Issue #301. Serialize accessor min/vax value as int if its component type is an integer.

Empty material

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1 @@
+blank_issues_enabled: false

.github/ISSUE_TEMPLATE/issue-report.md

@@ -0,0 +1,30 @@
+---
+name: Issue report
+about: Create a report
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+**Describe the issue**
+
+A clear and concise description of what the issue is.
+
+**To Reproduce**
+
+- OS
+- Compiler, compiler version, compile options
+- Please attach minimal and reproducible .glTF file if you got an issue related to .glTF data
+
+**Expected behaviour**
+
+A clear and concise description of what you expected to happen.
+
+**Screenshots**
+
+If applicable, add screenshots to help explain your problem.
+
+
+**Additional context**
+Add any other context about the problem here.

README.md

@@ -3,7 +3,7 @@
 `TinyGLTF` is a header only C++11 glTF 2.0 https://github.com/KhronosGroup/glTF library.
 
 `TinyGLTF` uses Niels Lohmann's json library(https://github.com/nlohmann/json), so now it requires C++11 compiler.
-If you are looking for old, C++03 version, please use `devel-picojson` branch.
+If you are looking for old, C++03 version, please use `devel-picojson` branch(but not maintained anymore).
 
 ## Status
 
@@ -13,6 +13,10 @@ If you are looking for old, C++03 version, please use `devel-picojson` branch.
  - v2.1.0 release(Draco support)
  - v2.0.0 release(22 Aug, 2018)!
 
+### Branches
+
+* `sajson` : Use sajson to parse JSON. Parsing only but faster compile time(2x reduction compared to json.hpp and RapidJson)
+
 ## Builds
 
 [![Build Status](https://travis-ci.org/syoyo/tinygltf.svg?branch=devel)](https://travis-ci.org/syoyo/tinygltf)
@@ -151,9 +155,12 @@ if (!ret) {
 }
 ```
 
+#### Loader options
+
+* `TinyGLTF::SetPreserveimageChannels(bool onoff)`. `true` to preserve image channels as stored in image file for loaded image. `false` by default for backward compatibility(image channels are widen to `RGBA` 4 channels). Effective only when using builtin image loader(STB image loader).
+
 ## Compile options
 
-* `TINYGLTF_ENABLE_SERIALIZER` : Enable glTF serialization feature.
 * `TINYGLTF_NOEXCEPTION` : Disable C++ exception in JSON parsing. You can use `-fno-exceptions` or by defining the symbol `JSON_NOEXCEPTION` and `TINYGLTF_NOEXCEPTION`  to fully remove C++ exception codes when compiling TinyGLTF.
 * `TINYGLTF_NO_STB_IMAGE` : Do not load images with stb_image. Instead use `TinyGLTF::SetImageLoader(LoadimageDataFunction LoadImageData, void *user_data)` to set a callback for loading images.
 * `TINYGLTF_NO_STB_IMAGE_WRITE` : Do not write images with stb_image_write. Instead use `TinyGLTF::SetImageWriter(WriteimageDataFunction WriteImageData, void *user_data)` to set a callback for writing images.

examples/basic/.gitignore

@@ -1,5 +1,6 @@
 .vs
 Debug
+Release
 x64
 packages
 

examples/basic/basic/basic.vcxproj

@@ -22,32 +22,32 @@
     <VCProjectVersion>15.0</VCProjectVersion>
     <ProjectGuid>{0589AC44-0CF3-40D8-8D89-68393CFD40F3}</ProjectGuid>
     <RootNamespace>basic</RootNamespace>
-    <WindowsTargetPlatformVersion>10.0.17134.0</WindowsTargetPlatformVersion>
+    <WindowsTargetPlatformVersion>10.0</WindowsTargetPlatformVersion>
   </PropertyGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Default.props" />
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'" Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <UseDebugLibraries>true</UseDebugLibraries>
-    <PlatformToolset>v141</PlatformToolset>
+    <PlatformToolset>v142</PlatformToolset>
     <CharacterSet>MultiByte</CharacterSet>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|Win32'" Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <UseDebugLibraries>false</UseDebugLibraries>
-    <PlatformToolset>v141</PlatformToolset>
+    <PlatformToolset>v142</PlatformToolset>
     <WholeProgramOptimization>true</WholeProgramOptimization>
     <CharacterSet>MultiByte</CharacterSet>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'" Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <UseDebugLibraries>true</UseDebugLibraries>
-    <PlatformToolset>v141</PlatformToolset>
+    <PlatformToolset>v142</PlatformToolset>
     <CharacterSet>MultiByte</CharacterSet>
   </PropertyGroup>
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|x64'" Label="Configuration">
     <ConfigurationType>Application</ConfigurationType>
     <UseDebugLibraries>false</UseDebugLibraries>
-    <PlatformToolset>v141</PlatformToolset>
+    <PlatformToolset>v142</PlatformToolset>
     <WholeProgramOptimization>true</WholeProgramOptimization>
     <CharacterSet>MultiByte</CharacterSet>
   </PropertyGroup>

examples/basic/main.cpp

@@ -329,7 +329,7 @@ static void error_callback(int error, const char *description) {
 }
 
 int main(int argc, char **argv) {
-  std::string filename = "../../models/Cube/Cube.gltf";
+  std::string filename = "../../../models/Cube/Cube.gltf";
 
   if (argc > 1) {
     filename = argv[1];
@@ -341,9 +341,12 @@ int main(int argc, char **argv) {
 
   // Force create OpenGL 3.3
   // NOTE(syoyo): Linux + NVIDIA driver segfaults for some reason? commenting out glfwWindowHint will work.
