assimp/code/AssetLib/LWO/LWOLoader.cpp

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/** @file  LWOLoader.cpp
 *  @brief Implementation of the LWO importer class
 */

#ifndef ASSIMP_BUILD_NO_LWO_IMPORTER

// internal headers
#include "AssetLib/LWO/LWOLoader.h"
#include "PostProcessing/ConvertToLHProcess.h"
#include "PostProcessing/ProcessHelper.h"

#include <assimp/ByteSwapper.h>
#include <assimp/SGSpatialSort.h>
#include <assimp/StringComparison.h>
#include <assimp/importerdesc.h>
#include <assimp/IOSystem.hpp>

#include <iomanip>
#include <map>
#include <memory>
#include <sstream>

using namespace Assimp;

static const aiImporterDesc desc = {
    "LightWave/Modo Object Importer",
    "",
    "",
    "https://www.lightwave3d.com/lightwave_sdk/",
    aiImporterFlags_SupportTextFlavour,
    0,
    0,
    0,
    0,
    "lwo lxo"
};

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
LWOImporter::LWOImporter() :
        mIsLWO2(),
        mIsLXOB(),
        mIsLWO3(),
        mLayers(),
        mCurLayer(),
        mTags(),
        mMapping(),
        mSurfaces(),
        mFileBuffer(),
        fileSize(),
        mScene(nullptr),
        configSpeedFlag(),
        configLayerIndex(),
        hasNamedLayer() {
    // empty
}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
LWOImporter::~LWOImporter() = default;

// ------------------------------------------------------------------------------------------------
// Returns whether the class can handle the format of the given file.
bool LWOImporter::CanRead(const std::string &file, IOSystem *pIOHandler, bool /*checkSig*/) const {
    static const uint32_t tokens[] = {
        AI_LWO_FOURCC_LWOB,
        AI_LWO_FOURCC_LWO2,
        AI_LWO_FOURCC_LXOB
    };
    return CheckMagicToken(pIOHandler, file, tokens, AI_COUNT_OF(tokens), 8);
}

// ------------------------------------------------------------------------------------------------
// Setup configuration properties
void LWOImporter::SetupProperties(const Importer *pImp) {
    configSpeedFlag = (0 != pImp->GetPropertyInteger(AI_CONFIG_FAVOUR_SPEED, 0) ? true : false);
    configLayerIndex = pImp->GetPropertyInteger(AI_CONFIG_IMPORT_LWO_ONE_LAYER_ONLY, UINT_MAX);
    configLayerName = pImp->GetPropertyString(AI_CONFIG_IMPORT_LWO_ONE_LAYER_ONLY, "");
}

// ------------------------------------------------------------------------------------------------
// Get list of file extensions
const aiImporterDesc *LWOImporter::GetInfo() const {
    return &desc;
}

// ------------------------------------------------------------------------------------------------
// Imports the given file into the given scene structure.
void LWOImporter::InternReadFile(const std::string &pFile,
        aiScene *pScene,
        IOSystem *pIOHandler) {
    std::unique_ptr<IOStream> file(pIOHandler->Open(pFile, "rb"));

    // Check whether we can read from the file
    if (file.get() == nullptr) {
        throw DeadlyImportError("Failed to open LWO file ", pFile, ".");
    }

    if ((this->fileSize = (unsigned int)file->FileSize()) < 12) {
        throw DeadlyImportError("LWO: The file is too small to contain the IFF header");
    }

    // Allocate storage and copy the contents of the file to a memory buffer
    std::vector<uint8_t> mBuffer(fileSize);
    file->Read(&mBuffer[0], 1, fileSize);
    mScene = pScene;

    // Determine the type of the file
    uint32_t fileType;
    const char *sz = IFF::ReadHeader(&mBuffer[0], fileType);
    if (sz) {
        throw DeadlyImportError(sz);
    }

    mFileBuffer = &mBuffer[0] + 12;
    fileSize -= 12;

    // Initialize some members with their default values
    hasNamedLayer = false;

    // Create temporary storage on the stack but store pointers to it in the class
    // instance. Therefore everything will be destructed properly if an exception
    // is thrown and we needn't take care of that.
    LayerList _mLayers;
    SurfaceList _mSurfaces;
    TagList _mTags;
    TagMappingTable _mMapping;

    mLayers = &_mLayers;
    mTags = &_mTags;
    mMapping = &_mMapping;
    mSurfaces = &_mSurfaces;

    // Allocate a default layer (layer indices are 1-based from now)
    mLayers->push_back(Layer());
    mCurLayer = &mLayers->back();
    mCurLayer->mName = "<LWODefault>";
    mCurLayer->mIndex = (uint16_t) -1;

    // old lightwave file format (prior to v6)
    mIsLWO2 = false;
    mIsLWO3 = false;
    mIsLXOB = false;

    if (AI_LWO_FOURCC_LWOB == fileType) {
        ASSIMP_LOG_INFO("LWO file format: LWOB (<= LightWave 5.5)");

        LoadLWOBFile();
    } else if (AI_LWO_FOURCC_LWO2 == fileType) {
        // New lightwave format
        ASSIMP_LOG_INFO("LWO file format: LWO2 (>= LightWave 6)");
    } else if ( AI_LWO_FOURCC_LWO3 == fileType ) {
        ASSIMP_LOG_INFO("LWO file format: LWO3 (>= LightWave 2018)");
    } else if (AI_LWO_FOURCC_LXOB == fileType) {
        // MODO file format
        mIsLXOB = true;
        ASSIMP_LOG_INFO("LWO file format: LXOB (Modo)");
    }
    else {
        char szBuff[5];
        szBuff[0] = (char)(fileType >> 24u);
        szBuff[1] = (char)(fileType >> 16u);
        szBuff[2] = (char)(fileType >> 8u);
        szBuff[3] = (char)(fileType);
        szBuff[4] = '\0';
        throw DeadlyImportError("Unknown LWO sub format: ", szBuff);
    }

    if (AI_LWO_FOURCC_LWOB != fileType) {   //
        if( AI_LWO_FOURCC_LWO3 == fileType ) {
            mIsLWO3 = true;
        } else {
            mIsLWO2 = true;
        }
        
        LoadLWO2File();

        // The newer lightwave format allows the user to configure the
        // loader that just one layer is used. If this is the case
        // we need to check now whether the requested layer has been found.
        if (UINT_MAX != configLayerIndex) {
            unsigned int layerCount = 0;
            for (std::list<LWO::Layer>::iterator itLayers = mLayers->begin(); itLayers != mLayers->end(); ++itLayers)
                if (!itLayers->skip)
                    layerCount++;
            if (layerCount != 2)
                throw DeadlyImportError("LWO2: The requested layer was not found");
        }

        if (configLayerName.length() && !hasNamedLayer) {
            throw DeadlyImportError("LWO2: Unable to find the requested layer: ", configLayerName);
        }
    }

    // now, as we have loaded all data, we can resolve cross-referenced tags and clips
    ResolveTags();
    ResolveClips();

