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*/

/** @file MDLLoader.cpp
 *  @brief Implementation of the main parts of the MDL importer class
 *  *TODO* Cleanup and further testing of some parts necessary
 */

// internal headers

#ifndef ASSIMP_BUILD_NO_MDL_IMPORTER

#include "MDLLoader.h"
#include "AssetLib/MD2/MD2FileData.h"
#include "HalfLife/HL1MDLLoader.h"
#include "MDLDefaultColorMap.h"

#include <assimp/StringUtils.h>
#include <assimp/importerdesc.h>
#include <assimp/qnan.h>
#include <assimp/scene.h>
#include <assimp/DefaultLogger.hpp>
#include <assimp/IOSystem.hpp>
#include <assimp/Importer.hpp>

#include <memory>

using namespace Assimp;

static constexpr aiImporterDesc desc = {
    "Quake Mesh / 3D GameStudio Mesh Importer",
    "",
    "",
    "",
    aiImporterFlags_SupportBinaryFlavour,
    0,
    0,
    7,
    0,
    "mdl"
};

// ------------------------------------------------------------------------------------------------
// Ugly stuff ... nevermind
#define _AI_MDL7_ACCESS(_data, _index, _limit, _type) \
    (*((const _type *)(((const char *)_data) + _index * _limit)))

#define _AI_MDL7_ACCESS_PTR(_data, _index, _limit, _type) \
    ((BE_NCONST _type *)(((const char *)_data) + _index * _limit))

#define _AI_MDL7_ACCESS_VERT(_data, _index, _limit) \
    _AI_MDL7_ACCESS(_data, _index, _limit, MDL::Vertex_MDL7)

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
MDLImporter::MDLImporter() :
        configFrameID(), mBuffer(), iGSFileVersion(), mIOHandler(nullptr), pScene(), iFileSize() {
    // empty
}

// ------------------------------------------------------------------------------------------------
// Returns whether the class can handle the format of the given file.
bool MDLImporter::CanRead(const std::string &pFile, IOSystem *pIOHandler, bool /*checkSig*/) const {
    static constexpr uint32_t tokens[] = {
        AI_MDL_MAGIC_NUMBER_LE_HL2a,
        AI_MDL_MAGIC_NUMBER_LE_HL2b,
        AI_MDL_MAGIC_NUMBER_LE_GS7,
        AI_MDL_MAGIC_NUMBER_LE_GS5b,
        AI_MDL_MAGIC_NUMBER_LE_GS5a,
        AI_MDL_MAGIC_NUMBER_LE_GS4,
        AI_MDL_MAGIC_NUMBER_LE_GS3,
        AI_MDL_MAGIC_NUMBER_LE
    };
    return CheckMagicToken(pIOHandler, pFile, tokens, AI_COUNT_OF(tokens));
}

// ------------------------------------------------------------------------------------------------
// Setup configuration properties
void MDLImporter::SetupProperties(const Importer *pImp) {
    configFrameID = pImp->GetPropertyInteger(AI_CONFIG_IMPORT_MDL_KEYFRAME, -1);

    // The
    // AI_CONFIG_IMPORT_MDL_KEYFRAME option overrides the
    // AI_CONFIG_IMPORT_GLOBAL_KEYFRAME option.
    if (static_cast<unsigned int>(-1) == configFrameID) {
        configFrameID = pImp->GetPropertyInteger(AI_CONFIG_IMPORT_GLOBAL_KEYFRAME, 0);
    }

    // AI_CONFIG_IMPORT_MDL_COLORMAP - palette file
    configPalette = pImp->GetPropertyString(AI_CONFIG_IMPORT_MDL_COLORMAP, "colormap.lmp");

    // Read configuration specific to MDL (Half-Life 1).
    mHL1ImportSettings.read_animations = pImp->GetPropertyBool(AI_CONFIG_IMPORT_MDL_HL1_READ_ANIMATIONS, true);
    if (mHL1ImportSettings.read_animations) {
        mHL1ImportSettings.read_animation_events = pImp->GetPropertyBool(AI_CONFIG_IMPORT_MDL_HL1_READ_ANIMATION_EVENTS, true);
        mHL1ImportSettings.read_blend_controllers = pImp->GetPropertyBool(AI_CONFIG_IMPORT_MDL_HL1_READ_BLEND_CONTROLLERS, true);
        mHL1ImportSettings.read_sequence_transitions = pImp->GetPropertyBool(AI_CONFIG_IMPORT_MDL_HL1_READ_SEQUENCE_TRANSITIONS, true);
    }
    mHL1ImportSettings.read_attachments = pImp->GetPropertyBool(AI_CONFIG_IMPORT_MDL_HL1_READ_ATTACHMENTS, true);
    mHL1ImportSettings.read_bone_controllers = pImp->GetPropertyBool(AI_CONFIG_IMPORT_MDL_HL1_READ_BONE_CONTROLLERS, true);
    mHL1ImportSettings.read_hitboxes = pImp->GetPropertyBool(AI_CONFIG_IMPORT_MDL_HL1_READ_HITBOXES, true);
    mHL1ImportSettings.read_misc_global_info = pImp->GetPropertyBool(AI_CONFIG_IMPORT_MDL_HL1_READ_MISC_GLOBAL_INFO, true);
    mHL1ImportSettings.transform_coord_system = pImp->GetPropertyBool(AI_CONFIG_IMPORT_MDL_HL1_TRANSFORM_COORD_SYSTEM);
}

// ------------------------------------------------------------------------------------------------
// Get a list of all supported extensions
const aiImporterDesc *MDLImporter::GetInfo() const {
    return &desc;
}

// ------------------------------------------------------------------------------------------------
static void transformCoordinateSystem(const aiScene *pScene) {
    if (pScene == nullptr) {
        return;
    }

    pScene->mRootNode->mTransformation = aiMatrix4x4(
        0.f, -1.f, 0.f, 0.f,
        0.f, 0.f, 1.f, 0.f,
        -1.f, 0.f, 0.f, 0.f,
        0.f, 0.f, 0.f, 1.f
    );
}

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

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

    // This should work for all other types of MDL files, too ...
    // the HL1 sequence group header is one of the smallest, afaik
    iFileSize = (unsigned int)file->FileSize();
    if (iFileSize < sizeof(MDL::HalfLife::SequenceHeader_HL1)) {
        throw DeadlyImportError("MDL File is too small.");
    }

    // delete the file buffer and cleanup.
    auto DeleteBufferAndCleanup = [&]() {
        if (mBuffer) {
            delete[] mBuffer;
            mBuffer = nullptr;
        }
        AI_DEBUG_INVALIDATE_PTR(mIOHandler);
        AI_DEBUG_INVALIDATE_PTR(pScene);
    };

    try {
        // Allocate storage and copy the contents of the file to a memory buffer
        mBuffer = new unsigned char[iFileSize + 1];
        file->Read((void *)mBuffer, 1, iFileSize);

        // Append a binary zero to the end of the buffer.
        // this is just for safety that string parsing routines
        // find the end of the buffer ...
        mBuffer[iFileSize] = '\0';
        const uint32_t iMagicWord = *((uint32_t *)mBuffer);

        // Determine the file subtype and call the appropriate member function
        bool is_half_life = false;

        // Original Quake1 format
        if (AI_MDL_MAGIC_NUMBER_BE == iMagicWord || AI_MDL_MAGIC_NUMBER_LE == iMagicWord) {
            ASSIMP_LOG_DEBUG("MDL subtype: Quake 1, magic word is IDPO");
            iGSFileVersion = 0;
            InternReadFile_Quake1();
        }
        // GameStudio A<old> MDL2 format - used by some test models that come with 3DGS
        else if (AI_MDL_MAGIC_NUMBER_BE_GS3 == iMagicWord || AI_MDL_MAGIC_NUMBER_LE_GS3 == iMagicWord) {
            ASSIMP_LOG_DEBUG("MDL subtype: 3D GameStudio A2, magic word is MDL2");
            iGSFileVersion = 2;
            InternReadFile_Quake1();
        }
        // GameStudio A4 MDL3 format
        else if (AI_MDL_MAGIC_NUMBER_BE_GS4 == iMagicWord || AI_MDL_MAGIC_NUMBER_LE_GS4 == iMagicWord) {
            ASSIMP_LOG_DEBUG("MDL subtype: 3D GameStudio A4, magic word is MDL3");
            iGSFileVersion = 3;
            InternReadFile_3DGS_MDL345();
        }
        // GameStudio A5+ MDL4 format
        else if (AI_MDL_MAGIC_NUMBER_BE_GS5a == iMagicWord || AI_MDL_MAGIC_NUMBER_LE_GS5a == iMagicWord) {
            ASSIMP_LOG_DEBUG("MDL subtype: 3D GameStudio A4, magic word is MDL4");
            iGSFileVersion = 4;
            InternReadFile_3DGS_MDL345();
        }
        // GameStudio A5+ MDL5 format
        else if (AI_MDL_MAGIC_NUMBER_BE_GS5b == iMagicWord || AI_MDL_MAGIC_NUMBER_LE_GS5b == iMagicWord) {
            ASSIMP_LOG_DEBUG("MDL subtype: 3D GameStudio A5, magic word is MDL5");
            iGSFileVersion = 5;
            InternReadFile_3DGS_MDL345();
        }
        // GameStudio A7 MDL7 format
        else if (AI_MDL_MAGIC_NUMBER_BE_GS7 == iMagicWord || AI_MDL_MAGIC_NUMBER_LE_GS7 == iMagicWord) {
            ASSIMP_LOG_DEBUG("MDL subtype: 3D GameStudio A7, magic word is MDL7");
            iGSFileVersion = 7;
            InternReadFile_3DGS_MDL7();
        }
        // IDST/IDSQ Format (CS:S/HL^2, etc ...)
        else if (AI_MDL_MAGIC_NUMBER_BE_HL2a == iMagicWord || AI_MDL_MAGIC_NUMBER_LE_HL2a == iMagicWord ||
                 AI_MDL_MAGIC_NUMBER_BE_HL2b == iMagicWord || AI_MDL_MAGIC_NUMBER_LE_HL2b == iMagicWord) {
            iGSFileVersion = 0;
            is_half_life = true;

            HalfLife::HalfLifeMDLBaseHeader *pHeader = (HalfLife::HalfLifeMDLBaseHeader *)mBuffer;
            if (pHeader->version == AI_MDL_HL1_VERSION) {
                ASSIMP_LOG_DEBUG("MDL subtype: Half-Life 1/Goldsrc Engine, magic word is IDST/IDSQ");
                InternReadFile_HL1(pFile, iMagicWord);
            } else {
                ASSIMP_LOG_DEBUG("MDL subtype: Source(tm) Engine, magic word is IDST/IDSQ");
                InternReadFile_HL2();
            }
        } else {
            // print the magic word to the log file
            throw DeadlyImportError("Unknown MDL subformat ", pFile,
                                    ". Magic word (", ai_str_toprintable((const char *)&iMagicWord, sizeof(iMagicWord)), ") is not known");
        }

        if (is_half_life && mHL1ImportSettings.transform_coord_system) {
            // Now rotate the whole scene 90 degrees around the z and x axes to convert to internal coordinate system
            transformCoordinateSystem(pScene);
        } else {
            // Now rotate the whole scene 90 degrees around the x axis to convert to internal coordinate system
            pScene->mRootNode->mTransformation = aiMatrix4x4(
                1.f,  0.f, 0.f, 0.f,
                0.f,  0.f, 1.f, 0.f,
                0.f, -1.f, 0.f, 0.f,
                0.f,  0.f, 0.f, 1.f);
        }

        DeleteBufferAndCleanup();
    } catch (...) {
        DeleteBufferAndCleanup();
        throw;
    }
}

// ------------------------------------------------------------------------------------------------
// Check whether we're still inside the valid file range
bool MDLImporter::IsPosValid(const void *szPos) const {
    return szPos && (const unsigned char *)szPos <= this->mBuffer + this->iFileSize && szPos >= this->mBuffer;
}