+  // Note (PE): On laptops with intel hd graphics card you can overcome the segfault by enabling experimental, see below (tested on lenovo thinkpad)
   glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
   glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
   glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
+  glewExperimental = GL_TRUE;
+
 #ifdef __APPLE__
   glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
 #endif

examples/dxview/CMakeLists.txt

@@ -0,0 +1,36 @@
+cmake_minimum_required(VERSION 3.5)
+project(dxview)
+
+find_package(glfw3 CONFIG REQUIRED)
+find_package(spdlog CONFIG REQUIRED)
+
+add_executable(dxview
+    src/Viewer.h
+    src/Viewer.cc
+    src/dxview.cc
+)
+
+target_include_directories(dxview
+PRIVATE
+    ../../
+)
+
+target_compile_definitions(dxview
+PRIVATE
+    DXVIEW_SWAP_CHAIN_BUFFER_COUNT=3
+    DXVIEW_RES_DIR=L"${PROJECT_SOURCE_DIR}/res"
+)
+
+target_link_libraries(dxview
+PRIVATE
+    dxgi
+    d3dcompiler
+    d3d12
+    glfw
+    spdlog::spdlog
+)
+
+set_target_properties(dxview
+PROPERTIES
+    CXX_STANDARD 17
+)

examples/dxview/README.md

@@ -0,0 +1,37 @@
+# DirectX glTF Viewer
+
+## Overview
+
+This project was motivated by a lack of sample code demonstrating the graphics API agnostic nature of the glTF specification. The sample code is written using modern C++ and DirectX 12 for the client application.
+
+## Features
+
+* [x] DirectX 12
+* [ ] Loader
+* [ ] Animation
+* [ ] Morph Target
+* [ ] Physical Base Rendering
+* [ ] Environment Map
+
+## Dependencies
+
+* [CMake](https://github.com/Kitware/CMake)
+* [Vcpkg](https://github.com/Microsoft/vcpkg)
+* [GLFW](https://github.com/glfw/glfw)
+* [spdlog](https://github.com/gabime/spdlog)
+
+## Building
+
+### Install dependencies
+
+```
+vcpkg install glfw3:x64-windows
+vcpkg install spdlog:x64-windows
+```
+
+### Generate Project Files
+
+```
+mkdir build
+cmake . -B build -DCMAKE_TOOLCHAIN_FILE=${VCPKG_DIR}/script/buildsystem/vcpkg.cmake
+```

examples/dxview/res/gray.hlsl

@@ -0,0 +1,3 @@
+float4 main() : SV_Target {
+    return float4(0.5, 0.5, 0.5, 1.0);
+}

examples/dxview/res/lighting.hlsl

@@ -0,0 +1,52 @@
+struct RS2PS {
+    float4 position : SV_POSITION;
+
+#ifdef HAS_TEXCOORD_0
+    float2 texcoord_0: TEXCOORD_0;
+#endif
+};
+
+struct TextureInfo {
+    uint textureIndex;
+    uint samplerIndex;
+};
+
+struct PBRMetallicRoughness {
+    float4 baseColorFactor;
+    TextureInfo baseColorTexture;
+    float metallicFactor;
+    float roughnessFactor;
+    TextureInfo metallicRoughnessTexture;
+};
+
+cbuffer Material : register(b2) {
+    PBRMetallicRoughness pbrMetallicRoughness;
+};
+
+Texture2D textures[5] : register(t0);
+SamplerState samplerState[5] : register(s0);
+
+float4 getBaseColor(float2 uv) {
+    float4 baseColor = pbrMetallicRoughness.baseColorFactor;
+
+#ifdef HAS_TEXCOORD_0
+    TextureInfo baseColorTexture = pbrMetallicRoughness.baseColorTexture;
+    if (baseColorTexture.textureIndex >= 0) {
+        baseColor *= textures[baseColorTexture.textureIndex].Sample(samplerState[baseColorTexture.samplerIndex], uv);
+    }
+#endif
+
+    return baseColor;
+}
+
+float4 main(RS2PS input) : SV_Target {
+    float2 uv = float2(0.0, 0.0);
+
+#ifdef HAS_TEXCOORD_0
+    uv = input.texcoord_0;
+#endif
+
