Support uint

Improve .obj export.
Use clipp to parse cmd options.
Add some handy python scripts.

README.md

@@ -71,6 +71,7 @@ In extension(`ExtensionMap`), JSON number value is parsed as int or float(number
 * [glview](examples/glview) : Simple glTF geometry viewer.
 * [validator](examples/validator) : Simple glTF validator with JSON schema.
 * [basic](examples/basic) : Basic glTF viewer with texturing support.
+* [mesh-conv](examples/mesh-conv) : Convert glTF mesh to wavefront .obj, wavefront .obj to glTF mesh.
 
 ## Projects using TinyGLTF
 
@@ -216,3 +217,7 @@ We may be better to introduce bounded memory size checking when parsing glTF dat
 * catch : Copyright (c) 2012 Two Blue Cubes Ltd. All rights reserved. Distributed under the Boost Software License, Version 1.0.
 * RapidJSON : Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved. http://rapidjson.org/
 * dlib(uridecode, uriencode) : Copyright (C) 2003  Davis E. King Boost Software License 1.0. http://dlib.net/dlib/server/server_http.cpp.html
+
+### Used in examples
+
+* clipp: MIT License. https://github.com/muellan/clipp

examples/common/clipp.LICENSE

@@ -0,0 +1,20 @@
+The MIT License (MIT)
+
+Copyright (c) 2017 André Müller; foss@andremueller-online.de
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

examples/mesh-conv/Makefile

@@ -0,0 +1,5 @@
+#EXTRA_CXXFLAGS := -fsanitize=address -fno-omit-frame-pointer -Wall -Werror -Weverything -Wno-c++11-long-long -Wno-c++98-compat -Wno-c++98-compat-pedantic -Wno-padded
+EXTRA_CXXFLAGS :=
+
+all:
+	clang++ -std=c++11 -g -O1 -I../../ -I../common $(EXTRA_CXXFLAGS) -o mesh-conv mesh-conv.cc mesh-util.cc tinygltf_impl.cc

examples/mesh-conv/Makefile.meson

@@ -0,0 +1,5 @@
+all:
+	ninja
+
+clean:
+	ninja -t clean

examples/mesh-conv/README.md

@@ -0,0 +1,58 @@
+# Mesh modify experiment
+
+Sometimes we want to tweak mesh attributes(e.g. vertex position, uv coord, etc).
+glTF itself does not allow ASCII representation of such data so we need to write a converter.
+
+This example show how to
+
+- Export mesh data from .bin to .obj
+- Import mesh data to .bin(update corresponding buffer data) from .obj
+
+## Features
+
+* Support skin weights(`JOINTS_N`, `WEIGHTS_N`)
+
+## Supported attributes
+
+* [x] POSITION
+* [x] NORMAL
+* [x] TANGENT
+* [ ] COLOR  (vertex color)
+* [x] TEXCOORD_N
+  * Only single texcoord(uv set) is supported
+  * Specify `--uvset 1` to specify which UV to use.
+* [x] WEIGHTS_N, JOINTS_N
+
+## Usage
+
+### Wavefront .obj to glTF
+
+```
+$ mesh-modify --op=obj2gltf input.obj
+```
+
+All shapes in .obj are concatenated and create single glTF mesh.
+(tinyobjloader's skin weight extension `vw` supported)
+
+#### Limitation
+
+Buffer is stored as external file(`.bin`)
+
+### glTF to Wavefront .obj
+
+```
+$ mesh-modify --op=gltf2obj input.gltf
+```
+
+.obj will be created for each glTF Mesh.
+(Skin weight data is exported to .obj using tinyobjloader's skin weight extension `vw`)
+
+#### Limitation
+
+Buffer is stored as external file(`.bin`)
+
+## TODO
+
+* [ ] obj2gltf: Assign glTF material from .mtl
+* [ ] modify/patch mesh geometry in glTF
+  * By using JSON Patch or JSON Merge feature

examples/mesh-conv/bootstrap-meson.sh

@@ -0,0 +1,3 @@
+rm -rf build
+CXX=clang++ CC=clang meson build -Db_sanitize=address -Db_lundef=false --buildtype=debug
+cp Makefile.meson build/Makefile

