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/** @file  3DSLoader.cpp
 *  @brief Implementation of the 3ds importer class
 *
 *  http://www.the-labs.com/Blender/3DS-details.html
 */

#ifndef ASSIMP_BUILD_NO_3DS_IMPORTER

#include "3DSLoader.h"
#include <assimp/StringComparison.h>
#include <assimp/importerdesc.h>
#include <assimp/scene.h>
#include <assimp/DefaultLogger.hpp>
#include <assimp/IOSystem.hpp>

using namespace Assimp;

static const aiImporterDesc desc = {
    "Discreet 3DS Importer",
    "",
    "",
    "Limited animation support",
    aiImporterFlags_SupportBinaryFlavour,
    0,
    0,
    0,
    0,
    "3ds prj"
};

// ------------------------------------------------------------------------------------------------
// Begins a new parsing block
// - Reads the current chunk and validates it
// - computes its length
#define ASSIMP_3DS_BEGIN_CHUNK()                                              \
    while (true) {                                                            \
        if (stream->GetRemainingSizeToLimit() < sizeof(Discreet3DS::Chunk)) { \
            return;                                                           \
        }                                                                     \
        Discreet3DS::Chunk chunk;                                             \
        ReadChunk(&chunk);                                                    \
        int chunkSize = chunk.Size - sizeof(Discreet3DS::Chunk);              \
        if (chunkSize <= 0)                                                   \
            continue;                                                         \
        const unsigned int oldReadLimit = stream->SetReadLimit(               \
                stream->GetCurrentPos() + chunkSize);

// ------------------------------------------------------------------------------------------------
// End a parsing block
// Must follow at the end of each parsing block, reset chunk end marker to previous value
#define ASSIMP_3DS_END_CHUNK()                  \
    stream->SkipToReadLimit();                  \
    stream->SetReadLimit(oldReadLimit);         \
    if (stream->GetRemainingSizeToLimit() == 0) \
        return;                                 \
    }

// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
Discreet3DSImporter::Discreet3DSImporter() :
        stream(), mLastNodeIndex(), mCurrentNode(), mRootNode(), mScene(), mMasterScale(), bHasBG(), bIsPrj() {
    // empty
}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well
Discreet3DSImporter::~Discreet3DSImporter() {
    // empty
}

// ------------------------------------------------------------------------------------------------
// Returns whether the class can handle the format of the given file.
bool Discreet3DSImporter::CanRead(const std::string &pFile, IOSystem *pIOHandler, bool checkSig) const {
    std::string extension = GetExtension(pFile);
    if (extension == "3ds" || extension == "prj") {
        return true;
    }

    if (!extension.length() || checkSig) {
        uint16_t token[3];
        token[0] = 0x4d4d;
        token[1] = 0x3dc2;
        //token[2] = 0x3daa;
        return CheckMagicToken(pIOHandler, pFile, token, 2, 0, 2);
    }
    return false;
}

// ------------------------------------------------------------------------------------------------
// Loader registry entry
const aiImporterDesc *Discreet3DSImporter::GetInfo() const {
    return &desc;
}

// ------------------------------------------------------------------------------------------------
// Setup configuration properties
void Discreet3DSImporter::SetupProperties(const Importer * /*pImp*/) {
    // nothing to be done for the moment
}

// ------------------------------------------------------------------------------------------------
// Imports the given file into the given scene structure.
void Discreet3DSImporter::InternReadFile(const std::string &pFile,
        aiScene *pScene, IOSystem *pIOHandler) {
    StreamReaderLE theStream(pIOHandler->Open(pFile, "rb"));

    // We should have at least one chunk
    if (theStream.GetRemainingSize() < 16) {
        throw DeadlyImportError("3DS file is either empty or corrupt: " + pFile);
    }
    this->stream = &theStream;

    // Allocate our temporary 3DS representation
    D3DS::Scene _scene;
    mScene = &_scene;

    // Initialize members
    D3DS::Node _rootNode("UNNAMED");
    mLastNodeIndex = -1;
    mCurrentNode = &_rootNode;
    mRootNode = mCurrentNode;
    mRootNode->mHierarchyPos = -1;
    mRootNode->mHierarchyIndex = -1;
    mRootNode->mParent = nullptr;
    mMasterScale = 1.0f;
    mBackgroundImage = "";
    bHasBG = false;
    bIsPrj = false;

    // Parse the file
    ParseMainChunk();

    // Process all meshes in the file. First check whether all
    // face indices have valid values. The generate our
    // internal verbose representation. Finally compute normal
    // vectors from the smoothing groups we read from the
    // file.
    for (auto &mesh : mScene->mMeshes) {
        if (mesh.mFaces.size() > 0 && mesh.mPositions.size() == 0) {
            throw DeadlyImportError("3DS file contains faces but no vertices: " + pFile);
        }
        CheckIndices(mesh);
        MakeUnique(mesh);
        ComputeNormalsWithSmoothingsGroups<D3DS::Face>(mesh);
    }

    // Replace all occurrences of the default material with a
    // valid material. Generate it if no material containing
    // DEFAULT in its name has been found in the file
    ReplaceDefaultMaterial();

    // Convert the scene from our internal representation to an
    // aiScene object. This involves copying all meshes, lights
    // and cameras to the scene
    ConvertScene(pScene);

    // Generate the node graph for the scene. This is a little bit
    // tricky since we'll need to split some meshes into sub-meshes
    GenerateNodeGraph(pScene);

    // Now apply the master scaling factor to the scene
    ApplyMasterScale(pScene);

    // Our internal scene representation and the root
    // node will be automatically deleted, so the whole hierarchy will follow

    AI_DEBUG_INVALIDATE_PTR(mRootNode);
    AI_DEBUG_INVALIDATE_PTR(mScene);
    AI_DEBUG_INVALIDATE_PTR(this->stream);
}

