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/// @file DeboneProcess.cpp
/** Implementation of the DeboneProcess post processing step */

// internal headers of the post-processing framework
#include "ProcessHelper.h"
#include "DeboneProcess.h"
#include <stdio.h>

using namespace Assimp;

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
DeboneProcess::DeboneProcess() : mNumBones(0), mNumBonesCanDoWithout(0), mThreshold(AI_DEBONE_THRESHOLD), mAllOrNone(false) {}

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

// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void DeboneProcess::SetupProperties(const Importer* pImp) {
    // get the current value of the property
    mAllOrNone = pImp->GetPropertyInteger(AI_CONFIG_PP_DB_ALL_OR_NONE,0)?true:false;
    mThreshold = pImp->GetPropertyFloat(AI_CONFIG_PP_DB_THRESHOLD,AI_DEBONE_THRESHOLD);
}

// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void DeboneProcess::Execute( aiScene* pScene) {
    ASSIMP_LOG_DEBUG("DeboneProcess begin");

    if(!pScene->mNumMeshes) {
        return;
    }

    std::vector<bool> splitList(pScene->mNumMeshes);
    for( unsigned int a = 0; a < pScene->mNumMeshes; a++) {
        splitList[a] = ConsiderMesh( pScene->mMeshes[a] );
    }

    int numSplits = 0;

    if(!!mNumBonesCanDoWithout && (!mAllOrNone||mNumBonesCanDoWithout==mNumBones))  {
        for(unsigned int a = 0; a < pScene->mNumMeshes; a++)    {
            if(splitList[a]) {
                ++numSplits;
            }
        }
    }

    if(numSplits)   {
        // we need to do something. Let's go.
        //mSubMeshIndices.clear();                  // really needed?
        mSubMeshIndices.resize(pScene->mNumMeshes); // because we're doing it here anyway

        // build a new array of meshes for the scene
        std::vector<aiMesh*> meshes;

        for (unsigned int a=0;a<pScene->mNumMeshes; ++a) {
            aiMesh* srcMesh = pScene->mMeshes[a];
            std::vector<std::pair<aiMesh*,const aiBone*> > newMeshes;

            if(splitList[a]) {
                SplitMesh(srcMesh,newMeshes);
            }

            // mesh was split
            if(!newMeshes.empty())  {
                unsigned int out = 0, in = srcMesh->mNumBones;

                // store new meshes and indices of the new meshes
                for(unsigned int b=0;b<newMeshes.size();b++)    {
                    const aiString *find = newMeshes[b].second ? &newMeshes[b].second->mName : nullptr;

                    aiNode *theNode = find ? pScene->mRootNode->FindNode(*find) : nullptr;
                    std::pair<unsigned int,aiNode*> push_pair(static_cast<unsigned int>(meshes.size()),theNode);

                    mSubMeshIndices[a].emplace_back(push_pair);
                    meshes.emplace_back(newMeshes[b].first);

                    out+=newMeshes[b].first->mNumBones;
                }

                if(!DefaultLogger::isNullLogger()) {
                    ASSIMP_LOG_INFO("Removed %u bones. Input bones:", in - out, ". Output bones: ", out);
                }

                // and destroy the source mesh. It should be completely contained inside the new submeshes
                delete srcMesh;
            } else {
                // Mesh is kept unchanged - store it's new place in the mesh array
                mSubMeshIndices[a].emplace_back(static_cast<unsigned int>(meshes.size()), (aiNode *)nullptr);
                meshes.push_back(srcMesh);
            }
        }

        // rebuild the scene's mesh array
        pScene->mNumMeshes = static_cast<unsigned int>(meshes.size());
        delete [] pScene->mMeshes;
        pScene->mMeshes = new aiMesh*[pScene->mNumMeshes];
        std::copy( meshes.begin(), meshes.end(), pScene->mMeshes);

        // recurse through all nodes and translate the node's mesh indices to fit the new mesh array
        UpdateNode( pScene->mRootNode);
    }

    ASSIMP_LOG_DEBUG("DeboneProcess end");
}

// ------------------------------------------------------------------------------------------------
// Counts bones total/removable in a given mesh.
bool DeboneProcess::ConsiderMesh(const aiMesh* pMesh) {
    if(!pMesh->HasBones()) {
        return false;
    }

    bool split = false;

