add assimp submodule

1 files changed, 1542 insertions, 0 deletions

diff --git a/src/mesh/assimp-master/code/AssetLib/glTF2/glTF2Exporter.cpp b/src/mesh/assimp-master/code/AssetLib/glTF2/glTF2Exporter.cpp
new file mode 100644
index 0000000..ffd8d22
--- /dev/null
+++ b/src/mesh/assimp-master/code/AssetLib/glTF2/glTF2Exporter.cpp
@@ -0,0 +1,1542 @@
+/*
+Open Asset Import Library (assimp)
+----------------------------------------------------------------------
+
+Copyright (c) 2006-2022, assimp team
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the
+following conditions are met:
+
+* Redistributions of source code must retain the above
+copyright notice, this list of conditions and the
+following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the
+following disclaimer in the documentation and/or other
+materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+contributors may be used to endorse or promote products
+derived from this software without specific prior
+written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+----------------------------------------------------------------------
+*/
+#ifndef ASSIMP_BUILD_NO_EXPORT
+#ifndef ASSIMP_BUILD_NO_GLTF_EXPORTER
+
+#include "AssetLib/glTF2/glTF2Exporter.h"
+#include "AssetLib/glTF2/glTF2AssetWriter.h"
+#include "PostProcessing/SplitLargeMeshes.h"
+
+#include <assimp/ByteSwapper.h>
+#include <assimp/Exceptional.h>
+#include <assimp/SceneCombiner.h>
+#include <assimp/StringComparison.h>
+#include <assimp/commonMetaData.h>
+#include <assimp/material.h>
+#include <assimp/scene.h>
+#include <assimp/version.h>
+#include <assimp/Exporter.hpp>
+#include <assimp/IOSystem.hpp>
+
+// Header files, standard library.
+#include <cinttypes>
+#include <limits>
+#include <memory>
+
+using namespace rapidjson;
+
+using namespace Assimp;
+using namespace glTF2;
+
+namespace Assimp {
+
+// ------------------------------------------------------------------------------------------------
+// Worker function for exporting a scene to GLTF. Prototyped and registered in Exporter.cpp
+void ExportSceneGLTF2(const char *pFile, IOSystem *pIOSystem, const aiScene *pScene, const ExportProperties *pProperties) {
+    // invoke the exporter
+    glTF2Exporter exporter(pFile, pIOSystem, pScene, pProperties, false);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Worker function for exporting a scene to GLB. Prototyped and registered in Exporter.cpp
+void ExportSceneGLB2(const char *pFile, IOSystem *pIOSystem, const aiScene *pScene, const ExportProperties *pProperties) {
+    // invoke the exporter
+    glTF2Exporter exporter(pFile, pIOSystem, pScene, pProperties, true);
+}
+
+} // end of namespace Assimp
+
+glTF2Exporter::glTF2Exporter(const char *filename, IOSystem *pIOSystem, const aiScene *pScene,
+        const ExportProperties *pProperties, bool isBinary) :
+        mFilename(filename), mIOSystem(pIOSystem), mScene(pScene), mProperties(pProperties), mAsset(new Asset(pIOSystem)) {
+    // Always on as our triangulation process is aware of this type of encoding
+    mAsset->extensionsUsed.FB_ngon_encoding = true;
+
+    if (isBinary) {
+        mAsset->SetAsBinary();
+    }
+
+    ExportMetadata();
+
+    ExportMaterials();
+
+    if (mScene->mRootNode) {
+        ExportNodeHierarchy(mScene->mRootNode);
+    }
+
+    ExportMeshes();
+    MergeMeshes();
+
+    ExportScene();
+
+    ExportAnimations();
+
+    // export extras
+    if (mProperties->HasPropertyCallback("extras")) {
+        std::function<void *(void *)> ExportExtras = mProperties->GetPropertyCallback("extras");
+        mAsset->extras = (rapidjson::Value *)ExportExtras(0);
+    }
+
+    AssetWriter writer(*mAsset);
+
+    if (isBinary) {
+        writer.WriteGLBFile(filename);
+    } else {
+        writer.WriteFile(filename);
+    }
+}
+
+glTF2Exporter::~glTF2Exporter() {
+    // empty
+}
+
+/*
+ * Copy a 4x4 matrix from struct aiMatrix to typedef mat4.
+ * Also converts from row-major to column-major storage.
+ */
+static void CopyValue(const aiMatrix4x4 &v, mat4 &o) {
+    o[0] = v.a1;
+    o[1] = v.b1;
+    o[2] = v.c1;
+    o[3] = v.d1;
+    o[4] = v.a2;
+    o[5] = v.b2;
+    o[6] = v.c2;
+    o[7] = v.d2;
+    o[8] = v.a3;
+    o[9] = v.b3;
+    o[10] = v.c3;
+    o[11] = v.d3;
+    o[12] = v.a4;
+    o[13] = v.b4;
+    o[14] = v.c4;
+    o[15] = v.d4;
+}
+
+static void CopyValue(const aiMatrix4x4 &v, aiMatrix4x4 &o) {
+    memcpy(&o, &v, sizeof(aiMatrix4x4));
+}
+
+static void IdentityMatrix4(mat4 &o) {
+    o[0] = 1;
+    o[1] = 0;
+    o[2] = 0;
+    o[3] = 0;
+    o[4] = 0;
+    o[5] = 1;
+    o[6] = 0;
+    o[7] = 0;
+    o[8] = 0;
+    o[9] = 0;
+    o[10] = 1;
+    o[11] = 0;
+    o[12] = 0;
+    o[13] = 0;
+    o[14] = 0;
+    o[15] = 1;
+}
+
+static bool IsBoneWeightFitted(vec4 &weight) {
+    return weight[0] + weight[1] + weight[2] + weight[3] >= 1.f;
+}
+
+static int FitBoneWeight(vec4 &weight, float value) {
+    int i = 0;
+    for (; i < 4; ++i) {
+        if (weight[i] < value) {
+            weight[i] = value;
+            return i;
+        }
+    }
+
+    return -1;
+}
+
+template <typename T>
+void SetAccessorRange(Ref<Accessor> acc, void *data, size_t count,
+        unsigned int numCompsIn, unsigned int numCompsOut) {
+    ai_assert(numCompsOut <= numCompsIn);
+
+    // Allocate and initialize with large values.
+    for (unsigned int i = 0; i < numCompsOut; i++) {
+        acc->min.push_back(std::numeric_limits<double>::max());
+        acc->max.push_back(-std::numeric_limits<double>::max());
+    }
+
+    size_t totalComps = count * numCompsIn;
+    T *buffer_ptr = static_cast<T *>(data);
+    T *buffer_end = buffer_ptr + totalComps;
+
+    // Search and set extreme values.
+    for (; buffer_ptr < buffer_end; buffer_ptr += numCompsIn) {
+        for (unsigned int j = 0; j < numCompsOut; j++) {
+            double valueTmp = buffer_ptr[j];
+
+            // Gracefully tolerate rogue NaN's in buffer data
+            // Any NaNs/Infs introduced in accessor bounds will end up in
+            // document and prevent rapidjson from writing out valid JSON
+            if (!std::isfinite(valueTmp)) {
+                continue;
+            }
+
+            if (valueTmp < acc->min[j]) {
+                acc->min[j] = valueTmp;
+            }
+            if (valueTmp > acc->max[j]) {
+                acc->max[j] = valueTmp;
+            }
+        }
+    }
+}
+
+inline void SetAccessorRange(ComponentType compType, Ref<Accessor> acc, void *data,
+        size_t count, unsigned int numCompsIn, unsigned int numCompsOut) {
+    switch (compType) {
+    case ComponentType_SHORT:
+        SetAccessorRange<short>(acc, data, count, numCompsIn, numCompsOut);
+        return;
+    case ComponentType_UNSIGNED_SHORT:
+        SetAccessorRange<unsigned short>(acc, data, count, numCompsIn, numCompsOut);
+        return;
+    case ComponentType_UNSIGNED_INT:
+        SetAccessorRange<unsigned int>(acc, data, count, numCompsIn, numCompsOut);
+        return;
+    case ComponentType_FLOAT:
+        SetAccessorRange<float>(acc, data, count, numCompsIn, numCompsOut);
+        return;
+    case ComponentType_BYTE:
+        SetAccessorRange<int8_t>(acc, data, count, numCompsIn, numCompsOut);
+        return;
+    case ComponentType_UNSIGNED_BYTE:
+        SetAccessorRange<uint8_t>(acc, data, count, numCompsIn, numCompsOut);
+        return;
+    }
+}
+
+// compute the (data-dataBase), store the non-zero data items
+template <typename T>
+size_t NZDiff(void *data, void *dataBase, size_t count, unsigned int numCompsIn, unsigned int numCompsOut, void *&outputNZDiff, void *&outputNZIdx) {
+    std::vector<T> vNZDiff;
+    std::vector<unsigned short> vNZIdx;
+    size_t totalComps = count * numCompsIn;
+    T *bufferData_ptr = static_cast<T *>(data);
+    T *bufferData_end = bufferData_ptr + totalComps;
+    T *bufferBase_ptr = static_cast<T *>(dataBase);
+
+    // Search and set extreme values.