// ------------------------------------------------------------------------------------------------
// Check whether we're still inside the valid file range
void MDLImporter::SizeCheck(const void *szPos) {
    if (!IsPosValid(szPos)) {
        throw DeadlyImportError("Invalid MDL file. The file is too small "
                                "or contains invalid data.");
    }
}

// ------------------------------------------------------------------------------------------------
// Just for debugging purposes
void MDLImporter::SizeCheck(const void *szPos, const char *szFile, unsigned int iLine) {
    ai_assert(nullptr != szFile);
    if (!IsPosValid(szPos)) {
        // remove a directory if there is one
        const char *szFilePtr = ::strrchr(szFile, '\\');
        if (!szFilePtr) {
            szFilePtr = ::strrchr(szFile, '/');
            if (nullptr == szFilePtr) {
                szFilePtr = szFile;
            }
        }
        if (szFilePtr) {
            ++szFilePtr;
        }

        char szBuffer[1024];
        ::snprintf(szBuffer, sizeof(szBuffer), "Invalid MDL file. The file is too small "
                            "or contains invalid data (File: %s Line: %u)",
                szFilePtr, iLine);

        throw DeadlyImportError(szBuffer);
    }
}

// ------------------------------------------------------------------------------------------------
// Validate a quake file header
void MDLImporter::ValidateHeader_Quake1(const MDL::Header *pcHeader) {
    // some values may not be nullptr
    if (pcHeader->num_frames <= 0)
        throw DeadlyImportError("[Quake 1 MDL] There are no frames in the file");

    if (pcHeader->num_verts <= 0)
        throw DeadlyImportError("[Quake 1 MDL] There are no vertices in the file");

    if (pcHeader->num_tris <= 0)
        throw DeadlyImportError("[Quake 1 MDL] There are no triangles in the file");

    // check whether the maxima are exceeded ...however, this applies for Quake 1 MDLs only
    if (!this->iGSFileVersion) {
        if (pcHeader->num_verts > AI_MDL_MAX_VERTS)
            ASSIMP_LOG_WARN("Quake 1 MDL model has more than AI_MDL_MAX_VERTS vertices");

        if (pcHeader->num_tris > AI_MDL_MAX_TRIANGLES)
            ASSIMP_LOG_WARN("Quake 1 MDL model has more than AI_MDL_MAX_TRIANGLES triangles");

        if (pcHeader->num_frames > AI_MDL_MAX_FRAMES)
            ASSIMP_LOG_WARN("Quake 1 MDL model has more than AI_MDL_MAX_FRAMES frames");

        // (this does not apply for 3DGS MDLs)
        if (!this->iGSFileVersion && pcHeader->version != AI_MDL_VERSION)
            ASSIMP_LOG_WARN("Quake 1 MDL model has an unknown version: AI_MDL_VERSION (=6) is "
                            "the expected file format version");
        if (pcHeader->num_skins && (!pcHeader->skinwidth || !pcHeader->skinheight))
            ASSIMP_LOG_WARN("Skin width or height are 0");
    }
}

#ifdef AI_BUILD_BIG_ENDIAN
// ------------------------------------------------------------------------------------------------
void FlipQuakeHeader(BE_NCONST MDL::Header *pcHeader) {
    AI_SWAP4(pcHeader->ident);
    AI_SWAP4(pcHeader->version);
    AI_SWAP4(pcHeader->boundingradius);
    AI_SWAP4(pcHeader->flags);
    AI_SWAP4(pcHeader->num_frames);
    AI_SWAP4(pcHeader->num_skins);
    AI_SWAP4(pcHeader->num_tris);
    AI_SWAP4(pcHeader->num_verts);
    for (unsigned int i = 0; i < 3; ++i) {
        AI_SWAP4(pcHeader->scale[i]);
        AI_SWAP4(pcHeader->translate[i]);
    }
    AI_SWAP4(pcHeader->size);
    AI_SWAP4(pcHeader->skinheight);
    AI_SWAP4(pcHeader->skinwidth);
    AI_SWAP4(pcHeader->synctype);
}
#endif

// ------------------------------------------------------------------------------------------------
// Read a Quake 1 file
void MDLImporter::InternReadFile_Quake1() {
    ai_assert(nullptr != pScene);

    BE_NCONST MDL::Header *pcHeader = (BE_NCONST MDL::Header *)this->mBuffer;

#ifdef AI_BUILD_BIG_ENDIAN
    FlipQuakeHeader(pcHeader);
#endif

    ValidateHeader_Quake1(pcHeader);

    // current cursor position in the file
    const unsigned char *szCurrent = (const unsigned char *)(pcHeader + 1);

    // need to read all textures
    for (unsigned int i = 0; i < (unsigned int)pcHeader->num_skins; ++i) {
        union {
            BE_NCONST MDL::Skin *pcSkin;
            BE_NCONST MDL::GroupSkin *pcGroupSkin;
        };
        if (szCurrent + sizeof(MDL::Skin) > this->mBuffer + this->iFileSize) {
            throw DeadlyImportError("[Quake 1 MDL] Unexpected EOF");
        }
        pcSkin = (BE_NCONST MDL::Skin *)szCurrent;

        AI_SWAP4(pcSkin->group);

        // Quake 1 group-skins
        if (1 == pcSkin->group) {
            AI_SWAP4(pcGroupSkin->nb);

            // need to skip multiple images
            const unsigned int iNumImages = (unsigned int)pcGroupSkin->nb;
            szCurrent += sizeof(uint32_t) * 2;

            if (0 != iNumImages) {
                if (!i) {
                    // however, create only one output image (the first)
                    this->CreateTextureARGB8_3DGS_MDL3(szCurrent + iNumImages * sizeof(float));
                }
                // go to the end of the skin section / the beginning of the next skin
                bool overflow = false;
                if (pcHeader->skinwidth != 0 && pcHeader->skinheight != 0) {
                    if ((pcHeader->skinheight > INT_MAX / pcHeader->skinwidth) || (pcHeader->skinwidth > INT_MAX / pcHeader->skinheight)){
                        overflow = true;
                    }
                    if (!overflow) {
                        szCurrent += pcHeader->skinheight * pcHeader->skinwidth +sizeof(float) * iNumImages;
                    }
                }
            }
        } else {
            szCurrent += sizeof(uint32_t);
            unsigned int iSkip = i ? UINT_MAX : 0;
            CreateTexture_3DGS_MDL4(szCurrent, pcSkin->group, &iSkip);
            szCurrent += iSkip;
        }
    }
    // get a pointer to the texture coordinates
    BE_NCONST MDL::TexCoord *pcTexCoords = (BE_NCONST MDL::TexCoord *)szCurrent;
    szCurrent += sizeof(MDL::TexCoord) * pcHeader->num_verts;

    // get a pointer to the triangles
    BE_NCONST MDL::Triangle *pcTriangles = (BE_NCONST MDL::Triangle *)szCurrent;
    szCurrent += sizeof(MDL::Triangle) * pcHeader->num_tris;
    VALIDATE_FILE_SIZE(szCurrent);

    // now get a pointer to the first frame in the file
    BE_NCONST MDL::Frame *pcFrames = (BE_NCONST MDL::Frame *)szCurrent;
    MDL::SimpleFrame *pcFirstFrame;

    if (0 == pcFrames->type) {
        // get address of single frame
        pcFirstFrame = (MDL::SimpleFrame *)&pcFrames->frame;
    } else {
        // get the first frame in the group
        BE_NCONST MDL::GroupFrame *pcFrames2 = (BE_NCONST MDL::GroupFrame *)szCurrent;
        pcFirstFrame = (MDL::SimpleFrame *)( szCurrent + sizeof(MDL::GroupFrame::type) + sizeof(MDL::GroupFrame::numframes)
        + sizeof(MDL::GroupFrame::min) + sizeof(MDL::GroupFrame::max) + sizeof(*MDL::GroupFrame::times) * pcFrames2->numframes );
    }
    BE_NCONST MDL::Vertex *pcVertices = (BE_NCONST MDL::Vertex *)((pcFirstFrame->name) + sizeof(pcFirstFrame->name));
    VALIDATE_FILE_SIZE((const unsigned char *)(pcVertices + pcHeader->num_verts));

#ifdef AI_BUILD_BIG_ENDIAN
    for (int i = 0; i < pcHeader->num_verts; ++i) {
        AI_SWAP4(pcTexCoords[i].onseam);
        AI_SWAP4(pcTexCoords[i].s);
        AI_SWAP4(pcTexCoords[i].t);
    }

    for (int i = 0; i < pcHeader->num_tris; ++i) {
        AI_SWAP4(pcTriangles[i].facesfront);
        AI_SWAP4(pcTriangles[i].vertex[0]);
        AI_SWAP4(pcTriangles[i].vertex[1]);
        AI_SWAP4(pcTriangles[i].vertex[2]);
    }
#endif

    // setup materials
    SetupMaterialProperties_3DGS_MDL5_Quake1();

    // allocate enough storage to hold all vertices and triangles
    aiMesh *pcMesh = new aiMesh();

    pcMesh->mPrimitiveTypes = aiPrimitiveType_TRIANGLE;
    pcMesh->mNumVertices = pcHeader->num_tris * 3;
    pcMesh->mNumFaces = pcHeader->num_tris;
    pcMesh->mVertices = new aiVector3D[pcMesh->mNumVertices];
    pcMesh->mTextureCoords[0] = new aiVector3D[pcMesh->mNumVertices];
    pcMesh->mFaces = new aiFace[pcMesh->mNumFaces];
    pcMesh->mNormals = new aiVector3D[pcMesh->mNumVertices];
    pcMesh->mNumUVComponents[0] = 2;

    // there won't be more than one mesh inside the file
    pScene->mRootNode = new aiNode();
    pScene->mRootNode->mNumMeshes = 1;
    pScene->mRootNode->mMeshes = new unsigned int[1];
    pScene->mRootNode->mMeshes[0] = 0;
    pScene->mNumMeshes = 1;
    pScene->mMeshes = new aiMesh *[1];
    pScene->mMeshes[0] = pcMesh;

    // now iterate through all triangles
    unsigned int iCurrent = 0;
    for (unsigned int i = 0; i < (unsigned int)pcHeader->num_tris; ++i) {
        pcMesh->mFaces[i].mIndices = new unsigned int[3];
        pcMesh->mFaces[i].mNumIndices = 3;

        unsigned int iTemp = iCurrent;
        for (unsigned int c = 0; c < 3; ++c, ++iCurrent) {
            pcMesh->mFaces[i].mIndices[c] = iCurrent;

            // read vertices
            unsigned int iIndex = pcTriangles->vertex[c];
            if (iIndex >= (unsigned int)pcHeader->num_verts) {
                iIndex = pcHeader->num_verts - 1;
                ASSIMP_LOG_WARN("Index overflow in Q1-MDL vertex list.");
            }

            aiVector3D &vec = pcMesh->mVertices[iCurrent];
            vec.x = (float)pcVertices[iIndex].v[0] * pcHeader->scale[0];
            vec.x += pcHeader->translate[0];

            vec.y = (float)pcVertices[iIndex].v[1] * pcHeader->scale[1];
            vec.y += pcHeader->translate[1];
            //vec.y *= -1.0f;

            vec.z = (float)pcVertices[iIndex].v[2] * pcHeader->scale[2];
            vec.z += pcHeader->translate[2];

            // read the normal vector from the precalculated normal table
            MD2::LookupNormalIndex(pcVertices[iIndex].normalIndex, pcMesh->mNormals[iCurrent]);
            //pcMesh->mNormals[iCurrent].y *= -1.0f;

            // read texture coordinates
            float s = (float)pcTexCoords[iIndex].s;
            float t = (float)pcTexCoords[iIndex].t;

            // translate texture coordinates
            if (0 == pcTriangles->facesfront && 0 != pcTexCoords[iIndex].onseam) {
                s += pcHeader->skinwidth * 0.5f;
            }