    //interstitial faces not permitted
    bool isInterstitialRequired = false;

    std::vector<bool> isBoneNecessary(pMesh->mNumBones,false);
    std::vector<unsigned int> vertexBones(pMesh->mNumVertices,UINT_MAX);

    const unsigned int cUnowned = UINT_MAX;
    const unsigned int cCoowned = UINT_MAX-1;

    for(unsigned int i=0;i<pMesh->mNumBones;i++)    {
        for(unsigned int j=0;j<pMesh->mBones[i]->mNumWeights;j++)   {
            float w = pMesh->mBones[i]->mWeights[j].mWeight;
            if (w == 0.0f) {
                continue;
            }

            unsigned int vid = pMesh->mBones[i]->mWeights[j].mVertexId;
            if (w >= mThreshold)   {
                if (vertexBones[vid] != cUnowned) {
                    //double entry
                    if(vertexBones[vid]==i)  {
                        ASSIMP_LOG_WARN("Encountered double entry in bone weights");
                    } else  {
                        //TODO: track attraction in order to break tie
                        vertexBones[vid] = cCoowned;
                    }
                } else {
                    vertexBones[vid] = i;
                } 
            }

            if(!isBoneNecessary[i]) {
                isBoneNecessary[i] = w<mThreshold;
            }
        }

        if(!isBoneNecessary[i])  {
            isInterstitialRequired = true;
        }
    }

    if(isInterstitialRequired) {
        for(unsigned int i=0;i<pMesh->mNumFaces;i++) {
            unsigned int v = vertexBones[pMesh->mFaces[i].mIndices[0]];
            for (unsigned int j=1;j<pMesh->mFaces[i].mNumIndices;j++) {
                unsigned int w = vertexBones[pMesh->mFaces[i].mIndices[j]];

                if (v != w) {
                    if(v<pMesh->mNumBones) {
                        isBoneNecessary[v] = true;
                    }
                    if (w<pMesh->mNumBones) {
                        isBoneNecessary[w] = true;
                    }
                }
            }
        }
    }

    for(unsigned int i=0;i<pMesh->mNumBones;i++)    {
        if(!isBoneNecessary[i]) {
            mNumBonesCanDoWithout++;
            split = true;
        }

        mNumBones++;
    }
    return split;
}

// ------------------------------------------------------------------------------------------------
// Splits the given mesh by bone count.
void DeboneProcess::SplitMesh( const aiMesh* pMesh, std::vector< std::pair< aiMesh*,const aiBone* > >& poNewMeshes) const {
    // same deal here as ConsiderMesh basically

    std::vector<bool> isBoneNecessary(pMesh->mNumBones,false);
    std::vector<unsigned int> vertexBones(pMesh->mNumVertices,UINT_MAX);

    const unsigned int cUnowned = UINT_MAX;
    const unsigned int cCoowned = UINT_MAX-1;

    for(unsigned int i=0;i<pMesh->mNumBones;i++)    {
        for(unsigned int j=0;j<pMesh->mBones[i]->mNumWeights;j++)   {
            float w = pMesh->mBones[i]->mWeights[j].mWeight;

            if(w==0.0f) {
                continue;
            }

            unsigned int vid = pMesh->mBones[i]->mWeights[j].mVertexId;

            if(w>=mThreshold) {
                if(vertexBones[vid]!=cUnowned)  {
                    if(vertexBones[vid]==i) //double entry
                    {
                        ASSIMP_LOG_WARN("Encountered double entry in bone weights");
                    }
                    else //TODO: track attraction in order to break tie
                    {
                        vertexBones[vid] = cCoowned;
                    }
                }
                else vertexBones[vid] = i;
            }

            if(!isBoneNecessary[i]) {
                isBoneNecessary[i] = w<mThreshold;
            }
        }
    }

    unsigned int nFacesUnowned = 0;

    std::vector<unsigned int> faceBones(pMesh->mNumFaces,UINT_MAX);
    std::vector<unsigned int> facesPerBone(pMesh->mNumBones,0);

    for(unsigned int i=0;i<pMesh->mNumFaces;i++) {
        unsigned int nInterstitial = 1;

        unsigned int v = vertexBones[pMesh->mFaces[i].mIndices[0]];

        for(unsigned int j=1;j<pMesh->mFaces[i].mNumIndices;j++) {
            unsigned int w = vertexBones[pMesh->mFaces[i].mIndices[j]];

            if(v!=w)    {
                if(v<pMesh->mNumBones) isBoneNecessary[v] = true;
                if(w<pMesh->mNumBones) isBoneNecessary[w] = true;
            }
            else nInterstitial++;
        }

        if(v<pMesh->mNumBones &&nInterstitial==pMesh->mFaces[i].mNumIndices)    {
            faceBones[i] = v; //primitive belongs to bone #v
            facesPerBone[v]++;
        }
        else nFacesUnowned++;
    }