// ------------------------------------------------------------------------------------------------
// Applies a master-scaling factor to the imported scene
void Discreet3DSImporter::ApplyMasterScale(aiScene *pScene) {
    // There are some 3DS files with a zero scaling factor
    if (!mMasterScale)
        mMasterScale = 1.0f;
    else
        mMasterScale = 1.0f / mMasterScale;

    // Construct an uniform scaling matrix and multiply with it
    pScene->mRootNode->mTransformation *= aiMatrix4x4(
            mMasterScale, 0.0f, 0.0f, 0.0f,
            0.0f, mMasterScale, 0.0f, 0.0f,
            0.0f, 0.0f, mMasterScale, 0.0f,
            0.0f, 0.0f, 0.0f, 1.0f);

    // Check whether a scaling track is assigned to the root node.
}

// ------------------------------------------------------------------------------------------------
// Reads a new chunk from the file
void Discreet3DSImporter::ReadChunk(Discreet3DS::Chunk *pcOut) {
    ai_assert(pcOut != nullptr);

    pcOut->Flag = stream->GetI2();
    pcOut->Size = stream->GetI4();

    if (pcOut->Size - sizeof(Discreet3DS::Chunk) > stream->GetRemainingSize()) {
        throw DeadlyImportError("Chunk is too large");
    }

    if (pcOut->Size - sizeof(Discreet3DS::Chunk) > stream->GetRemainingSizeToLimit()) {
        ASSIMP_LOG_ERROR("3DS: Chunk overflow");
    }
}

// ------------------------------------------------------------------------------------------------
// Skip a chunk
void Discreet3DSImporter::SkipChunk() {
    Discreet3DS::Chunk psChunk;
    ReadChunk(&psChunk);

    stream->IncPtr(psChunk.Size - sizeof(Discreet3DS::Chunk));
    return;
}

// ------------------------------------------------------------------------------------------------
// Process the primary chunk of the file
void Discreet3DSImporter::ParseMainChunk() {
    ASSIMP_3DS_BEGIN_CHUNK();

    // get chunk type
    switch (chunk.Flag) {

    case Discreet3DS::CHUNK_PRJ:
        bIsPrj = true;
    case Discreet3DS::CHUNK_MAIN:
        ParseEditorChunk();
        break;
    };

    ASSIMP_3DS_END_CHUNK();
    // recursively continue processing this hierarchy level
    return ParseMainChunk();
}

// ------------------------------------------------------------------------------------------------
void Discreet3DSImporter::ParseEditorChunk() {
    ASSIMP_3DS_BEGIN_CHUNK();

    // get chunk type
    switch (chunk.Flag) {
    case Discreet3DS::CHUNK_OBJMESH:

        ParseObjectChunk();
        break;

    // NOTE: In several documentations in the internet this
    // chunk appears at different locations
    case Discreet3DS::CHUNK_KEYFRAMER:

        ParseKeyframeChunk();
        break;

    case Discreet3DS::CHUNK_VERSION: {
        // print the version number
        char buff[10];
        ASSIMP_itoa10(buff, stream->GetI2());
        ASSIMP_LOG_INFO_F(std::string("3DS file format version: "), buff);
    } break;
    };
    ASSIMP_3DS_END_CHUNK();
}

// ------------------------------------------------------------------------------------------------
void Discreet3DSImporter::ParseObjectChunk() {
    ASSIMP_3DS_BEGIN_CHUNK();

    // get chunk type
    switch (chunk.Flag) {
    case Discreet3DS::CHUNK_OBJBLOCK: {
        unsigned int cnt = 0;
        const char *sz = (const char *)stream->GetPtr();

        // Get the name of the geometry object
        while (stream->GetI1())
            ++cnt;
        ParseChunk(sz, cnt);
    } break;

    case Discreet3DS::CHUNK_MAT_MATERIAL:

        // Add a new material to the list
        mScene->mMaterials.push_back(D3DS::Material(std::string("UNNAMED_" + to_string(mScene->mMaterials.size()))));
        ParseMaterialChunk();
        break;

    case Discreet3DS::CHUNK_AMBCOLOR:

        // This is the ambient base color of the scene.
        // We add it to the ambient color of all materials
        ParseColorChunk(&mClrAmbient, true);
        if (is_qnan(mClrAmbient.r)) {
            // We failed to read the ambient base color.
            ASSIMP_LOG_ERROR("3DS: Failed to read ambient base color");
            mClrAmbient.r = mClrAmbient.g = mClrAmbient.b = 0.0f;
        }
        break;

    case Discreet3DS::CHUNK_BIT_MAP: {
        // Specifies the background image. The string should already be
        // properly 0 terminated but we need to be sure
        unsigned int cnt = 0;
        const char *sz = (const char *)stream->GetPtr();
        while (stream->GetI1())
            ++cnt;
        mBackgroundImage = std::string(sz, cnt);
    } break;

    case Discreet3DS::CHUNK_BIT_MAP_EXISTS:
        bHasBG = true;
        break;

    case Discreet3DS::CHUNK_MASTER_SCALE:
        // Scene master scaling factor
        mMasterScale = stream->GetF4();
        break;
    };
    ASSIMP_3DS_END_CHUNK();
}

// ------------------------------------------------------------------------------------------------
void Discreet3DSImporter::ParseChunk(const char *name, unsigned int num) {
    ASSIMP_3DS_BEGIN_CHUNK();

    // IMPLEMENTATION NOTE;
    // Cameras or lights define their transformation in their parent node and in the
    // corresponding light or camera chunks. However, we read and process the latter
    // to to be able to return valid cameras/lights even if no scenegraph is given.