            // Scale s and t to range from 0.0 to 1.0
            pcMesh->mTextureCoords[0][iCurrent].x = (s + 0.5f) / pcHeader->skinwidth;
            pcMesh->mTextureCoords[0][iCurrent].y = 1.0f - (t + 0.5f) / pcHeader->skinheight;
        }
        pcMesh->mFaces[i].mIndices[0] = iTemp + 2;
        pcMesh->mFaces[i].mIndices[1] = iTemp + 1;
        pcMesh->mFaces[i].mIndices[2] = iTemp + 0;
        pcTriangles++;
    }
    return;
}

// ------------------------------------------------------------------------------------------------
// Setup material properties for Quake and older GameStudio files
void MDLImporter::SetupMaterialProperties_3DGS_MDL5_Quake1() {
    const MDL::Header *const pcHeader = (const MDL::Header *)this->mBuffer;

    // allocate ONE material
    pScene->mMaterials = new aiMaterial *[1];
    pScene->mMaterials[0] = new aiMaterial();
    pScene->mNumMaterials = 1;

    // setup the material's properties
    const int iMode = (int)aiShadingMode_Gouraud;
    aiMaterial *const pcHelper = (aiMaterial *)pScene->mMaterials[0];
    pcHelper->AddProperty<int>(&iMode, 1, AI_MATKEY_SHADING_MODEL);

    aiColor4D clr;
    if (0 != pcHeader->num_skins && pScene->mNumTextures) {
        // can we replace the texture with a single color?
        clr = this->ReplaceTextureWithColor(pScene->mTextures[0]);
        if (is_not_qnan(clr.r)) {
            delete pScene->mTextures[0];
            delete[] pScene->mTextures;

            pScene->mTextures = nullptr;
            pScene->mNumTextures = 0;
        } else {
            clr.b = clr.a = clr.g = clr.r = 1.0f;
            aiString szString;
            ::memcpy(szString.data, AI_MAKE_EMBEDDED_TEXNAME(0), 3);
            szString.length = 2;
            pcHelper->AddProperty(&szString, AI_MATKEY_TEXTURE_DIFFUSE(0));
        }
    }

    pcHelper->AddProperty<aiColor4D>(&clr, 1, AI_MATKEY_COLOR_DIFFUSE);
    pcHelper->AddProperty<aiColor4D>(&clr, 1, AI_MATKEY_COLOR_SPECULAR);

    clr.r *= 0.05f;
    clr.g *= 0.05f;
    clr.b *= 0.05f;
    clr.a = 1.0f;
    pcHelper->AddProperty<aiColor4D>(&clr, 1, AI_MATKEY_COLOR_AMBIENT);
}

// ------------------------------------------------------------------------------------------------
// Read a MDL 3,4,5 file
void MDLImporter::InternReadFile_3DGS_MDL345() {
    ai_assert(nullptr != pScene);

    // the header of MDL 3/4/5 is nearly identical to the original Quake1 header
    BE_NCONST MDL::Header *pcHeader = (BE_NCONST MDL::Header *)this->mBuffer;
#ifdef AI_BUILD_BIG_ENDIAN
    FlipQuakeHeader(pcHeader);
#endif
    ValidateHeader_Quake1(pcHeader);

    // current cursor position in the file
    const unsigned char *szCurrent = (const unsigned char *)(pcHeader + 1);
    const unsigned char *szEnd = mBuffer + iFileSize;

    // need to read all textures
    for (unsigned int i = 0; i < (unsigned int)pcHeader->num_skins; ++i) {
        if (szCurrent + sizeof(uint32_t) > szEnd) {
            throw DeadlyImportError("Texture data past end of file.");
        }
        BE_NCONST MDL::Skin *pcSkin;
        pcSkin = (BE_NCONST MDL::Skin *)szCurrent;
        AI_SWAP4(pcSkin->group);
        // create one output image
        unsigned int iSkip = i ? UINT_MAX : 0;
        if (5 <= iGSFileVersion) {
            // MDL5 format could contain MIPmaps
            CreateTexture_3DGS_MDL5((unsigned char *)pcSkin + sizeof(uint32_t),
                    pcSkin->group, &iSkip);
        } else {
            CreateTexture_3DGS_MDL4((unsigned char *)pcSkin + sizeof(uint32_t),
                    pcSkin->group, &iSkip);
        }
        // need to skip one image
        szCurrent += iSkip + sizeof(uint32_t);
    }
    // get a pointer to the texture coordinates
    BE_NCONST MDL::TexCoord_MDL3 *pcTexCoords = (BE_NCONST MDL::TexCoord_MDL3 *)szCurrent;
    szCurrent += sizeof(MDL::TexCoord_MDL3) * pcHeader->synctype;

    // NOTE: for MDLn formats "synctype" corresponds to the number of UV coords

    // get a pointer to the triangles
    BE_NCONST MDL::Triangle_MDL3 *pcTriangles = (BE_NCONST MDL::Triangle_MDL3 *)szCurrent;
    szCurrent += sizeof(MDL::Triangle_MDL3) * pcHeader->num_tris;

#ifdef AI_BUILD_BIG_ENDIAN

    for (int i = 0; i < pcHeader->synctype; ++i) {
        AI_SWAP2(pcTexCoords[i].u);
        AI_SWAP2(pcTexCoords[i].v);
    }

    for (int i = 0; i < pcHeader->num_tris; ++i) {
        AI_SWAP2(pcTriangles[i].index_xyz[0]);
        AI_SWAP2(pcTriangles[i].index_xyz[1]);
        AI_SWAP2(pcTriangles[i].index_xyz[2]);
        AI_SWAP2(pcTriangles[i].index_uv[0]);
        AI_SWAP2(pcTriangles[i].index_uv[1]);
        AI_SWAP2(pcTriangles[i].index_uv[2]);
    }

#endif

    VALIDATE_FILE_SIZE(szCurrent);

    // setup materials
    SetupMaterialProperties_3DGS_MDL5_Quake1();

    // allocate enough storage to hold all vertices and triangles
    aiMesh *pcMesh = new aiMesh();
    pcMesh->mPrimitiveTypes = aiPrimitiveType_TRIANGLE;

    pcMesh->mNumVertices = pcHeader->num_tris * 3;
    pcMesh->mNumFaces = pcHeader->num_tris;
    pcMesh->mFaces = new aiFace[pcMesh->mNumFaces];

    // there won't be more than one mesh inside the file
    pScene->mRootNode = new aiNode();
    pScene->mRootNode->mNumMeshes = 1;
    pScene->mRootNode->mMeshes = new unsigned int[1];
    pScene->mRootNode->mMeshes[0] = 0;
    pScene->mNumMeshes = 1;
    pScene->mMeshes = new aiMesh *[1];
    pScene->mMeshes[0] = pcMesh;

    // allocate output storage
    pcMesh->mNumVertices = (unsigned int)pcHeader->num_tris * 3;
    pcMesh->mVertices = new aiVector3D[pcMesh->mNumVertices];
    pcMesh->mNormals = new aiVector3D[pcMesh->mNumVertices];

    if (pcHeader->synctype) {
        pcMesh->mTextureCoords[0] = new aiVector3D[pcMesh->mNumVertices];
        pcMesh->mNumUVComponents[0] = 2;
    }

    // now get a pointer to the first frame in the file
    BE_NCONST MDL::Frame *pcFrames = (BE_NCONST MDL::Frame *)szCurrent;
    AI_SWAP4(pcFrames->type);

    // byte packed vertices
    // FIXME: these two snippets below are almost identical ... join them?
    /////////////////////////////////////////////////////////////////////////////////////
    if (0 == pcFrames->type || 3 >= this->iGSFileVersion) {

        const MDL::SimpleFrame *pcFirstFrame = (const MDL::SimpleFrame *)(szCurrent + sizeof(uint32_t));
        const MDL::Vertex *pcVertices = (const MDL::Vertex *)((pcFirstFrame->name) + sizeof(pcFirstFrame->name));

        VALIDATE_FILE_SIZE(pcVertices + pcHeader->num_verts);

        // now iterate through all triangles
        unsigned int iCurrent = 0;
        for (unsigned int i = 0; i < (unsigned int)pcHeader->num_tris; ++i) {
            pcMesh->mFaces[i].mIndices = new unsigned int[3];
            pcMesh->mFaces[i].mNumIndices = 3;

            unsigned int iTemp = iCurrent;
            for (unsigned int c = 0; c < 3; ++c, ++iCurrent) {
                // read vertices
                unsigned int iIndex = pcTriangles->index_xyz[c];
                if (iIndex >= (unsigned int)pcHeader->num_verts) {
                    iIndex = pcHeader->num_verts - 1;
                    ASSIMP_LOG_WARN("Index overflow in MDLn vertex list");
                }

                aiVector3D &vec = pcMesh->mVertices[iCurrent];
                vec.x = (float)pcVertices[iIndex].v[0] * pcHeader->scale[0];
                vec.x += pcHeader->translate[0];

                vec.y = (float)pcVertices[iIndex].v[1] * pcHeader->scale[1];
                vec.y += pcHeader->translate[1];
                // vec.y *= -1.0f;

                vec.z = (float)pcVertices[iIndex].v[2] * pcHeader->scale[2];
                vec.z += pcHeader->translate[2];

                // read the normal vector from the precalculated normal table
                MD2::LookupNormalIndex(pcVertices[iIndex].normalIndex, pcMesh->mNormals[iCurrent]);
                // pcMesh->mNormals[iCurrent].y *= -1.0f;

                // read texture coordinates
                if (pcHeader->synctype) {
                    ImportUVCoordinate_3DGS_MDL345(pcMesh->mTextureCoords[0][iCurrent],
                            pcTexCoords, pcTriangles->index_uv[c]);
                }
            }
            pcMesh->mFaces[i].mIndices[0] = iTemp + 2;
            pcMesh->mFaces[i].mIndices[1] = iTemp + 1;
            pcMesh->mFaces[i].mIndices[2] = iTemp + 0;
            pcTriangles++;
        }

    }
    // short packed vertices
    /////////////////////////////////////////////////////////////////////////////////////
    else {
        // now get a pointer to the first frame in the file
        const MDL::SimpleFrame_MDLn_SP *pcFirstFrame = (const MDL::SimpleFrame_MDLn_SP *)(szCurrent + sizeof(uint32_t));

        // get a pointer to the vertices
        const MDL::Vertex_MDL4 *pcVertices = (const MDL::Vertex_MDL4 *)((pcFirstFrame->name) +
                                                                        sizeof(pcFirstFrame->name));

        VALIDATE_FILE_SIZE(pcVertices + pcHeader->num_verts);

        // now iterate through all triangles
        unsigned int iCurrent = 0;
        for (unsigned int i = 0; i < (unsigned int)pcHeader->num_tris; ++i) {
            pcMesh->mFaces[i].mIndices = new unsigned int[3];
            pcMesh->mFaces[i].mNumIndices = 3;

            unsigned int iTemp = iCurrent;
            for (unsigned int c = 0; c < 3; ++c, ++iCurrent) {
                // read vertices
                unsigned int iIndex = pcTriangles->index_xyz[c];
                if (iIndex >= (unsigned int)pcHeader->num_verts) {
                    iIndex = pcHeader->num_verts - 1;
                    ASSIMP_LOG_WARN("Index overflow in MDLn vertex list");
                }

                aiVector3D &vec = pcMesh->mVertices[iCurrent];
                vec.x = (float)pcVertices[iIndex].v[0] * pcHeader->scale[0];
                vec.x += pcHeader->translate[0];

                vec.y = (float)pcVertices[iIndex].v[1] * pcHeader->scale[1];
                vec.y += pcHeader->translate[1];
                // vec.y *= -1.0f;

                vec.z = (float)pcVertices[iIndex].v[2] * pcHeader->scale[2];
                vec.z += pcHeader->translate[2];