+    for (short idx = 0; bufferData_ptr < bufferData_end; idx += 1, bufferData_ptr += numCompsIn) {
+        bool bNonZero = false;
+
+        //for the data, check any component Non Zero
+        for (unsigned int j = 0; j < numCompsOut; j++) {
+            double valueData = bufferData_ptr[j];
+            double valueBase = bufferBase_ptr ? bufferBase_ptr[j] : 0;
+            if ((valueData - valueBase) != 0) {
+                bNonZero = true;
+                break;
+            }
+        }
+
+        //all zeros, continue
+        if (!bNonZero)
+            continue;
+
+        //non zero, store the data
+        for (unsigned int j = 0; j < numCompsOut; j++) {
+            T valueData = bufferData_ptr[j];
+            T valueBase = bufferBase_ptr ? bufferBase_ptr[j] : 0;
+            vNZDiff.push_back(valueData - valueBase);
+        }
+        vNZIdx.push_back(idx);
+    }
+
+    //avoid all-0, put 1 item
+    if (vNZDiff.size() == 0) {
+        for (unsigned int j = 0; j < numCompsOut; j++)
+            vNZDiff.push_back(0);
+        vNZIdx.push_back(0);
+    }
+
+    //process data
+    outputNZDiff = new T[vNZDiff.size()];
+    memcpy(outputNZDiff, vNZDiff.data(), vNZDiff.size() * sizeof(T));
+
+    outputNZIdx = new unsigned short[vNZIdx.size()];
+    memcpy(outputNZIdx, vNZIdx.data(), vNZIdx.size() * sizeof(unsigned short));
+    return vNZIdx.size();
+}
+
+inline size_t NZDiff(ComponentType compType, void *data, void *dataBase, size_t count, unsigned int numCompsIn, unsigned int numCompsOut, void *&nzDiff, void *&nzIdx) {
+    switch (compType) {
+    case ComponentType_SHORT:
+        return NZDiff<short>(data, dataBase, count, numCompsIn, numCompsOut, nzDiff, nzIdx);
+    case ComponentType_UNSIGNED_SHORT:
+        return NZDiff<unsigned short>(data, dataBase, count, numCompsIn, numCompsOut, nzDiff, nzIdx);
+    case ComponentType_UNSIGNED_INT:
+        return NZDiff<unsigned int>(data, dataBase, count, numCompsIn, numCompsOut, nzDiff, nzIdx);
+    case ComponentType_FLOAT:
+        return NZDiff<float>(data, dataBase, count, numCompsIn, numCompsOut, nzDiff, nzIdx);
+    case ComponentType_BYTE:
+        return NZDiff<int8_t>(data, dataBase, count, numCompsIn, numCompsOut, nzDiff, nzIdx);
+    case ComponentType_UNSIGNED_BYTE:
+        return NZDiff<uint8_t>(data, dataBase, count, numCompsIn, numCompsOut, nzDiff, nzIdx);
+    }
+    return 0;
+}
+
+inline Ref<Accessor> ExportDataSparse(Asset &a, std::string &meshName, Ref<Buffer> &buffer,
+        size_t count, void *data, AttribType::Value typeIn, AttribType::Value typeOut, ComponentType compType, BufferViewTarget target = BufferViewTarget_NONE, void *dataBase = 0) {
+    if (!count || !data) {
+        return Ref<Accessor>();
+    }
+
+    unsigned int numCompsIn = AttribType::GetNumComponents(typeIn);
+    unsigned int numCompsOut = AttribType::GetNumComponents(typeOut);
+    unsigned int bytesPerComp = ComponentTypeSize(compType);
+
+    // accessor
+    Ref<Accessor> acc = a.accessors.Create(a.FindUniqueID(meshName, "accessor"));
+
+    // if there is a basic data vector
+    if (dataBase) {
+        size_t base_offset = buffer->byteLength;
+        size_t base_padding = base_offset % bytesPerComp;
+        base_offset += base_padding;
+        size_t base_length = count * numCompsOut * bytesPerComp;
+        buffer->Grow(base_length + base_padding);
+
+        Ref<BufferView> bv = a.bufferViews.Create(a.FindUniqueID(meshName, "view"));
+        bv->buffer = buffer;
+        bv->byteOffset = base_offset;
+        bv->byteLength = base_length; //! The target that the WebGL buffer should be bound to.
+        bv->byteStride = 0;
+        bv->target = target;
+        acc->bufferView = bv;
+        acc->WriteData(count, dataBase, numCompsIn * bytesPerComp);
+    }
+    acc->byteOffset = 0;
+    acc->componentType = compType;
+    acc->count = count;
+    acc->type = typeOut;
+
+    if (data) {
+        void *nzDiff = 0, *nzIdx = 0;
+        size_t nzCount = NZDiff(compType, data, dataBase, count, numCompsIn, numCompsOut, nzDiff, nzIdx);
+        acc->sparse.reset(new Accessor::Sparse);
+        acc->sparse->count = nzCount;
+
+        //indices
+        unsigned int bytesPerIdx = sizeof(unsigned short);
+        size_t indices_offset = buffer->byteLength;
+        size_t indices_padding = indices_offset % bytesPerIdx;
+        indices_offset += indices_padding;
+        size_t indices_length = nzCount * 1 * bytesPerIdx;
+        buffer->Grow(indices_length + indices_padding);
+
+        Ref<BufferView> indicesBV = a.bufferViews.Create(a.FindUniqueID(meshName, "view"));
+        indicesBV->buffer = buffer;
+        indicesBV->byteOffset = indices_offset;
+        indicesBV->byteLength = indices_length;
+        indicesBV->byteStride = 0;
+        acc->sparse->indices = indicesBV;
+        acc->sparse->indicesType = ComponentType_UNSIGNED_SHORT;
+        acc->sparse->indicesByteOffset = 0;
+        acc->WriteSparseIndices(nzCount, nzIdx, 1 * bytesPerIdx);
+
+        //values
+        size_t values_offset = buffer->byteLength;
+        size_t values_padding = values_offset % bytesPerComp;
+        values_offset += values_padding;
+        size_t values_length = nzCount * numCompsOut * bytesPerComp;
+        buffer->Grow(values_length + values_padding);
+
+        Ref<BufferView> valuesBV = a.bufferViews.Create(a.FindUniqueID(meshName, "view"));
+        valuesBV->buffer = buffer;
+        valuesBV->byteOffset = values_offset;
+        valuesBV->byteLength = values_length;
+        valuesBV->byteStride = 0;
+        acc->sparse->values = valuesBV;
+        acc->sparse->valuesByteOffset = 0;
+        acc->WriteSparseValues(nzCount, nzDiff, numCompsIn * bytesPerComp);
+
+        //clear
+        delete[](char *) nzDiff;
+        delete[](char *) nzIdx;
+    }
+    return acc;
+}
+inline Ref<Accessor> ExportData(Asset &a, std::string &meshName, Ref<Buffer> &buffer,
+        size_t count, void *data, AttribType::Value typeIn, AttribType::Value typeOut, ComponentType compType, BufferViewTarget target = BufferViewTarget_NONE) {
+    if (!count || !data) {
+        return Ref<Accessor>();
+    }
+
+    unsigned int numCompsIn = AttribType::GetNumComponents(typeIn);
+    unsigned int numCompsOut = AttribType::GetNumComponents(typeOut);
+    unsigned int bytesPerComp = ComponentTypeSize(compType);
+
+    size_t offset = buffer->byteLength;
+    // make sure offset is correctly byte-aligned, as required by spec
+    size_t padding = offset % bytesPerComp;
+    offset += padding;
+    size_t length = count * numCompsOut * bytesPerComp;
+    buffer->Grow(length + padding);
+
+    // bufferView
+    Ref<BufferView> bv = a.bufferViews.Create(a.FindUniqueID(meshName, "view"));
+    bv->buffer = buffer;
+    bv->byteOffset = offset;
+    bv->byteLength = length; //! The target that the WebGL buffer should be bound to.