    // get chunk type
    switch (chunk.Flag) {
    case Discreet3DS::CHUNK_TRIMESH: {
        // this starts a new triangle mesh
        mScene->mMeshes.push_back(D3DS::Mesh(std::string(name, num)));

        // Read mesh chunks
        ParseMeshChunk();
    } break;

    case Discreet3DS::CHUNK_LIGHT: {
        // This starts a new light
        aiLight *light = new aiLight();
        mScene->mLights.push_back(light);

        light->mName.Set(std::string(name, num));

        // First read the position of the light
        light->mPosition.x = stream->GetF4();
        light->mPosition.y = stream->GetF4();
        light->mPosition.z = stream->GetF4();

        light->mColorDiffuse = aiColor3D(1.f, 1.f, 1.f);

        // Now check for further subchunks
        if (!bIsPrj) /* fixme */
            ParseLightChunk();

        // The specular light color is identical the the diffuse light color. The ambient light color
        // is equal to the ambient base color of the whole scene.
        light->mColorSpecular = light->mColorDiffuse;
        light->mColorAmbient = mClrAmbient;

        if (light->mType == aiLightSource_UNDEFINED) {
            // It must be a point light
            light->mType = aiLightSource_POINT;
        }
    } break;

    case Discreet3DS::CHUNK_CAMERA: {
        // This starts a new camera
        aiCamera *camera = new aiCamera();
        mScene->mCameras.push_back(camera);
        camera->mName.Set(std::string(name, num));

        // First read the position of the camera
        camera->mPosition.x = stream->GetF4();
        camera->mPosition.y = stream->GetF4();
        camera->mPosition.z = stream->GetF4();

        // Then the camera target
        camera->mLookAt.x = stream->GetF4() - camera->mPosition.x;
        camera->mLookAt.y = stream->GetF4() - camera->mPosition.y;
        camera->mLookAt.z = stream->GetF4() - camera->mPosition.z;
        ai_real len = camera->mLookAt.Length();
        if (len < 1e-5) {

            // There are some files with lookat == position. Don't know why or whether it's ok or not.
            ASSIMP_LOG_ERROR("3DS: Unable to read proper camera look-at vector");
            camera->mLookAt = aiVector3D(0.0, 1.0, 0.0);

        } else
            camera->mLookAt /= len;

        // And finally - the camera rotation angle, in counter clockwise direction
        const ai_real angle = AI_DEG_TO_RAD(stream->GetF4());
        aiQuaternion quat(camera->mLookAt, angle);
        camera->mUp = quat.GetMatrix() * aiVector3D(0.0, 1.0, 0.0);

        // Read the lense angle
        camera->mHorizontalFOV = AI_DEG_TO_RAD(stream->GetF4());
        if (camera->mHorizontalFOV < 0.001f) {
            camera->mHorizontalFOV = AI_DEG_TO_RAD(45.f);
        }

        // Now check for further subchunks
        if (!bIsPrj) /* fixme */ {
            ParseCameraChunk();
        }
    } break;
    };
    ASSIMP_3DS_END_CHUNK();
}

// ------------------------------------------------------------------------------------------------
void Discreet3DSImporter::ParseLightChunk() {
    ASSIMP_3DS_BEGIN_CHUNK();
    aiLight *light = mScene->mLights.back();

    // get chunk type
    switch (chunk.Flag) {
    case Discreet3DS::CHUNK_DL_SPOTLIGHT:
        // Now we can be sure that the light is a spot light
        light->mType = aiLightSource_SPOT;

        // We wouldn't need to normalize here, but we do it
        light->mDirection.x = stream->GetF4() - light->mPosition.x;
        light->mDirection.y = stream->GetF4() - light->mPosition.y;
        light->mDirection.z = stream->GetF4() - light->mPosition.z;
        light->mDirection.Normalize();

        // Now the hotspot and falloff angles - in degrees
        light->mAngleInnerCone = AI_DEG_TO_RAD(stream->GetF4());

        // FIX: the falloff angle is just an offset
        light->mAngleOuterCone = light->mAngleInnerCone + AI_DEG_TO_RAD(stream->GetF4());
        break;

        // intensity multiplier
    case Discreet3DS::CHUNK_DL_MULTIPLIER:
        light->mColorDiffuse = light->mColorDiffuse * stream->GetF4();
        break;

        // light color
    case Discreet3DS::CHUNK_RGBF:
    case Discreet3DS::CHUNK_LINRGBF:
        light->mColorDiffuse.r *= stream->GetF4();
        light->mColorDiffuse.g *= stream->GetF4();
        light->mColorDiffuse.b *= stream->GetF4();
        break;

        // light attenuation
    case Discreet3DS::CHUNK_DL_ATTENUATE:
        light->mAttenuationLinear = stream->GetF4();
        break;
    };

    ASSIMP_3DS_END_CHUNK();
}

// ------------------------------------------------------------------------------------------------
void Discreet3DSImporter::ParseCameraChunk() {
    ASSIMP_3DS_BEGIN_CHUNK();
    aiCamera *camera = mScene->mCameras.back();

    // get chunk type
    switch (chunk.Flag) {
        // near and far clip plane
    case Discreet3DS::CHUNK_CAM_RANGES:
        camera->mClipPlaneNear = stream->GetF4();
        camera->mClipPlaneFar = stream->GetF4();
        break;
    }

    ASSIMP_3DS_END_CHUNK();
}

// ------------------------------------------------------------------------------------------------
void Discreet3DSImporter::ParseKeyframeChunk() {
    ASSIMP_3DS_BEGIN_CHUNK();

    // get chunk type
    switch (chunk.Flag) {
    case Discreet3DS::CHUNK_TRACKCAMTGT:
    case Discreet3DS::CHUNK_TRACKSPOTL:
    case Discreet3DS::CHUNK_TRACKCAMERA:
    case Discreet3DS::CHUNK_TRACKINFO:
    case Discreet3DS::CHUNK_TRACKLIGHT:
    case Discreet3DS::CHUNK_TRACKLIGTGT:

        // this starts a new mesh hierarchy chunk
        ParseHierarchyChunk(chunk.Flag);
        break;
    };