    // now process all layers and build meshes and nodes
    std::vector<aiMesh *> apcMeshes;
    std::map<uint16_t, aiNode *> apcNodes;

    apcMeshes.reserve(mLayers->size() * std::min(((unsigned int)mSurfaces->size() / 2u), 1u));

    unsigned int iDefaultSurface = UINT_MAX; // index of the default surface
    for (LWO::Layer &layer : *mLayers) {
        if (layer.skip)
            continue;

        // I don't know whether there could be dummy layers, but it would be possible
        const unsigned int meshStart = (unsigned int)apcMeshes.size();
        if (!layer.mFaces.empty() && !layer.mTempPoints.empty()) {

            // now sort all faces by the surfaces assigned to them
            std::vector<SortedRep> pSorted(mSurfaces->size() + 1);

            unsigned int i = 0;
            for (FaceList::iterator it = layer.mFaces.begin(), end = layer.mFaces.end(); it != end; ++it, ++i) {
                // Check whether we support this face's type
                if ((*it).type != AI_LWO_FACE && (*it).type != AI_LWO_PTCH &&
                        (*it).type != AI_LWO_BONE && (*it).type != AI_LWO_SUBD) {
                    continue;
                }

                unsigned int idx = (*it).surfaceIndex;
                if (idx >= mTags->size()) {
                    ASSIMP_LOG_WARN("LWO: Invalid face surface index");
                    idx = UINT_MAX;
                }
                if (UINT_MAX == idx || UINT_MAX == (idx = _mMapping[idx])) {
                    if (UINT_MAX == iDefaultSurface) {
                        iDefaultSurface = (unsigned int)mSurfaces->size();
                        mSurfaces->push_back(LWO::Surface());
                        LWO::Surface &surf = mSurfaces->back();
                        surf.mColor.r = surf.mColor.g = surf.mColor.b = 0.6f;
                        surf.mName = "LWODefaultSurface";
                    }
                    idx = iDefaultSurface;
                }
                pSorted[idx].push_back(i);
            }
            if (UINT_MAX == iDefaultSurface) {
                pSorted.erase(pSorted.end() - 1);
            }
            for (unsigned int j = 0; j < mSurfaces->size(); ++j) {
                SortedRep &sorted = pSorted[j];
                if (sorted.empty())
                    continue;

                // generate the mesh
                aiMesh *mesh = new aiMesh();
                apcMeshes.push_back(mesh);
                mesh->mNumFaces = (unsigned int)sorted.size();

                // count the number of vertices
                SortedRep::const_iterator it = sorted.begin(), end = sorted.end();
                for (; it != end; ++it) {
                    mesh->mNumVertices += layer.mFaces[*it].mNumIndices;
                }

                aiVector3D *nrm = nullptr, *pv = mesh->mVertices = new aiVector3D[mesh->mNumVertices];
                aiFace *pf = mesh->mFaces = new aiFace[mesh->mNumFaces];
                mesh->mMaterialIndex = j;

                // find out which vertex color channels and which texture coordinate
                // channels are really required by the material attached to this mesh
                unsigned int vUVChannelIndices[AI_MAX_NUMBER_OF_TEXTURECOORDS];
                unsigned int vVColorIndices[AI_MAX_NUMBER_OF_COLOR_SETS];

#ifdef ASSIMP_BUILD_DEBUG
                for (unsigned int mui = 0; mui < AI_MAX_NUMBER_OF_TEXTURECOORDS; ++mui) {
                    vUVChannelIndices[mui] = UINT_MAX;
                }
                for (unsigned int mui = 0; mui < AI_MAX_NUMBER_OF_COLOR_SETS; ++mui) {
                    vVColorIndices[mui] = UINT_MAX;
                }
#endif

                FindUVChannels(_mSurfaces[j], sorted, layer, vUVChannelIndices);
                FindVCChannels(_mSurfaces[j], sorted, layer, vVColorIndices);

                // allocate storage for UV and CV channels
                aiVector3D *pvUV[AI_MAX_NUMBER_OF_TEXTURECOORDS];
                for (unsigned int mui = 0; mui < AI_MAX_NUMBER_OF_TEXTURECOORDS; ++mui) {
                    if (UINT_MAX == vUVChannelIndices[mui]) {
                        break;
                    }

                    pvUV[mui] = mesh->mTextureCoords[mui] = new aiVector3D[mesh->mNumVertices];

                    // LightWave doesn't support more than 2 UV components (?)
                    mesh->mNumUVComponents[0] = 2;
                }

                if (layer.mNormals.name.length()) {
                    nrm = mesh->mNormals = new aiVector3D[mesh->mNumVertices];
                }

                aiColor4D *pvVC[AI_MAX_NUMBER_OF_COLOR_SETS];
                for (unsigned int mui = 0; mui < AI_MAX_NUMBER_OF_COLOR_SETS; ++mui) {
                    if (UINT_MAX == vVColorIndices[mui]) {
                        break;
                    }
                    pvVC[mui] = mesh->mColors[mui] = new aiColor4D[mesh->mNumVertices];
                }

                // we would not need this extra array, but the code is much cleaner if we use it
                std::vector<unsigned int> &smoothingGroups = layer.mPointReferrers;
                smoothingGroups.erase(smoothingGroups.begin(), smoothingGroups.end());
                smoothingGroups.resize(mesh->mNumFaces, 0);

                // now convert all faces
                unsigned int vert = 0;
                std::vector<unsigned int>::iterator outIt = smoothingGroups.begin();
                for (it = sorted.begin(); it != end; ++it, ++outIt) {
                    const LWO::Face &face = layer.mFaces[*it];
                    *outIt = face.smoothGroup;

                    // copy all vertices
                    for (unsigned int q = 0; q < face.mNumIndices; ++q, ++vert) {
                        unsigned int idx = face.mIndices[q];
                        *pv++ = layer.mTempPoints[idx] /*- layer.mPivot*/;

                        // process UV coordinates
                        for (unsigned int w = 0; w < AI_MAX_NUMBER_OF_TEXTURECOORDS; ++w) {
                            if (UINT_MAX == vUVChannelIndices[w]) {
                                break;
                            }
                            aiVector3D *&pp = pvUV[w];
                            const aiVector2D &src = ((aiVector2D *)&layer.mUVChannels[vUVChannelIndices[w]].rawData[0])[idx];
                            pp->x = src.x;
                            pp->y = src.y;
                            pp++;
                        }

                        // process normals (MODO extension)
                        if (nrm) {
                            *nrm = ((aiVector3D *)&layer.mNormals.rawData[0])[idx];
                            nrm->z *= -1.f;
                            ++nrm;
                        }

                        // process vertex colors
                        for (unsigned int w = 0; w < AI_MAX_NUMBER_OF_COLOR_SETS; ++w) {
                            if (UINT_MAX == vVColorIndices[w]) {
                                break;
                            }
                            *pvVC[w] = ((aiColor4D *)&layer.mVColorChannels[vVColorIndices[w]].rawData[0])[idx];

                            // If a RGB color map is explicitly requested delete the
                            // alpha channel - it could theoretically be != 1.
                            if (_mSurfaces[j].mVCMapType == AI_LWO_RGB)
                                pvVC[w]->a = 1.f;