+    bv->byteStride = 0;
+    bv->target = target;
+
+    // accessor
+    Ref<Accessor> acc = a.accessors.Create(a.FindUniqueID(meshName, "accessor"));
+    acc->bufferView = bv;
+    acc->byteOffset = 0;
+    acc->componentType = compType;
+    acc->count = count;
+    acc->type = typeOut;
+
+    // calculate min and max values
+    SetAccessorRange(compType, acc, data, count, numCompsIn, numCompsOut);
+
+    // copy the data
+    acc->WriteData(count, data, numCompsIn * bytesPerComp);
+
+    return acc;
+}
+
+inline void SetSamplerWrap(SamplerWrap &wrap, aiTextureMapMode map) {
+    switch (map) {
+    case aiTextureMapMode_Clamp:
+        wrap = SamplerWrap::Clamp_To_Edge;
+        break;
+    case aiTextureMapMode_Mirror:
+        wrap = SamplerWrap::Mirrored_Repeat;
+        break;
+    case aiTextureMapMode_Wrap:
+    case aiTextureMapMode_Decal:
+    default:
+        wrap = SamplerWrap::Repeat;
+        break;
+    };
+}
+
+void glTF2Exporter::GetTexSampler(const aiMaterial &mat, Ref<Texture> texture, aiTextureType tt, unsigned int slot) {
+    aiString aId;
+    std::string id;
+    if (aiGetMaterialString(&mat, AI_MATKEY_GLTF_MAPPINGID(tt, slot), &aId) == AI_SUCCESS) {
+        id = aId.C_Str();
+    }
+
+    if (Ref<Sampler> ref = mAsset->samplers.Get(id.c_str())) {
+        texture->sampler = ref;
+    } else {
+        id = mAsset->FindUniqueID(id, "sampler");
+
+        texture->sampler = mAsset->samplers.Create(id.c_str());
+
+        aiTextureMapMode mapU, mapV;
+        SamplerMagFilter filterMag;
+        SamplerMinFilter filterMin;
+
+        if (aiGetMaterialInteger(&mat, AI_MATKEY_MAPPINGMODE_U(tt, slot), (int *)&mapU) == AI_SUCCESS) {
+            SetSamplerWrap(texture->sampler->wrapS, mapU);
+        }
+
+        if (aiGetMaterialInteger(&mat, AI_MATKEY_MAPPINGMODE_V(tt, slot), (int *)&mapV) == AI_SUCCESS) {
+            SetSamplerWrap(texture->sampler->wrapT, mapV);
+        }
+
+        if (aiGetMaterialInteger(&mat, AI_MATKEY_GLTF_MAPPINGFILTER_MAG(tt, slot), (int *)&filterMag) == AI_SUCCESS) {
+            texture->sampler->magFilter = filterMag;
+        }
+
+        if (aiGetMaterialInteger(&mat, AI_MATKEY_GLTF_MAPPINGFILTER_MIN(tt, slot), (int *)&filterMin) == AI_SUCCESS) {
+            texture->sampler->minFilter = filterMin;
+        }
+
+        aiString name;
+        if (aiGetMaterialString(&mat, AI_MATKEY_GLTF_MAPPINGNAME(tt, slot), &name) == AI_SUCCESS) {
+            texture->sampler->name = name.C_Str();
+        }
+    }
+}
+
+void glTF2Exporter::GetMatTexProp(const aiMaterial &mat, unsigned int &prop, const char *propName, aiTextureType tt, unsigned int slot) {
+    std::string textureKey = std::string(_AI_MATKEY_TEXTURE_BASE) + "." + propName;
+
+    mat.Get(textureKey.c_str(), tt, slot, prop);
+}
+
+void glTF2Exporter::GetMatTexProp(const aiMaterial &mat, float &prop, const char *propName, aiTextureType tt, unsigned int slot) {
+    std::string textureKey = std::string(_AI_MATKEY_TEXTURE_BASE) + "." + propName;
+
+    mat.Get(textureKey.c_str(), tt, slot, prop);
+}
+
+void glTF2Exporter::GetMatTex(const aiMaterial &mat, Ref<Texture> &texture, unsigned int &texCoord, aiTextureType tt, unsigned int slot = 0) {
+    if (mat.GetTextureCount(tt) == 0) {
+        return;
+    }
+        
+    aiString tex;
+
+    // Read texcoord (UV map index)
+    mat.Get(AI_MATKEY_UVWSRC(tt, slot), texCoord);
+
+    if (mat.Get(AI_MATKEY_TEXTURE(tt, slot), tex) == AI_SUCCESS) {
+        std::string path = tex.C_Str();
+
+        if (path.size() > 0) {
+            std::map<std::string, unsigned int>::iterator it = mTexturesByPath.find(path);
+            if (it != mTexturesByPath.end()) {
+                texture = mAsset->textures.Get(it->second);
+            }
+
+            bool useBasisUniversal = false;
+            if (!texture) {
+                std::string texId = mAsset->FindUniqueID("", "texture");
+                texture = mAsset->textures.Create(texId);
+                mTexturesByPath[path] = texture.GetIndex();
+
+                std::string imgId = mAsset->FindUniqueID("", "image");
+                texture->source = mAsset->images.Create(imgId);
+
+                const aiTexture *curTex = mScene->GetEmbeddedTexture(path.c_str());
+                if (curTex != nullptr) { // embedded
+                    texture->source->name = curTex->mFilename.C_Str();
+
+                    //basisu: embedded ktx2, bu
+                    if (curTex->achFormatHint[0]) {
+                        std::string mimeType = "image/";
+                        if (memcmp(curTex->achFormatHint, "jpg", 3) == 0)
+                            mimeType += "jpeg";
+                        else if (memcmp(curTex->achFormatHint, "ktx", 3) == 0) {
+                            useBasisUniversal = true;
+                            mimeType += "ktx";
+                        } else if (memcmp(curTex->achFormatHint, "kx2", 3) == 0) {
+                            useBasisUniversal = true;
+                            mimeType += "ktx2";
+                        } else if (memcmp(curTex->achFormatHint, "bu", 2) == 0) {
+                            useBasisUniversal = true;
+                            mimeType += "basis";
+                        } else
+                            mimeType += curTex->achFormatHint;
+                        texture->source->mimeType = mimeType;
+                    }
+
+                    // The asset has its own buffer, see Image::SetData
+                    //basisu: "image/ktx2", "image/basis" as is
+                    texture->source->SetData(reinterpret_cast<uint8_t *>(curTex->pcData), curTex->mWidth, *mAsset);
+                } else {
+                    texture->source->uri = path;
+                    if (texture->source->uri.find(".ktx") != std::string::npos ||
+                            texture->source->uri.find(".basis") != std::string::npos) {
+                        useBasisUniversal = true;
+                    }
+                }
+
+                //basisu
+                if (useBasisUniversal) {
+                    mAsset->extensionsUsed.KHR_texture_basisu = true;
+                    mAsset->extensionsRequired.KHR_texture_basisu = true;
+                }
+
+                GetTexSampler(mat, texture, tt, slot);
+            }
+        }
+    }
+}
+
+void glTF2Exporter::GetMatTex(const aiMaterial &mat, TextureInfo &prop, aiTextureType tt, unsigned int slot = 0) {
+    Ref<Texture> &texture = prop.texture;
+    GetMatTex(mat, texture, prop.texCoord, tt, slot);
+}
+
+void glTF2Exporter::GetMatTex(const aiMaterial &mat, NormalTextureInfo &prop, aiTextureType tt, unsigned int slot = 0) {
+    Ref<Texture> &texture = prop.texture;
+
+    GetMatTex(mat, texture, prop.texCoord, tt, slot);
+
+    if (texture) {
+        //GetMatTexProp(mat, prop.texCoord, "texCoord", tt, slot);
+        GetMatTexProp(mat, prop.scale, "scale", tt, slot);
+    }
+}
+
+void glTF2Exporter::GetMatTex(const aiMaterial &mat, OcclusionTextureInfo &prop, aiTextureType tt, unsigned int slot = 0) {
+    Ref<Texture> &texture = prop.texture;
+
+    GetMatTex(mat, texture, prop.texCoord, tt, slot);
+
+    if (texture) {
+        //GetMatTexProp(mat, prop.texCoord, "texCoord", tt, slot);
+        GetMatTexProp(mat, prop.strength, "strength", tt, slot);
+    }
+}
+
+aiReturn glTF2Exporter::GetMatColor(const aiMaterial &mat, vec4 &prop, const char *propName, int type, int idx) const {
+    aiColor4D col;
+    aiReturn result = mat.Get(propName, type, idx, col);