examples/mesh-conv/mesh-conv.cc

@@ -0,0 +1,798 @@
+#include <cassert>
+#include <cmath>
+#include <cstdio>
+#include <cstdlib>
+#include <fstream>
+#include <iostream>
+#include <limits>
+#include <string>
+#include <vector>
+
+#if !defined(__ANDROID__) && !defined(_WIN32)
+#include <wordexp.h>
+#endif
+
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Weverything"
+#endif
+
+#include "../../json.hpp"
+#include "../common/clipp.h"
+
+using json = nlohmann::json;
+
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
+
+#ifdef _WIN32
+#include "../../tiny_gltf.h"
+#else
+#include "tiny_gltf.h"
+#endif
+
+#include "mesh-util.hh"
+
+#ifdef __clang__
+#pragma clang diagnostic ignored "-Wunused-function"
+#endif
+
+namespace {
+
+static std::string PrintMode(int mode) {
+  if (mode == TINYGLTF_MODE_POINTS) {
+    return "POINTS";
+  } else if (mode == TINYGLTF_MODE_LINE) {
+    return "LINE";
+  } else if (mode == TINYGLTF_MODE_LINE_LOOP) {
+    return "LINE_LOOP";
+  } else if (mode == TINYGLTF_MODE_TRIANGLES) {
+    return "TRIANGLES";
+  } else if (mode == TINYGLTF_MODE_TRIANGLE_FAN) {
+    return "TRIANGLE_FAN";
+  } else if (mode == TINYGLTF_MODE_TRIANGLE_STRIP) {
+    return "TRIANGLE_STRIP";
+  }
+  return "**UNKNOWN**";
+}
+
+static std::string PrintTarget(int target) {
+  if (target == 34962) {
+    return "GL_ARRAY_BUFFER";
+  } else if (target == 34963) {
+    return "GL_ELEMENT_ARRAY_BUFFER";
+  } else {
+    return "**UNKNOWN**";
+  }
+}
+
+static std::string PrintType(int ty) {
+  if (ty == TINYGLTF_TYPE_SCALAR) {
+    return "SCALAR";
+  } else if (ty == TINYGLTF_TYPE_VECTOR) {
+    return "VECTOR";
+  } else if (ty == TINYGLTF_TYPE_VEC2) {
+    return "VEC2";
+  } else if (ty == TINYGLTF_TYPE_VEC3) {
+    return "VEC3";
+  } else if (ty == TINYGLTF_TYPE_VEC4) {
+    return "VEC4";
+  } else if (ty == TINYGLTF_TYPE_MATRIX) {
+    return "MATRIX";
+  } else if (ty == TINYGLTF_TYPE_MAT2) {
+    return "MAT2";
+  } else if (ty == TINYGLTF_TYPE_MAT3) {
+    return "MAT3";
+  } else if (ty == TINYGLTF_TYPE_MAT4) {
+    return "MAT4";
+  }
+  return "**UNKNOWN**";
+}
+
+static std::string PrintComponentType(int ty) {
+  if (ty == TINYGLTF_COMPONENT_TYPE_BYTE) {
+    return "BYTE";
+  } else if (ty == TINYGLTF_COMPONENT_TYPE_UNSIGNED_BYTE) {
+    return "UNSIGNED_BYTE";
+  } else if (ty == TINYGLTF_COMPONENT_TYPE_SHORT) {
+    return "SHORT";
+  } else if (ty == TINYGLTF_COMPONENT_TYPE_UNSIGNED_SHORT) {
+    return "UNSIGNED_SHORT";
+  } else if (ty == TINYGLTF_COMPONENT_TYPE_INT) {
+    return "INT";
+  } else if (ty == TINYGLTF_COMPONENT_TYPE_UNSIGNED_INT) {
+    return "UNSIGNED_INT";
+  } else if (ty == TINYGLTF_COMPONENT_TYPE_FLOAT) {
+    return "FLOAT";
+  } else if (ty == TINYGLTF_COMPONENT_TYPE_DOUBLE) {
+    return "DOUBLE";
+  }
+
+  return "**UNKNOWN**";
+}
+
+#if 0
+// TODO(syoyo): Support sparse accessor(sparse vertex attribute).
+// TODO(syoyo): Support more data type
+struct VertexAttrib {
+  std::string name;
+
+  // Value are converted to float type.
+  std::vector<float> data;
+
+  // Corresponding info in binary data
+  int data_type;       // e.g. TINYGLTF_TYPE_VEC2
+  int component_type;  // storage type. e.g.
+                       // TINYGLTF_COMPONENT_TYPE_UNSIGNED_INT
+  uint64_t buffer_offset{0};
+  size_t buffer_length{0};
+};
+
+struct MeshPrim {
+  std::string name;
+  int32_t id{-1};
+
+  int mode{TINYGLTF_MODE_TRIANGLES};
+
+  VertexAttrib position;                  // vec3