                            pvVC[w]++;
                        }

#if 0
                        // process vertex weights. We can't properly reconstruct the whole skeleton for now,
                        // but we can create dummy bones for all weight channels which we have.
                        for (unsigned int w = 0; w < layer.mWeightChannels.size();++w)
                        {
                        }
#endif

                        face.mIndices[q] = vert;
                    }
                    pf->mIndices = face.mIndices;
                    pf->mNumIndices = face.mNumIndices;
                    unsigned int **facePtr = (unsigned int **)&face.mIndices;
                    *facePtr = nullptr; // HACK: make sure it won't be deleted
                    pf++;
                }

                if (!mesh->mNormals) {
                    // Compute normal vectors for the mesh - we can't use our GenSmoothNormal-
                    // Step here since it wouldn't handle smoothing groups correctly for LWO.
                    // So we use a separate implementation.
                    ComputeNormals(mesh, smoothingGroups, _mSurfaces[j]);
                } else {
                    ASSIMP_LOG_VERBOSE_DEBUG("LWO2: No need to compute normals, they're already there");
                }
            }
        }

        // Generate nodes to render the mesh. Store the source layer in the mParent member of the nodes
        unsigned int num = static_cast<unsigned int>(apcMeshes.size() - meshStart);
        if (layer.mName != "<LWODefault>" || num > 0) {
            aiNode *pcNode = new aiNode();
            pcNode->mName.Set(layer.mName);
            pcNode->mParent = (aiNode *)&layer;
            pcNode->mNumMeshes = num;

            if (pcNode->mNumMeshes) {
                pcNode->mMeshes = new unsigned int[pcNode->mNumMeshes];
                for (unsigned int p = 0; p < pcNode->mNumMeshes; ++p)
                    pcNode->mMeshes[p] = p + meshStart;
            }
            apcNodes[layer.mIndex] = pcNode;
        }
    }

    if (apcNodes.empty() || apcMeshes.empty())
        throw DeadlyImportError("LWO: No meshes loaded");

    // The RemoveRedundantMaterials step will clean this up later
    pScene->mMaterials = new aiMaterial *[pScene->mNumMaterials = (unsigned int)mSurfaces->size()];

    for (unsigned int mat = 0; mat < pScene->mNumMaterials; ++mat) {
        aiMaterial *pcMat = new aiMaterial();
        pScene->mMaterials[mat] = pcMat;
        ConvertMaterial((*mSurfaces)[mat], pcMat);
    }

    // copy the meshes to the output structure
    pScene->mMeshes = new aiMesh *[pScene->mNumMeshes = (unsigned int)apcMeshes.size()];
    ::memcpy(pScene->mMeshes, &apcMeshes[0], pScene->mNumMeshes * sizeof(void *));

    // generate the final node graph
    GenerateNodeGraph(apcNodes);
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::ComputeNormals(aiMesh *mesh, const std::vector<unsigned int> &smoothingGroups,
        const LWO::Surface &surface) {
    // Allocate output storage
    mesh->mNormals = new aiVector3D[mesh->mNumVertices];

    // First generate per-face normals
    aiVector3D *out;
    std::vector<aiVector3D> faceNormals;

    // ... in some cases that's already enough
    if (!surface.mMaximumSmoothAngle)
        out = mesh->mNormals;
    else {
        faceNormals.resize(mesh->mNumVertices);
        out = &faceNormals[0];
    }

    aiFace *begin = mesh->mFaces, *const end = mesh->mFaces + mesh->mNumFaces;
    for (; begin != end; ++begin) {
        aiFace &face = *begin;

        if (face.mNumIndices < 3) {
            continue;
        }

        // LWO doc: "the normal is defined as the cross product of the first and last edges"
        aiVector3D *pV1 = mesh->mVertices + face.mIndices[0];
        aiVector3D *pV2 = mesh->mVertices + face.mIndices[1];
        aiVector3D *pV3 = mesh->mVertices + face.mIndices[face.mNumIndices - 1];

        aiVector3D vNor = ((*pV2 - *pV1) ^ (*pV3 - *pV1)).Normalize();
        for (unsigned int i = 0; i < face.mNumIndices; ++i)
            out[face.mIndices[i]] = vNor;
    }
    if (!surface.mMaximumSmoothAngle) return;
    const float posEpsilon = ComputePositionEpsilon(mesh);

    // Now generate the spatial sort tree
    SGSpatialSort sSort;
    std::vector<unsigned int>::const_iterator it = smoothingGroups.begin();
    for (begin = mesh->mFaces; begin != end; ++begin, ++it) {
        aiFace &face = *begin;
        for (unsigned int i = 0; i < face.mNumIndices; ++i) {
            unsigned int tt = face.mIndices[i];
            sSort.Add(mesh->mVertices[tt], tt, *it);
        }
    }
    // Sort everything - this takes O(nlogn) time
    sSort.Prepare();
    std::vector<unsigned int> poResult;
    poResult.reserve(20);

    // Generate vertex normals. We have O(logn) for the binary lookup, which we need
    // for n elements, thus the EXPECTED complexity is O(nlogn)
    if (surface.mMaximumSmoothAngle < 3.f && !configSpeedFlag) {
        const float fLimit = std::cos(surface.mMaximumSmoothAngle);

        for (begin = mesh->mFaces, it = smoothingGroups.begin(); begin != end; ++begin, ++it) {
            const aiFace &face = *begin;
            unsigned int *beginIdx = face.mIndices, *const endIdx = face.mIndices + face.mNumIndices;
            for (; beginIdx != endIdx; ++beginIdx) {
                unsigned int idx = *beginIdx;
                sSort.FindPositions(mesh->mVertices[idx], *it, posEpsilon, poResult, true);

                aiVector3D vNormals;
                 for (std::vector<unsigned int>::const_iterator a = poResult.begin(); a != poResult.end(); ++a) {
                    const aiVector3D &v = faceNormals[*a];
                    if (v * faceNormals[idx] < fLimit)
                        continue;
                    vNormals += v;
                }
                mesh->mNormals[idx] = vNormals.Normalize();
            }
        }
    }
    // faster code path in case there is no smooth angle
    else {
        std::vector<bool> vertexDone(mesh->mNumVertices, false);
        for (begin = mesh->mFaces, it = smoothingGroups.begin(); begin != end; ++begin, ++it) {
            const aiFace &face = *begin;
            unsigned int *beginIdx = face.mIndices, *const endIdx = face.mIndices + face.mNumIndices;
            for (; beginIdx != endIdx; ++beginIdx) {
                unsigned int idx = *beginIdx;
                if (vertexDone[idx])
                    continue;
                sSort.FindPositions(mesh->mVertices[idx], *it, posEpsilon, poResult, true);

                aiVector3D vNormals;
                 for (std::vector<unsigned int>::const_iterator a = poResult.begin(); a != poResult.end(); ++a) {
                    const aiVector3D &v = faceNormals[*a];
                    vNormals += v;
                }
                vNormals.Normalize();
                for (std::vector<unsigned int>::const_iterator a = poResult.begin(); a != poResult.end(); ++a) {
                    mesh->mNormals[*a] = vNormals;
                    vertexDone[*a] = true;
                }
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::GenerateNodeGraph(std::map<uint16_t, aiNode *> &apcNodes) {
    // now generate the final nodegraph - generate a root node and attach children
    aiNode *root = mScene->mRootNode = new aiNode();
    root->mName.Set("<LWORoot>");