+    float4 color = getBaseColor(uv);
+
+    return color;
+}

examples/dxview/res/primitive.hlsl

@@ -0,0 +1,46 @@
+struct IA2VS {
+    float3 position  : POSITION;
+
+#ifdef HAS_NORMAL
+    float3 normal : NORMAL;
+#endif
+
+#ifdef HAS_TANGENT
+    float4 tangent : TANGENT;
+#endif
+
+#ifdef HAS_TEXCOORD_0
+    float2 texcoord_0: TEXCOORD_0;
+#endif
+};
+
+struct VS2RS {
+    float4 position : SV_POSITION;
+
+#ifdef HAS_TEXCOORD_0
+    float2 texcoord_0: TEXCOORD_0;
+#endif
+};
+
+cbuffer Camera : register(b0) {
+    float4x4 V;
+    float4x4 P;
+    float4x4 VP;
+};
+
+cbuffer Node : register(b1) {
+    float4x4 M;
+};
+
+VS2RS main(IA2VS input) {
+    VS2RS output;
+    output.position = mul(float4(input.position, 1.0), M);
+    output.position = mul(output.position, V);
+    output.position = mul(output.position, P);
+
+#ifdef HAS_TEXCOORD_0
+    output.texcoord_0 = input.texcoord_0;
+#endif
+
+    return output;
+}

examples/dxview/src/Viewer.h

@@ -0,0 +1,130 @@
+#ifndef DXVIEW_VIEWER_GUARD
+#define DXVIEW_VIEWER_GUARD
+
+#include <DirectXMath.h>
+#include <d3d12.h>
+#include <dxgi1_6.h>
+#include <tiny_gltf.h>
+#include <wrl.h>
+
+#include <filesystem>
+#include <map>
+#include <string>
+#include <vector>
+
+using Microsoft::WRL::ComPtr;
+
+enum RenderPassType { RENDER_PASS_TYPE_PRESENT = 0, RENDER_PASS_TYPE_COUNT };
+
+struct RenderTarget {
+  ComPtr<ID3D12Resource> pTexture;
+  D3D12_CPU_DESCRIPTOR_HANDLE viewDescriptor;
+};
+
+struct TextureInfo {
+  int32_t textureIndex;
+  int32_t samplerIndex;
+};
+
+struct PBRMetallicRoughness {
+  DirectX::XMFLOAT4 baseColorFactor;
+  TextureInfo baseColorTexture;
+  float metallicFactor;
+  float roughnessFactor;
+  TextureInfo metallicRoughnessTexture;
+};
+
+struct Material {
+  std::string name;
+  D3D12_BLEND_DESC blendDesc;
+  D3D12_RASTERIZER_DESC rasterizerDesc;
+  ComPtr<ID3D12Resource> pBuffer;
+  void* pBufferData;
+  ComPtr<ID3D12DescriptorHeap> pSRVDescriptorHeap;
+  ComPtr<ID3D12DescriptorHeap> pSamplerDescriptorHeap;
+};
+
+struct Attribute {
+  std::string name;
+  DXGI_FORMAT format;
+  D3D12_VERTEX_BUFFER_VIEW vertexBufferView;
+};
+
+struct Primitive {
+  std::vector<Attribute> attributes;
+  uint32_t vertexCount;
+  D3D12_PRIMITIVE_TOPOLOGY primitiveTopology;
+  D3D12_INDEX_BUFFER_VIEW indexBufferView;
+  uint32_t indexCount;
+  Material* pMaterial;
+  ComPtr<ID3D12RootSignature> pRootSignature;
+  ComPtr<ID3D12PipelineState> pPipelineState;
+};
+
+struct Mesh {
+  std::string name;
+  std::vector<Primitive> primitives;
+};
+
+struct Node {
+  DirectX::XMFLOAT4X4 M;
+};
+
+struct Camera {
+  DirectX::XMFLOAT4X4 V;
+  DirectX::XMFLOAT4X4 P;
+  DirectX::XMFLOAT4X4 VP;
+};
+
+class Viewer {
+ public:
+  Viewer(HWND window, tinygltf::Model* pModel);
+
+  void update(double deltaTime);
+  void render(double deltaTime);
+
+ private:
+  void initDirectX(HWND window);
+  void buildRenderTargets();
+  void buildResources();
+  void buildBuffers(std::vector<ComPtr<ID3D12Resource> >* pStagingResources);
+  void buildImages(std::vector<ComPtr<ID3D12Resource> >* pStagingResources);
+  void buildSamplerDescs();
+  void buildMaterials();
+  void buildMeshes();
+  void buildNodes();
+
+  void drawNode(uint64_t nodeIndex);
+
+ private:
+  tinygltf::Model* pModel_;
+  ComPtr<IDXGIFactory1> pFactory_;