    ASSIMP_3DS_END_CHUNK();
}

// ------------------------------------------------------------------------------------------------
// Little helper function for ParseHierarchyChunk
void Discreet3DSImporter::InverseNodeSearch(D3DS::Node *pcNode, D3DS::Node *pcCurrent) {
    if (!pcCurrent) {
        mRootNode->push_back(pcNode);
        return;
    }

    if (pcCurrent->mHierarchyPos == pcNode->mHierarchyPos) {
        if (pcCurrent->mParent) {
            pcCurrent->mParent->push_back(pcNode);
        } else
            pcCurrent->push_back(pcNode);
        return;
    }
    return InverseNodeSearch(pcNode, pcCurrent->mParent);
}

// ------------------------------------------------------------------------------------------------
// Find a node with a specific name in the import hierarchy
D3DS::Node *FindNode(D3DS::Node *root, const std::string &name) {
    if (root->mName == name) {
        return root;
    }

    for (std::vector<D3DS::Node *>::iterator it = root->mChildren.begin(); it != root->mChildren.end(); ++it) {
        D3DS::Node *nd = FindNode(*it, name);
        if (nullptr != nd) {
            return nd;
        }
    }

    return nullptr;
}

// ------------------------------------------------------------------------------------------------
// Binary predicate for std::unique()
template <class T>
bool KeyUniqueCompare(const T &first, const T &second) {
    return first.mTime == second.mTime;
}

// ------------------------------------------------------------------------------------------------
// Skip some additional import data.
void Discreet3DSImporter::SkipTCBInfo() {
    unsigned int flags = stream->GetI2();

    if (!flags) {
        // Currently we can't do anything with these values. They occur
        // quite rare, so it wouldn't be worth the effort implementing
        // them. 3DS is not really suitable for complex animations,
        // so full support is not required.
        ASSIMP_LOG_WARN("3DS: Skipping TCB animation info");
    }

    if (flags & Discreet3DS::KEY_USE_TENS) {
        stream->IncPtr(4);
    }
    if (flags & Discreet3DS::KEY_USE_BIAS) {
        stream->IncPtr(4);
    }
    if (flags & Discreet3DS::KEY_USE_CONT) {
        stream->IncPtr(4);
    }
    if (flags & Discreet3DS::KEY_USE_EASE_FROM) {
        stream->IncPtr(4);
    }
    if (flags & Discreet3DS::KEY_USE_EASE_TO) {
        stream->IncPtr(4);
    }
}

// ------------------------------------------------------------------------------------------------
// Read hierarchy and keyframe info
void Discreet3DSImporter::ParseHierarchyChunk(uint16_t parent) {
    ASSIMP_3DS_BEGIN_CHUNK();

    // get chunk type
    switch (chunk.Flag) {
    case Discreet3DS::CHUNK_TRACKOBJNAME:

        // This is the name of the object to which the track applies. The chunk also
        // defines the position of this object in the hierarchy.
        {

            // First of all: get the name of the object
            unsigned int cnt = 0;
            const char *sz = (const char *)stream->GetPtr();

            while (stream->GetI1())
                ++cnt;
            std::string name = std::string(sz, cnt);

            // Now find out whether we have this node already (target animation channels
            // are stored with a separate object ID)
            D3DS::Node *pcNode = FindNode(mRootNode, name);
            int instanceNumber = 1;

            if (pcNode) {
                // if the source is not a CHUNK_TRACKINFO block it won't be an object instance
                if (parent != Discreet3DS::CHUNK_TRACKINFO) {
                    mCurrentNode = pcNode;
                    break;
                }
                pcNode->mInstanceCount++;
                instanceNumber = pcNode->mInstanceCount;
            }
            pcNode = new D3DS::Node(name);
            pcNode->mInstanceNumber = instanceNumber;

            // There are two unknown values which we can safely ignore
            stream->IncPtr(4);

            // Now read the hierarchy position of the object
            uint16_t hierarchy = stream->GetI2() + 1;
            pcNode->mHierarchyPos = hierarchy;
            pcNode->mHierarchyIndex = mLastNodeIndex;

            // And find a proper position in the graph for it
            if (mCurrentNode && mCurrentNode->mHierarchyPos == hierarchy) {

                // add to the parent of the last touched node
                mCurrentNode->mParent->push_back(pcNode);
                mLastNodeIndex++;
            } else if (hierarchy >= mLastNodeIndex) {

                // place it at the current position in the hierarchy
                mCurrentNode->push_back(pcNode);
                mLastNodeIndex = hierarchy;
            } else {
                // need to go back to the specified position in the hierarchy.
                InverseNodeSearch(pcNode, mCurrentNode);
                mLastNodeIndex++;
            }
            // Make this node the current node
            mCurrentNode = pcNode;
        }
        break;

    case Discreet3DS::CHUNK_TRACKDUMMYOBJNAME:

        // This is the "real" name of a $$$DUMMY object
        {
            const char *sz = (const char *)stream->GetPtr();
            while (stream->GetI1())
                ;

            // If object name is DUMMY, take this one instead
            if (mCurrentNode->mName == "$$$DUMMY") {
                mCurrentNode->mName = std::string(sz);
                break;
            }
        }
        break;

    case Discreet3DS::CHUNK_TRACKPIVOT:

        if (Discreet3DS::CHUNK_TRACKINFO != parent) {
            ASSIMP_LOG_WARN("3DS: Skipping pivot subchunk for non usual object");
            break;
        }

        // Pivot = origin of rotation and scaling
        mCurrentNode->vPivot.x = stream->GetF4();
        mCurrentNode->vPivot.y = stream->GetF4();
        mCurrentNode->vPivot.z = stream->GetF4();
        break;

        // ////////////////////////////////////////////////////////////////////
        // POSITION KEYFRAME
    case Discreet3DS::CHUNK_TRACKPOS: {
        stream->IncPtr(10);
        const unsigned int numFrames = stream->GetI4();
        bool sortKeys = false;