    //Set parent of all children, inserting pivots
    std::map<uint16_t, aiNode *> mapPivot;
    for (auto itapcNodes = apcNodes.begin(); itapcNodes != apcNodes.end(); ++itapcNodes) {

        //Get the parent index
        LWO::Layer *nodeLayer = (LWO::Layer *)(itapcNodes->second->mParent);
        uint16_t parentIndex = nodeLayer->mParent;

        //Create pivot node, store it into the pivot map, and set the parent as the pivot
        aiNode *pivotNode = new aiNode();
        pivotNode->mName.Set("Pivot-" + std::string(itapcNodes->second->mName.data));
        itapcNodes->second->mParent = pivotNode;

        //Look for the parent node to attach the pivot to
        if (apcNodes.find(parentIndex) != apcNodes.end()) {
            pivotNode->mParent = apcNodes[parentIndex];
        } else {
            //If not, attach to the root node
            pivotNode->mParent = root;
        }

        //Set the node and the pivot node transformation
        itapcNodes->second->mTransformation.a4 = -nodeLayer->mPivot.x;
        itapcNodes->second->mTransformation.b4 = -nodeLayer->mPivot.y;
        itapcNodes->second->mTransformation.c4 = -nodeLayer->mPivot.z;
        pivotNode->mTransformation.a4 = nodeLayer->mPivot.x;
        pivotNode->mTransformation.b4 = nodeLayer->mPivot.y;
        pivotNode->mTransformation.c4 = nodeLayer->mPivot.z;
        mapPivot[-(itapcNodes->first + 2)] = pivotNode;
    }

    //Merge pivot map into node map
    for (auto itMapPivot = mapPivot.begin(); itMapPivot != mapPivot.end(); ++itMapPivot) {
        apcNodes[itMapPivot->first] = itMapPivot->second;
    }

    //Set children of all parents
    apcNodes[(uint16_t)-1] = root;
    for (auto itMapParentNodes = apcNodes.begin(); itMapParentNodes != apcNodes.end(); ++itMapParentNodes) {
        for (auto itMapChildNodes = apcNodes.begin(); itMapChildNodes != apcNodes.end(); ++itMapChildNodes) {
            if ((itMapParentNodes->first != itMapChildNodes->first) && (itMapParentNodes->second == itMapChildNodes->second->mParent)) {
                ++(itMapParentNodes->second->mNumChildren);
            }
        }
        if (itMapParentNodes->second->mNumChildren) {
            itMapParentNodes->second->mChildren = new aiNode *[itMapParentNodes->second->mNumChildren];
            uint16_t p = 0;
            for (auto itMapChildNodes = apcNodes.begin(); itMapChildNodes != apcNodes.end(); ++itMapChildNodes) {
                if ((itMapParentNodes->first != itMapChildNodes->first) && (itMapParentNodes->second == itMapChildNodes->second->mParent)) {
                    itMapParentNodes->second->mChildren[p++] = itMapChildNodes->second;
                }
            }
        }
    }

    if (!mScene->mRootNode->mNumChildren)
        throw DeadlyImportError("LWO: Unable to build a valid node graph");

    // Remove a single root node with no meshes assigned to it ...
    if (1 == mScene->mRootNode->mNumChildren) {
        aiNode *pc = mScene->mRootNode->mChildren[0];
        pc->mParent = mScene->mRootNode->mChildren[0] = nullptr;
        delete mScene->mRootNode;
        mScene->mRootNode = pc;
    }

    // convert the whole stuff to RH with CCW winding
    MakeLeftHandedProcess maker;
    maker.Execute(mScene);

    FlipWindingOrderProcess flipper;
    flipper.Execute(mScene);
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::ResolveTags() {
    // --- this function is used for both LWO2 and LWOB
    mMapping->resize(mTags->size(), UINT_MAX);
    for (unsigned int a = 0; a < mTags->size(); ++a) {

        const std::string &c = (*mTags)[a];
        for (unsigned int i = 0; i < mSurfaces->size(); ++i) {

            const std::string &d = (*mSurfaces)[i].mName;
            if (!ASSIMP_stricmp(c, d)) {

                (*mMapping)[a] = i;
                break;
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::ResolveClips() {
    for (unsigned int i = 0; i < mClips.size(); ++i) {

        Clip &clip = mClips[i];
        if (Clip::REF == clip.type) {

            if (clip.clipRef >= mClips.size()) {
                ASSIMP_LOG_ERROR("LWO2: Clip referrer index is out of range");
                clip.clipRef = 0;
            }

            Clip &dest = mClips[clip.clipRef];
            if (Clip::REF == dest.type) {
                ASSIMP_LOG_ERROR("LWO2: Clip references another clip reference");
                clip.type = Clip::UNSUPPORTED;
            }

            else {
                clip.path = dest.path;
                clip.type = dest.type;
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::AdjustTexturePath(std::string &out) {
    // --- this function is used for both LWO2 and LWOB
    if (!mIsLWO2 && !mIsLWO3 && ::strstr(out.c_str(), "(sequence)")) {

        // remove the (sequence) and append 000
        ASSIMP_LOG_INFO("LWOB: Sequence of animated texture found. It will be ignored");
        out = out.substr(0, out.length() - 10) + "000";
    }

    // format: drive:path/file - we just need to insert a slash after the drive
    std::string::size_type n = out.find_first_of(':');
    if (std::string::npos != n) {
        out.insert(n + 1, "/");
    }
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::LoadLWOTags(unsigned int size) {
    // --- this function is used for both LWO2 and LWOB

    const char *szCur = (const char *)mFileBuffer, *szLast = szCur;
    const char *const szEnd = szLast + size;
    while (szCur < szEnd) {
        if (!(*szCur)) {
            const size_t len = (size_t)(szCur - szLast);
            // FIX: skip empty-sized tags
            if (len)
                mTags->push_back(std::string(szLast, len));
            szCur += (len & 0x1 ? 1 : 2);
            szLast = szCur;
        }
        szCur++;
    }
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::LoadLWOPoints(unsigned int length) {
    // --- this function is used for both LWO2 and LWOB but for
    // LWO2 we need to allocate 25% more storage - it could be we'll
    // need to duplicate some points later.
    const size_t vertexLen = 12;
    if ((length % vertexLen) != 0) {
        throw DeadlyImportError("LWO2: Points chunk length is not multiple of vertexLen (12)");
    }
    unsigned int regularSize = (unsigned int)mCurLayer->mTempPoints.size() + length / 12;
    if (mIsLWO2 || mIsLWO3) {
        mCurLayer->mTempPoints.reserve(regularSize + (regularSize >> 2u));
        mCurLayer->mTempPoints.resize(regularSize);

