assimp/code/PostProcessing/SplitLargeMeshes.cpp

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 ///  @file Implementation of the SplitLargeMeshes postprocessing step

// internal headers of the post-processing framework
#include "SplitLargeMeshes.h"
#include "ProcessHelper.h"

using namespace Assimp;

// ------------------------------------------------------------------------------------------------
SplitLargeMeshesProcess_Triangle::SplitLargeMeshesProcess_Triangle() {
    LIMIT = AI_SLM_DEFAULT_MAX_TRIANGLES;
}

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

// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void SplitLargeMeshesProcess_Triangle::Execute( aiScene* pScene) {
    if (0xffffffff == this->LIMIT || nullptr == pScene ) {
        return;
    }

    ASSIMP_LOG_DEBUG("SplitLargeMeshesProcess_Triangle begin");
    std::vector<std::pair<aiMesh*, unsigned int> > avList;

    for( unsigned int a = 0; a < pScene->mNumMeshes; ++a) {
        this->SplitMesh(a, pScene->mMeshes[a],avList);
    }

    if (avList.size() == pScene->mNumMeshes) {
        ASSIMP_LOG_DEBUG("SplitLargeMeshesProcess_Triangle finished. There was nothing to do");
    }

    // it seems something has been split. rebuild the mesh list
    delete[] pScene->mMeshes;
    pScene->mNumMeshes = (unsigned int)avList.size();
    pScene->mMeshes = new aiMesh*[avList.size()];

    for (unsigned int i = 0; i < avList.size();++i) {
        pScene->mMeshes[i] = avList[i].first;
    }

    // now we need to update all nodes
    this->UpdateNode(pScene->mRootNode,avList);
    ASSIMP_LOG_INFO("SplitLargeMeshesProcess_Triangle finished. Meshes have been split");
}

// ------------------------------------------------------------------------------------------------
// Setup properties
void SplitLargeMeshesProcess_Triangle::SetupProperties( const Importer* pImp) {
    // get the current value of the split property
    this->LIMIT = pImp->GetPropertyInteger(AI_CONFIG_PP_SLM_TRIANGLE_LIMIT,AI_SLM_DEFAULT_MAX_TRIANGLES);
}

// ------------------------------------------------------------------------------------------------
// Update a node after some meshes have been split
void SplitLargeMeshesProcess_Triangle::UpdateNode(aiNode* pcNode, const std::vector<std::pair<aiMesh*, unsigned int> >& avList) {
    // for every index in out list build a new entry
    std::vector<unsigned int> aiEntries;
    aiEntries.reserve(pcNode->mNumMeshes + 1);
    for (unsigned int i = 0; i < pcNode->mNumMeshes;++i) {
        for (unsigned int a = 0; a < avList.size();++a) {
            if (avList[a].second == pcNode->mMeshes[i]) {
                aiEntries.push_back(a);
            }
        }
    }

    // now build the new list
    delete[] pcNode->mMeshes;
    pcNode->mNumMeshes = (unsigned int)aiEntries.size();
    pcNode->mMeshes = new unsigned int[pcNode->mNumMeshes];

    for (unsigned int b = 0; b < pcNode->mNumMeshes;++b) {
        pcNode->mMeshes[b] = aiEntries[b];
    }

    // recursively update all other nodes
    for (unsigned int i = 0; i < pcNode->mNumChildren;++i) {
        UpdateNode ( pcNode->mChildren[i], avList );
    }
}

// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void SplitLargeMeshesProcess_Triangle::SplitMesh(
        unsigned int a,
        aiMesh* pMesh,
        std::vector<std::pair<aiMesh*, unsigned int> >& avList) {
    if (pMesh->mNumFaces > SplitLargeMeshesProcess_Triangle::LIMIT) {
        ASSIMP_LOG_INFO("Mesh exceeds the triangle limit. It will be split ...");