+  VertexAttrib normal;                    // vec3
+  VertexAttrib tangent;                   // vec4
+  VertexAttrib color;                     // vec3 or vec4
+  std::map<int, VertexAttrib> texcoords;  // <slot, attrib>  vec2
+  std::map<int, VertexAttrib> weights;    // <slot, attrib>
+  std::map<int, VertexAttrib>
+      joints;  // <slot, attrib> store data as float type
+
+  int indices_type{-1}; // storage type(componentType) of `indices`.
+  std::vector<uint32_t> indices; // vertex indices
+};
+#endif
+
+static std::string GetFilePathExtension(const std::string &FileName) {
+  if (FileName.find_last_of(".") != std::string::npos)
+    return FileName.substr(FileName.find_last_of(".") + 1);
+  return "";
+}
+
+static size_t ComponentTypeByteSize(int type) {
+  switch (type) {
+    case TINYGLTF_COMPONENT_TYPE_UNSIGNED_BYTE:
+    case TINYGLTF_COMPONENT_TYPE_BYTE:
+      return sizeof(char);
+    case TINYGLTF_COMPONENT_TYPE_UNSIGNED_SHORT:
+    case TINYGLTF_COMPONENT_TYPE_SHORT:
+      return sizeof(short);
+    case TINYGLTF_COMPONENT_TYPE_UNSIGNED_INT:
+    case TINYGLTF_COMPONENT_TYPE_INT:
+      return sizeof(int);
+    case TINYGLTF_COMPONENT_TYPE_FLOAT:
+      return sizeof(float);
+    case TINYGLTF_COMPONENT_TYPE_DOUBLE:
+      return sizeof(double);
+    default:
+      return 0;
+  }
+}
+
+std::vector<uint8_t> LoadBin(const std::string &filename) {
+  std::vector<uint8_t> data;
+
+  std::ifstream is(filename, std::ios::binary | std::ios::in | std::ios::ate);
+
+  if (is.is_open()) {
+    size_t size = size_t(is.tellg());
+    is.seekg(0, std::ios::beg);
+    if (size < 4) {
+      std::cerr << "File size is zero or too short: " << size << "\n";
+      return data;
+    }
+
+    data.resize(size);
+    is.read(reinterpret_cast<char *>(data.data()), std::streamsize(size));
+  }
+
+  return data;
+}
+
+// TODO(syoyo): Use C++17 like filesystem library
+
+bool FileExists(const std::string &abs_filename) {
+  bool ret;
+#ifdef _WIN32
+  // TODO(syoyo): Support utf8 filepath
+  FILE *fp = nullptr;
+  errno_t err = fopen_s(&fp, abs_filename.c_str(), "rb");
+  if (err != 0) {
+    return false;
+  }
+#else
+  FILE *fp = fopen(abs_filename.c_str(), "rb");
+#endif
+  if (fp) {
+    ret = true;
+    fclose(fp);
+  } else {
+    ret = false;
+  }
+
+  return ret;
+}
+
+static std::string JoinPath(const std::string &path0,
+                            const std::string &path1) {
+  if (path0.empty()) {
+    return path1;
+  } else {
+    // check '/'
+    char lastChar = *path0.rbegin();
+    if (lastChar != '/') {
+      return path0 + std::string("/") + path1;
+    } else {
+      return path0 + path1;
+    }
+  }
+}
+
+std::string ExpandFilePath(const std::string &filepath) {
+#ifdef _WIN32
+  DWORD len = ExpandEnvironmentStringsA(filepath.c_str(), NULL, 0);
+  char *str = new char[len];
+  ExpandEnvironmentStringsA(filepath.c_str(), str, len);
+
+  std::string s(str);
+
+  delete[] str;
+
+  return s;
+#else
+
+#if defined(TARGET_OS_IPHONE) || defined(TARGET_IPHONE_SIMULATOR) || \
+    defined(__ANDROID__) || defined(__EMSCRIPTEN__)
+  // no expansion
+  std::string s = filepath;
+#else
+  std::string s;
+  wordexp_t p;
+
+  if (filepath.empty()) {
+    return "";
+  }
+
+  // Quote the string to keep any spaces in filepath intact.
+  std::string quoted_path = "\"" + filepath + "\"";
+  // char** w;
+  int ret = wordexp(quoted_path.c_str(), &p, 0);
+  if (ret) {
+    // err
+    s = filepath;
+    return s;
+  }
+
+  // Use first element only.