        // This could also be meant as the target position for
        // (targeted) lights and cameras
        std::vector<aiVectorKey> *l;
        if (Discreet3DS::CHUNK_TRACKCAMTGT == parent || Discreet3DS::CHUNK_TRACKLIGTGT == parent) {
            l = &mCurrentNode->aTargetPositionKeys;
        } else
            l = &mCurrentNode->aPositionKeys;

        l->reserve(numFrames);
        for (unsigned int i = 0; i < numFrames; ++i) {
            const unsigned int fidx = stream->GetI4();

            // Setup a new position key
            aiVectorKey v;
            v.mTime = (double)fidx;

            SkipTCBInfo();
            v.mValue.x = stream->GetF4();
            v.mValue.y = stream->GetF4();
            v.mValue.z = stream->GetF4();

            // check whether we'll need to sort the keys
            if (!l->empty() && v.mTime <= l->back().mTime)
                sortKeys = true;

            // Add the new keyframe to the list
            l->push_back(v);
        }

        // Sort all keys with ascending time values and remove duplicates?
        if (sortKeys) {
            std::stable_sort(l->begin(), l->end());
            l->erase(std::unique(l->begin(), l->end(), &KeyUniqueCompare<aiVectorKey>), l->end());
        }
    }

    break;

        // ////////////////////////////////////////////////////////////////////
        // CAMERA ROLL KEYFRAME
    case Discreet3DS::CHUNK_TRACKROLL: {
        // roll keys are accepted for cameras only
        if (parent != Discreet3DS::CHUNK_TRACKCAMERA) {
            ASSIMP_LOG_WARN("3DS: Ignoring roll track for non-camera object");
            break;
        }
        bool sortKeys = false;
        std::vector<aiFloatKey> *l = &mCurrentNode->aCameraRollKeys;

        stream->IncPtr(10);
        const unsigned int numFrames = stream->GetI4();
        l->reserve(numFrames);
        for (unsigned int i = 0; i < numFrames; ++i) {
            const unsigned int fidx = stream->GetI4();

            // Setup a new position key
            aiFloatKey v;
            v.mTime = (double)fidx;

            // This is just a single float
            SkipTCBInfo();
            v.mValue = stream->GetF4();

            // Check whether we'll need to sort the keys
            if (!l->empty() && v.mTime <= l->back().mTime)
                sortKeys = true;

            // Add the new keyframe to the list
            l->push_back(v);
        }

        // Sort all keys with ascending time values and remove duplicates?
        if (sortKeys) {
            std::stable_sort(l->begin(), l->end());
            l->erase(std::unique(l->begin(), l->end(), &KeyUniqueCompare<aiFloatKey>), l->end());
        }
    } break;

        // ////////////////////////////////////////////////////////////////////
        // CAMERA FOV KEYFRAME
    case Discreet3DS::CHUNK_TRACKFOV: {
        ASSIMP_LOG_ERROR("3DS: Skipping FOV animation track. "
                         "This is not supported");
    } break;

        // ////////////////////////////////////////////////////////////////////
        // ROTATION KEYFRAME
    case Discreet3DS::CHUNK_TRACKROTATE: {
        stream->IncPtr(10);
        const unsigned int numFrames = stream->GetI4();

        bool sortKeys = false;
        std::vector<aiQuatKey> *l = &mCurrentNode->aRotationKeys;
        l->reserve(numFrames);

        for (unsigned int i = 0; i < numFrames; ++i) {
            const unsigned int fidx = stream->GetI4();
            SkipTCBInfo();

            aiQuatKey v;
            v.mTime = (double)fidx;

            // The rotation keyframe is given as an axis-angle pair
            const float rad = stream->GetF4();
            aiVector3D axis;
            axis.x = stream->GetF4();
            axis.y = stream->GetF4();
            axis.z = stream->GetF4();

            if (!axis.x && !axis.y && !axis.z)
                axis.y = 1.f;

            // Construct a rotation quaternion from the axis-angle pair
            v.mValue = aiQuaternion(axis, rad);

            // Check whether we'll need to sort the keys
            if (!l->empty() && v.mTime <= l->back().mTime)
                sortKeys = true;

            // add the new keyframe to the list
            l->push_back(v);
        }
        // Sort all keys with ascending time values and remove duplicates?
        if (sortKeys) {
            std::stable_sort(l->begin(), l->end());
            l->erase(std::unique(l->begin(), l->end(), &KeyUniqueCompare<aiQuatKey>), l->end());
        }
    } break;

        // ////////////////////////////////////////////////////////////////////
        // SCALING KEYFRAME
    case Discreet3DS::CHUNK_TRACKSCALE: {
        stream->IncPtr(10);
        const unsigned int numFrames = stream->GetI2();
        stream->IncPtr(2);

        bool sortKeys = false;
        std::vector<aiVectorKey> *l = &mCurrentNode->aScalingKeys;
        l->reserve(numFrames);

        for (unsigned int i = 0; i < numFrames; ++i) {
            const unsigned int fidx = stream->GetI4();
            SkipTCBInfo();

            // Setup a new key
            aiVectorKey v;
            v.mTime = (double)fidx;

            // ... and read its value
            v.mValue.x = stream->GetF4();
            v.mValue.y = stream->GetF4();
            v.mValue.z = stream->GetF4();

            // check whether we'll need to sort the keys
            if (!l->empty() && v.mTime <= l->back().mTime)
                sortKeys = true;

            // Remove zero-scalings on singular axes - they've been reported to be there erroneously in some strange files
            if (!v.mValue.x) v.mValue.x = 1.f;
            if (!v.mValue.y) v.mValue.y = 1.f;
            if (!v.mValue.z) v.mValue.z = 1.f;

            l->push_back(v);
        }
        // Sort all keys with ascending time values and remove duplicates?
        if (sortKeys) {
            std::stable_sort(l->begin(), l->end());
            l->erase(std::unique(l->begin(), l->end(), &KeyUniqueCompare<aiVectorKey>), l->end());
        }
    } break;
    };

    ASSIMP_3DS_END_CHUNK();
}

// ------------------------------------------------------------------------------------------------
// Read a face chunk - it contains smoothing groups and material assignments
void Discreet3DSImporter::ParseFaceChunk() {
    ASSIMP_3DS_BEGIN_CHUNK();