        // we need to split this mesh into sub meshes
        // determine the size of a submesh
        const unsigned int iSubMeshes = (pMesh->mNumFaces / LIMIT) + 1;

        const unsigned int iOutFaceNum = pMesh->mNumFaces / iSubMeshes;
        const unsigned int iOutVertexNum = iOutFaceNum * 3;

        // now generate all submeshes
        for (unsigned int i = 0; i < iSubMeshes;++i) {
            aiMesh* pcMesh          = new aiMesh;
            pcMesh->mNumFaces       = iOutFaceNum;
            pcMesh->mMaterialIndex  = pMesh->mMaterialIndex;

            // the name carries the adjacency information between the meshes
            pcMesh->mName = pMesh->mName;

            if (i == iSubMeshes-1) {
                pcMesh->mNumFaces = iOutFaceNum + (
                    pMesh->mNumFaces - iOutFaceNum * iSubMeshes);
            }
            // copy the list of faces
            pcMesh->mFaces = new aiFace[pcMesh->mNumFaces];

            const unsigned int iBase = iOutFaceNum * i;

            // get the total number of indices
            unsigned int iCnt = 0;
            for (unsigned int p = iBase; p < pcMesh->mNumFaces + iBase;++p) {
                iCnt += pMesh->mFaces[p].mNumIndices;
            }
            pcMesh->mNumVertices = iCnt;

            // allocate storage
            if (pMesh->mVertices != nullptr) {
                pcMesh->mVertices = new aiVector3D[iCnt];
            }

            if (pMesh->HasNormals()) {
                pcMesh->mNormals = new aiVector3D[iCnt];
            }

            if (pMesh->HasTangentsAndBitangents()) {
                pcMesh->mTangents = new aiVector3D[iCnt];
                pcMesh->mBitangents = new aiVector3D[iCnt];
            }

            // texture coordinates
            for (unsigned int c = 0;  c < AI_MAX_NUMBER_OF_TEXTURECOORDS;++c) {
                pcMesh->mNumUVComponents[c] = pMesh->mNumUVComponents[c];
                if (pMesh->HasTextureCoords( c)) {
                    pcMesh->mTextureCoords[c] = new aiVector3D[iCnt];
                }
            }

            // vertex colors
            for (unsigned int c = 0;  c < AI_MAX_NUMBER_OF_COLOR_SETS;++c) {
                if (pMesh->HasVertexColors( c)) {
                    pcMesh->mColors[c] = new aiColor4D[iCnt];
                }
            }

            if (pMesh->HasBones()) {
                // assume the number of bones won't change in most cases
                pcMesh->mBones = new aiBone*[pMesh->mNumBones];

                // iterate through all bones of the mesh and find those which
                // need to be copied to the split mesh
                std::vector<aiVertexWeight> avTempWeights;
                for (unsigned int p = 0; p < pcMesh->mNumBones;++p) {
                    aiBone* const bone = pcMesh->mBones[p];
                    avTempWeights.clear();
                    avTempWeights.reserve(bone->mNumWeights / iSubMeshes);

                    for (unsigned int q = 0; q < bone->mNumWeights;++q) {
                        aiVertexWeight& weight = bone->mWeights[q];
                        if(weight.mVertexId >= iBase && weight.mVertexId < iBase + iOutVertexNum) {
                            avTempWeights.push_back(weight);
                            weight = avTempWeights.back();
                            weight.mVertexId -= iBase;
                        }
                    }

                    if (!avTempWeights.empty()) {
                        // we'll need this bone. Copy it ...
                        aiBone* pc = new aiBone();
                        pcMesh->mBones[pcMesh->mNumBones++] = pc;
                        pc->mName = aiString(bone->mName);
                        pc->mNumWeights = (unsigned int)avTempWeights.size();
                        pc->mOffsetMatrix = bone->mOffsetMatrix;