+  if (p.we_wordv) {
+    s = std::string(p.we_wordv[0]);
+    wordfree(&p);
+  } else {
+    s = filepath;
+  }
+
+#endif
+
+  return s;
+#endif
+}
+
+static std::string FindFile(const std::vector<std::string> &paths,
+                            const std::string &filepath) {
+  for (size_t i = 0; i < paths.size(); i++) {
+    std::string absPath = ExpandFilePath(JoinPath(paths[i], filepath));
+    if (FileExists(absPath)) {
+      return absPath;
+    }
+  }
+
+  return std::string();
+}
+
+static std::string GetBaseDir(const std::string &filepath) {
+  if (filepath.find_last_of("/\\") != std::string::npos)
+    return filepath.substr(0, filepath.find_last_of("/\\"));
+  return "";
+}
+
+static int GetSlotId(const std::string &name) {
+  if (name.rfind("TEXCOORD_", 0) == 0) {
+    int id = 0;
+    sscanf(name.c_str(), "TEXCOORD_%d", &id);
+    return id;
+  } else if (name.rfind("WEIGHTS_", 0) == 0) {
+    int id = 0;
+    sscanf(name.c_str(), "WEIGHTS_%d", &id);
+    return id;
+  } else if (name.rfind("JOINTS_", 0) == 0) {
+    int id = 0;
+    sscanf(name.c_str(), "JOINTS_%d", &id);
+    return id;
+  }
+
+  return -1;
+}
+
+static bool IsAttributeSupported(const std::string &name) {
+  constexpr int max_slots = 8;
+
+  if (name.compare("POSITION") == 0) {
+    return true;
+  }
+
+  if (name.compare("NORMAL") == 0) {
+    return true;
+  }
+
+  if (name.compare("TANGENT") == 0) {
+    return true;
+  }
+
+  for (int i = 0; i < max_slots; i++) {
+    std::string n = "TEXCOORD_" + std::to_string(i);
+    if (n.compare(name) == 0) {
+      return true;
+    }
+  }
+
+  for (int i = 0; i < max_slots; i++) {
+    std::string n = "WEIGHTS_" + std::to_string(i);
+    if (n.compare(name) == 0) {
+      return true;
+    }
+  }
+
+  for (int i = 0; i < max_slots; i++) {
+    std::string n = "JOINTS_" + std::to_string(i);
+    if (n.compare(name) == 0) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+static float Unpack(const unsigned char *ptr, int type) {
+  if (type == TINYGLTF_COMPONENT_TYPE_UNSIGNED_BYTE) {
+    unsigned char data = *ptr;
+    return float(data);
+  } else if (type == TINYGLTF_COMPONENT_TYPE_BYTE) {
+    char data = static_cast<char>(*ptr);
+    return float(data);
+  } else if (type == TINYGLTF_COMPONENT_TYPE_UNSIGNED_SHORT) {
+    uint16_t data = *reinterpret_cast<const uint16_t *>(ptr);
+    return float(data);
+  } else if (type == TINYGLTF_COMPONENT_TYPE_SHORT) {
+    int16_t data = *reinterpret_cast<const int16_t *>(ptr);
+    return float(data);
+  } else if (type == TINYGLTF_COMPONENT_TYPE_FLOAT) {
+    float data = *reinterpret_cast<const float *>(ptr);
+    return data;
+  } else {
+    std::cerr << "???: Unsupported type: " << PrintComponentType(type) << "\n";
+    return 0.0f;
+  }
+}
+
+static uint32_t UnpackIndex(const unsigned char *ptr, int type) {
+  if (type == TINYGLTF_COMPONENT_TYPE_UNSIGNED_BYTE) {
+    unsigned char data = *ptr;
+    return uint32_t(data);
+  } else if (type == TINYGLTF_COMPONENT_TYPE_BYTE) {
+    char data = static_cast<char>(*ptr);
+    return uint32_t(data);
+  } else if (type == TINYGLTF_COMPONENT_TYPE_UNSIGNED_SHORT) {
+    uint16_t data = *reinterpret_cast<const uint16_t *>(ptr);
+    return uint32_t(data);
+  } else if (type == TINYGLTF_COMPONENT_TYPE_SHORT) {
+    int16_t data = *reinterpret_cast<const int16_t *>(ptr);
+    return uint32_t(data);
+  } else if (type == TINYGLTF_COMPONENT_TYPE_INT) {
+    // TODO(syoyo): Check overflow(2G+ index)