        // initialize all point referrers with the default values
        mCurLayer->mPointReferrers.reserve(regularSize + (regularSize >> 2u));
        mCurLayer->mPointReferrers.resize(regularSize, UINT_MAX);
    } else
        mCurLayer->mTempPoints.resize(regularSize);

        // perform endianness conversions
#ifndef AI_BUILD_BIG_ENDIAN
    for (unsigned int i = 0; i<length >> 2; ++i)
        ByteSwap::Swap4(mFileBuffer + (i << 2));
#endif
    ::memcpy(&mCurLayer->mTempPoints[0], mFileBuffer, length);
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::LoadLWO2Polygons(unsigned int length) {
    LE_NCONST uint16_t *const end = (LE_NCONST uint16_t *)(mFileBuffer + length);
    const uint32_t type = GetU4();

    // Determine the type of the polygons
    switch (type) {
            // read unsupported stuff too (although we won't process it)
        case AI_LWO_MBAL:
            ASSIMP_LOG_WARN("LWO2: Encountered unsupported primitive chunk (METABALL)");
            break;
        case AI_LWO_CURV:
            ASSIMP_LOG_WARN("LWO2: Encountered unsupported primitive chunk (SPLINE)");
            ;
            break;

            // These are ok with no restrictions
        case AI_LWO_PTCH:
        case AI_LWO_FACE:
        case AI_LWO_BONE:
        case AI_LWO_SUBD:
            break;
        default:

            // hm!? wtf is this? ok ...
            ASSIMP_LOG_ERROR("LWO2: Ignoring unknown polygon type.");
            break;
    }

    // first find out how many faces and vertices we'll finally need
    uint16_t *cursor = (uint16_t *)mFileBuffer;

    unsigned int iNumFaces = 0, iNumVertices = 0;
    CountVertsAndFacesLWO2(iNumVertices, iNumFaces, cursor, end);

    // allocate the output array and copy face indices
    if (iNumFaces) {
        cursor = (uint16_t *)mFileBuffer;

        mCurLayer->mFaces.resize(iNumFaces, LWO::Face(type));
        FaceList::iterator it = mCurLayer->mFaces.begin();
        CopyFaceIndicesLWO2(it, cursor, end);
    }
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::CountVertsAndFacesLWO2(unsigned int &verts, unsigned int &faces,
        uint16_t *&cursor, const uint16_t *const end, unsigned int max) {
    while (cursor < end && max--) {
        uint16_t numIndices;
        ::memcpy(&numIndices, cursor++, 2);
        AI_LSWAP2(numIndices);
        numIndices &= 0x03FF;

        verts += numIndices;
        ++faces;

        for (uint16_t i = 0; i < numIndices; i++) {
            ReadVSizedIntLWO2((uint8_t *&)cursor);
        }
    }
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::CopyFaceIndicesLWO2(FaceList::iterator &it,
        uint16_t *&cursor,
        const uint16_t *const end) {
    while (cursor < end) {
        LWO::Face &face = *it++;
        uint16_t numIndices;
        ::memcpy(&numIndices, cursor++, 2);
        AI_LSWAP2(numIndices);
        face.mNumIndices = numIndices & 0x03FF;

        if (face.mNumIndices) /* byte swapping has already been done */
        {
            face.mIndices = new unsigned int[face.mNumIndices];
            for (unsigned int i = 0; i < face.mNumIndices; i++) {
                face.mIndices[i] = ReadVSizedIntLWO2((uint8_t *&)cursor) + mCurLayer->mPointIDXOfs;
                if (face.mIndices[i] > mCurLayer->mTempPoints.size()) {
                    ASSIMP_LOG_WARN("LWO2: Failure evaluating face record, index is out of range");
                    face.mIndices[i] = (unsigned int)mCurLayer->mTempPoints.size() - 1;
                }
            }
        } else
            throw DeadlyImportError("LWO2: Encountered invalid face record with zero indices");
    }
}

// ------------------------------------------------------------------------------------------------
void LWOImporter::LoadLWO2PolygonTags(unsigned int length) {
    LE_NCONST uint8_t *const end = mFileBuffer + length;

    AI_LWO_VALIDATE_CHUNK_LENGTH(length, PTAG, 4);
    uint32_t type = GetU4();

    if (type != AI_LWO_SURF && type != AI_LWO_SMGP)
        return;

    while (mFileBuffer < end) {
        unsigned int i = ReadVSizedIntLWO2(mFileBuffer) + mCurLayer->mFaceIDXOfs;
        unsigned int j = GetU2();

        if (i >= mCurLayer->mFaces.size()) {
            ASSIMP_LOG_WARN("LWO2: face index in PTAG is out of range");
            continue;
        }

        switch (type) {

            case AI_LWO_SURF:
                mCurLayer->mFaces[i].surfaceIndex = j;
                break;
            case AI_LWO_SMGP: /* is that really used? */
                mCurLayer->mFaces[i].smoothGroup = j;
                break;
        };
    }
}

// ------------------------------------------------------------------------------------------------
template <class T>
VMapEntry *FindEntry(std::vector<T> &list, const std::string &name, bool perPoly) {
    for (auto &elem : list) {
        if (elem.name == name) {
            if (!perPoly) {
                ASSIMP_LOG_WARN("LWO2: Found two VMAP sections with equal names");
            }
            return &elem;
        }
    }
    list.push_back(T());
    VMapEntry *p = &list.back();
    p->name = name;
    return p;
}

// ------------------------------------------------------------------------------------------------
template <class T>
inline void CreateNewEntry(T &chan, unsigned int srcIdx) {
    if (!chan.name.length())
        return;

    chan.abAssigned[srcIdx] = true;
    chan.abAssigned.resize(chan.abAssigned.size() + 1, false);

    for (unsigned int a = 0; a < chan.dims; ++a)
        chan.rawData.push_back(chan.rawData[srcIdx * chan.dims + a]);
}

// ------------------------------------------------------------------------------------------------
template <class T>
inline void CreateNewEntry(std::vector<T> &list, unsigned int srcIdx) {
    for (auto &elem : list) {
        CreateNewEntry(elem, srcIdx);
    }
}

// ------------------------------------------------------------------------------------------------
inline void LWOImporter::DoRecursiveVMAPAssignment(VMapEntry *base, unsigned int numRead,
        unsigned int idx, float *data) {
    ai_assert(nullptr != data);
    LWO::ReferrerList &refList = mCurLayer->mPointReferrers;
    unsigned int i;

    if (idx >= base->abAssigned.size()) {
        throw DeadlyImportError("Bad index");
    }
    base->abAssigned[idx] = true;
    for (i = 0; i < numRead; ++i) {
        base->rawData[idx * base->dims + i] = data[i];
    }

    if (UINT_MAX != (i = refList[idx])) {
        DoRecursiveVMAPAssignment(base, numRead, i, data);
    }
}

// ------------------------------------------------------------------------------------------------
inline void AddToSingleLinkedList(ReferrerList &refList, unsigned int srcIdx, unsigned int destIdx) {
    if (UINT_MAX == refList[srcIdx]) {
        refList[srcIdx] = destIdx;
        return;
    }
    AddToSingleLinkedList(refList, refList[srcIdx], destIdx);
}