                        // no need to reallocate the array for the last submesh.
                        // Here we can reuse the (large) source array, although
                        // we'll waste some memory
                        if (iSubMeshes-1 == i) {
                            pc->mWeights = bone->mWeights;
                            bone->mWeights = nullptr;
                        } else {
                            pc->mWeights = new aiVertexWeight[pc->mNumWeights];
                        }

                        // copy the weights
                        ::memcpy(pc->mWeights,&avTempWeights[0],sizeof(aiVertexWeight)*pc->mNumWeights);
                    }
                }
            }

            // (we will also need to copy the array of indices)
            unsigned int iCurrent = 0;
            for (unsigned int p = 0; p < pcMesh->mNumFaces;++p) {
                pcMesh->mFaces[p].mNumIndices = 3;
                // allocate a new array
                const unsigned int iTemp = p + iBase;
                const unsigned int iNumIndices = pMesh->mFaces[iTemp].mNumIndices;

                // setup face type and number of indices
                pcMesh->mFaces[p].mNumIndices = iNumIndices;
                unsigned int* pi = pMesh->mFaces[iTemp].mIndices;
                unsigned int* piOut = pcMesh->mFaces[p].mIndices = new unsigned int[iNumIndices];

                // need to update the output primitive types
                switch (iNumIndices) {
                case 1:
                    pcMesh->mPrimitiveTypes |= aiPrimitiveType_POINT;
                    break;
                case 2:
                    pcMesh->mPrimitiveTypes |= aiPrimitiveType_LINE;
                    break;
                case 3:
                    pcMesh->mPrimitiveTypes |= aiPrimitiveType_TRIANGLE;
                    break;
                default:
                    pcMesh->mPrimitiveTypes |= aiPrimitiveType_POLYGON;
                }

                // and copy the contents of the old array, offset by current base
                for (unsigned int v = 0; v < iNumIndices;++v) {
                    unsigned int iIndex = pi[v];
                    unsigned int iIndexOut = iCurrent++;
                    piOut[v] = iIndexOut;

                    // copy positions
                    if (pMesh->mVertices != nullptr) {
                        pcMesh->mVertices[iIndexOut] = pMesh->mVertices[iIndex];
                    }

                    // copy normals
                    if (pMesh->HasNormals()) {
                        pcMesh->mNormals[iIndexOut] = pMesh->mNormals[iIndex];
                    }

                    // copy tangents/bitangents
                    if (pMesh->HasTangentsAndBitangents()) {
                        pcMesh->mTangents[iIndexOut] = pMesh->mTangents[iIndex];
                        pcMesh->mBitangents[iIndexOut] = pMesh->mBitangents[iIndex];
                    }

                    // texture coordinates
                    for (unsigned int c = 0;  c < AI_MAX_NUMBER_OF_TEXTURECOORDS;++c) {
                        if (pMesh->HasTextureCoords( c ) ) {
                            pcMesh->mTextureCoords[c][iIndexOut] = pMesh->mTextureCoords[c][iIndex];
                        }
                    }
                    // vertex colors
                    for (unsigned int c = 0;  c < AI_MAX_NUMBER_OF_COLOR_SETS;++c) {
                        if (pMesh->HasVertexColors( c)) {
                            pcMesh->mColors[c][iIndexOut] = pMesh->mColors[c][iIndex];
                        }
                    }
                }
            }

            // add the newly created mesh to the list
            avList.emplace_back(pcMesh,a);
        }

        // now delete the old mesh data
        delete pMesh;
    } else {
        avList.emplace_back(pMesh,a);
    }
}

// ------------------------------------------------------------------------------------------------
SplitLargeMeshesProcess_Vertex::SplitLargeMeshesProcess_Vertex() {
    LIMIT = AI_SLM_DEFAULT_MAX_VERTICES;
}

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

// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void SplitLargeMeshesProcess_Vertex::Execute( aiScene* pScene) {
    if (0xffffffff == this->LIMIT || nullptr == pScene ) {
        return;
    }