                // read the normal vector from the precalculated normal table
                MD2::LookupNormalIndex(pcVertices[iIndex].normalIndex, pcMesh->mNormals[iCurrent]);
                // pcMesh->mNormals[iCurrent].y *= -1.0f;

                // read texture coordinates
                if (pcHeader->synctype) {
                    ImportUVCoordinate_3DGS_MDL345(pcMesh->mTextureCoords[0][iCurrent],
                            pcTexCoords, pcTriangles->index_uv[c]);
                }
            }
            pcMesh->mFaces[i].mIndices[0] = iTemp + 2;
            pcMesh->mFaces[i].mIndices[1] = iTemp + 1;
            pcMesh->mFaces[i].mIndices[2] = iTemp + 0;
            pcTriangles++;
        }
    }

    // For MDL5 we will need to build valid texture coordinates
    // basing upon the file loaded (only support one file as skin)
    if (0x5 == iGSFileVersion)
        CalculateUVCoordinates_MDL5();
    return;
}

// ------------------------------------------------------------------------------------------------
// Get a single UV coordinate for Quake and older GameStudio files
void MDLImporter::ImportUVCoordinate_3DGS_MDL345(
        aiVector3D &vOut,
        const MDL::TexCoord_MDL3 *pcSrc,
        unsigned int iIndex) {
    ai_assert(nullptr != pcSrc);
    const MDL::Header *const pcHeader = (const MDL::Header *)this->mBuffer;

    // validate UV indices
    if (iIndex >= (unsigned int)pcHeader->synctype) {
        iIndex = pcHeader->synctype - 1;
        ASSIMP_LOG_WARN("Index overflow in MDLn UV coord list");
    }

    float s = (float)pcSrc[iIndex].u;
    float t = (float)pcSrc[iIndex].v;

    // Scale s and t to range from 0.0 to 1.0
    if (0x5 != iGSFileVersion) {
        s = (s + 0.5f) / pcHeader->skinwidth;
        t = 1.0f - (t + 0.5f) / pcHeader->skinheight;
    }

    vOut.x = s;
    vOut.y = t;
    vOut.z = 0.0f;
}

// ------------------------------------------------------------------------------------------------
// Compute UV coordinates for a MDL5 file
void MDLImporter::CalculateUVCoordinates_MDL5() {
    const MDL::Header *const pcHeader = (const MDL::Header *)this->mBuffer;
    if (pcHeader->num_skins && this->pScene->mNumTextures) {
        const aiTexture *pcTex = this->pScene->mTextures[0];

        // if the file is loaded in DDS format: get the size of the
        // texture from the header of the DDS file
        // skip three DWORDs and read first height, then the width
        unsigned int iWidth, iHeight;
        if (!pcTex->mHeight) {
            const uint32_t *piPtr = (uint32_t *)pcTex->pcData;

            piPtr += 3;
            iHeight = (unsigned int)*piPtr++;
            iWidth = (unsigned int)*piPtr;
            if (!iHeight || !iWidth) {
                ASSIMP_LOG_WARN("Either the width or the height of the "
                                "embedded DDS texture is zero. Unable to compute final texture "
                                "coordinates. The texture coordinates remain in their original "
                                "0-x/0-y (x,y = texture size) range.");
                iWidth = 1;
                iHeight = 1;
            }
        } else {
            iWidth = pcTex->mWidth;
            iHeight = pcTex->mHeight;
        }

        if (1 != iWidth || 1 != iHeight) {
            const float fWidth = (float)iWidth;
            const float fHeight = (float)iHeight;
            aiMesh *pcMesh = this->pScene->mMeshes[0];
            for (unsigned int i = 0; i < pcMesh->mNumVertices; ++i) {
                if (!pcMesh->HasTextureCoords(0)) {
                    continue;
                }
                pcMesh->mTextureCoords[0][i].x /= fWidth;
                pcMesh->mTextureCoords[0][i].y /= fHeight;
                pcMesh->mTextureCoords[0][i].y = 1.0f - pcMesh->mTextureCoords[0][i].y; // DX to OGL
            }
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Validate the header of a MDL7 file
void MDLImporter::ValidateHeader_3DGS_MDL7(const MDL::Header_MDL7 *pcHeader) {
    ai_assert(nullptr != pcHeader);

    // There are some fixed sizes ...
    if (sizeof(MDL::ColorValue_MDL7) != pcHeader->colorvalue_stc_size) {
        throw DeadlyImportError(
                "[3DGS MDL7] sizeof(MDL::ColorValue_MDL7) != pcHeader->colorvalue_stc_size");
    }
    if (sizeof(MDL::TexCoord_MDL7) != pcHeader->skinpoint_stc_size) {
        throw DeadlyImportError(
                "[3DGS MDL7] sizeof(MDL::TexCoord_MDL7) != pcHeader->skinpoint_stc_size");
    }
    if (sizeof(MDL::Skin_MDL7) != pcHeader->skin_stc_size) {
        throw DeadlyImportError(
                "sizeof(MDL::Skin_MDL7) != pcHeader->skin_stc_size");
    }

    // if there are no groups ... how should we load such a file?
    if (!pcHeader->groups_num) {
        throw DeadlyImportError("[3DGS MDL7] No frames found");
    }
}

// ------------------------------------------------------------------------------------------------
// resolve bone animation matrices
void MDLImporter::CalcAbsBoneMatrices_3DGS_MDL7(MDL::IntBone_MDL7 **apcOutBones) {
    const MDL::Header_MDL7 *pcHeader = (const MDL::Header_MDL7 *)this->mBuffer;
    const MDL::Bone_MDL7 *pcBones = (const MDL::Bone_MDL7 *)(pcHeader + 1);
    ai_assert(nullptr != apcOutBones);

    // first find the bone that has NO parent, calculate the
    // animation matrix for it, then go on and search for the next parent
    // index (0) and so on until we can't find a new node.
    uint16_t iParent = 0xffff;
    uint32_t iIterations = 0;
    while (iIterations++ < pcHeader->bones_num) {
        for (uint32_t iBone = 0; iBone < pcHeader->bones_num; ++iBone) {
            BE_NCONST MDL::Bone_MDL7 *pcBone = _AI_MDL7_ACCESS_PTR(pcBones, iBone,
                    pcHeader->bone_stc_size, MDL::Bone_MDL7);

            AI_SWAP2(pcBone->parent_index);
            AI_SWAP4(pcBone->x);
            AI_SWAP4(pcBone->y);
            AI_SWAP4(pcBone->z);

            if (iParent == pcBone->parent_index) {
                // MDL7 readme
                ////////////////////////////////////////////////////////////////
                /*
                The animation matrix is then calculated the following way:

                vector3 bPos = <absolute bone position>
                matrix44 laM;   // local animation matrix
                sphrvector key_rotate = <bone rotation>

                matrix44 m1,m2;
                create_trans_matrix(m1, -bPos.x, -bPos.y, -bPos.z);
                create_trans_matrix(m2, -bPos.x, -bPos.y, -bPos.z);

                create_rotation_matrix(laM,key_rotate);

                laM = sm1 * laM;
                laM = laM * sm2;
                */
                /////////////////////////////////////////////////////////////////

                MDL::IntBone_MDL7 *const pcOutBone = apcOutBones[iBone];

                // store the parent index of the bone
                pcOutBone->iParent = pcBone->parent_index;
                if (0xffff != iParent) {
                    const MDL::IntBone_MDL7 *pcParentBone = apcOutBones[iParent];
                    pcOutBone->mOffsetMatrix.a4 = -pcParentBone->vPosition.x;
                    pcOutBone->mOffsetMatrix.b4 = -pcParentBone->vPosition.y;
                    pcOutBone->mOffsetMatrix.c4 = -pcParentBone->vPosition.z;
                }
                pcOutBone->vPosition.x = pcBone->x;
                pcOutBone->vPosition.y = pcBone->y;
                pcOutBone->vPosition.z = pcBone->z;
                pcOutBone->mOffsetMatrix.a4 -= pcBone->x;
                pcOutBone->mOffsetMatrix.b4 -= pcBone->y;
                pcOutBone->mOffsetMatrix.c4 -= pcBone->z;

                if (AI_MDL7_BONE_STRUCT_SIZE__NAME_IS_NOT_THERE == pcHeader->bone_stc_size) {
                    // no real name for our poor bone is specified :-(
                    pcOutBone->mName.length = ai_snprintf(pcOutBone->mName.data, AI_MAXLEN,
                            "UnnamedBone_%i", iBone);
                } else {
                    // Make sure we won't run over the buffer's end if there is no
                    // terminal 0 character (however the documentation says there
                    // should be one)
                    uint32_t iMaxLen = pcHeader->bone_stc_size - 16;
                    for (uint32_t qq = 0; qq < iMaxLen; ++qq) {
                        if (!pcBone->name[qq]) {
                            iMaxLen = qq;
                            break;
                        }
                    }

                    // store the name of the bone
                    pcOutBone->mName.length = static_cast<ai_uint32>(iMaxLen);
                    ::memcpy(pcOutBone->mName.data, pcBone->name, pcOutBone->mName.length);
                    pcOutBone->mName.data[pcOutBone->mName.length] = '\0';
                }
            }
        }
        ++iParent;
    }
}

// ------------------------------------------------------------------------------------------------
// read bones from a MDL7 file
MDL::IntBone_MDL7 **MDLImporter::LoadBones_3DGS_MDL7() {
    const MDL::Header_MDL7 *pcHeader = (const MDL::Header_MDL7 *)this->mBuffer;
    if (pcHeader->bones_num) {
        // validate the size of the bone data structure in the file
        if (AI_MDL7_BONE_STRUCT_SIZE__NAME_IS_20_CHARS != pcHeader->bone_stc_size &&
                AI_MDL7_BONE_STRUCT_SIZE__NAME_IS_32_CHARS != pcHeader->bone_stc_size &&
                AI_MDL7_BONE_STRUCT_SIZE__NAME_IS_NOT_THERE != pcHeader->bone_stc_size) {
            ASSIMP_LOG_WARN("Unknown size of bone data structure");
            return nullptr;
        }

        MDL::IntBone_MDL7 **apcBonesOut = new MDL::IntBone_MDL7 *[pcHeader->bones_num];
        for (uint32_t crank = 0; crank < pcHeader->bones_num; ++crank)
            apcBonesOut[crank] = new MDL::IntBone_MDL7();

        // and calculate absolute bone offset matrices ...
        CalcAbsBoneMatrices_3DGS_MDL7(apcBonesOut);
        return apcBonesOut;
    }
    return nullptr;
}

// ------------------------------------------------------------------------------------------------
// read faces from a MDL7 file
void MDLImporter::ReadFaces_3DGS_MDL7(const MDL::IntGroupInfo_MDL7 &groupInfo,
        MDL::IntGroupData_MDL7 &groupData) {
    const MDL::Header_MDL7 *pcHeader = (const MDL::Header_MDL7 *)this->mBuffer;
    MDL::Triangle_MDL7 *pcGroupTris = groupInfo.pcGroupTris;

    // iterate through all triangles and build valid display lists
    unsigned int iOutIndex = 0;
    for (unsigned int iTriangle = 0; iTriangle < (unsigned int)groupInfo.pcGroup->numtris; ++iTriangle) {
        AI_SWAP2(pcGroupTris->v_index[0]);
        AI_SWAP2(pcGroupTris->v_index[1]);
        AI_SWAP2(pcGroupTris->v_index[2]);

        // iterate through all indices of the current triangle
        for (unsigned int c = 0; c < 3; ++c, ++iOutIndex) {

            // validate the vertex index
            unsigned int iIndex = pcGroupTris->v_index[c];
            if (iIndex > (unsigned int)groupInfo.pcGroup->numverts) {
                // (we might need to read this section a second time - to process frame vertices correctly)
                pcGroupTris->v_index[c] = (uint16_t)(iIndex = groupInfo.pcGroup->numverts - 1);
                ASSIMP_LOG_WARN("Index overflow in MDL7 vertex list");
            }