+
+    if (result == AI_SUCCESS) {
+        prop[0] = col.r;
+        prop[1] = col.g;
+        prop[2] = col.b;
+        prop[3] = col.a;
+    }
+
+    return result;
+}
+
+aiReturn glTF2Exporter::GetMatColor(const aiMaterial &mat, vec3 &prop, const char *propName, int type, int idx) const {
+    aiColor3D col;
+    aiReturn result = mat.Get(propName, type, idx, col);
+
+    if (result == AI_SUCCESS) {
+        prop[0] = col.r;
+        prop[1] = col.g;
+        prop[2] = col.b;
+    }
+
+    return result;
+}
+
+bool glTF2Exporter::GetMatSpecGloss(const aiMaterial &mat, glTF2::PbrSpecularGlossiness &pbrSG) {
+    bool result = false;
+    // If has Glossiness, a Specular Color or Specular Texture, use the KHR_materials_pbrSpecularGlossiness extension
+    // NOTE: This extension is being considered for deprecation (Dec 2020), may be replaced by KHR_material_specular
+
+    if (mat.Get(AI_MATKEY_GLOSSINESS_FACTOR, pbrSG.glossinessFactor) == AI_SUCCESS) {
+        result = true;
+    } else {
+        // Don't have explicit glossiness, convert from pbr roughness or legacy shininess
+        float shininess;
+        if (mat.Get(AI_MATKEY_ROUGHNESS_FACTOR, shininess) == AI_SUCCESS) {
+            pbrSG.glossinessFactor = 1.0f - shininess; // Extension defines this way
+        } else if (mat.Get(AI_MATKEY_SHININESS, shininess) == AI_SUCCESS) {
+            pbrSG.glossinessFactor = shininess / 1000;
+        }
+    }
+
+    if (GetMatColor(mat, pbrSG.specularFactor, AI_MATKEY_COLOR_SPECULAR) == AI_SUCCESS) {
+        result = true;
+    }
+    // Add any appropriate textures
+    GetMatTex(mat, pbrSG.specularGlossinessTexture, aiTextureType_SPECULAR);
+
+    result = result || pbrSG.specularGlossinessTexture.texture;
+
+    if (result) {
+        // Likely to always have diffuse
+        GetMatTex(mat, pbrSG.diffuseTexture, aiTextureType_DIFFUSE);
+        GetMatColor(mat, pbrSG.diffuseFactor, AI_MATKEY_COLOR_DIFFUSE);
+    }
+
+    return result;
+}
+
+bool glTF2Exporter::GetMatSheen(const aiMaterial &mat, glTF2::MaterialSheen &sheen) {
+    // Return true if got any valid Sheen properties or textures
+    if (GetMatColor(mat, sheen.sheenColorFactor, AI_MATKEY_SHEEN_COLOR_FACTOR) != aiReturn_SUCCESS) {
+        return false;
+    }
+
+    // Default Sheen color factor {0,0,0} disables Sheen, so do not export
+    if (sheen.sheenColorFactor == defaultSheenFactor) {
+        return false;
+    }
+
+    mat.Get(AI_MATKEY_SHEEN_ROUGHNESS_FACTOR, sheen.sheenRoughnessFactor);
+
+    GetMatTex(mat, sheen.sheenColorTexture, AI_MATKEY_SHEEN_COLOR_TEXTURE);
+    GetMatTex(mat, sheen.sheenRoughnessTexture, AI_MATKEY_SHEEN_ROUGHNESS_TEXTURE);
+
+    return true;
+}
+
+bool glTF2Exporter::GetMatClearcoat(const aiMaterial &mat, glTF2::MaterialClearcoat &clearcoat) {
+    if (mat.Get(AI_MATKEY_CLEARCOAT_FACTOR, clearcoat.clearcoatFactor) != aiReturn_SUCCESS) {
+        return false;
+    }
+
+    // Clearcoat factor of zero disables Clearcoat, so do not export
+    if (clearcoat.clearcoatFactor == 0.0f)
+        return false;
+
+    mat.Get(AI_MATKEY_CLEARCOAT_ROUGHNESS_FACTOR, clearcoat.clearcoatRoughnessFactor);
+
+    GetMatTex(mat, clearcoat.clearcoatTexture, AI_MATKEY_CLEARCOAT_TEXTURE);
+    GetMatTex(mat, clearcoat.clearcoatRoughnessTexture, AI_MATKEY_CLEARCOAT_ROUGHNESS_TEXTURE);
+    GetMatTex(mat, clearcoat.clearcoatNormalTexture, AI_MATKEY_CLEARCOAT_NORMAL_TEXTURE);
+
+    return true;
+}
+
+bool glTF2Exporter::GetMatTransmission(const aiMaterial &mat, glTF2::MaterialTransmission &transmission) {
+    bool result = mat.Get(AI_MATKEY_TRANSMISSION_FACTOR, transmission.transmissionFactor) == aiReturn_SUCCESS;
+    GetMatTex(mat, transmission.transmissionTexture, AI_MATKEY_TRANSMISSION_TEXTURE);
+    return result || transmission.transmissionTexture.texture;
+}
+
+bool glTF2Exporter::GetMatVolume(const aiMaterial &mat, glTF2::MaterialVolume &volume) {
+    bool result = mat.Get(AI_MATKEY_VOLUME_THICKNESS_FACTOR, volume.thicknessFactor) != aiReturn_SUCCESS;
+
+    GetMatTex(mat, volume.thicknessTexture, AI_MATKEY_VOLUME_THICKNESS_TEXTURE);
+
+    result = result || mat.Get(AI_MATKEY_VOLUME_ATTENUATION_DISTANCE, volume.attenuationDistance);
+    result = result || GetMatColor(mat, volume.attenuationColor, AI_MATKEY_VOLUME_ATTENUATION_COLOR) != aiReturn_SUCCESS;
+
+    // Valid if any of these properties are available
+    return result || volume.thicknessTexture.texture;
+}
+
+bool glTF2Exporter::GetMatIOR(const aiMaterial &mat, glTF2::MaterialIOR &ior) {
+    return mat.Get(AI_MATKEY_REFRACTI, ior.ior) == aiReturn_SUCCESS;
+}
+
+void glTF2Exporter::ExportMaterials() {
+    aiString aiName;
+    for (unsigned int i = 0; i < mScene->mNumMaterials; ++i) {
+        ai_assert(mScene->mMaterials[i] != nullptr);
+
+        const aiMaterial &mat = *(mScene->mMaterials[i]);
+
+        std::string id = "material_" + ai_to_string(i);
+
+        Ref<Material> m = mAsset->materials.Create(id);
+
+        std::string name;
+        if (mat.Get(AI_MATKEY_NAME, aiName) == AI_SUCCESS) {
+            name = aiName.C_Str();
+        }
+        name = mAsset->FindUniqueID(name, "material");
+
+        m->name = name;
+
+        GetMatTex(mat, m->pbrMetallicRoughness.baseColorTexture, aiTextureType_BASE_COLOR);
+
+        if (!m->pbrMetallicRoughness.baseColorTexture.texture) {
+            //if there wasn't a baseColorTexture defined in the source, fallback to any diffuse texture
+            GetMatTex(mat, m->pbrMetallicRoughness.baseColorTexture, aiTextureType_DIFFUSE);
+        }
+
+        GetMatTex(mat, m->pbrMetallicRoughness.metallicRoughnessTexture, AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_METALLICROUGHNESS_TEXTURE);
+
+        if (GetMatColor(mat, m->pbrMetallicRoughness.baseColorFactor, AI_MATKEY_BASE_COLOR) != AI_SUCCESS) {
+            // if baseColorFactor wasn't defined, then the source is likely not a metallic roughness material.
+            //a fallback to any diffuse color should be used instead
+            GetMatColor(mat, m->pbrMetallicRoughness.baseColorFactor, AI_MATKEY_COLOR_DIFFUSE);
+        }
+
+        if (mat.Get(AI_MATKEY_METALLIC_FACTOR, m->pbrMetallicRoughness.metallicFactor) != AI_SUCCESS) {
+            //if metallicFactor wasn't defined, then the source is likely not a PBR file, and the metallicFactor should be 0
+            m->pbrMetallicRoughness.metallicFactor = 0;
+        }
+
+        // get roughness if source is gltf2 file
+        if (mat.Get(AI_MATKEY_ROUGHNESS_FACTOR, m->pbrMetallicRoughness.roughnessFactor) != AI_SUCCESS) {
+            // otherwise, try to derive and convert from specular + shininess values
+            aiColor4D specularColor;
+            ai_real shininess;
+
+            if (mat.Get(AI_MATKEY_COLOR_SPECULAR, specularColor) == AI_SUCCESS && mat.Get(AI_MATKEY_SHININESS, shininess) == AI_SUCCESS) {
+                // convert specular color to luminance
+                float specularIntensity = specularColor[0] * 0.2125f + specularColor[1] * 0.7154f + specularColor[2] * 0.0721f;
+                //normalize shininess (assuming max is 1000) with an inverse exponentional curve
+                float normalizedShininess = std::sqrt(shininess / 1000);
+
+                //clamp the shininess value between 0 and 1
+                normalizedShininess = std::min(std::max(normalizedShininess, 0.0f), 1.0f);
+                // low specular intensity values should produce a rough material even if shininess is high.