    ASSIMP_LOG_DEBUG("SplitLargeMeshesProcess_Vertex begin");

    std::vector<std::pair<aiMesh*, unsigned int> > avList;

    //Check for point cloud first,
    //Do not process point cloud, splitMesh works only with faces data
    for (unsigned int a = 0; a < pScene->mNumMeshes; a++) {
        if ( pScene->mMeshes[a]->mPrimitiveTypes == aiPrimitiveType_POINT ) {
            return;
        }
    }

    for( unsigned int a = 0; a < pScene->mNumMeshes; ++a ) {
        this->SplitMesh(a, pScene->mMeshes[a], avList);
    }

    if (avList.size() != pScene->mNumMeshes) {
        // it seems something has been split. rebuild the mesh list
        delete[] pScene->mMeshes;
        pScene->mNumMeshes = (unsigned int)avList.size();
        pScene->mMeshes = new aiMesh*[avList.size()];

        for (unsigned int i = 0; i < avList.size();++i) {
            pScene->mMeshes[i] = avList[i].first;
        }

        // now we need to update all nodes
        SplitLargeMeshesProcess_Triangle::UpdateNode(pScene->mRootNode,avList);
        ASSIMP_LOG_INFO("SplitLargeMeshesProcess_Vertex finished. Meshes have been split");
    } else {
        ASSIMP_LOG_DEBUG("SplitLargeMeshesProcess_Vertex finished. There was nothing to do");
    }
}

// ------------------------------------------------------------------------------------------------
// Setup properties
void SplitLargeMeshesProcess_Vertex::SetupProperties( const Importer* pImp) {
    this->LIMIT = pImp->GetPropertyInteger(AI_CONFIG_PP_SLM_VERTEX_LIMIT,AI_SLM_DEFAULT_MAX_VERTICES);
}

// ------------------------------------------------------------------------------------------------
// Executes the post processing step on the given imported data.
void SplitLargeMeshesProcess_Vertex::SplitMesh(
        unsigned int a,
        aiMesh* pMesh,
        std::vector<std::pair<aiMesh*, unsigned int> >& avList) {
    if (pMesh->mNumVertices > SplitLargeMeshesProcess_Vertex::LIMIT) {
        typedef std::vector< std::pair<unsigned int,float> > VertexWeightTable;

        // build a per-vertex weight list if necessary
        VertexWeightTable* avPerVertexWeights = ComputeVertexBoneWeightTable(pMesh);

        // we need to split this mesh into sub meshes
        // determine the estimated size of a submesh
        // (this could be too large. Max waste is a single digit percentage)
        const unsigned int iSubMeshes = (pMesh->mNumVertices / SplitLargeMeshesProcess_Vertex::LIMIT) + 1;

        // create a std::vector<unsigned int> to indicate which vertices
        // have already been copied
        std::vector<unsigned int> avWasCopied;
        avWasCopied.resize(pMesh->mNumVertices,0xFFFFFFFF);

        // try to find a good estimate for the number of output faces
        // per mesh. Add 12.5% as buffer
        unsigned int iEstimatedSize = pMesh->mNumFaces / iSubMeshes;
        iEstimatedSize += iEstimatedSize >> 3;

        // now generate all submeshes
        unsigned int iBase( 0 );
        while (true) {
            const unsigned int iOutVertexNum = SplitLargeMeshesProcess_Vertex::LIMIT;
            aiMesh* pcMesh          = new aiMesh;
            pcMesh->mNumVertices    = 0;
            pcMesh->mMaterialIndex  = pMesh->mMaterialIndex;

            // the name carries the adjacency information between the meshes
            pcMesh->mName = pMesh->mName;

            typedef std::vector<aiVertexWeight> BoneWeightList;
            if (pMesh->HasBones()) {
                pcMesh->mBones = new aiBone*[pMesh->mNumBones];
                ::memset(pcMesh->mBones,0,sizeof(void*)*pMesh->mNumBones);
            }