            // write the output face index
            groupData.pcFaces[iTriangle].mIndices[2 - c] = iOutIndex;

            aiVector3D &vPosition = groupData.vPositions[iOutIndex];
            vPosition.x = _AI_MDL7_ACCESS_VERT(groupInfo.pcGroupVerts, iIndex, pcHeader->mainvertex_stc_size).x;
            vPosition.y = _AI_MDL7_ACCESS_VERT(groupInfo.pcGroupVerts, iIndex, pcHeader->mainvertex_stc_size).y;
            vPosition.z = _AI_MDL7_ACCESS_VERT(groupInfo.pcGroupVerts, iIndex, pcHeader->mainvertex_stc_size).z;

            // if we have bones, save the index
            if (!groupData.aiBones.empty()) {
                groupData.aiBones[iOutIndex] = _AI_MDL7_ACCESS_VERT(groupInfo.pcGroupVerts,
                        iIndex, pcHeader->mainvertex_stc_size)
                                                       .vertindex;
            }

            // now read the normal vector
            if (AI_MDL7_FRAMEVERTEX030305_STCSIZE <= pcHeader->mainvertex_stc_size) {
                // read the full normal vector
                aiVector3D &vNormal = groupData.vNormals[iOutIndex];
                vNormal.x = _AI_MDL7_ACCESS_VERT(groupInfo.pcGroupVerts, iIndex, pcHeader->mainvertex_stc_size).norm[0];
                AI_SWAP4(vNormal.x);
                vNormal.y = _AI_MDL7_ACCESS_VERT(groupInfo.pcGroupVerts, iIndex, pcHeader->mainvertex_stc_size).norm[1];
                AI_SWAP4(vNormal.y);
                vNormal.z = _AI_MDL7_ACCESS_VERT(groupInfo.pcGroupVerts, iIndex, pcHeader->mainvertex_stc_size).norm[2];
                AI_SWAP4(vNormal.z);
            } else if (AI_MDL7_FRAMEVERTEX120503_STCSIZE <= pcHeader->mainvertex_stc_size) {
                // read the normal vector from Quake2's smart table
                aiVector3D &vNormal = groupData.vNormals[iOutIndex];
                MD2::LookupNormalIndex(_AI_MDL7_ACCESS_VERT(groupInfo.pcGroupVerts, iIndex,
                                               pcHeader->mainvertex_stc_size)
                                               .norm162index,
                        vNormal);
            }
            // validate and process the first uv coordinate set
            if (pcHeader->triangle_stc_size >= AI_MDL7_TRIANGLE_STD_SIZE_ONE_UV) {

                if (groupInfo.pcGroup->num_stpts) {
                    AI_SWAP2(pcGroupTris->skinsets[0].st_index[0]);
                    AI_SWAP2(pcGroupTris->skinsets[0].st_index[1]);
                    AI_SWAP2(pcGroupTris->skinsets[0].st_index[2]);

                    iIndex = pcGroupTris->skinsets[0].st_index[c];
                    if (iIndex > (unsigned int)groupInfo.pcGroup->num_stpts) {
                        iIndex = groupInfo.pcGroup->num_stpts - 1;
                        ASSIMP_LOG_WARN("Index overflow in MDL7 UV coordinate list (#1)");
                    }

                    float u = groupInfo.pcGroupUVs[iIndex].u;
                    float v = 1.0f - groupInfo.pcGroupUVs[iIndex].v; // DX to OGL

                    groupData.vTextureCoords1[iOutIndex].x = u;
                    groupData.vTextureCoords1[iOutIndex].y = v;
                }
                // assign the material index, but only if it is existing
                if (pcHeader->triangle_stc_size >= AI_MDL7_TRIANGLE_STD_SIZE_ONE_UV_WITH_MATINDEX) {
                    AI_SWAP4(pcGroupTris->skinsets[0].material);
                    groupData.pcFaces[iTriangle].iMatIndex[0] = pcGroupTris->skinsets[0].material;
                }
            }
            // validate and process the second uv coordinate set
            if (pcHeader->triangle_stc_size >= AI_MDL7_TRIANGLE_STD_SIZE_TWO_UV) {

                if (groupInfo.pcGroup->num_stpts) {
                    AI_SWAP2(pcGroupTris->skinsets[1].st_index[0]);
                    AI_SWAP2(pcGroupTris->skinsets[1].st_index[1]);
                    AI_SWAP2(pcGroupTris->skinsets[1].st_index[2]);
                    AI_SWAP4(pcGroupTris->skinsets[1].material);

                    iIndex = pcGroupTris->skinsets[1].st_index[c];
                    if (iIndex > (unsigned int)groupInfo.pcGroup->num_stpts) {
                        iIndex = groupInfo.pcGroup->num_stpts - 1;
                        ASSIMP_LOG_WARN("Index overflow in MDL7 UV coordinate list (#2)");
                    }

                    float u = groupInfo.pcGroupUVs[iIndex].u;
                    float v = 1.0f - groupInfo.pcGroupUVs[iIndex].v;

                    groupData.vTextureCoords2[iOutIndex].x = u;
                    groupData.vTextureCoords2[iOutIndex].y = v; // DX to OGL

                    // check whether we do really need the second texture
                    // coordinate set ... wastes memory and loading time
                    if (0 != iIndex && (u != groupData.vTextureCoords1[iOutIndex].x ||
                                               v != groupData.vTextureCoords1[iOutIndex].y))
                        groupData.bNeed2UV = true;

                    // if the material differs, we need a second skin, too
                    if (pcGroupTris->skinsets[1].material != pcGroupTris->skinsets[0].material)
                        groupData.bNeed2UV = true;
                }
                // assign the material index
                groupData.pcFaces[iTriangle].iMatIndex[1] = pcGroupTris->skinsets[1].material;
            }
        }
        // get the next triangle in the list
        pcGroupTris = (MDL::Triangle_MDL7 *)((const char *)pcGroupTris + pcHeader->triangle_stc_size);
    }
}

// ------------------------------------------------------------------------------------------------
// handle frames in a MDL7 file
bool MDLImporter::ProcessFrames_3DGS_MDL7(const MDL::IntGroupInfo_MDL7 &groupInfo,
        MDL::IntGroupData_MDL7 &groupData,
        MDL::IntSharedData_MDL7 &shared,
        const unsigned char *szCurrent,
        const unsigned char **szCurrentOut) {
    ai_assert(nullptr != szCurrent);
    ai_assert(nullptr != szCurrentOut);

    const MDL::Header_MDL7 *pcHeader = (const MDL::Header_MDL7 *)mBuffer;

    // if we have no bones we can simply skip all frames,
    // otherwise we'll need to process them.
    // FIX: If we need another frame than the first we must apply frame vertex replacements ...
    for (unsigned int iFrame = 0; iFrame < (unsigned int)groupInfo.pcGroup->numframes; ++iFrame) {
        MDL::IntFrameInfo_MDL7 frame((BE_NCONST MDL::Frame_MDL7 *)szCurrent, iFrame);

        AI_SWAP4(frame.pcFrame->vertices_count);
        AI_SWAP4(frame.pcFrame->transmatrix_count);

        const unsigned int iAdd = pcHeader->frame_stc_size +
                                  frame.pcFrame->vertices_count * pcHeader->framevertex_stc_size +
                                  frame.pcFrame->transmatrix_count * pcHeader->bonetrans_stc_size;

        if (((const char *)szCurrent - (const char *)pcHeader) + iAdd > (unsigned int)pcHeader->data_size) {
            ASSIMP_LOG_WARN("Index overflow in frame area. "
                            "Ignoring all frames and all further mesh groups, too.");

            // don't parse more groups if we can't even read one
            // FIXME: sometimes this seems to occur even for valid files ...
            *szCurrentOut = szCurrent;
            return false;
        }
        // our output frame?
        if (configFrameID == iFrame) {
            BE_NCONST MDL::Vertex_MDL7 *pcFrameVertices = (BE_NCONST MDL::Vertex_MDL7 *)(szCurrent + pcHeader->frame_stc_size);

            for (unsigned int qq = 0; qq < frame.pcFrame->vertices_count; ++qq) {
                // I assume this are simple replacements for normal vertices, the bone index serving
                // as the index of the vertex to be replaced.
                uint16_t iIndex = _AI_MDL7_ACCESS(pcFrameVertices, qq, pcHeader->framevertex_stc_size, MDL::Vertex_MDL7).vertindex;
                AI_SWAP2(iIndex);
                if (iIndex >= groupInfo.pcGroup->numverts) {
                    ASSIMP_LOG_WARN("Invalid vertex index in frame vertex section");
                    continue;
                }

                aiVector3D vPosition, vNormal;

                vPosition.x = _AI_MDL7_ACCESS_VERT(pcFrameVertices, qq, pcHeader->framevertex_stc_size).x;
                AI_SWAP4(vPosition.x);
                vPosition.y = _AI_MDL7_ACCESS_VERT(pcFrameVertices, qq, pcHeader->framevertex_stc_size).y;
                AI_SWAP4(vPosition.y);
                vPosition.z = _AI_MDL7_ACCESS_VERT(pcFrameVertices, qq, pcHeader->framevertex_stc_size).z;
                AI_SWAP4(vPosition.z);

                // now read the normal vector
                if (AI_MDL7_FRAMEVERTEX030305_STCSIZE <= pcHeader->mainvertex_stc_size) {
                    // read the full normal vector
                    vNormal.x = _AI_MDL7_ACCESS_VERT(pcFrameVertices, qq, pcHeader->framevertex_stc_size).norm[0];
                    AI_SWAP4(vNormal.x);
                    vNormal.y = _AI_MDL7_ACCESS_VERT(pcFrameVertices, qq, pcHeader->framevertex_stc_size).norm[1];
                    AI_SWAP4(vNormal.y);
                    vNormal.z = _AI_MDL7_ACCESS_VERT(pcFrameVertices, qq, pcHeader->framevertex_stc_size).norm[2];
                    AI_SWAP4(vNormal.z);
                } else if (AI_MDL7_FRAMEVERTEX120503_STCSIZE <= pcHeader->mainvertex_stc_size) {
                    // read the normal vector from Quake2's smart table
                    MD2::LookupNormalIndex(_AI_MDL7_ACCESS_VERT(pcFrameVertices, qq,
                                                   pcHeader->framevertex_stc_size)
                                                   .norm162index,
                            vNormal);
                }

                // FIXME: O(n^2) at the moment ...
                BE_NCONST MDL::Triangle_MDL7 *pcGroupTris = groupInfo.pcGroupTris;
                unsigned int iOutIndex = 0;
                for (unsigned int iTriangle = 0; iTriangle < (unsigned int)groupInfo.pcGroup->numtris; ++iTriangle) {
                    // iterate through all indices of the current triangle
                    for (unsigned int c = 0; c < 3; ++c, ++iOutIndex) {
                        // replace the vertex with the new data
                        const unsigned int iCurIndex = pcGroupTris->v_index[c];
                        if (iCurIndex == iIndex) {
                            groupData.vPositions[iOutIndex] = vPosition;
                            groupData.vNormals[iOutIndex] = vNormal;
                        }
                    }
                    // get the next triangle in the list
                    pcGroupTris = (BE_NCONST MDL::Triangle_MDL7 *)((const char *)
                                                                           pcGroupTris +
                                                                   pcHeader->triangle_stc_size);
                }
            }
        }
        // parse bone trafo matrix keys (only if there are bones ...)
        if (shared.apcOutBones) {
            ParseBoneTrafoKeys_3DGS_MDL7(groupInfo, frame, shared);
        }
        szCurrent += iAdd;
    }
    *szCurrentOut = szCurrent;
    return true;
}

// ------------------------------------------------------------------------------------------------
// Sort faces by material, handle multiple UVs correctly
void MDLImporter::SortByMaterials_3DGS_MDL7(
        const MDL::IntGroupInfo_MDL7 &groupInfo,
        MDL::IntGroupData_MDL7 &groupData,
        MDL::IntSplitGroupData_MDL7 &splitGroupData) {
    const unsigned int iNumMaterials = (unsigned int)splitGroupData.shared.pcMats.size();
    if (!groupData.bNeed2UV) {
        // if we don't need a second set of texture coordinates there is no reason to keep it in memory ...
        groupData.vTextureCoords2.clear();