+                normalizedShininess = normalizedShininess * specularIntensity;
+
+                m->pbrMetallicRoughness.roughnessFactor = 1 - normalizedShininess;
+            }
+        }
+
+        GetMatTex(mat, m->normalTexture, aiTextureType_NORMALS);
+        GetMatTex(mat, m->occlusionTexture, aiTextureType_LIGHTMAP);
+        GetMatTex(mat, m->emissiveTexture, aiTextureType_EMISSIVE);
+        GetMatColor(mat, m->emissiveFactor, AI_MATKEY_COLOR_EMISSIVE);
+
+        mat.Get(AI_MATKEY_TWOSIDED, m->doubleSided);
+        mat.Get(AI_MATKEY_GLTF_ALPHACUTOFF, m->alphaCutoff);
+
+        float opacity;
+        aiString alphaMode;
+
+        if (mat.Get(AI_MATKEY_OPACITY, opacity) == AI_SUCCESS) {
+            if (opacity < 1) {
+                m->alphaMode = "BLEND";
+                m->pbrMetallicRoughness.baseColorFactor[3] *= opacity;
+            }
+        }
+        if (mat.Get(AI_MATKEY_GLTF_ALPHAMODE, alphaMode) == AI_SUCCESS) {
+            m->alphaMode = alphaMode.C_Str();
+        }
+
+        {
+            // KHR_materials_pbrSpecularGlossiness extension
+            // NOTE: This extension is being considered for deprecation (Dec 2020)
+            PbrSpecularGlossiness pbrSG;
+            if (GetMatSpecGloss(mat, pbrSG)) {
+                mAsset->extensionsUsed.KHR_materials_pbrSpecularGlossiness = true;
+                m->pbrSpecularGlossiness = Nullable<PbrSpecularGlossiness>(pbrSG);
+            }
+        }
+
+        // glTFv2 is either PBR or Unlit
+        aiShadingMode shadingMode = aiShadingMode_PBR_BRDF;
+        mat.Get(AI_MATKEY_SHADING_MODEL, shadingMode);
+        if (shadingMode == aiShadingMode_Unlit) {
+            mAsset->extensionsUsed.KHR_materials_unlit = true;
+            m->unlit = true;
+        } else {
+            // These extensions are not compatible with KHR_materials_unlit or KHR_materials_pbrSpecularGlossiness
+            if (!m->pbrSpecularGlossiness.isPresent) {
+                // Sheen
+                MaterialSheen sheen;
+                if (GetMatSheen(mat, sheen)) {
+                    mAsset->extensionsUsed.KHR_materials_sheen = true;
+                    m->materialSheen = Nullable<MaterialSheen>(sheen);
+                }
+
+                MaterialClearcoat clearcoat;
+                if (GetMatClearcoat(mat, clearcoat)) {
+                    mAsset->extensionsUsed.KHR_materials_clearcoat = true;
+                    m->materialClearcoat = Nullable<MaterialClearcoat>(clearcoat);
+                }
+
+                MaterialTransmission transmission;
+                if (GetMatTransmission(mat, transmission)) {
+                    mAsset->extensionsUsed.KHR_materials_transmission = true;
+                    m->materialTransmission = Nullable<MaterialTransmission>(transmission);
+                }
+                
+                MaterialVolume volume;
+                if (GetMatVolume(mat, volume)) {
+                    mAsset->extensionsUsed.KHR_materials_volume = true;
+                    m->materialVolume = Nullable<MaterialVolume>(volume);
+                }
+                                
+                MaterialIOR ior;
+                if (GetMatIOR(mat, ior)) {
+                    mAsset->extensionsUsed.KHR_materials_ior = true;
+                    m->materialIOR = Nullable<MaterialIOR>(ior);
+                }
+            }
+        }
+    }
+}
+
+/*
+ * Search through node hierarchy and find the node containing the given meshID.
+ * Returns true on success, and false otherwise.
+ */
+bool FindMeshNode(Ref<Node> &nodeIn, Ref<Node> &meshNode, const std::string &meshID) {
+    for (unsigned int i = 0; i < nodeIn->meshes.size(); ++i) {
+        if (meshID.compare(nodeIn->meshes[i]->id) == 0) {
+            meshNode = nodeIn;
+            return true;
+        }
+    }
+
+    for (unsigned int i = 0; i < nodeIn->children.size(); ++i) {
+        if (FindMeshNode(nodeIn->children[i], meshNode, meshID)) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+/*
+ * Find the root joint of the skeleton.
+ * Starts will any joint node and traces up the tree,
+ * until a parent is found that does not have a jointName.
+ * Returns the first parent Ref<Node> found that does not have a jointName.
+ */
+Ref<Node> FindSkeletonRootJoint(Ref<Skin> &skinRef) {
+    Ref<Node> startNodeRef;
+    Ref<Node> parentNodeRef;
+
+    // Arbitrarily use the first joint to start the search.
+    startNodeRef = skinRef->jointNames[0];
+    parentNodeRef = skinRef->jointNames[0];
+
+    do {
+        startNodeRef = parentNodeRef;
+        parentNodeRef = startNodeRef->parent;
+    } while (!parentNodeRef->jointName.empty());
+
+    return parentNodeRef;
+}
+
+void ExportSkin(Asset &mAsset, const aiMesh *aimesh, Ref<Mesh> &meshRef, Ref<Buffer> &bufferRef, Ref<Skin> &skinRef, 
+        std::vector<aiMatrix4x4> &inverseBindMatricesData) {
+    if (aimesh->mNumBones < 1) {
+        return;
+    }
+
+    // Store the vertex joint and weight data.
+    const size_t NumVerts(aimesh->mNumVertices);
+    vec4 *vertexJointData = new vec4[NumVerts];
+    vec4 *vertexWeightData = new vec4[NumVerts];
+    int *jointsPerVertex = new int[NumVerts];
+    for (size_t i = 0; i < NumVerts; ++i) {
+        jointsPerVertex[i] = 0;
+        for (size_t j = 0; j < 4; ++j) {
+            vertexJointData[i][j] = 0;
+            vertexWeightData[i][j] = 0;
+        }
+    }
+
+    for (unsigned int idx_bone = 0; idx_bone < aimesh->mNumBones; ++idx_bone) {
+        const aiBone *aib = aimesh->mBones[idx_bone];
+
+        // aib->mName   =====>  skinRef->jointNames
+        // Find the node with id = mName.
+        Ref<Node> nodeRef = mAsset.nodes.Get(aib->mName.C_Str());
+        nodeRef->jointName = nodeRef->name;
+
+        unsigned int jointNamesIndex = 0;
+        bool addJointToJointNames = true;
+        for (unsigned int idx_joint = 0; idx_joint < skinRef->jointNames.size(); ++idx_joint) {
+            if (skinRef->jointNames[idx_joint]->jointName.compare(nodeRef->jointName) == 0) {
+                addJointToJointNames = false;
+                jointNamesIndex = idx_joint;
+            }
+        }
+
+        if (addJointToJointNames) {
+            skinRef->jointNames.push_back(nodeRef);
+
+            // aib->mOffsetMatrix   =====>  skinRef->inverseBindMatrices
+            aiMatrix4x4 tmpMatrix4;
+            CopyValue(aib->mOffsetMatrix, tmpMatrix4);
+            inverseBindMatricesData.push_back(tmpMatrix4);
+            jointNamesIndex = static_cast<unsigned int>(inverseBindMatricesData.size() - 1);
+        }
+
+        // aib->mWeights   =====>  vertexWeightData
+        for (unsigned int idx_weights = 0; idx_weights < aib->mNumWeights; ++idx_weights) {
+            unsigned int vertexId = aib->mWeights[idx_weights].mVertexId;
+            float vertWeight = aib->mWeights[idx_weights].mWeight;
+
+            // A vertex can only have at most four joint weights, which ideally sum up to 1
+            if (IsBoneWeightFitted(vertexWeightData[vertexId])) {
+                continue;
+            }
+            if (jointsPerVertex[vertexId] > 3) {
+                int boneIndexFitted = FitBoneWeight(vertexWeightData[vertexId], vertWeight);
+                if (boneIndexFitted != -1) {
+                    vertexJointData[vertexId][boneIndexFitted] = static_cast<float>(jointNamesIndex);
+                }
+            }else {
+                vertexJointData[vertexId][jointsPerVertex[vertexId]] = static_cast<float>(jointNamesIndex);
+                vertexWeightData[vertexId][jointsPerVertex[vertexId]] = vertWeight;
+
+                jointsPerVertex[vertexId] += 1;   
+            }
+        }
+
+    } // End: for-loop mNumMeshes
+
+    Mesh::Primitive &p = meshRef->primitives.back();
+    Ref<Accessor> vertexJointAccessor = ExportData(mAsset, skinRef->id, bufferRef, aimesh->mNumVertices, 
+        vertexJointData, AttribType::VEC4, AttribType::VEC4, ComponentType_FLOAT);
+    if (vertexJointAccessor) {
+        size_t offset = vertexJointAccessor->bufferView->byteOffset;
+        size_t bytesLen = vertexJointAccessor->bufferView->byteLength;
+        unsigned int s_bytesPerComp = ComponentTypeSize(ComponentType_UNSIGNED_SHORT);
+        unsigned int bytesPerComp = ComponentTypeSize(vertexJointAccessor->componentType);
+        size_t s_bytesLen = bytesLen * s_bytesPerComp / bytesPerComp;
+        Ref<Buffer> buf = vertexJointAccessor->bufferView->buffer;
+        uint8_t *arrys = new uint8_t[bytesLen];
+        unsigned int i = 0;
+        for (unsigned int j = 0; j < bytesLen; j += bytesPerComp) {
+            size_t len_p = offset + j;
+            float f_value = *(float *)&buf->GetPointer()[len_p];
+            unsigned short c = static_cast<unsigned short>(f_value);
+            memcpy(&arrys[i * s_bytesPerComp], &c, s_bytesPerComp);
+            ++i;
+        }
+        buf->ReplaceData_joint(offset, bytesLen, arrys, bytesLen);
+        vertexJointAccessor->componentType = ComponentType_UNSIGNED_SHORT;
+        vertexJointAccessor->bufferView->byteLength = s_bytesLen;
+
+        p.attributes.joint.push_back(vertexJointAccessor);
+        delete[] arrys;
+    }
+
+    Ref<Accessor> vertexWeightAccessor = ExportData(mAsset, skinRef->id, bufferRef, aimesh->mNumVertices,