+  ComPtr<IDXGIAdapter1> pAdapter_;
+  ComPtr<ID3D12Device> pDevice_;
+  ComPtr<ID3D12CommandQueue> pDirectCommandQueue_;
+  UINT64 directFenceValue_;
+  ComPtr<ID3D12Fence> pDirectFence_;
+  ComPtr<ID3D12CommandQueue> pCopyCommandQueue_;
+  UINT64 copyFenceValue_;
+  ComPtr<ID3D12Fence> pCopyFence_;
+  ComPtr<IDXGISwapChain3> pSwapChain_;
+  ComPtr<ID3D12Resource> pSwapChainBuffers_[DXVIEW_SWAP_CHAIN_BUFFER_COUNT];
+  ComPtr<ID3D12CommandAllocator>
+      pDirectCommandAllocators_[DXVIEW_SWAP_CHAIN_BUFFER_COUNT];
+  ComPtr<ID3D12GraphicsCommandList> pDirectCommandList_;
+  ComPtr<ID3D12CommandAllocator> pCopyCommandAllocator_;
+  ComPtr<ID3D12GraphicsCommandList> pCopyCommandList_;
+  UINT descriptorIncrementSize_[D3D12_DESCRIPTOR_HEAP_TYPE_NUM_TYPES];
+  ComPtr<ID3D12DescriptorHeap>
+      pRTVDescriptorHeaps_[DXVIEW_SWAP_CHAIN_BUFFER_COUNT];
+  std::vector<RenderTarget> renderTargets_[DXVIEW_SWAP_CHAIN_BUFFER_COUNT];
+  std::vector<ComPtr<ID3D12Resource> > pBuffers_;
+  std::vector<ComPtr<ID3D12Resource> > pTextures_;
+  std::vector<D3D12_SAMPLER_DESC> samplerDescs_;
+  std::vector<Material> materials_;
+  std::vector<Mesh> meshes_;
+  std::vector<ComPtr<ID3D12Resource> > pNodeBuffers_;
+  ComPtr<ID3D12Resource> pCameraBuffer_;
+};
+
+#endif

examples/dxview/src/dxview.cc

@@ -0,0 +1,90 @@
+#define GLFW_EXPOSE_NATIVE_WIN32
+#define TINYGLTF_IMPLEMENTATION
+#define STBI_MSC_SECURE_CRT
+#define STB_IMAGE_IMPLEMENTATION
+#define STB_IMAGE_WRITE_IMPLEMENTATION
+
+#include <GLFW/glfw3.h>
+#include <GLFW/glfw3native.h>
+#include <spdlog/spdlog.h>
+#include <tiny_gltf.h>
+
+#undef GLFW_EXPOSE_NATIVE_WIN32
+#undef TINYGLTF_IMPLEMENTATION
+#undef STBI_MSC_SECURE_CRT
+#undef STB_IMAGE_IMPLEMENTATION
+#undef STB_IMAGE_WRITE_IMPLEMENTATION
+
+#include <iostream>
+#include <string>
+
+#include "Viewer.h"
+
+static void onError(int error, const char* message) {
+  spdlog::error("[{}] {}", error, message);
+}
+
+static void onRender(Viewer* pViewer, double deltaTime) {
+  pViewer->update(deltaTime);
+  pViewer->render(deltaTime);
+}
+
+int main(int argc, char* argv[]) {
+  tinygltf::TinyGLTF context;
+
+  tinygltf::Model model;
+  std::string error;
+  std::string warning;
+  if (!context.LoadASCIIFromFile(&model, &error, &warning, argv[1])) {
+    if (!error.empty()) {
+      spdlog::error("{}", error);
+    }
+
+    if (!warning.empty()) {
+      spdlog::warn("{}", warning);
+    }
+
+    exit(EXIT_FAILURE);
+  }
+
+  GLFWwindow* pWindow;
+
+  glfwSetErrorCallback(onError);
+
+  if (!glfwInit()) {
+    spdlog::error("Fail to initialize GLFW!!!");
+    exit(EXIT_FAILURE);
+  }
+
+  glfwWindowHint(GLFW_CLIENT_API, GLFW_NO_API);
+  glfwWindowHint(GLFW_RESIZABLE, GLFW_FALSE);
+
+  pWindow = glfwCreateWindow(512, 512, "dxview", nullptr, nullptr);
+  if (!pWindow) {
+    spdlog::error("Fail to create GLFWwindow!!!");
+    glfwTerminate();
+    exit(EXIT_FAILURE);
+  }
+
+  auto pViewer = std::make_unique<Viewer>(glfwGetWin32Window(pWindow), &model);
+  if (!pViewer) {
+    spdlog::error("Fail to create Viewer");
+    glfwDestroyWindow(pWindow);
+    glfwTerminate();
+    exit(EXIT_FAILURE);
+  }
+
+  auto prevTimeStamp = glfwGetTime();
+  while (!glfwWindowShouldClose(pWindow)) {
+    auto currTimeStamp = glfwGetTime();
+
+    onRender(pViewer.get(), currTimeStamp - prevTimeStamp);