        // allocate the array
        splitGroupData.aiSplit = new std::vector<unsigned int> *[iNumMaterials];

        for (unsigned int m = 0; m < iNumMaterials; ++m)
            splitGroupData.aiSplit[m] = new std::vector<unsigned int>();

        // iterate through all faces and sort by material
        for (unsigned int iFace = 0; iFace < (unsigned int)groupInfo.pcGroup->numtris; ++iFace) {
            // check range
            if (groupData.pcFaces[iFace].iMatIndex[0] >= iNumMaterials) {
                // use the last material instead
                splitGroupData.aiSplit[iNumMaterials - 1]->push_back(iFace);

                // sometimes MED writes -1, but normally only if there is only
                // one skin assigned. No warning in this case
                if (0xFFFFFFFF != groupData.pcFaces[iFace].iMatIndex[0])
                    ASSIMP_LOG_WARN("Index overflow in MDL7 material list [#0]");
            } else
                splitGroupData.aiSplit[groupData.pcFaces[iFace].iMatIndex[0]]->push_back(iFace);
        }
    } else {
        // we need to build combined materials for each combination of
        std::vector<MDL::IntMaterial_MDL7> avMats;
        avMats.reserve(iNumMaterials * 2);

        // fixme: why on the heap?
        std::vector<std::vector<unsigned int> *> aiTempSplit(iNumMaterials * 2);
        for (unsigned int m = 0; m < iNumMaterials; ++m)
            aiTempSplit[m] = new std::vector<unsigned int>();

        // iterate through all faces and sort by material
        for (unsigned int iFace = 0; iFace < (unsigned int)groupInfo.pcGroup->numtris; ++iFace) {
            // check range
            unsigned int iMatIndex = groupData.pcFaces[iFace].iMatIndex[0];
            if (iMatIndex >= iNumMaterials) {
                // sometimes MED writes -1, but normally only if there is only
                // one skin assigned. No warning in this case
                if (UINT_MAX != iMatIndex)
                    ASSIMP_LOG_WARN("Index overflow in MDL7 material list [#1]");
                iMatIndex = iNumMaterials - 1;
            }
            unsigned int iMatIndex2 = groupData.pcFaces[iFace].iMatIndex[1];

            unsigned int iNum = iMatIndex;
            if (UINT_MAX != iMatIndex2 && iMatIndex != iMatIndex2) {
                if (iMatIndex2 >= iNumMaterials) {
                    // sometimes MED writes -1, but normally only if there is only
                    // one skin assigned. No warning in this case
                    ASSIMP_LOG_WARN("Index overflow in MDL7 material list [#2]");
                    iMatIndex2 = iNumMaterials - 1;
                }

                // do a slow search in the list ...
                iNum = 0;
                bool bFound = false;
                for (std::vector<MDL::IntMaterial_MDL7>::iterator i = avMats.begin(); i != avMats.end(); ++i, ++iNum) {
                    if ((*i).iOldMatIndices[0] == iMatIndex && (*i).iOldMatIndices[1] == iMatIndex2) {
                        // reuse this material
                        bFound = true;
                        break;
                    }
                }
                if (!bFound) {
                    //  build a new material ...
                    MDL::IntMaterial_MDL7 sHelper;
                    sHelper.pcMat = new aiMaterial();
                    sHelper.iOldMatIndices[0] = iMatIndex;
                    sHelper.iOldMatIndices[1] = iMatIndex2;
                    JoinSkins_3DGS_MDL7(splitGroupData.shared.pcMats[iMatIndex],
                            splitGroupData.shared.pcMats[iMatIndex2], sHelper.pcMat);

                    // and add it to the list
                    avMats.push_back(sHelper);
                    iNum = (unsigned int)avMats.size() - 1;
                }
                // adjust the size of the file array
                if (iNum == aiTempSplit.size()) {
                    aiTempSplit.push_back(new std::vector<unsigned int>());
                }
            }
            aiTempSplit[iNum]->push_back(iFace);
        }

        // now add the newly created materials to the old list
        if (0 == groupInfo.iIndex) {
            splitGroupData.shared.pcMats.resize(avMats.size());
            for (unsigned int o = 0; o < avMats.size(); ++o)
                splitGroupData.shared.pcMats[o] = avMats[o].pcMat;
        } else {
            // This might result in redundant materials ...
            splitGroupData.shared.pcMats.resize(iNumMaterials + avMats.size());
            for (unsigned int o = iNumMaterials; o < avMats.size(); ++o)
                splitGroupData.shared.pcMats[o] = avMats[o].pcMat;
        }

        // and build the final face-to-material array
        splitGroupData.aiSplit = new std::vector<unsigned int> *[aiTempSplit.size()];
        for (unsigned int m = 0; m < iNumMaterials; ++m)
            splitGroupData.aiSplit[m] = aiTempSplit[m];
    }
}

// ------------------------------------------------------------------------------------------------
// Read a MDL7 file
void MDLImporter::InternReadFile_3DGS_MDL7() {
    ai_assert(nullptr != pScene);

    MDL::IntSharedData_MDL7 sharedData;

    // current cursor position in the file
    BE_NCONST MDL::Header_MDL7 *pcHeader = (BE_NCONST MDL::Header_MDL7 *)this->mBuffer;
    const unsigned char *szCurrent = (const unsigned char *)(pcHeader + 1);

    AI_SWAP4(pcHeader->version);
    AI_SWAP4(pcHeader->bones_num);
    AI_SWAP4(pcHeader->groups_num);
    AI_SWAP4(pcHeader->data_size);
    AI_SWAP4(pcHeader->entlump_size);
    AI_SWAP4(pcHeader->medlump_size);
    AI_SWAP2(pcHeader->bone_stc_size);
    AI_SWAP2(pcHeader->skin_stc_size);
    AI_SWAP2(pcHeader->colorvalue_stc_size);
    AI_SWAP2(pcHeader->material_stc_size);
    AI_SWAP2(pcHeader->skinpoint_stc_size);
    AI_SWAP2(pcHeader->triangle_stc_size);
    AI_SWAP2(pcHeader->mainvertex_stc_size);
    AI_SWAP2(pcHeader->framevertex_stc_size);
    AI_SWAP2(pcHeader->bonetrans_stc_size);
    AI_SWAP2(pcHeader->frame_stc_size);

    // validate the header of the file. There are some structure
    // sizes that are expected by the loader to be constant
    this->ValidateHeader_3DGS_MDL7(pcHeader);

    // load all bones (they are shared by all groups, so
    // we'll need to add them to all groups/meshes later)
    // apcBonesOut is a list of all bones or nullptr if they could not been loaded
    szCurrent += pcHeader->bones_num * pcHeader->bone_stc_size;
    sharedData.apcOutBones = this->LoadBones_3DGS_MDL7();

    // vector to held all created meshes
    std::vector<aiMesh *> *avOutList;

    // 3 meshes per group - that should be OK for most models
    avOutList = new std::vector<aiMesh *>[pcHeader->groups_num];
    for (uint32_t i = 0; i < pcHeader->groups_num; ++i)
        avOutList[i].reserve(3);

    // buffer to held the names of all groups in the file
    const size_t buffersize(AI_MDL7_MAX_GROUPNAMESIZE * pcHeader->groups_num);
    char *aszGroupNameBuffer = new char[buffersize];

    // read all groups
    for (unsigned int iGroup = 0; iGroup < (unsigned int)pcHeader->groups_num; ++iGroup) {
        MDL::IntGroupInfo_MDL7 groupInfo((BE_NCONST MDL::Group_MDL7 *)szCurrent, iGroup);
        szCurrent = (const unsigned char *)(groupInfo.pcGroup + 1);

        VALIDATE_FILE_SIZE(szCurrent);

        AI_SWAP4(groupInfo.pcGroup->groupdata_size);
        AI_SWAP4(groupInfo.pcGroup->numskins);
        AI_SWAP4(groupInfo.pcGroup->num_stpts);
        AI_SWAP4(groupInfo.pcGroup->numtris);
        AI_SWAP4(groupInfo.pcGroup->numverts);
        AI_SWAP4(groupInfo.pcGroup->numframes);

        if (1 != groupInfo.pcGroup->typ) {
            // Not a triangle-based mesh
            ASSIMP_LOG_WARN("[3DGS MDL7] Not a triangle mesh group. Continuing happily");
        }

        // store the name of the group
        const unsigned int ofs = iGroup * AI_MDL7_MAX_GROUPNAMESIZE;
        ::memcpy(&aszGroupNameBuffer[ofs],
                groupInfo.pcGroup->name, AI_MDL7_MAX_GROUPNAMESIZE);

        // make sure '\0' is at the end
        aszGroupNameBuffer[ofs + AI_MDL7_MAX_GROUPNAMESIZE - 1] = '\0';

        // read all skins
        sharedData.pcMats.reserve(sharedData.pcMats.size() + groupInfo.pcGroup->numskins);
        sharedData.abNeedMaterials.resize(sharedData.abNeedMaterials.size() +
                                                  groupInfo.pcGroup->numskins,
                false);

        for (unsigned int iSkin = 0; iSkin < (unsigned int)groupInfo.pcGroup->numskins; ++iSkin) {
            ParseSkinLump_3DGS_MDL7(szCurrent, &szCurrent, sharedData.pcMats);
        }
        // if we have absolutely no skin loaded we need to generate a default material
        if (sharedData.pcMats.empty()) {
            const int iMode = (int)aiShadingMode_Gouraud;
            sharedData.pcMats.push_back(new aiMaterial());
            aiMaterial *pcHelper = (aiMaterial *)sharedData.pcMats[0];
            pcHelper->AddProperty<int>(&iMode, 1, AI_MATKEY_SHADING_MODEL);

            aiColor3D clr;
            clr.b = clr.g = clr.r = 0.6f;
            pcHelper->AddProperty<aiColor3D>(&clr, 1, AI_MATKEY_COLOR_DIFFUSE);
            pcHelper->AddProperty<aiColor3D>(&clr, 1, AI_MATKEY_COLOR_SPECULAR);

            clr.b = clr.g = clr.r = 0.05f;
            pcHelper->AddProperty<aiColor3D>(&clr, 1, AI_MATKEY_COLOR_AMBIENT);

            aiString szName;
            szName.Set(AI_DEFAULT_MATERIAL_NAME);
            pcHelper->AddProperty(&szName, AI_MATKEY_NAME);

            sharedData.abNeedMaterials.resize(1, false);
        }

        // now get a pointer to all texture coords in the group
        groupInfo.pcGroupUVs = (BE_NCONST MDL::TexCoord_MDL7 *)szCurrent;
        for (int i = 0; i < groupInfo.pcGroup->num_stpts; ++i) {
            AI_SWAP4(groupInfo.pcGroupUVs[i].u);
            AI_SWAP4(groupInfo.pcGroupUVs[i].v);
        }
        szCurrent += pcHeader->skinpoint_stc_size * groupInfo.pcGroup->num_stpts;

        // now get a pointer to all triangle in the group
        groupInfo.pcGroupTris = (Triangle_MDL7 *)szCurrent;
        szCurrent += pcHeader->triangle_stc_size * groupInfo.pcGroup->numtris;

        // now get a pointer to all vertices in the group
        groupInfo.pcGroupVerts = (BE_NCONST MDL::Vertex_MDL7 *)szCurrent;
        for (int i = 0; i < groupInfo.pcGroup->numverts; ++i) {
            AI_SWAP4(groupInfo.pcGroupVerts[i].x);
            AI_SWAP4(groupInfo.pcGroupVerts[i].y);
            AI_SWAP4(groupInfo.pcGroupVerts[i].z);