+            vertexWeightData, AttribType::VEC4, AttribType::VEC4, ComponentType_FLOAT);
+    if (vertexWeightAccessor) {
+        p.attributes.weight.push_back(vertexWeightAccessor);
+    }
+    delete[] jointsPerVertex;
+    delete[] vertexWeightData;
+    delete[] vertexJointData;
+}
+
+void glTF2Exporter::ExportMeshes() {
+    typedef decltype(aiFace::mNumIndices) IndicesType;
+
+    std::string fname = std::string(mFilename);
+    std::string bufferIdPrefix = fname.substr(0, fname.rfind(".gltf"));
+    std::string bufferId = mAsset->FindUniqueID("", bufferIdPrefix.c_str());
+
+    Ref<Buffer> b = mAsset->GetBodyBuffer();
+    if (!b) {
+        b = mAsset->buffers.Create(bufferId);
+    }
+
+    //----------------------------------------
+    // Initialize variables for the skin
+    bool createSkin = false;
+    for (unsigned int idx_mesh = 0; idx_mesh < mScene->mNumMeshes; ++idx_mesh) {
+        const aiMesh *aim = mScene->mMeshes[idx_mesh];
+        if (aim->HasBones()) {
+            createSkin = true;
+            break;
+        }
+    }
+
+    Ref<Skin> skinRef;
+    std::string skinName = mAsset->FindUniqueID("skin", "skin");
+    std::vector<aiMatrix4x4> inverseBindMatricesData;
+    if (createSkin) {
+        skinRef = mAsset->skins.Create(skinName);
+        skinRef->name = skinName;
+    }
+    //----------------------------------------
+
+    for (unsigned int idx_mesh = 0; idx_mesh < mScene->mNumMeshes; ++idx_mesh) {
+        const aiMesh *aim = mScene->mMeshes[idx_mesh];
+
+        std::string name = aim->mName.C_Str();
+
+        std::string meshId = mAsset->FindUniqueID(name, "mesh");
+        Ref<Mesh> m = mAsset->meshes.Create(meshId);
+        m->primitives.resize(1);
+        Mesh::Primitive &p = m->primitives.back();
+
+        m->name = name;
+
+        p.material = mAsset->materials.Get(aim->mMaterialIndex);
+        p.ngonEncoded = (aim->mPrimitiveTypes & aiPrimitiveType_NGONEncodingFlag) != 0;
+
+        /******************* Vertices ********************/
+        Ref<Accessor> v = ExportData(*mAsset, meshId, b, aim->mNumVertices, aim->mVertices, AttribType::VEC3,
+            AttribType::VEC3, ComponentType_FLOAT, BufferViewTarget_ARRAY_BUFFER);
+        if (v) {
+            p.attributes.position.push_back(v);
+        }
+
+        /******************** Normals ********************/
+        // Normalize all normals as the validator can emit a warning otherwise
+        if (nullptr != aim->mNormals) {
+            for (auto i = 0u; i < aim->mNumVertices; ++i) {
+                aim->mNormals[i].NormalizeSafe();
+            }
+        }
+
+        Ref<Accessor> n = ExportData(*mAsset, meshId, b, aim->mNumVertices, aim->mNormals, AttribType::VEC3, 
+            AttribType::VEC3, ComponentType_FLOAT, BufferViewTarget_ARRAY_BUFFER);
+        if (n) {
+            p.attributes.normal.push_back(n);
+        }
+
+        /************** Texture coordinates **************/
+        for (int i = 0; i < AI_MAX_NUMBER_OF_TEXTURECOORDS; ++i) {
+            if (!aim->HasTextureCoords(i)) {
+                continue;
+            }
+
+            // Flip UV y coords
+            if (aim->mNumUVComponents[i] > 1) {
+                for (unsigned int j = 0; j < aim->mNumVertices; ++j) {
+                    aim->mTextureCoords[i][j].y = 1 - aim->mTextureCoords[i][j].y;
+                }
+            }
+
+            if (aim->mNumUVComponents[i] > 0) {
+                AttribType::Value type = (aim->mNumUVComponents[i] == 2) ? AttribType::VEC2 : AttribType::VEC3;
+
+                Ref<Accessor> tc = ExportData(*mAsset, meshId, b, aim->mNumVertices, aim->mTextureCoords[i], 
+                    AttribType::VEC3, type, ComponentType_FLOAT, BufferViewTarget_ARRAY_BUFFER);
+                if (tc) {
+                    p.attributes.texcoord.push_back(tc);
+                }
+            }
+        }
+
+        /*************** Vertex colors ****************/
+        for (unsigned int indexColorChannel = 0; indexColorChannel < aim->GetNumColorChannels(); ++indexColorChannel) {
+            Ref<Accessor> c = ExportData(*mAsset, meshId, b, aim->mNumVertices, aim->mColors[indexColorChannel],
+                AttribType::VEC4, AttribType::VEC4, ComponentType_FLOAT, BufferViewTarget_ARRAY_BUFFER);
+            if (c) {
+                p.attributes.color.push_back(c);
+            }
+        }
+
+        /*************** Vertices indices ****************/
+        if (aim->mNumFaces > 0) {
+            std::vector<IndicesType> indices;
+            unsigned int nIndicesPerFace = aim->mFaces[0].mNumIndices;
+            indices.resize(aim->mNumFaces * nIndicesPerFace);
+            for (size_t i = 0; i < aim->mNumFaces; ++i) {
+                for (size_t j = 0; j < nIndicesPerFace; ++j) {
+                    indices[i * nIndicesPerFace + j] = IndicesType(aim->mFaces[i].mIndices[j]);
+                }
+            }
+
+            p.indices = ExportData(*mAsset, meshId, b, indices.size(), &indices[0], AttribType::SCALAR, AttribType::SCALAR, 
+                ComponentType_UNSIGNED_INT, BufferViewTarget_ELEMENT_ARRAY_BUFFER);
+        }
+
+        switch (aim->mPrimitiveTypes) {
+        case aiPrimitiveType_POLYGON:
+            p.mode = PrimitiveMode_TRIANGLES;
+            break; // TODO implement this
+        case aiPrimitiveType_LINE:
+            p.mode = PrimitiveMode_LINES;
+            break;
+        case aiPrimitiveType_POINT:
+            p.mode = PrimitiveMode_POINTS;
+            break;
+        default: // aiPrimitiveType_TRIANGLE
+            p.mode = PrimitiveMode_TRIANGLES;
+            break;
+        }
+
+        /*************** Skins ****************/
+        if (aim->HasBones()) {
+            ExportSkin(*mAsset, aim, m, b, skinRef, inverseBindMatricesData);
+        }
+
+        /*************** Targets for blendshapes ****************/
+        if (aim->mNumAnimMeshes > 0) {
+            bool bUseSparse = this->mProperties->HasPropertyBool("GLTF2_SPARSE_ACCESSOR_EXP") &&
+                              this->mProperties->GetPropertyBool("GLTF2_SPARSE_ACCESSOR_EXP");
+            bool bIncludeNormal = this->mProperties->HasPropertyBool("GLTF2_TARGET_NORMAL_EXP") &&
+                                  this->mProperties->GetPropertyBool("GLTF2_TARGET_NORMAL_EXP");
+            bool bExportTargetNames = this->mProperties->HasPropertyBool("GLTF2_TARGETNAMES_EXP") &&
+                                      this->mProperties->GetPropertyBool("GLTF2_TARGETNAMES_EXP");
+
+            p.targets.resize(aim->mNumAnimMeshes);
+            for (unsigned int am = 0; am < aim->mNumAnimMeshes; ++am) {
+                aiAnimMesh *pAnimMesh = aim->mAnimMeshes[am];
+                if (bExportTargetNames) {
+                    m->targetNames.emplace_back(pAnimMesh->mName.data);
+                }
+                // position
+                if (pAnimMesh->HasPositions()) {
+                    // NOTE: in gltf it is the diff stored
+                    aiVector3D *pPositionDiff = new aiVector3D[pAnimMesh->mNumVertices];
+                    for (unsigned int vt = 0; vt < pAnimMesh->mNumVertices; ++vt) {
+                        pPositionDiff[vt] = pAnimMesh->mVertices[vt] - aim->mVertices[vt];
+                    }
+                    Ref<Accessor> vec;
+                    if (bUseSparse) {
+                        vec = ExportDataSparse(*mAsset, meshId, b,
+                                pAnimMesh->mNumVertices, pPositionDiff,
+                                AttribType::VEC3, AttribType::VEC3, ComponentType_FLOAT);
+                    } else {
+                        vec = ExportData(*mAsset, meshId, b,
+                                pAnimMesh->mNumVertices, pPositionDiff,
+                                AttribType::VEC3, AttribType::VEC3, ComponentType_FLOAT);
+                    }
+                    if (vec) {
+                        p.targets[am].position.push_back(vec);
+                    }
+                    delete[] pPositionDiff;
+                }
+
+                // normal
+                if (pAnimMesh->HasNormals() && bIncludeNormal) {
+                    aiVector3D *pNormalDiff = new aiVector3D[pAnimMesh->mNumVertices];
+                    for (unsigned int vt = 0; vt < pAnimMesh->mNumVertices; ++vt) {
+                        pNormalDiff[vt] = pAnimMesh->mNormals[vt] - aim->mNormals[vt];
+                    }
+                    Ref<Accessor> vec;
+                    if (bUseSparse) {
+                        vec = ExportDataSparse(*mAsset, meshId, b,
+                                pAnimMesh->mNumVertices, pNormalDiff,
+                                AttribType::VEC3, AttribType::VEC3, ComponentType_FLOAT);
+                    } else {
+                        vec = ExportData(*mAsset, meshId, b,
+                                pAnimMesh->mNumVertices, pNormalDiff,
+                                AttribType::VEC3, AttribType::VEC3, ComponentType_FLOAT);
+                    }
+                    if (vec) {
+                        p.targets[am].normal.push_back(vec);
+                    }
+                    delete[] pNormalDiff;
+                }
+
+                // tangent?