            // clear the temporary helper array
            if (iBase) {
                // we can't use memset here we unsigned int needn' be 32 bits
                for (auto &elem : avWasCopied) {
                    elem = 0xffffffff;
                }
            }

            // output vectors
            std::vector<aiFace> vFaces;

            // reserve enough storage for most cases
            if (pMesh->HasPositions()) {
                pcMesh->mVertices = new aiVector3D[iOutVertexNum];
            }
            if (pMesh->HasNormals()) {
                pcMesh->mNormals = new aiVector3D[iOutVertexNum];
            }
            if (pMesh->HasTangentsAndBitangents()) {
                pcMesh->mTangents = new aiVector3D[iOutVertexNum];
                pcMesh->mBitangents = new aiVector3D[iOutVertexNum];
            }
            for (unsigned int c = 0; pMesh->HasVertexColors(c);++c) {
                pcMesh->mColors[c] = new aiColor4D[iOutVertexNum];
            }
            for (unsigned int c = 0; pMesh->HasTextureCoords(c);++c) {
                pcMesh->mNumUVComponents[c] = pMesh->mNumUVComponents[c];
                pcMesh->mTextureCoords[c] = new aiVector3D[iOutVertexNum];
            }
            vFaces.reserve(iEstimatedSize);

            // (we will also need to copy the array of indices)
            while (iBase < pMesh->mNumFaces) {
                // allocate a new array
                const unsigned int iNumIndices = pMesh->mFaces[iBase].mNumIndices;

                // doesn't catch degenerates but is quite fast
                unsigned int iNeed = 0;
                for (unsigned int v = 0; v < iNumIndices;++v) {
                    unsigned int iIndex = pMesh->mFaces[iBase].mIndices[v];

                    // check whether we do already have this vertex
                    if (0xFFFFFFFF == avWasCopied[iIndex]) {
                        iNeed++;
                    }
                }
                if (pcMesh->mNumVertices + iNeed > iOutVertexNum) {
                    // don't use this face
                    break;
                }

                vFaces.emplace_back();
                aiFace& rFace = vFaces.back();

                // setup face type and number of indices
                rFace.mNumIndices = iNumIndices;
                rFace.mIndices = new unsigned int[iNumIndices];

                // need to update the output primitive types
                switch (rFace.mNumIndices) {
                case 1:
                    pcMesh->mPrimitiveTypes |= aiPrimitiveType_POINT;
                    break;
                case 2:
                    pcMesh->mPrimitiveTypes |= aiPrimitiveType_LINE;
                    break;
                case 3:
                    pcMesh->mPrimitiveTypes |= aiPrimitiveType_TRIANGLE;
                    break;
                default:
                    pcMesh->mPrimitiveTypes |= aiPrimitiveType_POLYGON;
                }

                // and copy the contents of the old array, offset by current base
                for (unsigned int v = 0; v < iNumIndices;++v) {
                    unsigned int iIndex = pMesh->mFaces[iBase].mIndices[v];

                    // check whether we do already have this vertex
                    if (0xFFFFFFFF != avWasCopied[iIndex]) {
                        rFace.mIndices[v] = avWasCopied[iIndex];
                        continue;
                    }

                    // copy positions
                    pcMesh->mVertices[pcMesh->mNumVertices] = (pMesh->mVertices[iIndex]);

                    // copy normals
                    if (pMesh->HasNormals()) {
                        pcMesh->mNormals[pcMesh->mNumVertices] = (pMesh->mNormals[iIndex]);
                    }

                    // copy tangents/bitangents
                    if (pMesh->HasTangentsAndBitangents()) {
                        pcMesh->mTangents[pcMesh->mNumVertices] = (pMesh->mTangents[iIndex]);
                        pcMesh->mBitangents[pcMesh->mNumVertices] = (pMesh->mBitangents[iIndex]);
                    }