// ------------------------------------------------------------------------------------------------
// Load LWO2 vertex map
void LWOImporter::LoadLWO2VertexMap(unsigned int length, bool perPoly) {
    LE_NCONST uint8_t *const end = mFileBuffer + length;

    AI_LWO_VALIDATE_CHUNK_LENGTH(length, VMAP, 6);
    unsigned int type = GetU4();
    unsigned int dims = GetU2();

    VMapEntry *base;

    // read the name of the vertex map
    std::string name;
    GetS0(name, length);

    switch (type) {
        case AI_LWO_TXUV:
            if (dims != 2) {
                ASSIMP_LOG_WARN("LWO2: Skipping UV channel \'", name, "\' with !2 components");
                return;
            }
            base = FindEntry(mCurLayer->mUVChannels, name, perPoly);
            break;
        case AI_LWO_WGHT:
        case AI_LWO_MNVW:
            if (dims != 1) {
                ASSIMP_LOG_WARN("LWO2: Skipping Weight Channel \'", name, "\' with !1 components");
                return;
            }
            base = FindEntry((type == AI_LWO_WGHT ? mCurLayer->mWeightChannels : mCurLayer->mSWeightChannels), name, perPoly);
            break;
        case AI_LWO_RGB:
        case AI_LWO_RGBA:
            if (dims != 3 && dims != 4) {
                ASSIMP_LOG_WARN("LWO2: Skipping Color Map \'", name, "\' with a dimension > 4 or < 3");
                return;
            }
            base = FindEntry(mCurLayer->mVColorChannels, name, perPoly);
            break;

        case AI_LWO_MODO_NORM:
            /*  This is a non-standard extension chunk used by Luxology's MODO.
         *  It stores per-vertex normals. This VMAP exists just once, has
         *  3 dimensions and is btw extremely beautiful.
         */
            if (name != "vert_normals" || dims != 3 || mCurLayer->mNormals.name.length())
                return;

            ASSIMP_LOG_INFO("Processing non-standard extension: MODO VMAP.NORM.vert_normals");

            mCurLayer->mNormals.name = name;
            base = &mCurLayer->mNormals;
            break;

        case AI_LWO_PICK: /* these VMAPs are just silently dropped */
        case AI_LWO_MORF:
        case AI_LWO_SPOT:
            return;

        default:
            if (name == "APS.Level") {
                // XXX handle this (seems to be subdivision-related).
            }
            ASSIMP_LOG_WARN("LWO2: Skipping unknown VMAP/VMAD channel \'", name, "\'");
            return;
    };
    base->Allocate((unsigned int)mCurLayer->mTempPoints.size());

    // now read all entries in the map
    type = std::min(dims, base->dims);
    const unsigned int diff = (dims - type) << 2u;

    LWO::FaceList &list = mCurLayer->mFaces;
    LWO::PointList &pointList = mCurLayer->mTempPoints;
    LWO::ReferrerList &refList = mCurLayer->mPointReferrers;

    const unsigned int numPoints = (unsigned int)pointList.size();
    const unsigned int numFaces = (unsigned int)list.size();

    while (mFileBuffer < end) {

        unsigned int idx = ReadVSizedIntLWO2(mFileBuffer) + mCurLayer->mPointIDXOfs;
        if (idx >= numPoints) {
            ASSIMP_LOG_WARN("LWO2: Failure evaluating VMAP/VMAD entry \'", name, "\', vertex index is out of range");
            mFileBuffer += base->dims << 2u;
            continue;
        }
        if (perPoly) {
            unsigned int polyIdx = ReadVSizedIntLWO2(mFileBuffer) + mCurLayer->mFaceIDXOfs;
            if (base->abAssigned[idx]) {
                // we have already a VMAP entry for this vertex - thus
                // we need to duplicate the corresponding polygon.
                if (polyIdx >= numFaces) {
                    ASSIMP_LOG_WARN("LWO2: Failure evaluating VMAD entry \'", name, "\', polygon index is out of range");
                    mFileBuffer += base->dims << 2u;
                    continue;
                }

                LWO::Face &src = list[polyIdx];

                // generate a new unique vertex for the corresponding index - but only
                // if we can find the index in the face
                bool had = false;
                for (unsigned int i = 0; i < src.mNumIndices; ++i) {

                    unsigned int srcIdx = src.mIndices[i], tmp = idx;
                    do {
                        if (tmp == srcIdx)
                            break;
                    } while ((tmp = refList[tmp]) != UINT_MAX);
                    if (tmp == UINT_MAX) {
                        continue;
                    }

                    had = true;
                    refList.resize(refList.size() + 1, UINT_MAX);

                    idx = (unsigned int)pointList.size();
                    src.mIndices[i] = (unsigned int)pointList.size();

                    // store the index of the new vertex in the old vertex
                    // so we get a single linked list we can traverse in
                    // only one direction
                    AddToSingleLinkedList(refList, srcIdx, src.mIndices[i]);
                    pointList.push_back(pointList[srcIdx]);

                    CreateNewEntry(mCurLayer->mVColorChannels, srcIdx);
                    CreateNewEntry(mCurLayer->mUVChannels, srcIdx);
                    CreateNewEntry(mCurLayer->mWeightChannels, srcIdx);
                    CreateNewEntry(mCurLayer->mSWeightChannels, srcIdx);
                    CreateNewEntry(mCurLayer->mNormals, srcIdx);
                }
                if (!had) {
                    ASSIMP_LOG_WARN("LWO2: Failure evaluating VMAD entry \'", name, "\', vertex index wasn't found in that polygon");
                    ai_assert(had);
                }
            }
        }

        std::unique_ptr<float[]> temp(new float[type]);
        for (unsigned int l = 0; l < type; ++l)
            temp[l] = GetF4();

        DoRecursiveVMAPAssignment(base, type, idx, temp.get());
        mFileBuffer += diff;
    }
}

// ------------------------------------------------------------------------------------------------
// Load LWO2 clip
void LWOImporter::LoadLWO2Clip(unsigned int length) {
    AI_LWO_VALIDATE_CHUNK_LENGTH(length, CLIP, 10);

    mClips.emplace_back();
    LWO::Clip &clip = mClips.back();

    // first - get the index of the clip
    clip.idx = GetU4();

    IFF::SubChunkHeader head = IFF::LoadSubChunk(mFileBuffer);
    switch (head.type) {
        case AI_LWO_STIL:
            AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, STIL, 1);

            // "Normal" texture
            GetS0(clip.path, head.length);
            clip.type = Clip::STILL;
            break;

        case AI_LWO_ISEQ:
            AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, ISEQ, 16);
            // Image sequence. We'll later take the first.
            {
                uint8_t digits = GetU1();
                mFileBuffer++;
                int16_t offset = GetU2();
                mFileBuffer += 4;
                int16_t start = GetU2();
                mFileBuffer += 4;

                std::string s;
                std::ostringstream ss;
                GetS0(s, head.length);

                head.length -= (uint16_t)s.length() + 1;
                ss << s;
                ss << std::setw(digits) << offset + start;
                GetS0(s, head.length);
                ss << s;
                clip.path = ss.str();
                clip.type = Clip::SEQ;
            }
            break;

        case AI_LWO_STCC:
            ASSIMP_LOG_WARN("LWO2: Color shifted images are not supported");
            break;

        case AI_LWO_ANIM:
            ASSIMP_LOG_WARN("LWO2: Animated textures are not supported");
            break;

        case AI_LWO_XREF:
            AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, XREF, 4);

