProcess::Execute( aiScene* pScene)
{
    DefaultLogger::get()->debug("LimitBoneWeightsProcess begin");
    for( unsigned int a = 0; a < pScene->mNumMeshes; a++)
        ProcessMesh( pScene->mMeshes[a]);

    DefaultLogger::get()->debug("LimitBoneWeightsProcess end");
}

// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void LimitBoneWeightsProcess::SetupProperties(const Importer* pImp)
{
    // get the current value of the property
    this->mMaxWeights = pImp->GetPropertyInteger(AI_CONFIG_PP_LBW_MAX_WEIGHTS,AI_LMW_MAX_WEIGHTS);
}

// ------------------------------------------------------------------------------------------------
// Unites identical vertices in the given mesh
void LimitBoneWeightsProcess::ProcessMesh( aiMesh* pMesh)
{
    if( !pMesh->HasBones())
        return;

    // collect all bone weights per vertex
    typedef std::vector< std::vector< Weight > > WeightsPerVertex;
    WeightsPerVertex vertexWeights( pMesh->mNumVertices);

    // collect all weights per vertex
    for( unsigned int a = 0; a < pMesh->mNumBones; a++)
    {
        const aiBone* bone = pMesh->mBones[a];
        for( unsigned int b = 0; b < bone->mNumWeights; b++)
        {
            const aiVertexWeight& w = bone->mWeights[b];
            vertexWeights[w.mVertexId].push_back( Weight( a, w.mWeight));
        }
    }

    unsigned int removed = 0, old_bones = pMesh->mNumBones;

    // now cut the weight count if it exceeds the maximum
    bool bChanged = false;
    for( WeightsPerVertex::iterator vit = vertexWeights.begin(); vit != vertexWeights.end(); ++vit)
    {
        if( vit->size() <= mMaxWeights)
            continue;

        bChanged = true;

        // more than the defined maximum -> first sort by weight in descending order. That's
        // why we defined the < operator in such a weird way.
        std::stable_sort( vit->begin(), vit->end());

        // now kill everything beyond the maximum count
        unsigned int m = vit->size();
        vit->erase( vit->begin() + mMaxWeights, vit->end());
        removed += m-vit->size();

        // and renormalize the weights
        float sum = 0.0f;
        for( std::vector<Weight>::const_iterator it = vit->begin(); it != vit->end(); ++it ) {
            sum += it->mWeight;
        }
        if( 0.0f != sum ) {
            const float invSum = 1.0f / sum;
            for( std::vector<Weight>::iterator it = vit->begin(); it != vit->end(); ++it ) {
                it->mWeight *= invSum;
            }
        }
    }

    if (bChanged)   {
        // rebuild the vertex weight array for all bones
        typedef std::vector< std::vector< aiVertexWeight > > WeightsPerBone;
        WeightsPerBone boneWeights( pMesh->mNumBones);
        for( unsigned int a = 0; a < vertexWeights.size(); a++)
        {
            const std::vector<Weight>& vw = vertexWeights[a];
            for( std::vector<Weight>::const_iterator it = vw.begin(); it != vw.end(); ++it)
                boneWeights[it->mBone].push_back( aiVertexWeight( a, it->mWeight));
        }

        // and finally copy the vertex weight list over to the mesh's bones
        std::vector<bool> abNoNeed(pMesh->mNumBones,false);
        bChanged = false;

        for( unsigned int a = 0; a < pMesh->mNumBones; a++)
        {
            const std::vector<aiVertexWeight>& bw = boneWeights[a];
            aiBone* bone = pMesh->mBones[a];

            if ( bw.empty() )
            {
                abNoNeed[a] = bChanged = true;
                continue;
            }

            // copy the weight list. should always be less weights than before, so we don't need a new allocation
            ai_assert( bw.size() <= bone->mNumWeights);
            bone->mNumWeights = static_cast<unsigned int>( bw.size() );
            ::memcpy( bone->mWeights, &bw[0], bw.size() * sizeof( aiVertexWeight));
        }

        if (bChanged)   {
            // the number of new bones is smaller than before, so we can reuse the old array
            aiBone** ppcCur = pMesh->mBones;aiBone** ppcSrc = ppcCur;

            for (std::vector<bool>::const_iterator iter  = abNoNeed.begin();iter != abNoNeed.end()  ;++iter)    {
                if (*iter)  {
                    delete *ppcSrc;
                    --pMesh->mNumBones;
                }
                else *ppcCur++ = *ppcSrc;
                ++ppcSrc;
            }
        }

        if (!DefaultLogger::isNullLogger()) {
            char buffer[1024];
            ai_snprintf(buffer,1024,"Removed %u weights. Input bones: %u. Output bones: %u",removed,old_bones,pMesh->mNumBones);
            DefaultLogger::get()->info(buffer);
        }
    }
}