    // Get the mesh we're currently working on
    D3DS::Mesh &mMesh = mScene->mMeshes.back();

    // Get chunk type
    switch (chunk.Flag) {
    case Discreet3DS::CHUNK_SMOOLIST: {
        // This is the list of smoothing groups - a bitfield for every face.
        // Up to 32 smoothing groups assigned to a single face.
        unsigned int num = chunkSize / 4, m = 0;
        if (num > mMesh.mFaces.size()) {
            throw DeadlyImportError("3DS: More smoothing groups than faces");
        }
        for (std::vector<D3DS::Face>::iterator i = mMesh.mFaces.begin(); m != num; ++i, ++m) {
            // nth bit is set for nth smoothing group
            (*i).iSmoothGroup = stream->GetI4();
        }
    } break;

    case Discreet3DS::CHUNK_FACEMAT: {
        // at fist an asciiz with the material name
        const char *sz = (const char *)stream->GetPtr();
        while (stream->GetI1())
            ;

        // find the index of the material
        unsigned int idx = 0xcdcdcdcd, cnt = 0;
        for (std::vector<D3DS::Material>::const_iterator i = mScene->mMaterials.begin(); i != mScene->mMaterials.end(); ++i, ++cnt) {
            // use case independent comparisons. hopefully it will work.
            if ((*i).mName.length() && !ASSIMP_stricmp(sz, (*i).mName.c_str())) {
                idx = cnt;
                break;
            }
        }
        if (0xcdcdcdcd == idx) {
            ASSIMP_LOG_ERROR_F("3DS: Unknown material: ", sz);
        }

        // Now continue and read all material indices
        cnt = (uint16_t)stream->GetI2();
        for (unsigned int i = 0; i < cnt; ++i) {
            unsigned int fidx = (uint16_t)stream->GetI2();

            // check range
            if (fidx >= mMesh.mFaceMaterials.size()) {
                ASSIMP_LOG_ERROR("3DS: Invalid face index in face material list");
            } else
                mMesh.mFaceMaterials[fidx] = idx;
        }
    } break;
    };
    ASSIMP_3DS_END_CHUNK();
}

// ------------------------------------------------------------------------------------------------
// Read a mesh chunk. Here's the actual mesh data
void Discreet3DSImporter::ParseMeshChunk() {
    ASSIMP_3DS_BEGIN_CHUNK();

    // Get the mesh we're currently working on
    D3DS::Mesh &mMesh = mScene->mMeshes.back();

    // get chunk type
    switch (chunk.Flag) {
    case Discreet3DS::CHUNK_VERTLIST: {
        // This is the list of all vertices in the current mesh
        int num = (int)(uint16_t)stream->GetI2();
        mMesh.mPositions.reserve(num);
        while (num-- > 0) {
            aiVector3D v;
            v.x = stream->GetF4();
            v.y = stream->GetF4();
            v.z = stream->GetF4();
            mMesh.mPositions.push_back(v);
        }
    } break;
    case Discreet3DS::CHUNK_TRMATRIX: {
        // This is the RLEATIVE transformation matrix of the current mesh. Vertices are
        // pretransformed by this matrix wonder.
        mMesh.mMat.a1 = stream->GetF4();
        mMesh.mMat.b1 = stream->GetF4();
        mMesh.mMat.c1 = stream->GetF4();
        mMesh.mMat.a2 = stream->GetF4();
        mMesh.mMat.b2 = stream->GetF4();
        mMesh.mMat.c2 = stream->GetF4();
        mMesh.mMat.a3 = stream->GetF4();
        mMesh.mMat.b3 = stream->GetF4();
        mMesh.mMat.c3 = stream->GetF4();
        mMesh.mMat.a4 = stream->GetF4();
        mMesh.mMat.b4 = stream->GetF4();
        mMesh.mMat.c4 = stream->GetF4();
    } break;

    case Discreet3DS::CHUNK_MAPLIST: {
        // This is the list of all UV coords in the current mesh
        int num = (int)(uint16_t)stream->GetI2();
        mMesh.mTexCoords.reserve(num);
        while (num-- > 0) {
            aiVector3D v;
            v.x = stream->GetF4();
            v.y = stream->GetF4();
            mMesh.mTexCoords.push_back(v);
        }
    } break;

    case Discreet3DS::CHUNK_FACELIST: {
        // This is the list of all faces in the current mesh
        int num = (int)(uint16_t)stream->GetI2();
        mMesh.mFaces.reserve(num);
        while (num-- > 0) {
            // 3DS faces are ALWAYS triangles
            mMesh.mFaces.push_back(D3DS::Face());
            D3DS::Face &sFace = mMesh.mFaces.back();

            sFace.mIndices[0] = (uint16_t)stream->GetI2();
            sFace.mIndices[1] = (uint16_t)stream->GetI2();
            sFace.mIndices[2] = (uint16_t)stream->GetI2();

            stream->IncPtr(2); // skip edge visibility flag
        }

        // Resize the material array (0xcdcdcdcd marks the default material; so if a face is
        // not referenced by a material, $$DEFAULT will be assigned to it)
        mMesh.mFaceMaterials.resize(mMesh.mFaces.size(), 0xcdcdcdcd);

        // Larger 3DS files could have multiple FACE chunks here
        chunkSize = (int)stream->GetRemainingSizeToLimit();
        if (chunkSize > (int)sizeof(Discreet3DS::Chunk))
            ParseFaceChunk();
    } break;
    };
    ASSIMP_3DS_END_CHUNK();
}

// ------------------------------------------------------------------------------------------------
// Read a 3DS material chunk
void Discreet3DSImporter::ParseMaterialChunk() {
    ASSIMP_3DS_BEGIN_CHUNK();
    switch (chunk.Flag) {
    case Discreet3DS::CHUNK_MAT_MATNAME:

    {
        // The material name string is already zero-terminated, but we need to be sure ...
        const char *sz = (const char *)stream->GetPtr();
        unsigned int cnt = 0;
        while (stream->GetI1())
            ++cnt;

        if (!cnt) {
            // This may not be, we use the default name instead
            ASSIMP_LOG_ERROR("3DS: Empty material name");
        } else
            mScene->mMaterials.back().mName = std::string(sz, cnt);
    } break;

    case Discreet3DS::CHUNK_MAT_DIFFUSE: {
        // This is the diffuse material color
        aiColor3D *pc = &mScene->mMaterials.back().mDiffuse;
        ParseColorChunk(pc);
        if (is_qnan(pc->r)) {
            // color chunk is invalid. Simply ignore it
            ASSIMP_LOG_ERROR("3DS: Unable to read DIFFUSE chunk");
            pc->r = pc->g = pc->b = 1.0f;
        }
    } break;

    case Discreet3DS::CHUNK_MAT_SPECULAR: {
        // This is the specular material color
        aiColor3D *pc = &mScene->mMaterials.back().mSpecular;
        ParseColorChunk(pc);
        if (is_qnan(pc->r)) {
            // color chunk is invalid. Simply ignore it
            ASSIMP_LOG_ERROR("3DS: Unable to read SPECULAR chunk");
            pc->r = pc->g = pc->b = 1.0f;
        }
    } break;

    case Discreet3DS::CHUNK_MAT_AMBIENT: {
        // This is the ambient material color
        aiColor3D *pc = &mScene->mMaterials.back().mAmbient;
        ParseColorChunk(pc);
        if (is_qnan(pc->r)) {
            // color chunk is invalid. Simply ignore it
            ASSIMP_LOG_ERROR("3DS: Unable to read AMBIENT chunk");
            pc->r = pc->g = pc->b = 0.0f;
        }
    } break;

    case Discreet3DS::CHUNK_MAT_SELF_ILLUM: {
        // This is the emissive material color
        aiColor3D *pc = &mScene->mMaterials.back().mEmissive;
        ParseColorChunk(pc);
        if (is_qnan(pc->r)) {
            // color chunk is invalid. Simply ignore it
            ASSIMP_LOG_ERROR("3DS: Unable to read EMISSIVE chunk");
            pc->r = pc->g = pc->b = 0.0f;
        }
    } break;

    case Discreet3DS::CHUNK_MAT_TRANSPARENCY: {
        // This is the material's transparency
        ai_real *pcf = &mScene->mMaterials.back().mTransparency;
        *pcf = ParsePercentageChunk();

        // NOTE: transparency, not opacity
        if (is_qnan(*pcf))
            *pcf = ai_real(1.0);
        else
            *pcf = ai_real(1.0) - *pcf * (ai_real)0xFFFF / ai_real(100.0);
    } break;

    case Discreet3DS::CHUNK_MAT_SHADING:
        // This is the material shading mode
        mScene->mMaterials.back().mShading = (D3DS::Discreet3DS::shadetype3ds)stream->GetI2();
        break;

    case Discreet3DS::CHUNK_MAT_TWO_SIDE:
        // This is the two-sided flag
        mScene->mMaterials.back().mTwoSided = true;
        break;

    case Discreet3DS::CHUNK_MAT_SHININESS: { // This is the shininess of the material
        ai_real *pcf = &mScene->mMaterials.back().mSpecularExponent;
        *pcf = ParsePercentageChunk();
        if (is_qnan(*pcf))
            *pcf = 0.0;
        else
            *pcf *= (ai_real)0xFFFF;
    } break;

    case Discreet3DS::CHUNK_MAT_SHININESS_PERCENT: { // This is the shininess strength of the material
        ai_real *pcf = &mScene->mMaterials.back().mShininessStrength;
        *pcf = ParsePercentageChunk();
        if (is_qnan(*pcf))
            *pcf = ai_real(0.0);
        else
            *pcf *= (ai_real)0xffff / ai_real(100.0);
    } break;

    case Discreet3DS::CHUNK_MAT_SELF_ILPCT: { // This is the self illumination strength of the material
        ai_real f = ParsePercentageChunk();
        if (is_qnan(f))
            f = ai_real(0.0);
        else
            f *= (ai_real)0xFFFF / ai_real(100.0);
        mScene->mMaterials.back().mEmissive = aiColor3D(f, f, f);
    } break;

    // Parse texture chunks
    case Discreet3DS::CHUNK_MAT_TEXTURE:
        // Diffuse texture
        ParseTextureChunk(&mScene->mMaterials.back().sTexDiffuse);
        break;
    case Discreet3DS::CHUNK_MAT_BUMPMAP:
        // Height map
        ParseTextureChunk(&mScene->mMaterials.back().sTexBump);
        break;
    case Discreet3DS::CHUNK_MAT_OPACMAP:
        // Opacity texture
        ParseTextureChunk(&mScene->mMaterials.back().sTexOpacity);
        break;
    case Discreet3DS::CHUNK_MAT_MAT_SHINMAP:
        // Shininess map
        ParseTextureChunk(&mScene->mMaterials.back().sTexShininess);
        break;
    case Discreet3DS::CHUNK_MAT_SPECMAP:
        // Specular map
        ParseTextureChunk(&mScene->mMaterials.back().sTexSpecular);
        break;
    case Discreet3DS::CHUNK_MAT_SELFIMAP:
        // Self-illumination (emissive) map
        ParseTextureChunk(&mScene->mMaterials.back().sTexEmissive);
        break;
    case Discreet3DS::CHUNK_MAT_REFLMAP:
        // Reflection map
        ParseTextureChunk(&mScene->mMaterials.back().sTexReflective);
        break;
    };
    ASSIMP_3DS_END_CHUNK();
}

// ------------------------------------------------------------------------------------------------
void Discreet3DSImporter::ParseTextureChunk(D3DS::Texture *pcOut) {
    ASSIMP_3DS_BEGIN_CHUNK();