    // invalidate any "cojoined" faces
    for(unsigned int i=0;i<pMesh->mNumFaces;i++) {
        if(faceBones[i]<pMesh->mNumBones&&isBoneNecessary[faceBones[i]])
        {
            ai_assert(facesPerBone[faceBones[i]]>0);
            facesPerBone[faceBones[i]]--;

            nFacesUnowned++;
            faceBones[i] = cUnowned;
        }
    }

    if(nFacesUnowned) {
        std::vector<unsigned int> subFaces;

        for(unsigned int i=0;i<pMesh->mNumFaces;i++)    {
            if(faceBones[i]==cUnowned) {
                subFaces.push_back(i);
            }
        }

        aiMesh *baseMesh = MakeSubmesh(pMesh,subFaces,0);
        std::pair<aiMesh *, const aiBone *> push_pair(baseMesh, (const aiBone *)nullptr);

        poNewMeshes.push_back(push_pair);
    }

    for(unsigned int i=0;i<pMesh->mNumBones;i++) {

        if(!isBoneNecessary[i]&&facesPerBone[i]>0)  {
            std::vector<unsigned int> subFaces;

            for(unsigned int j=0;j<pMesh->mNumFaces;j++)    {
                if(faceBones[j]==i) {
                    subFaces.push_back(j);
                }
            }

            unsigned int f = AI_SUBMESH_FLAGS_SANS_BONES;
            aiMesh *subMesh =MakeSubmesh(pMesh,subFaces,f);

            //Lifted from PretransformVertices.cpp
            ApplyTransform(subMesh,pMesh->mBones[i]->mOffsetMatrix);
            std::pair<aiMesh*,const aiBone*> push_pair(subMesh,pMesh->mBones[i]);

            poNewMeshes.push_back(push_pair);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Recursively updates the node's mesh list to account for the changed mesh list
void DeboneProcess::UpdateNode(aiNode* pNode) const {
    // rebuild the node's mesh index list

    std::vector<unsigned int> newMeshList;

    // this will require two passes

    unsigned int m = static_cast<unsigned int>(pNode->mNumMeshes), n = static_cast<unsigned int>(mSubMeshIndices.size());

    // first pass, look for meshes which have not moved
    for(unsigned int a=0;a<m;a++)   {
        unsigned int srcIndex = pNode->mMeshes[a];
        const std::vector< std::pair< unsigned int,aiNode* > > &subMeshes = mSubMeshIndices[srcIndex];
        unsigned int nSubmeshes = static_cast<unsigned int>(subMeshes.size());

        for(unsigned int b=0;b<nSubmeshes;b++) {
            if(!subMeshes[b].second) {
                newMeshList.push_back(subMeshes[b].first);
            }
        }
    }

    // second pass, collect deboned meshes

    for(unsigned int a=0;a<n;a++) {
        const std::vector< std::pair< unsigned int,aiNode* > > &subMeshes = mSubMeshIndices[a];
        unsigned int nSubmeshes = static_cast<unsigned int>(subMeshes.size());

        for(unsigned int b=0;b<nSubmeshes;b++) {
            if(subMeshes[b].second == pNode)    {
                newMeshList.push_back(subMeshes[b].first);
            }
        }
    }

    if( pNode->mNumMeshes > 0 ) {
        delete[] pNode->mMeshes;
        pNode->mMeshes = nullptr;
    }

    pNode->mNumMeshes = static_cast<unsigned int>(newMeshList.size());

    if(pNode->mNumMeshes)   {
        pNode->mMeshes = new unsigned int[pNode->mNumMeshes];
        std::copy( newMeshList.begin(), newMeshList.end(), pNode->mMeshes);
    }

    // do that also recursively for all children
    for( unsigned int a = 0; a < pNode->mNumChildren; ++a ) {
        UpdateNode( pNode->mChildren[a]);
    }
}

// ------------------------------------------------------------------------------------------------
// Apply the node transformation to a mesh
void DeboneProcess::ApplyTransform(aiMesh* mesh, const aiMatrix4x4& mat)const {
    // Check whether we need to transform the coordinates at all
    if (!mat.IsIdentity()) {

        if (mesh->HasPositions()) {
            for (unsigned int i = 0; i < mesh->mNumVertices; ++i) {
                mesh->mVertices[i] = mat * mesh->mVertices[i];
            }
        }
        if (mesh->HasNormals() || mesh->HasTangentsAndBitangents()) {
            aiMatrix4x4 mWorldIT = mat;
            mWorldIT.Inverse().Transpose();

            // TODO: implement Inverse() for aiMatrix3x3
            aiMatrix3x3 m = aiMatrix3x3(mWorldIT);

            if (mesh->HasNormals()) {
                for (unsigned int i = 0; i < mesh->mNumVertices; ++i) {
                    mesh->mNormals[i] = (m * mesh->mNormals[i]).Normalize();
                }
            }
            if (mesh->HasTangentsAndBitangents()) {
                for (unsigned int i = 0; i < mesh->mNumVertices; ++i) {
                    mesh->mTangents[i]   = (m * mesh->mTangents[i]).Normalize();
                    mesh->mBitangents[i] = (m * mesh->mBitangents[i]).Normalize();
                }
            }
        }
    }
}