            // Just a cross-reference to another CLIp
            clip.type = Clip::REF;
            clip.clipRef = GetU4();
            break;

        case AI_LWO_NEGA:
            AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, NEGA, 2);
            clip.negate = (0 != GetU2());
            break;

        default:
            ASSIMP_LOG_WARN("LWO2: Encountered unknown CLIP sub-chunk");
    }
}

void LWOImporter::LoadLWO3Clip(unsigned int length) {
    AI_LWO_VALIDATE_CHUNK_LENGTH(length, CLIP, 12);

    mClips.emplace_back();
    LWO::Clip &clip = mClips.back();

    // first - get the index of the clip
    clip.idx = GetU4();

    IFF::ChunkHeader head = IFF::LoadChunk(mFileBuffer);
    switch (head.type) {
        case AI_LWO_STIL:
            AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, STIL, 1);

            // "Normal" texture
            GetS0(clip.path, head.length);
            clip.type = Clip::STILL;
            break;

        case AI_LWO_ISEQ:
            AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, ISEQ, 16);
            // Image sequence. We'll later take the first.
            {
                uint8_t digits = GetU1();
                mFileBuffer++;
                int16_t offset = GetU2();
                mFileBuffer += 4;
                int16_t start = GetU2();
                mFileBuffer += 4;

                std::string s;
                std::ostringstream ss;
                GetS0(s, head.length);

                head.length -= (uint16_t)s.length() + 1;
                ss << s;
                ss << std::setw(digits) << offset + start;
                GetS0(s, head.length);
                ss << s;
                clip.path = ss.str();
                clip.type = Clip::SEQ;
            }
            break;

        case AI_LWO_STCC:
            ASSIMP_LOG_WARN("LWO3: Color shifted images are not supported");
            break;

        case AI_LWO_ANIM:
            ASSIMP_LOG_WARN("LWO3: Animated textures are not supported");
            break;

        case AI_LWO_XREF:
            AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, XREF, 4);

            // Just a cross-reference to another CLIp
            clip.type = Clip::REF;
            clip.clipRef = GetU4();
            break;

        case AI_LWO_NEGA:
            AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, NEGA, 2);
            clip.negate = (0 != GetU2());
            break;

        default:
            ASSIMP_LOG_WARN("LWO3: Encountered unknown CLIP sub-chunk");
    }
}

// ------------------------------------------------------------------------------------------------
// Load envelope description
void LWOImporter::LoadLWO2Envelope(unsigned int length) {
    LE_NCONST uint8_t *const end = mFileBuffer + length;
    AI_LWO_VALIDATE_CHUNK_LENGTH(length, ENVL, 4);

    mEnvelopes.emplace_back();
    LWO::Envelope &envelope = mEnvelopes.back();

    // Get the index of the envelope
    envelope.index = ReadVSizedIntLWO2(mFileBuffer);

    // It looks like there might be an extra U4 right after the index,
    // at least in modo (LXOB) files: we'll ignore it if it's zero,
    // otherwise it represents the start of a subchunk, so we backtrack.
    if (mIsLXOB) {
        uint32_t extra = GetU4();
        if (extra) {
            mFileBuffer -= 4;
        }
    }

    // ... and read all subchunks
    while (true) {
        if (mFileBuffer + 6 >= end) break;
        LE_NCONST IFF::SubChunkHeader head = IFF::LoadSubChunk(mFileBuffer);

        if (mFileBuffer + head.length > end)
            throw DeadlyImportError("LWO2: Invalid envelope chunk length");

        uint8_t *const next = mFileBuffer + head.length;
        switch (head.type) {
                // Type & representation of the envelope
            case AI_LWO_TYPE:
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, TYPE, 2);
                mFileBuffer++; // skip user format

                // Determine type of envelope
                envelope.type = (LWO::EnvelopeType)*mFileBuffer;
                ++mFileBuffer;
                break;

                // precondition
            case AI_LWO_PRE:
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, PRE, 2);
                envelope.pre = (LWO::PrePostBehaviour)GetU2();
                break;

                // postcondition
            case AI_LWO_POST:
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, POST, 2);
                envelope.post = (LWO::PrePostBehaviour)GetU2();
                break;

                // keyframe
            case AI_LWO_KEY: {
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, KEY, 8);

                envelope.keys.emplace_back();
                LWO::Key &key = envelope.keys.back();

                key.time = GetF4();
                key.value = GetF4();
                break;
            }

                // interval interpolation
            case AI_LWO_SPAN: {
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, SPAN, 4);
                if (envelope.keys.size() < 2)
                    ASSIMP_LOG_WARN("LWO2: Unexpected SPAN chunk");
                else {
                    LWO::Key &key = envelope.keys.back();
                    switch (GetU4()) {
                        case AI_LWO_STEP:
                            key.inter = LWO::IT_STEP;
                            break;
                        case AI_LWO_LINE:
                            key.inter = LWO::IT_LINE;
                            break;
                        case AI_LWO_TCB:
                            key.inter = LWO::IT_TCB;
                            break;
                        case AI_LWO_HERM:
                            key.inter = LWO::IT_HERM;
                            break;
                        case AI_LWO_BEZI:
                            key.inter = LWO::IT_BEZI;
                            break;
                        case AI_LWO_BEZ2:
                            key.inter = LWO::IT_BEZ2;
                            break;
                        default:
                            ASSIMP_LOG_WARN("LWO2: Unknown interval interpolation mode");
                    };

                    // todo ... read params
                }
                break;
            }

            default:
                ASSIMP_LOG_WARN("LWO2: Encountered unknown ENVL subchunk");
                break;
        }
        // regardless how much we did actually read, go to the next chunk
        mFileBuffer = next;
    }
}

void LWOImporter::LoadLWO3Envelope(unsigned int length) {
    LE_NCONST uint8_t *const end = mFileBuffer + length;
    AI_LWO_VALIDATE_CHUNK_LENGTH(length, ENVL, 4);

    mEnvelopes.emplace_back();
    LWO::Envelope &envelope = mEnvelopes.back();

    // Get the index of the envelope
    envelope.index = ReadVSizedIntLWO2(mFileBuffer);

    // ... and read all blocks
    while (true) {
        if (mFileBuffer + 8 >= end) break;
        LE_NCONST IFF::ChunkHeader head = IFF::LoadChunk(mFileBuffer);

        if (mFileBuffer + head.length > end)
            throw DeadlyImportError("LWO3: Invalid envelope chunk length");

        uint8_t *const next = mFileBuffer + head.length;
        switch (head.type) {
                // Type & representation of the envelope
            case AI_LWO_TYPE:
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, TYPE, 4);
                mFileBuffer++; // skip user format