+            }
+        }
+    }
+
+    //----------------------------------------
+    // Finish the skin
+    // Create the Accessor for skinRef->inverseBindMatrices
+    bool bAddCustomizedProperty = this->mProperties->HasPropertyBool("GLTF2_CUSTOMIZE_PROPERTY");
+    if (createSkin) {
+        mat4 *invBindMatrixData = new mat4[inverseBindMatricesData.size()];
+        for (unsigned int idx_joint = 0; idx_joint < inverseBindMatricesData.size(); ++idx_joint) {
+            CopyValue(inverseBindMatricesData[idx_joint], invBindMatrixData[idx_joint]);
+        }
+
+        Ref<Accessor> invBindMatrixAccessor = ExportData(*mAsset, skinName, b,
+                static_cast<unsigned int>(inverseBindMatricesData.size()),
+                invBindMatrixData, AttribType::MAT4, AttribType::MAT4, ComponentType_FLOAT);
+        if (invBindMatrixAccessor) {
+            skinRef->inverseBindMatrices = invBindMatrixAccessor;
+        }
+
+        // Identity Matrix   =====>  skinRef->bindShapeMatrix
+        // Temporary. Hard-coded identity matrix here
+        skinRef->bindShapeMatrix.isPresent = bAddCustomizedProperty;
+        IdentityMatrix4(skinRef->bindShapeMatrix.value);
+
+        // Find nodes that contain a mesh with bones and add "skeletons" and "skin" attributes to those nodes.
+        Ref<Node> rootNode = mAsset->nodes.Get(unsigned(0));
+        Ref<Node> meshNode;
+        for (unsigned int meshIndex = 0; meshIndex < mAsset->meshes.Size(); ++meshIndex) {
+            Ref<Mesh> mesh = mAsset->meshes.Get(meshIndex);
+            bool hasBones = false;
+            for (unsigned int i = 0; i < mesh->primitives.size(); ++i) {
+                if (!mesh->primitives[i].attributes.weight.empty()) {
+                    hasBones = true;
+                    break;
+                }
+            }
+            if (!hasBones) {
+                continue;
+            }
+            std::string meshID = mesh->id;
+            FindMeshNode(rootNode, meshNode, meshID);
+            Ref<Node> rootJoint = FindSkeletonRootJoint(skinRef);
+            if (bAddCustomizedProperty)
+                meshNode->skeletons.push_back(rootJoint);
+            meshNode->skin = skinRef;
+        }
+        delete[] invBindMatrixData;
+    }
+}
+
+// Merges a node's multiple meshes (with one primitive each) into one mesh with multiple primitives
+void glTF2Exporter::MergeMeshes() {
+    for (unsigned int n = 0; n < mAsset->nodes.Size(); ++n) {
+        Ref<Node> node = mAsset->nodes.Get(n);
+
+        unsigned int nMeshes = static_cast<unsigned int>(node->meshes.size());
+
+        //skip if it's 1 or less meshes per node
+        if (nMeshes > 1) {
+            Ref<Mesh> firstMesh = node->meshes.at(0);
+
+            //loop backwards to allow easy removal of a mesh from a node once it's merged
+            for (unsigned int m = nMeshes - 1; m >= 1; --m) {
+                Ref<Mesh> mesh = node->meshes.at(m);
+
+                //append this mesh's primitives to the first mesh's primitives
+                firstMesh->primitives.insert(
+                        firstMesh->primitives.end(),
+                        mesh->primitives.begin(),
+                        mesh->primitives.end());
+
+                //remove the mesh from the list of meshes
+                unsigned int removedIndex = mAsset->meshes.Remove(mesh->id.c_str());
+
+                //find the presence of the removed mesh in other nodes
+                for (unsigned int nn = 0; nn < mAsset->nodes.Size(); ++nn) {
+                    Ref<Node> curNode = mAsset->nodes.Get(nn);
+
+                    for (unsigned int mm = 0; mm < curNode->meshes.size(); ++mm) {
+                        Ref<Mesh> &meshRef = curNode->meshes.at(mm);
+                        unsigned int meshIndex = meshRef.GetIndex();
+
+                        if (meshIndex == removedIndex) {
+                            curNode->meshes.erase(curNode->meshes.begin() + mm);
+                        } else if (meshIndex > removedIndex) {
+                            Ref<Mesh> newMeshRef = mAsset->meshes.Get(meshIndex - 1);
+
+                            meshRef = newMeshRef;
+                        }
+                    }
+                }
+            }
+
+            //since we were looping backwards, reverse the order of merged primitives to their original order
+            std::reverse(firstMesh->primitives.begin() + 1, firstMesh->primitives.end());
+        }
+    }
+}
+
+/*
+ * Export the root node of the node hierarchy.
+ * Calls ExportNode for all children.
+ */
+unsigned int glTF2Exporter::ExportNodeHierarchy(const aiNode *n) {
+    Ref<Node> node = mAsset->nodes.Create(mAsset->FindUniqueID(n->mName.C_Str(), "node"));
+
+    node->name = n->mName.C_Str();
+
+    if (!n->mTransformation.IsIdentity()) {
+        node->matrix.isPresent = true;
+        CopyValue(n->mTransformation, node->matrix.value);
+    }
+
+    for (unsigned int i = 0; i < n->mNumMeshes; ++i) {
+        node->meshes.emplace_back(mAsset->meshes.Get(n->mMeshes[i]));
+    }
+
+    for (unsigned int i = 0; i < n->mNumChildren; ++i) {
+        unsigned int idx = ExportNode(n->mChildren[i], node);
+        node->children.emplace_back(mAsset->nodes.Get(idx));
+    }
+
+    return node.GetIndex();
+}
+
+/*
+ * Export node and recursively calls ExportNode for all children.