+    prevTimeStamp = currTimeStamp;
+
+    glfwPollEvents();
+  }
+
+  glfwDestroyWindow(pWindow);
+  glfwTerminate();
+  exit(EXIT_SUCCESS);
+}

tests/tester.cc

@@ -3,6 +3,9 @@
 #define STB_IMAGE_WRITE_IMPLEMENTATION
 #include "tiny_gltf.h"
 
+// Nlohmann json(include ../json.hpp)
+#include "json.hpp"
+
 #define CATCH_CONFIG_MAIN  // This tells Catch to provide a main() - only do this in one cpp file
 #include "catch.hpp"
 
@@ -412,6 +415,28 @@ TEST_CASE("image-uri-spaces", "[issue-236]") {
   REQUIRE(true == ret);
 }
 
+TEST_CASE("serialize-empty-material", "[issue-294]") {
+
+  tinygltf::Model m;
+
+  tinygltf::Material mat;
+  mat.pbrMetallicRoughness.baseColorFactor = {1.0f, 1.0f, 1.0f, 1.0f}; // default baseColorFactor
+  m.materials.push_back(mat);
+
+  std::stringstream os;
+
+  tinygltf::TinyGLTF ctx;
+  ctx.WriteGltfSceneToStream(&m, os, false, false);
+
+  // use nlohmann json
+  nlohmann::json j = nlohmann::json::parse(os.str());
+
+  REQUIRE(1 == j["materials"].size());
+  REQUIRE(j["asset"].is_null());
+  REQUIRE(j["materials"][0].is_object());
+
+}
+
 #ifndef TINYGLTF_NO_FS
 TEST_CASE("expandpath-utf-8", "[pr-226]") {
 

tiny_gltf.h

@@ -26,7 +26,9 @@
 // THE SOFTWARE.
 
 // Version:
-//  - v2.4.3 Introduce TINYGLTF_ENABLE_SERIALIZER.
+//  - v2.5.0 Add SetPreserveImageChannels() option to load image data as is.
+//  - v2.4.3 Fix null object output when when material has all default
+//  parameters.
 //  - v2.4.2 Decode percent-encoded URI.
 //  - v2.4.1 Fix some glTF object class does not have `extensions` and/or
 //  `extras` property.
@@ -665,6 +667,8 @@ struct Image {
     width = -1;
     height = -1;
     component = -1;
+    bits = -1;
+    pixel_type = -1;
   }
   DEFAULT_METHODS(Image)
 
@@ -847,8 +851,10 @@ struct Accessor {
   std::string extras_json_string;
   std::string extensions_json_string;
 
-  std::vector<double> minValues;  // optional
-  std::vector<double> maxValues;  // optional
+  std::vector<double>
+      minValues;  // optional. integer value is promoted to double
+  std::vector<double>
+      maxValues;  // optional. integer value is promoted to double
 
   struct {
     int count;
@@ -997,6 +1003,7 @@ struct Primitive {
   Primitive() {
     material = -1;
     indices = -1;
+    mode = -1;
   }
   DEFAULT_METHODS(Primitive)
   bool operator==(const Primitive &) const;
@@ -1187,7 +1194,8 @@ enum SectionCheck {
 ///
 typedef bool (*LoadImageDataFunction)(Image *, const int, std::string *,
                                       std::string *, int, int,
-                                      const unsigned char *, int, void *);
+                                      const unsigned char *, int,
+                                      void *user_pointer);
 
 ///
 /// WriteImageDataFunction type. Signature for custom image writing callbacks.
@@ -1251,7 +1259,8 @@ struct FsCallbacks {
 bool FileExists(const std::string &abs_filename, void *);
 
 ///
-/// Expand file path(e.g. `~` to home directory on posix, `%APPDATA%` to `C:\Users\tinygltf\AppData`)
+/// Expand file path(e.g. `~` to home directory on posix, `%APPDATA%` to
+/// `C:\Users\tinygltf\AppData`)
 ///
 /// @param[in] filepath File path string. Assume UTF-8
 /// @param[in] userdata User data. Set to `nullptr` if you don't need it.