                // Determine type of envelope
                envelope.type = (LWO::EnvelopeType)*mFileBuffer;
                ++mFileBuffer;
                break;

                // precondition
            case AI_LWO_PRE:
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, PRE, 4);
                envelope.pre = (LWO::PrePostBehaviour)GetU2();
                break;

                // postcondition
            case AI_LWO_POST:
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, POST, 4);
                envelope.post = (LWO::PrePostBehaviour)GetU2();
                break;

                // keyframe
            case AI_LWO_KEY: {
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, KEY, 10);

                envelope.keys.emplace_back();
                LWO::Key &key = envelope.keys.back();

                key.time = GetF4();
                key.value = GetF4();
                break;
            }

                // interval interpolation
            case AI_LWO_SPAN: {
                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, SPAN, 6);
                if (envelope.keys.size() < 2)
                    ASSIMP_LOG_WARN("LWO3: Unexpected SPAN chunk");
                else {
                    LWO::Key &key = envelope.keys.back();
                    switch (GetU4()) {
                        case AI_LWO_STEP:
                            key.inter = LWO::IT_STEP;
                            break;
                        case AI_LWO_LINE:
                            key.inter = LWO::IT_LINE;
                            break;
                        case AI_LWO_TCB:
                            key.inter = LWO::IT_TCB;
                            break;
                        case AI_LWO_HERM:
                            key.inter = LWO::IT_HERM;
                            break;
                        case AI_LWO_BEZI:
                            key.inter = LWO::IT_BEZI;
                            break;
                        case AI_LWO_BEZ2:
                            key.inter = LWO::IT_BEZ2;
                            break;
                        default:
                            ASSIMP_LOG_WARN("LWO3: Unknown interval interpolation mode");
                    };

                    // todo ... read params
                }
                break;
            }

            default:
                ASSIMP_LOG_WARN("LWO3: Encountered unknown ENVL subchunk");
                break;
        }
        // regardless how much we did actually read, go to the next chunk
        mFileBuffer = next;
    }
}

// ------------------------------------------------------------------------------------------------
// Load file - master function
void LWOImporter::LoadLWO2File() {
    bool skip = false;

    LE_NCONST uint8_t *const end = mFileBuffer + fileSize;
    unsigned int iUnnamed = 0;

    while (true) {
        if (mFileBuffer + sizeof(IFF::ChunkHeader) > end) break;

        IFF::ChunkHeader head = IFF::LoadChunk(mFileBuffer);

        int bufOffset = 0;
        if( head.type == AI_IFF_FOURCC_FORM ) { // not chunk, it's a form
            mFileBuffer -= 8;
            head = IFF::LoadForm(mFileBuffer);
            bufOffset = 4;
        }

        if (mFileBuffer + head.length > end) {
            throw DeadlyImportError("LWO2: Chunk length points behind the file");
            break;
        }
        uint8_t *const next = mFileBuffer + head.length;
        mFileBuffer += bufOffset;
        if (!head.length) {
            mFileBuffer = next;
            continue;
        }

        switch (head.type) {
                // new layer
            case AI_LWO_LAYR: {
                // add a new layer to the list ....
                mLayers->push_back(LWO::Layer());
                LWO::Layer &layer = mLayers->back();
                mCurLayer = &layer;

                AI_LWO_VALIDATE_CHUNK_LENGTH(head.length, LAYR, 16);

                // layer index.
                layer.mIndex = GetU2();

                // Continue loading this layer or ignore it? Check the layer index property
                if (UINT_MAX != configLayerIndex && (configLayerIndex - 1) != layer.mIndex) {
                    skip = true;
                } else
                    skip = false;

                // pivot point
                mFileBuffer += 2; /* unknown */
                mCurLayer->mPivot.x = GetF4();
                mCurLayer->mPivot.y = GetF4();
                mCurLayer->mPivot.z = GetF4();
                GetS0(layer.mName, head.length - 16);

                // if the name is empty, generate a default name
                if (layer.mName.empty()) {
                    char buffer[128]; // should be sufficiently large
                    ::ai_snprintf(buffer, 128, "Layer_%i", iUnnamed++);
                    layer.mName = buffer;
                }

                // load this layer or ignore it? Check the layer name property
                if (configLayerName.length() && configLayerName != layer.mName) {
                    skip = true;
                } else
                    hasNamedLayer = true;

                // optional: parent of this layer
                if (mFileBuffer + 2 <= next)
                    layer.mParent = GetU2();
                else
                    layer.mParent = (uint16_t) -1;

                // Set layer skip parameter
                layer.skip = skip;

                break;
            }
                // vertex list
            case AI_LWO_PNTS: {
                if (skip)
                    break;

                unsigned int old = (unsigned int)mCurLayer->mTempPoints.size();
                LoadLWOPoints(head.length);
                mCurLayer->mPointIDXOfs = old;
                break;
            }
                // vertex tags
            case AI_LWO_VMAD:
                if (mCurLayer->mFaces.empty()) {
                    ASSIMP_LOG_WARN("LWO2: Unexpected VMAD chunk");
                    break;
                }
                // --- intentionally no break here
                // fallthrough
            case AI_LWO_VMAP: {
                if (skip)
                    break;

                if (mCurLayer->mTempPoints.empty())
                    ASSIMP_LOG_WARN("LWO2: Unexpected VMAP chunk");
                else
                    LoadLWO2VertexMap(head.length, head.type == AI_LWO_VMAD);
                break;
            }
                // face list
            case AI_LWO_POLS: {
                if (skip)
                    break;

                unsigned int old = (unsigned int)mCurLayer->mFaces.size();
                LoadLWO2Polygons(head.length);
                mCurLayer->mFaceIDXOfs = old;
                break;
            }
                // polygon tags
            case AI_LWO_PTAG: {
                if (skip)
                    break;

                if (mCurLayer->mFaces.empty()) {
                    ASSIMP_LOG_WARN("LWO2: Unexpected PTAG");
                } else {
                    LoadLWO2PolygonTags(head.length);
                }
                break;
            }
                // list of tags
            case AI_LWO_TAGS: {
                if (!mTags->empty()) {
                    ASSIMP_LOG_WARN("LWO2: SRFS chunk encountered twice");
                } else {
                    LoadLWOTags(head.length);
                }
                break;
            }

                // surface chunk
            case AI_LWO_SURF: {
                if( mIsLWO3 )
                    LoadLWO3Surface(head.length);
                else
                    LoadLWO2Surface(head.length);

                break;
            }

                // clip chunk
            case AI_LWO_CLIP: {
                if( mIsLWO3 )
                    LoadLWO3Clip(head.length);
                else
                    LoadLWO2Clip(head.length);
                break;
            }

                // envelope chunk
            case AI_LWO_ENVL: {
                if( mIsLWO3 )
                    LoadLWO3Envelope(head.length);
                else
                    LoadLWO2Envelope(head.length);
                break;
            }
        }
        mFileBuffer = next;
    }
}

#endif // !! ASSIMP_BUILD_NO_LWO_IMPORTER