    // get chunk type
    switch (chunk.Flag) {
    case Discreet3DS::CHUNK_MAPFILE: {
        // The material name string is already zero-terminated, but we need to be sure ...
        const char *sz = (const char *)stream->GetPtr();
        unsigned int cnt = 0;
        while (stream->GetI1())
            ++cnt;
        pcOut->mMapName = std::string(sz, cnt);
    } break;

    case Discreet3DS::CHUNK_PERCENTD:
        // Manually parse the blend factor
        pcOut->mTextureBlend = ai_real(stream->GetF8());
        break;

    case Discreet3DS::CHUNK_PERCENTF:
        // Manually parse the blend factor
        pcOut->mTextureBlend = stream->GetF4();
        break;

    case Discreet3DS::CHUNK_PERCENTW:
        // Manually parse the blend factor
        pcOut->mTextureBlend = (ai_real)((uint16_t)stream->GetI2()) / ai_real(100.0);
        break;

    case Discreet3DS::CHUNK_MAT_MAP_USCALE:
        // Texture coordinate scaling in the U direction
        pcOut->mScaleU = stream->GetF4();
        if (0.0f == pcOut->mScaleU) {
            ASSIMP_LOG_WARN("Texture coordinate scaling in the x direction is zero. Assuming 1.");
            pcOut->mScaleU = 1.0f;
        }
        break;
    case Discreet3DS::CHUNK_MAT_MAP_VSCALE:
        // Texture coordinate scaling in the V direction
        pcOut->mScaleV = stream->GetF4();
        if (0.0f == pcOut->mScaleV) {
            ASSIMP_LOG_WARN("Texture coordinate scaling in the y direction is zero. Assuming 1.");
            pcOut->mScaleV = 1.0f;
        }
        break;

    case Discreet3DS::CHUNK_MAT_MAP_UOFFSET:
        // Texture coordinate offset in the U direction
        pcOut->mOffsetU = -stream->GetF4();
        break;

    case Discreet3DS::CHUNK_MAT_MAP_VOFFSET:
        // Texture coordinate offset in the V direction
        pcOut->mOffsetV = stream->GetF4();
        break;

    case Discreet3DS::CHUNK_MAT_MAP_ANG:
        // Texture coordinate rotation, CCW in DEGREES
        pcOut->mRotation = -AI_DEG_TO_RAD(stream->GetF4());
        break;

    case Discreet3DS::CHUNK_MAT_MAP_TILING: {
        const uint16_t iFlags = stream->GetI2();

        // Get the mapping mode (for both axes)
        if (iFlags & 0x2u)
            pcOut->mMapMode = aiTextureMapMode_Mirror;

        else if (iFlags & 0x10u)
            pcOut->mMapMode = aiTextureMapMode_Decal;

        // wrapping in all remaining cases
        else
            pcOut->mMapMode = aiTextureMapMode_Wrap;
    } break;
    };

    ASSIMP_3DS_END_CHUNK();
}

// ------------------------------------------------------------------------------------------------
// Read a percentage chunk
ai_real Discreet3DSImporter::ParsePercentageChunk() {
    Discreet3DS::Chunk chunk;
    ReadChunk(&chunk);

    if (Discreet3DS::CHUNK_PERCENTF == chunk.Flag) {
        return stream->GetF4() * ai_real(100) / ai_real(0xFFFF);
    } else if (Discreet3DS::CHUNK_PERCENTW == chunk.Flag) {
        return (ai_real)((uint16_t)stream->GetI2()) / (ai_real)0xFFFF;
    }

    return get_qnan();
}

// ------------------------------------------------------------------------------------------------
// Read a color chunk. If a percentage chunk is found instead it is read as a grayscale color
void Discreet3DSImporter::ParseColorChunk(aiColor3D *out, bool acceptPercent) {
    ai_assert(out != nullptr);

    // error return value
    const ai_real qnan = get_qnan();
    static const aiColor3D clrError = aiColor3D(qnan, qnan, qnan);

    Discreet3DS::Chunk chunk;
    ReadChunk(&chunk);
    const unsigned int diff = chunk.Size - sizeof(Discreet3DS::Chunk);

    bool bGamma = false;

    // Get the type of the chunk
    switch (chunk.Flag) {
    case Discreet3DS::CHUNK_LINRGBF:
        bGamma = true;

    case Discreet3DS::CHUNK_RGBF:
        if (sizeof(float) * 3 > diff) {
            *out = clrError;
            return;
        }
        out->r = stream->GetF4();
        out->g = stream->GetF4();
        out->b = stream->GetF4();
        break;

    case Discreet3DS::CHUNK_LINRGBB:
        bGamma = true;
    case Discreet3DS::CHUNK_RGBB: {
        if (sizeof(char) * 3 > diff) {
            *out = clrError;
            return;
        }
        const ai_real invVal = ai_real(1.0) / ai_real(255.0);
        out->r = (ai_real)(uint8_t)stream->GetI1() * invVal;
        out->g = (ai_real)(uint8_t)stream->GetI1() * invVal;
        out->b = (ai_real)(uint8_t)stream->GetI1() * invVal;
    } break;

    // Percentage chunks are accepted, too.
    case Discreet3DS::CHUNK_PERCENTF:
        if (acceptPercent && 4 <= diff) {
            out->g = out->b = out->r = stream->GetF4();
            break;
        }
        *out = clrError;
        return;

    case Discreet3DS::CHUNK_PERCENTW:
        if (acceptPercent && 1 <= diff) {
            out->g = out->b = out->r = (ai_real)(uint8_t)stream->GetI1() / ai_real(255.0);
            break;
        }
        *out = clrError;
        return;

    default:
        stream->IncPtr(diff);
        // Skip unknown chunks, hope this won't cause any problems.
        return ParseColorChunk(out, acceptPercent);
    };
    (void)bGamma;
}

#endif // !! ASSIMP_BUILD_NO_3DS_IMPORTER