@@ -1324,8 +1333,6 @@ class TinyGLTF {
                             const std::string &base_dir = "",
                             unsigned int check_sections = REQUIRE_VERSION);
 
-#if defined(TINYGLTF_ENABLE_SERIALIZER)
-
   ///
   /// Write glTF to stream, buffers and images will be embeded
   ///
@@ -1339,22 +1346,21 @@ class TinyGLTF {
                             bool embedImages, bool embedBuffers,
                             bool prettyPrint, bool writeBinary);
 
-#endif
-
   ///
   /// Set callback to use for loading image data
   ///
   void SetImageLoader(LoadImageDataFunction LoadImageData, void *user_data);
 
-#if defined(TINYGLTF_ENABLE_SERIALIZER)
+  ///
+  /// Unset(remove) callback of loading image data
+  ///
+  void RemoveImageLoader();
 
   ///
   /// Set callback to use for writing image data
   ///
   void SetImageWriter(WriteImageDataFunction WriteImageData, void *user_data);
 
-#endif
-
   ///
   /// Set callbacks to use for filesystem (fs) access and their user data
   ///
@@ -1388,6 +1394,16 @@ class TinyGLTF {
     return store_original_json_for_extras_and_extensions_;
   }
 
+  ///
+  /// Specify whether preserve image channales when loading images or not.
+  /// (Not effective when the user suppy their own LoadImageData callbacks)
+  ///
+  void SetPreserveImageChannels(bool onoff) {
+    preserve_image_channels_ = onoff;
+  }
+
+  bool GetPreserveImageChannels() const { return preserve_image_channels_; }
+
  private:
   ///
   /// Loads glTF asset from string(memory).
@@ -1407,6 +1423,9 @@ class TinyGLTF {
 
   bool store_original_json_for_extras_and_extensions_ = false;
 
+  bool preserve_image_channels_ = false;  /// Default false(expand channels to
+                                          /// RGBA) for backward compatibility.
+
   FsCallbacks fs = {
 #ifndef TINYGLTF_NO_FS
       &tinygltf::FileExists, &tinygltf::ExpandFilePath,
@@ -1426,7 +1445,8 @@ class TinyGLTF {
 #else
       nullptr;
 #endif
-  void *load_image_user_data_ = reinterpret_cast<void *>(&fs);
+  void *load_image_user_data_{nullptr};
+  bool user_image_loader_{false};
 
   WriteImageDataFunction WriteImageData =
 #ifndef TINYGLTF_NO_STB_IMAGE_WRITE
@@ -1434,7 +1454,7 @@ class TinyGLTF {
 #else
       nullptr;
 #endif
-  void *write_image_user_data_ = reinterpret_cast<void *>(&fs);
+  void *write_image_user_data_{nullptr};
 };
 
 #ifdef __clang__
@@ -1688,6 +1708,19 @@ void JsonParse(JsonDocument &doc, const char *str, size_t length,
 
 namespace tinygltf {
 
+///
+/// Internal LoadImageDataOption struct.
+/// This struct is passed through `user_pointer` in LoadImageData.
+/// The struct is not passed when the user supply their own LoadImageData
+/// callbacks.
+///
+struct LoadImageDataOption {
+  // true: preserve image channels(e.g. load as RGB image if the image has RGB
+  // channels) default `false`(channels are expanded to RGBA for backward
+  // compatiblity).
+  bool preserve_channels{false};
+};
+
 // Equals function for Value, for recursivity
 static bool Equals(const tinygltf::Value &one, const tinygltf::Value &other) {
   if (one.Type() != other.Type()) return false;
@@ -2302,22 +2335,40 @@ static bool LoadExternalFile(std::vector<unsigned char> *out, std::string *err,
 void TinyGLTF::SetImageLoader(LoadImageDataFunction func, void *user_data) {
   LoadImageData = func;
   load_image_user_data_ = user_data;
+  user_image_loader_ = true;
+}
+
+void TinyGLTF::RemoveImageLoader() {
+  LoadImageData =
+#ifndef TINYGLTF_NO_STB_IMAGE
+      &tinygltf::LoadImageData;
+#else
+      nullptr;
+#endif
+
+  load_image_user_data_ = nullptr;
+  user_image_loader_ = false;
 }
 
 #ifndef TINYGLTF_NO_STB_IMAGE
 bool LoadImageData(Image *image, const int image_idx, std::string *err,
                    std::string *warn, int req_width, int req_height,
                    const unsigned char *bytes, int size, void *user_data) {
-  (void)user_data;
   (void)warn;
 
+  LoadImageDataOption option;
+  if (user_data) {
+    option = *reinterpret_cast<LoadImageDataOption *>(user_data);
+  }
+
   int w = 0, h = 0, comp = 0, req_comp = 0;
 
   unsigned char *data = nullptr;
 
-  // force 32-bit textures for common Vulkan compatibility. It appears that
-  // some GPU drivers do not support 24-bit images for Vulkan
-  req_comp = 4;
+  // preserve_channels true: Use channels stored in the image file.