+ * Since these nodes are not the root node, we also export the parent Ref<Node>
+ */
+unsigned int glTF2Exporter::ExportNode(const aiNode *n, Ref<Node> &parent) {
+    std::string name = mAsset->FindUniqueID(n->mName.C_Str(), "node");
+    Ref<Node> node = mAsset->nodes.Create(name);
+
+    node->parent = parent;
+    node->name = name;
+
+    if (!n->mTransformation.IsIdentity()) {
+        if (mScene->mNumAnimations > 0 || (mProperties && mProperties->HasPropertyBool("GLTF2_NODE_IN_TRS"))) {
+            aiQuaternion quaternion;
+            n->mTransformation.Decompose(*reinterpret_cast<aiVector3D *>(&node->scale.value), quaternion, *reinterpret_cast<aiVector3D *>(&node->translation.value));
+
+            aiVector3D vector(static_cast<ai_real>(1.0f), static_cast<ai_real>(1.0f), static_cast<ai_real>(1.0f));
+            if (!reinterpret_cast<aiVector3D *>(&node->scale.value)->Equal(vector)) {
+                node->scale.isPresent = true;
+            }
+            if (!reinterpret_cast<aiVector3D *>(&node->translation.value)->Equal(vector)) {
+                node->translation.isPresent = true;
+            }
+            node->rotation.isPresent = true;
+            node->rotation.value[0] = quaternion.x;
+            node->rotation.value[1] = quaternion.y;
+            node->rotation.value[2] = quaternion.z;
+            node->rotation.value[3] = quaternion.w;
+            node->matrix.isPresent = false;
+        } else {
+            node->matrix.isPresent = true;
+            CopyValue(n->mTransformation, node->matrix.value);
+        }
+    }
+
+    for (unsigned int i = 0; i < n->mNumMeshes; ++i) {
+        node->meshes.emplace_back(mAsset->meshes.Get(n->mMeshes[i]));
+    }
+
+    for (unsigned int i = 0; i < n->mNumChildren; ++i) {
+        unsigned int idx = ExportNode(n->mChildren[i], node);
+        node->children.emplace_back(mAsset->nodes.Get(idx));
+    }
+
+    return node.GetIndex();
+}
+
+void glTF2Exporter::ExportScene() {
+    // Use the name of the scene if specified
+    const std::string sceneName = (mScene->mName.length > 0) ? mScene->mName.C_Str() : "defaultScene";
+
+    // Ensure unique
+    Ref<Scene> scene = mAsset->scenes.Create(mAsset->FindUniqueID(sceneName, ""));
+
+    // root node will be the first one exported (idx 0)
+    if (mAsset->nodes.Size() > 0) {
+        scene->nodes.emplace_back(mAsset->nodes.Get(0u));
+    }
+
+    // set as the default scene
+    mAsset->scene = scene;
+}
+
+void glTF2Exporter::ExportMetadata() {
+    AssetMetadata &asset = mAsset->asset;
+    asset.version = "2.0";
+
+    char buffer[256];
+    ai_snprintf(buffer, 256, "Open Asset Import Library (assimp v%d.%d.%x)",
+            aiGetVersionMajor(), aiGetVersionMinor(), aiGetVersionRevision());
+
+    asset.generator = buffer;
+
+    // Copyright
+    aiString copyright_str;
+    if (mScene->mMetaData != nullptr && mScene->mMetaData->Get(AI_METADATA_SOURCE_COPYRIGHT, copyright_str)) {
+        asset.copyright = copyright_str.C_Str();
+    }
+}
+
+inline Ref<Accessor> GetSamplerInputRef(Asset &asset, std::string &animId, Ref<Buffer> &buffer, std::vector<ai_real> &times) {
+    return ExportData(asset, animId, buffer, (unsigned int)times.size(), &times[0], AttribType::SCALAR, AttribType::SCALAR, ComponentType_FLOAT);
+}
+
+inline void ExtractTranslationSampler(Asset &asset, std::string &animId, Ref<Buffer> &buffer, const aiNodeAnim *nodeChannel, float ticksPerSecond, Animation::Sampler &sampler) {
+    const unsigned int numKeyframes = nodeChannel->mNumPositionKeys;
+
+    std::vector<ai_real> times(numKeyframes);
+    std::vector<ai_real> values(numKeyframes * 3);
+    for (unsigned int i = 0; i < numKeyframes; ++i) {
+        const aiVectorKey &key = nodeChannel->mPositionKeys[i];
+        // mTime is measured in ticks, but GLTF time is measured in seconds, so convert.
+        times[i] = static_cast<float>(key.mTime / ticksPerSecond);
+        values[(i * 3) + 0] = (ai_real) key.mValue.x;
+        values[(i * 3) + 1] = (ai_real) key.mValue.y;
+        values[(i * 3) + 2] = (ai_real) key.mValue.z;
+    }
+
+    sampler.input = GetSamplerInputRef(asset, animId, buffer, times);
+    sampler.output = ExportData(asset, animId, buffer, numKeyframes, &values[0], AttribType::VEC3, AttribType::VEC3, ComponentType_FLOAT);
+    sampler.interpolation = Interpolation_LINEAR;
+}
+
+inline void ExtractScaleSampler(Asset &asset, std::string &animId, Ref<Buffer> &buffer, const aiNodeAnim *nodeChannel, float ticksPerSecond, Animation::Sampler &sampler) {
+    const unsigned int numKeyframes = nodeChannel->mNumScalingKeys;
+
+    std::vector<ai_real> times(numKeyframes);
+    std::vector<ai_real> values(numKeyframes * 3);
+    for (unsigned int i = 0; i < numKeyframes; ++i) {
+        const aiVectorKey &key = nodeChannel->mScalingKeys[i];
+        // mTime is measured in ticks, but GLTF time is measured in seconds, so convert.
+        times[i] = static_cast<float>(key.mTime / ticksPerSecond);
+        values[(i * 3) + 0] = (ai_real) key.mValue.x;
+        values[(i * 3) + 1] = (ai_real) key.mValue.y;
+        values[(i * 3) + 2] = (ai_real) key.mValue.z;
+    }
+
+    sampler.input = GetSamplerInputRef(asset, animId, buffer, times);
+    sampler.output = ExportData(asset, animId, buffer, numKeyframes, &values[0], AttribType::VEC3, AttribType::VEC3, ComponentType_FLOAT);
+    sampler.interpolation = Interpolation_LINEAR;
+}
+
+inline void ExtractRotationSampler(Asset &asset, std::string &animId, Ref<Buffer> &buffer, const aiNodeAnim *nodeChannel, float ticksPerSecond, Animation::Sampler &sampler) {
+    const unsigned int numKeyframes = nodeChannel->mNumRotationKeys;
+
+    std::vector<ai_real> times(numKeyframes);
+    std::vector<ai_real> values(numKeyframes * 4);
+    for (unsigned int i = 0; i < numKeyframes; ++i) {
+        const aiQuatKey &key = nodeChannel->mRotationKeys[i];
+        // mTime is measured in ticks, but GLTF time is measured in seconds, so convert.
+        times[i] = static_cast<float>(key.mTime / ticksPerSecond);
+        values[(i * 4) + 0] = (ai_real) key.mValue.x;
+        values[(i * 4) + 1] = (ai_real) key.mValue.y;
+        values[(i * 4) + 2] = (ai_real) key.mValue.z;
+        values[(i * 4) + 3] = (ai_real) key.mValue.w;
+    }
+
+    sampler.input = GetSamplerInputRef(asset, animId, buffer, times);
+    sampler.output = ExportData(asset, animId, buffer, numKeyframes, &values[0], AttribType::VEC4, AttribType::VEC4, ComponentType_FLOAT);
+    sampler.interpolation = Interpolation_LINEAR;
+}
+
+static void AddSampler(Ref<Animation> &animRef, Ref<Node> &nodeRef, Animation::Sampler &sampler, AnimationPath path) {
+    Animation::Channel channel;
+    channel.sampler = static_cast<int>(animRef->samplers.size());
+    channel.target.path = path;
+    channel.target.node = nodeRef;
+    animRef->channels.push_back(channel);
+    animRef->samplers.push_back(sampler);
+}
+
+void glTF2Exporter::ExportAnimations() {
+    Ref<Buffer> bufferRef = mAsset->buffers.Get(unsigned(0));
+
+    for (unsigned int i = 0; i < mScene->mNumAnimations; ++i) {
+        const aiAnimation *anim = mScene->mAnimations[i];
+        const float ticksPerSecond = static_cast<float>(anim->mTicksPerSecond);
+
+        std::string nameAnim = "anim";
+        if (anim->mName.length > 0) {
+            nameAnim = anim->mName.C_Str();
+        }
+        Ref<Animation> animRef = mAsset->animations.Create(nameAnim);
+        animRef->name = nameAnim;
+
+        for (unsigned int channelIndex = 0; channelIndex < anim->mNumChannels; ++channelIndex) {
+            const aiNodeAnim *nodeChannel = anim->mChannels[channelIndex];
+
+            std::string name = nameAnim + "_" + ai_to_string(channelIndex);
+            name = mAsset->FindUniqueID(name, "animation");
+
+            Ref<Node> animNode = mAsset->nodes.Get(nodeChannel->mNodeName.C_Str());
+
+            if (nodeChannel->mNumPositionKeys > 0) {
+                Animation::Sampler translationSampler;
+                ExtractTranslationSampler(*mAsset, name, bufferRef, nodeChannel, ticksPerSecond, translationSampler);
+                AddSampler(animRef, animNode, translationSampler, AnimationPath_TRANSLATION);
+            }
+
+            if (nodeChannel->mNumRotationKeys > 0) {
+                Animation::Sampler rotationSampler;
+                ExtractRotationSampler(*mAsset, name, bufferRef, nodeChannel, ticksPerSecond, rotationSampler);
+                AddSampler(animRef, animNode, rotationSampler, AnimationPath_ROTATION);
+            }
+
+            if (nodeChannel->mNumScalingKeys > 0) {
+                Animation::Sampler scaleSampler;
+                ExtractScaleSampler(*mAsset, name, bufferRef, nodeChannel, ticksPerSecond, scaleSampler);
+                AddSampler(animRef, animNode, scaleSampler, AnimationPath_SCALE);
+            }
+        }
+    } // End: for-loop mNumAnimations
+}
+
+#endif // ASSIMP_BUILD_NO_GLTF_EXPORTER
+#endif // ASSIMP_BUILD_NO_EXPORT