            AI_SWAP2(groupInfo.pcGroupVerts[i].vertindex);
            //We can not swap the normal information now as we don't know which of the two kinds it is
        }
        szCurrent += pcHeader->mainvertex_stc_size * groupInfo.pcGroup->numverts;
        VALIDATE_FILE_SIZE(szCurrent);

        MDL::IntSplitGroupData_MDL7 splitGroupData(sharedData, avOutList[iGroup]);
        MDL::IntGroupData_MDL7 groupData;
        if (groupInfo.pcGroup->numtris && groupInfo.pcGroup->numverts) {
            // build output vectors
            const unsigned int iNumVertices = groupInfo.pcGroup->numtris * 3;
            groupData.vPositions.resize(iNumVertices);
            groupData.vNormals.resize(iNumVertices);

            if (sharedData.apcOutBones) groupData.aiBones.resize(iNumVertices, UINT_MAX);

            // it is also possible that there are 0 UV coordinate sets
            if (groupInfo.pcGroup->num_stpts) {
                groupData.vTextureCoords1.resize(iNumVertices, aiVector3D());

                // check whether the triangle data structure is large enough
                // to contain a second UV coordinate set
                if (pcHeader->triangle_stc_size >= AI_MDL7_TRIANGLE_STD_SIZE_TWO_UV) {
                    groupData.vTextureCoords2.resize(iNumVertices, aiVector3D());
                    groupData.bNeed2UV = true;
                }
            }
            groupData.pcFaces.resize(groupInfo.pcGroup->numtris);

            // read all faces into the preallocated arrays
            ReadFaces_3DGS_MDL7(groupInfo, groupData);

            // sort by materials
            SortByMaterials_3DGS_MDL7(groupInfo, groupData,
                    splitGroupData);

            for (unsigned int qq = 0; qq < sharedData.pcMats.size(); ++qq) {
                if (!splitGroupData.aiSplit[qq]->empty())
                    sharedData.abNeedMaterials[qq] = true;
            }
        } else
            ASSIMP_LOG_WARN("[3DGS MDL7] Mesh group consists of 0 "
                            "vertices or faces. It will be skipped.");

        // process all frames and generate output meshes
        ProcessFrames_3DGS_MDL7(groupInfo, groupData, sharedData, szCurrent, &szCurrent);
        GenerateOutputMeshes_3DGS_MDL7(groupData, splitGroupData);
    }

    // generate a nodegraph and subnodes for each group
    pScene->mRootNode = new aiNode();

    // now we need to build a final mesh list
    for (uint32_t i = 0; i < pcHeader->groups_num; ++i)
        pScene->mNumMeshes += (unsigned int)avOutList[i].size();

    pScene->mMeshes = new aiMesh *[pScene->mNumMeshes];
    {
        unsigned int p = 0, q = 0;
        for (uint32_t i = 0; i < pcHeader->groups_num; ++i) {
            for (unsigned int a = 0; a < avOutList[i].size(); ++a) {
                pScene->mMeshes[p++] = avOutList[i][a];
            }
            if (!avOutList[i].empty()) ++pScene->mRootNode->mNumChildren;
        }
        // we will later need an extra node to serve as parent for all bones
        if (sharedData.apcOutBones) ++pScene->mRootNode->mNumChildren;
        this->pScene->mRootNode->mChildren = new aiNode *[pScene->mRootNode->mNumChildren];
        p = 0;
        for (uint32_t i = 0; i < pcHeader->groups_num; ++i) {
            if (avOutList[i].empty()) continue;

            aiNode *const pcNode = pScene->mRootNode->mChildren[p] = new aiNode();
            pcNode->mNumMeshes = (unsigned int)avOutList[i].size();
            pcNode->mMeshes = new unsigned int[pcNode->mNumMeshes];
            pcNode->mParent = this->pScene->mRootNode;
            for (unsigned int a = 0; a < pcNode->mNumMeshes; ++a)
                pcNode->mMeshes[a] = q + a;
            q += (unsigned int)avOutList[i].size();

            // setup the name of the node
            char *const szBuffer = &aszGroupNameBuffer[i * AI_MDL7_MAX_GROUPNAMESIZE];
            if ('\0' == *szBuffer) {
                const size_t maxSize(buffersize - (i * AI_MDL7_MAX_GROUPNAMESIZE));
                pcNode->mName.length = ai_snprintf(szBuffer, maxSize, "Group_%u", p);
            } else {
                pcNode->mName.length = (ai_uint32)::strlen(szBuffer);
            }
            ::strncpy(pcNode->mName.data, szBuffer, AI_MAXLEN - 1);
            ++p;
        }
    }

    // if there is only one root node with a single child we can optimize it a bit ...
    if (1 == pScene->mRootNode->mNumChildren && !sharedData.apcOutBones) {
        aiNode *pcOldRoot = this->pScene->mRootNode;
        pScene->mRootNode = pcOldRoot->mChildren[0];
        pcOldRoot->mChildren[0] = nullptr;
        delete pcOldRoot;
        pScene->mRootNode->mParent = nullptr;
    } else
        pScene->mRootNode->mName.Set("<mesh_root>");

    delete[] avOutList;
    delete[] aszGroupNameBuffer;
    AI_DEBUG_INVALIDATE_PTR(avOutList);
    AI_DEBUG_INVALIDATE_PTR(aszGroupNameBuffer);

    // build a final material list.
    CopyMaterials_3DGS_MDL7(sharedData);
    HandleMaterialReferences_3DGS_MDL7();

    // generate output bone animations and add all bones to the scenegraph
    if (sharedData.apcOutBones) {
        // this step adds empty dummy bones to the nodegraph
        // insert another dummy node to avoid name conflicts
        aiNode *const pc = pScene->mRootNode->mChildren[pScene->mRootNode->mNumChildren - 1] = new aiNode();

        pc->mName.Set("<skeleton_root>");

        // add bones to the nodegraph
        AddBonesToNodeGraph_3DGS_MDL7((const Assimp::MDL::IntBone_MDL7 **)
                                              sharedData.apcOutBones,
                pc, 0xffff);

        // this steps build a valid output animation
        BuildOutputAnims_3DGS_MDL7((const Assimp::MDL::IntBone_MDL7 **)
                                           sharedData.apcOutBones);
    }
}

// ------------------------------------------------------------------------------------------------
// Copy materials
void MDLImporter::CopyMaterials_3DGS_MDL7(MDL::IntSharedData_MDL7 &shared) {
    pScene->mNumMaterials = (unsigned int)shared.pcMats.size();
    pScene->mMaterials = new aiMaterial *[pScene->mNumMaterials];
    for (unsigned int i = 0; i < pScene->mNumMaterials; ++i)
        pScene->mMaterials[i] = shared.pcMats[i];
}

// ------------------------------------------------------------------------------------------------
// Process material references
void MDLImporter::HandleMaterialReferences_3DGS_MDL7() {
    // search for referrer materials
    for (unsigned int i = 0; i < pScene->mNumMaterials; ++i) {
        int iIndex = 0;
        if (AI_SUCCESS == aiGetMaterialInteger(pScene->mMaterials[i], AI_MDL7_REFERRER_MATERIAL, &iIndex)) {
            for (unsigned int a = 0; a < pScene->mNumMeshes; ++a) {
                aiMesh *const pcMesh = pScene->mMeshes[a];
                if (i == pcMesh->mMaterialIndex) {
                    pcMesh->mMaterialIndex = iIndex;
                }
            }
            // collapse the rest of the array
            delete pScene->mMaterials[i];
            for (unsigned int pp = i; pp < pScene->mNumMaterials - 1; ++pp) {

                pScene->mMaterials[pp] = pScene->mMaterials[pp + 1];
                for (unsigned int a = 0; a < pScene->mNumMeshes; ++a) {
                    aiMesh *const pcMesh = pScene->mMeshes[a];
                    if (pcMesh->mMaterialIndex > i) --pcMesh->mMaterialIndex;
                }
            }
            --pScene->mNumMaterials;
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Read bone transformation keys
void MDLImporter::ParseBoneTrafoKeys_3DGS_MDL7(
        const MDL::IntGroupInfo_MDL7 &groupInfo,
        IntFrameInfo_MDL7 &frame,
        MDL::IntSharedData_MDL7 &shared) {
    const MDL::Header_MDL7 *const pcHeader = (const MDL::Header_MDL7 *)this->mBuffer;

    // only the first group contains bone animation keys
    if (frame.pcFrame->transmatrix_count) {
        if (!groupInfo.iIndex) {
            // skip all frames vertices. We can't support them
            const MDL::BoneTransform_MDL7 *pcBoneTransforms = (const MDL::BoneTransform_MDL7 *)(((const char *)frame.pcFrame) + pcHeader->frame_stc_size +
                                                                                                frame.pcFrame->vertices_count * pcHeader->framevertex_stc_size);

            // read all transformation matrices
            for (unsigned int iTrafo = 0; iTrafo < frame.pcFrame->transmatrix_count; ++iTrafo) {
                if (pcBoneTransforms->bone_index >= pcHeader->bones_num) {
                    ASSIMP_LOG_WARN("Index overflow in frame area. "
                                    "Unable to parse this bone transformation");
                } else {
                    AddAnimationBoneTrafoKey_3DGS_MDL7(frame.iIndex,
                            pcBoneTransforms, shared.apcOutBones);
                }
                pcBoneTransforms = (const MDL::BoneTransform_MDL7 *)((const char *)pcBoneTransforms + pcHeader->bonetrans_stc_size);
            }
        } else {
            ASSIMP_LOG_WARN("Ignoring animation keyframes in groups != 0");
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Attach bones to the output nodegraph
void MDLImporter::AddBonesToNodeGraph_3DGS_MDL7(const MDL::IntBone_MDL7 **apcBones,
        aiNode *pcParent, uint16_t iParentIndex) {
    ai_assert(nullptr != apcBones);
    ai_assert(nullptr != pcParent);

    // get a pointer to the header ...
    const MDL::Header_MDL7 *const pcHeader = (const MDL::Header_MDL7 *)this->mBuffer;

    const MDL::IntBone_MDL7 **apcBones2 = apcBones;
    for (uint32_t i = 0; i < pcHeader->bones_num; ++i) {

        const MDL::IntBone_MDL7 *const pcBone = *apcBones2++;
        if (pcBone->iParent == iParentIndex) {
            ++pcParent->mNumChildren;
        }
    }
    pcParent->mChildren = new aiNode *[pcParent->mNumChildren];
    unsigned int qq = 0;
    for (uint32_t i = 0; i < pcHeader->bones_num; ++i) {

        const MDL::IntBone_MDL7 *const pcBone = *apcBones++;
        if (pcBone->iParent != iParentIndex) continue;

        aiNode *pcNode = pcParent->mChildren[qq++] = new aiNode();
        pcNode->mName = aiString(pcBone->mName);

        AddBonesToNodeGraph_3DGS_MDL7(apcBones, pcNode, (uint16_t)i);
    }
}

// ------------------------------------------------------------------------------------------------
// Build output animations
void MDLImporter::BuildOutputAnims_3DGS_MDL7(
        const MDL::IntBone_MDL7 **apcBonesOut) {
    ai_assert(nullptr != apcBonesOut);
    const MDL::Header_MDL7 *const pcHeader = (const MDL::Header_MDL7 *)mBuffer;

    // one animation ...
    aiAnimation *pcAnim = new aiAnimation();
    for (uint32_t i = 0; i < pcHeader->bones_num; ++i) {
        if (!apcBonesOut[i]->pkeyPositions.empty()) {

            // get the last frame ... (needn't be equal to pcHeader->frames_num)
            for (size_t qq = 0; qq < apcBonesOut[i]->pkeyPositions.size(); ++qq) {
                pcAnim->mDuration = std::max(pcAnim->mDuration, (double)
                                                                        apcBonesOut[i]
                                                                                ->pkeyPositions[qq]
                                                                                .mTime);
            }
            ++pcAnim->mNumChannels;
        }
    }
    if (pcAnim->mDuration) {
        pcAnim->mChannels = new aiNodeAnim *[pcAnim->mNumChannels];

        unsigned int iCnt = 0;
        for (uint32_t i = 0; i < pcHeader->bones_num; ++i) {
            if (!apcBonesOut[i]->pkeyPositions.empty()) {
                const MDL::IntBone_MDL7 *const intBone = apcBonesOut[i];

                aiNodeAnim *const pcNodeAnim = pcAnim->mChannels[iCnt++] = new aiNodeAnim();
                pcNodeAnim->mNodeName = aiString(intBone->mName);