+  // false: force 32-bit textures for common Vulkan compatibility. It appears
+  // that some GPU drivers do not support 24-bit images for Vulkan
+  req_comp = option.preserve_channels ? 0 : 4;
   int bits = 8;
   int pixel_type = TINYGLTF_COMPONENT_TYPE_UNSIGNED_BYTE;
 
@@ -2389,28 +2440,29 @@ bool LoadImageData(Image *image, const int image_idx, std::string *err,
     }
   }
 
+  if (req_comp != 0) {
+    // loaded data has `req_comp` channels(components)
+    comp = req_comp;
+  }
+
   image->width = w;
   image->height = h;
-  image->component = req_comp;
+  image->component = comp;
   image->bits = bits;
   image->pixel_type = pixel_type;
-  image->image.resize(static_cast<size_t>(w * h * req_comp) * size_t(bits / 8));
-  std::copy(data, data + w * h * req_comp * (bits / 8), image->image.begin());
+  image->image.resize(static_cast<size_t>(w * h * comp) * size_t(bits / 8));
+  std::copy(data, data + w * h * comp * (bits / 8), image->image.begin());
   stbi_image_free(data);
 
   return true;
 }
 #endif
 
-#if defined(TINYGLTF_ENABLE_SERIALIZER)
-
 void TinyGLTF::SetImageWriter(WriteImageDataFunction func, void *user_data) {
   WriteImageData = func;
   write_image_user_data_ = user_data;
 }
 
-#endif
-
 #ifndef TINYGLTF_NO_STB_IMAGE_WRITE
 static void WriteToMemory_stbi(void *context, void *data, int size) {
   std::vector<unsigned char> *buffer =
@@ -2505,7 +2557,7 @@ static inline std::wstring UTF8ToWchar(const std::string &str) {
 
 static inline std::string WcharToUTF8(const std::wstring &wstr) {
   int str_size = WideCharToMultiByte(CP_UTF8, 0, wstr.data(), (int)wstr.size(),
-                                      nullptr, 0, NULL, NULL);
+                                     nullptr, 0, NULL, NULL);
   std::string str(str_size, 0);
   WideCharToMultiByte(CP_UTF8, 0, wstr.data(), (int)wstr.size(), &str[0],
                       (int)str.size(), NULL, NULL);
@@ -2648,7 +2700,8 @@ bool ReadWholeFile(std::vector<unsigned char> *out, std::string *err,
   __gnu_cxx::stdio_filebuf<char> wfile_buf(file_descriptor, std::ios_base::in);
   std::istream f(&wfile_buf);
 #elif defined(_MSC_VER) || defined(_LIBCPP_VERSION)
-  // For libcxx, assume _LIBCPP_HAS_OPEN_WITH_WCHAR is defined to accept `wchar_t *`
+  // For libcxx, assume _LIBCPP_HAS_OPEN_WITH_WCHAR is defined to accept
+  // `wchar_t *`
   std::ifstream f(UTF8ToWchar(filepath).c_str(), std::ifstream::binary);
 #else
   // Unknown compiler/runtime
@@ -3010,7 +3063,9 @@ json_const_iterator ObjectEnd(const json &o) {
 #endif
 }
 
-const char *GetKey(json_const_iterator &it) {
+// Making this a const char* results in a pointer to a temporary when
+// TINYGLTF_USE_RAPIDJSON is off.