                    // texture coordinates
                    for (unsigned int c = 0;  c < AI_MAX_NUMBER_OF_TEXTURECOORDS;++c) {
                        if (pMesh->HasTextureCoords( c)) {
                            pcMesh->mTextureCoords[c][pcMesh->mNumVertices] = pMesh->mTextureCoords[c][iIndex];
                        }
                    }
                    // vertex colors
                    for (unsigned int c = 0;  c < AI_MAX_NUMBER_OF_COLOR_SETS;++c) {
                        if (pMesh->HasVertexColors( c)) {
                            pcMesh->mColors[c][pcMesh->mNumVertices] = pMesh->mColors[c][iIndex];
                        }
                    }
                    // check whether we have bone weights assigned to this vertex
                    rFace.mIndices[v] = pcMesh->mNumVertices;
                    if (avPerVertexWeights) {
                        VertexWeightTable& table = avPerVertexWeights[ pcMesh->mNumVertices ];
                        if( !table.empty() ) {
                            for (VertexWeightTable::const_iterator iter =  table.begin();
                                    iter != table.end();++iter) {
                                // allocate the bone weight array if necessary
                                BoneWeightList* pcWeightList = (BoneWeightList*)pcMesh->mBones[(*iter).first];
                                if (nullptr == pcWeightList) {
                                    pcMesh->mBones[(*iter).first] = (aiBone*)(pcWeightList = new BoneWeightList());
                                }
                                pcWeightList->push_back(aiVertexWeight(pcMesh->mNumVertices,(*iter).second));
                            }
                        }
                    }

                    avWasCopied[iIndex] = pcMesh->mNumVertices;
                    pcMesh->mNumVertices++;
                }
                ++iBase;
                if(pcMesh->mNumVertices == iOutVertexNum) {
                    // break here. The face is only added if it was complete
                    break;
                }
            }

            // check which bones we'll need to create for this submesh
            if (pMesh->HasBones()) {
                aiBone** ppCurrent = pcMesh->mBones;
                for (unsigned int k = 0; k < pMesh->mNumBones;++k) {
                    // check whether the bone is existing
                    BoneWeightList* pcWeightList;
                    pcWeightList = (BoneWeightList *)pcMesh->mBones[k];
                    if (nullptr != pcWeightList) {
                        aiBone *pcOldBone = pMesh->mBones[k];
                        aiBone* pcOut( nullptr );
                        *ppCurrent++ = pcOut = new aiBone();
                        pcOut->mName = aiString(pcOldBone->mName);
                        pcOut->mOffsetMatrix = pcOldBone->mOffsetMatrix;
                        pcOut->mNumWeights = (unsigned int)pcWeightList->size();
                        pcOut->mWeights = new aiVertexWeight[pcOut->mNumWeights];

                        // copy the vertex weights
                        ::memcpy(pcOut->mWeights,&pcWeightList->operator[](0),
                            pcOut->mNumWeights * sizeof(aiVertexWeight));

                        // delete the temporary bone weight list
                        delete pcWeightList;
                        pcMesh->mNumBones++;
                    }
                }
            }

            // copy the face list to the mesh
            pcMesh->mFaces = new aiFace[vFaces.size()];
            pcMesh->mNumFaces = (unsigned int)vFaces.size();

            for (unsigned int p = 0; p < pcMesh->mNumFaces;++p) {
                pcMesh->mFaces[p] = vFaces[p];
            }

            // add the newly created mesh to the list
            avList.emplace_back(pcMesh,a);

            if (iBase == pMesh->mNumFaces) {
                // have all faces ... finish the outer loop, too
                break;
            }
        }

        // delete the per-vertex weight list again
        delete[] avPerVertexWeights;

        // now delete the old mesh data
        delete pMesh;
        return;
    }
    avList.emplace_back(pMesh,a);
}