                // allocate enough storage for all keys
                pcNodeAnim->mNumPositionKeys = (unsigned int)intBone->pkeyPositions.size();
                pcNodeAnim->mNumScalingKeys = (unsigned int)intBone->pkeyPositions.size();
                pcNodeAnim->mNumRotationKeys = (unsigned int)intBone->pkeyPositions.size();

                pcNodeAnim->mPositionKeys = new aiVectorKey[pcNodeAnim->mNumPositionKeys];
                pcNodeAnim->mScalingKeys = new aiVectorKey[pcNodeAnim->mNumPositionKeys];
                pcNodeAnim->mRotationKeys = new aiQuatKey[pcNodeAnim->mNumPositionKeys];

                // copy all keys
                for (unsigned int qq = 0; qq < pcNodeAnim->mNumPositionKeys; ++qq) {
                    pcNodeAnim->mPositionKeys[qq] = intBone->pkeyPositions[qq];
                    pcNodeAnim->mScalingKeys[qq] = intBone->pkeyScalings[qq];
                    pcNodeAnim->mRotationKeys[qq] = intBone->pkeyRotations[qq];
                }
            }
        }

        // store the output animation
        pScene->mNumAnimations = 1;
        pScene->mAnimations = new aiAnimation *[1];
        pScene->mAnimations[0] = pcAnim;
    } else
        delete pcAnim;
}

// ------------------------------------------------------------------------------------------------
void MDLImporter::AddAnimationBoneTrafoKey_3DGS_MDL7(unsigned int iTrafo,
        const MDL::BoneTransform_MDL7 *pcBoneTransforms,
        MDL::IntBone_MDL7 **apcBonesOut) {
    ai_assert(nullptr != pcBoneTransforms);
    ai_assert(nullptr != apcBonesOut);

    // first .. get the transformation matrix
    aiMatrix4x4 mTransform;
    mTransform.a1 = pcBoneTransforms->m[0];
    mTransform.b1 = pcBoneTransforms->m[1];
    mTransform.c1 = pcBoneTransforms->m[2];
    mTransform.d1 = pcBoneTransforms->m[3];

    mTransform.a2 = pcBoneTransforms->m[4];
    mTransform.b2 = pcBoneTransforms->m[5];
    mTransform.c2 = pcBoneTransforms->m[6];
    mTransform.d2 = pcBoneTransforms->m[7];

    mTransform.a3 = pcBoneTransforms->m[8];
    mTransform.b3 = pcBoneTransforms->m[9];
    mTransform.c3 = pcBoneTransforms->m[10];
    mTransform.d3 = pcBoneTransforms->m[11];

    // now decompose the transformation matrix into separate
    // scaling, rotation and translation
    aiVectorKey vScaling, vPosition;
    aiQuatKey qRotation;

    // FIXME: Decompose will assert in debug builds if the matrix is invalid ...
    mTransform.Decompose(vScaling.mValue, qRotation.mValue, vPosition.mValue);

    // now generate keys
    vScaling.mTime = qRotation.mTime = vPosition.mTime = (double)iTrafo;

    // add the keys to the bone
    MDL::IntBone_MDL7 *const pcBoneOut = apcBonesOut[pcBoneTransforms->bone_index];
    pcBoneOut->pkeyPositions.push_back(vPosition);
    pcBoneOut->pkeyScalings.push_back(vScaling);
    pcBoneOut->pkeyRotations.push_back(qRotation);
}

// ------------------------------------------------------------------------------------------------
// Construct output meshes
void MDLImporter::GenerateOutputMeshes_3DGS_MDL7(
        MDL::IntGroupData_MDL7 &groupData,
        MDL::IntSplitGroupData_MDL7 &splitGroupData) {
    const MDL::IntSharedData_MDL7 &shared = splitGroupData.shared;

    // get a pointer to the header ...
    const MDL::Header_MDL7 *const pcHeader = (const MDL::Header_MDL7 *)this->mBuffer;
    const unsigned int iNumOutBones = pcHeader->bones_num;

    for (std::vector<aiMaterial *>::size_type i = 0; i < shared.pcMats.size(); ++i) {
        if (!splitGroupData.aiSplit[i]->empty()) {

            // allocate the output mesh
            aiMesh *pcMesh = new aiMesh();

            pcMesh->mPrimitiveTypes = aiPrimitiveType_TRIANGLE;
            pcMesh->mMaterialIndex = (unsigned int)i;

            // allocate output storage
            pcMesh->mNumFaces = (unsigned int)splitGroupData.aiSplit[i]->size();
            pcMesh->mFaces = new aiFace[pcMesh->mNumFaces];

            pcMesh->mNumVertices = pcMesh->mNumFaces * 3;
            pcMesh->mVertices = new aiVector3D[pcMesh->mNumVertices];
            pcMesh->mNormals = new aiVector3D[pcMesh->mNumVertices];

            if (!groupData.vTextureCoords1.empty()) {
                pcMesh->mNumUVComponents[0] = 2;
                pcMesh->mTextureCoords[0] = new aiVector3D[pcMesh->mNumVertices];
                if (!groupData.vTextureCoords2.empty()) {
                    pcMesh->mNumUVComponents[1] = 2;
                    pcMesh->mTextureCoords[1] = new aiVector3D[pcMesh->mNumVertices];
                }
            }

            // iterate through all faces and build an unique set of vertices
            unsigned int iCurrent = 0;
            for (unsigned int iFace = 0; iFace < pcMesh->mNumFaces; ++iFace) {
                pcMesh->mFaces[iFace].mNumIndices = 3;
                pcMesh->mFaces[iFace].mIndices = new unsigned int[3];

                unsigned int iSrcFace = splitGroupData.aiSplit[i]->operator[](iFace);
                const MDL::IntFace_MDL7 &oldFace = groupData.pcFaces[iSrcFace];

                // iterate through all face indices
                for (unsigned int c = 0; c < 3; ++c) {
                    const uint32_t iIndex = oldFace.mIndices[c];
                    pcMesh->mVertices[iCurrent] = groupData.vPositions[iIndex];
                    pcMesh->mNormals[iCurrent] = groupData.vNormals[iIndex];

                    if (!groupData.vTextureCoords1.empty()) {

                        pcMesh->mTextureCoords[0][iCurrent] = groupData.vTextureCoords1[iIndex];
                        if (!groupData.vTextureCoords2.empty()) {
                            pcMesh->mTextureCoords[1][iCurrent] = groupData.vTextureCoords2[iIndex];
                        }
                    }
                    pcMesh->mFaces[iFace].mIndices[c] = iCurrent++;
                }
            }

            // if we have bones in the mesh we'll need to generate
            // proper vertex weights for them
            if (!groupData.aiBones.empty()) {
                std::vector<std::vector<unsigned int>> aaiVWeightList;
                aaiVWeightList.resize(iNumOutBones);

                int iCurrentWeight = 0;
                for (unsigned int iFace = 0; iFace < pcMesh->mNumFaces; ++iFace) {
                    unsigned int iSrcFace = splitGroupData.aiSplit[i]->operator[](iFace);
                    const MDL::IntFace_MDL7 &oldFace = groupData.pcFaces[iSrcFace];

                    // iterate through all face indices
                    for (unsigned int c = 0; c < 3; ++c) {
                        unsigned int iBone = groupData.aiBones[oldFace.mIndices[c]];
                        if (UINT_MAX != iBone) {
                            if (iBone >= iNumOutBones) {
                                ASSIMP_LOG_ERROR("Bone index overflow. "
                                                 "The bone index of a vertex exceeds the allowed range. ");
                                iBone = iNumOutBones - 1;
                            }
                            aaiVWeightList[iBone].push_back(iCurrentWeight);
                        }
                        ++iCurrentWeight;
                    }
                }
                // now check which bones are required ...
                for (std::vector<std::vector<unsigned int>>::const_iterator k = aaiVWeightList.begin(); k != aaiVWeightList.end(); ++k) {
                    if (!(*k).empty()) {
                        ++pcMesh->mNumBones;
                    }
                }
                pcMesh->mBones = new aiBone *[pcMesh->mNumBones];
                iCurrent = 0;
                for (std::vector<std::vector<unsigned int>>::const_iterator k = aaiVWeightList.begin(); k != aaiVWeightList.end(); ++k, ++iCurrent) {
                    if ((*k).empty())
                        continue;

                    // seems we'll need this node
                    aiBone *pcBone = pcMesh->mBones[iCurrent] = new aiBone();
                    pcBone->mName = aiString(shared.apcOutBones[iCurrent]->mName);
                    pcBone->mOffsetMatrix = shared.apcOutBones[iCurrent]->mOffsetMatrix;

                    // setup vertex weights
                    pcBone->mNumWeights = (unsigned int)(*k).size();
                    pcBone->mWeights = new aiVertexWeight[pcBone->mNumWeights];

                    for (unsigned int weight = 0; weight < pcBone->mNumWeights; ++weight) {
                        pcBone->mWeights[weight].mVertexId = (*k)[weight];
                        pcBone->mWeights[weight].mWeight = 1.0f;
                    }
                }
            }
            // add the mesh to the list of output meshes
            splitGroupData.avOutList.push_back(pcMesh);
        }
    }
}

// ------------------------------------------------------------------------------------------------
// Join to materials
void MDLImporter::JoinSkins_3DGS_MDL7(
        aiMaterial *pcMat1,
        aiMaterial *pcMat2,
        aiMaterial *pcMatOut) {
    ai_assert(nullptr != pcMat1);
    ai_assert(nullptr != pcMat2);
    ai_assert(nullptr != pcMatOut);

    // first create a full copy of the first skin property set
    // and assign it to the output material
    aiMaterial::CopyPropertyList(pcMatOut, pcMat1);

    int iVal = 0;
    pcMatOut->AddProperty<int>(&iVal, 1, AI_MATKEY_UVWSRC_DIFFUSE(0));

    // then extract the diffuse texture from the second skin,
    // setup 1 as UV source and we have it
    aiString sString;
    if (AI_SUCCESS == aiGetMaterialString(pcMat2, AI_MATKEY_TEXTURE_DIFFUSE(0), &sString)) {
        iVal = 1;
        pcMatOut->AddProperty<int>(&iVal, 1, AI_MATKEY_UVWSRC_DIFFUSE(1));
        pcMatOut->AddProperty(&sString, AI_MATKEY_TEXTURE_DIFFUSE(1));
    }
}

// ------------------------------------------------------------------------------------------------
// Read a Half-life 1 MDL
void MDLImporter::InternReadFile_HL1(const std::string &pFile, const uint32_t iMagicWord) {
    // We can't correctly load an MDL from a MDL "sequence" file.
    if (iMagicWord == AI_MDL_MAGIC_NUMBER_BE_HL2b || iMagicWord == AI_MDL_MAGIC_NUMBER_LE_HL2b)
        throw DeadlyImportError("Impossible to properly load a model from an MDL sequence file.");

    // Read the MDL file.
    HalfLife::HL1MDLLoader loader(
            pScene,
            mIOHandler,
            mBuffer,
            pFile,
            mHL1ImportSettings);
}

// ------------------------------------------------------------------------------------------------
// Read a half-life 2 MDL
void MDLImporter::InternReadFile_HL2() {
    //const MDL::Header_HL2* pcHeader = (const MDL::Header_HL2*)this->mBuffer;
    throw DeadlyImportError("HL2 MDLs are not implemented");
}

#endif // !! ASSIMP_BUILD_NO_MDL_IMPORTER