+std::string GetKey(json_const_iterator &it) {
 #ifdef TINYGLTF_USE_RAPIDJSON
   return it->name.GetString();
 #else
@@ -5715,10 +5770,13 @@ bool TinyGLTF::LoadFromString(Model *model, std::string *err, std::string *warn,
 
       for (auto &target : primitive.targets) {
         for (auto &attribute : target) {
-          model
-              ->bufferViews[size_t(
-                  model->accessors[size_t(attribute.second)].bufferView)]
-              .target = TINYGLTF_TARGET_ARRAY_BUFFER;
+          auto bufferView =
+              model->accessors[size_t(attribute.second)].bufferView;
+          // bufferView could be null(-1) for sparse morph target
+          if (bufferView >= 0) {
+            model->bufferViews[size_t(bufferView)].target =
+                TINYGLTF_TARGET_ARRAY_BUFFER;
+          }
         }
       }
     }
@@ -5828,6 +5886,18 @@ bool TinyGLTF::LoadFromString(Model *model, std::string *err, std::string *warn,
   }
 
   // 11. Parse Image
+  void *load_image_user_data{nullptr};
+
+  LoadImageDataOption load_image_option;
+
+  if (user_image_loader_) {
+    // Use user supplied pointer
+    load_image_user_data = load_image_user_data_;
+  } else {
+    load_image_option.preserve_channels = preserve_image_channels_;
+    load_image_user_data = reinterpret_cast<void *>(&load_image_option);
+  }
+
   {
     int idx = 0;
     bool success = ForEachInArray(v, "images", [&](const json &o) {
@@ -5840,7 +5910,7 @@ bool TinyGLTF::LoadFromString(Model *model, std::string *err, std::string *warn,
       Image image;
       if (!ParseImage(&image, idx, err, warn, o,
                       store_original_json_for_extras_and_extensions_, base_dir,
-                      &fs, &this->LoadImageData, load_image_user_data_)) {
+                      &fs, &this->LoadImageData, load_image_user_data)) {
         return false;
       }
 
@@ -5878,7 +5948,7 @@ bool TinyGLTF::LoadFromString(Model *model, std::string *err, std::string *warn,
         bool ret = LoadImageData(
             &image, idx, err, warn, image.width, image.height,
             &buffer.data[bufferView.byteOffset],
-            static_cast<int>(bufferView.byteLength), load_image_user_data_);
+            static_cast<int>(bufferView.byteLength), load_image_user_data);
         if (!ret) {
           return false;
         }
@@ -6227,8 +6297,6 @@ bool TinyGLTF::LoadBinaryFromFile(Model *model, std::string *err,
   return ret;
 }
 
-#if defined(TINYGLTF_ENABLE_SERIALIZER)
-
 ///////////////////////
 // GLTF Serialization
 ///////////////////////
@@ -6556,8 +6624,33 @@ static void SerializeGltfAccessor(Accessor &accessor, json &o) {
 
   SerializeNumberProperty<int>("componentType", accessor.componentType, o);
   SerializeNumberProperty<size_t>("count", accessor.count, o);
-  SerializeNumberArrayProperty<double>("min", accessor.minValues, o);
-  SerializeNumberArrayProperty<double>("max", accessor.maxValues, o);
+
+  if ((accessor.componentType == TINYGLTF_COMPONENT_TYPE_FLOAT) ||
+      (accessor.componentType == TINYGLTF_COMPONENT_TYPE_DOUBLE)) {
+    SerializeNumberArrayProperty<double>("min", accessor.minValues, o);
+    SerializeNumberArrayProperty<double>("max", accessor.maxValues, o);
+  } else {
+    // Issue #301. Serialize as integer.
+    // Assume int value is within [-2**31-1, 2**31-1]
+    {
+      std::vector<int> values;
+      std::transform(accessor.minValues.begin(), accessor.minValues.end(),
+                     std::back_inserter(values),
+                     [](double v) { return static_cast<int>(v); });
+
+      SerializeNumberArrayProperty<int>("min", values, o);
+    }
+
+    {
+      std::vector<int> values;
+      std::transform(accessor.maxValues.begin(), accessor.maxValues.end(),
+                     std::back_inserter(values),
+                     [](double v) { return static_cast<int>(v); });
+
+      SerializeNumberArrayProperty<int>("max", values, o);
+    }
+  }
+
   if (accessor.normalized)
     SerializeValue("normalized", Value(accessor.normalized), o);
   std::string type;
@@ -7230,6 +7323,16 @@ static void SerializeGltfModel(Model *model, json &o) {
     for (unsigned int i = 0; i < model->materials.size(); ++i) {
       json material;
       SerializeGltfMaterial(model->materials[i], material);
+
+      if (JsonIsNull(material)) {
+        // Issue 294.
+        // `material` does not have any required parameters
+        // so the result may be null(unmodified) when all material parameters
+        // have default value.
+        //
+        // null is not allowed thus we create an empty JSON object.
+        JsonSetObject(material);
+      }
       JsonPushBack(materials, std::move(material));
     }
     JsonAddMember(o, "materials", std::move(materials));
@@ -7355,8 +7458,9 @@ static void SerializeGltfModel(Model *model, json &o) {
 
     // Also add "KHR_lights_punctual" to `extensionsUsed`
     {
-      auto has_khr_lights_punctual = std::find_if(
-          extensionsUsed.begin(), extensionsUsed.end(), [](const std::string &s) {
+      auto has_khr_lights_punctual =
+          std::find_if(extensionsUsed.begin(), extensionsUsed.end(),
+                       [](const std::string &s) {
                          return (s.compare("KHR_lights_punctual") == 0);
                        });
 
@@ -7634,8 +7738,6 @@ bool TinyGLTF::WriteGltfSceneToFile(Model *model, const std::string &filename,
   return true;
 }
 
-#endif // TINYGLTF_ENABLE_SERIALIZER
-
 }  // namespace tinygltf
 
 #ifdef __clang__