+    int32_t data = *reinterpret_cast<const int32_t *>(ptr);
+    return uint32_t(data);
+  } else if (type == TINYGLTF_COMPONENT_TYPE_UNSIGNED_INT) {
+    uint32_t data = *reinterpret_cast<const uint32_t *>(ptr);
+    return uint32_t(data);
+  } else if (type == TINYGLTF_COMPONENT_TYPE_SHORT) {
+    uint32_t data = *reinterpret_cast<const uint32_t *>(ptr);
+    return data;
+  } else {
+    std::cerr << "???: Unsupported type: " << PrintComponentType(type) << "\n";
+    return static_cast<uint32_t>(-1);
+  }
+}
+
+static bool DumpMesh(const tinygltf::Model &model, const tinygltf::Mesh &mesh,
+                     bool verbose, example::MeshPrim *out) {
+  out->prims.clear();
+
+  for (size_t i = 0; i < mesh.primitives.size(); i++) {
+    const tinygltf::Primitive &primitive = mesh.primitives[i];
+
+    if (primitive.indices < 0) {
+      std::cerr << "Primitive indices must be provided\n";
+      return false;
+    }
+
+    example::PrimSet out_prim;
+
+    // indices.
+    {
+      const tinygltf::Accessor &indexAccessor =
+          model.accessors[size_t(primitive.indices)];
+
+      size_t num_elements = indexAccessor.count;
+      std::cout << "index.elements = " << num_elements << "\n";
+
+      size_t byte_stride = ComponentTypeByteSize(indexAccessor.componentType);
+
+      const tinygltf::BufferView &indexBufferView =
+          model.bufferViews[size_t(indexAccessor.bufferView)];
+
+      // should be 34963(ELEMENT_ARRAY_BUFFER)
+      std::cout << "index.target = " << PrintTarget(indexBufferView.target)
+                << "\n";
+      if (indexBufferView.target != TINYGLTF_TARGET_ELEMENT_ARRAY_BUFFER) {
+        std::cerr << "indexBufferView.target must be ELEMENT_ARRAY_BUFFER\n";
+        return false;
+      }
+
+      const tinygltf::Buffer &indexBuffer =
+          model.buffers[size_t(indexBufferView.buffer)];
+
+      std::vector<uint32_t> indices;
+
+      for (size_t k = 0; k < num_elements; k++) {
+        // TODO(syoyo): out-of-bounds check.
+        const unsigned char *ptr = indexBuffer.data.data() +
+                                   indexBufferView.byteOffset +
+                                   (k * byte_stride) + indexAccessor.byteOffset;
+
+        uint32_t idx = UnpackIndex(ptr, indexAccessor.componentType);
+
+        if (verbose) {
+          std::cout << "vertex_index[" << k << "] = " << idx << "\n";
+        }
+
+        indices.push_back(idx);
+      }
+
+      out_prim.indices = indices;
+      out_prim.indices_type = indexAccessor.componentType;
+    }
+
+    // attributes
+    {
+      std::map<std::string, int>::const_iterator it(
+          primitive.attributes.begin());
+      std::map<std::string, int>::const_iterator itEnd(
+          primitive.attributes.end());
+
+      for (; it != itEnd; it++) {
+        // it->first would be "POSITION", "NORMAL", "TEXCOORD_0", ...
+        if (!IsAttributeSupported(it->first)) {
+          std::cout << "Unsupported attribute: " << it->first << "\n";
+          continue;
+        }
+
+        if (size_t(it->second) >= model.accessors.size()) {
+          std::cerr << "Invalid accessor id: " << it->second << "\n";
+          return false;
+        }
+
+        const tinygltf::Accessor &accessor =
+            model.accessors[size_t(it->second)];
+
+        size_t elem_size = 1;
+        if (accessor.type == TINYGLTF_TYPE_SCALAR) {
+          elem_size = 1;
+        } else if (accessor.type == TINYGLTF_TYPE_VEC2) {
+          elem_size = 2;
+        } else if (accessor.type == TINYGLTF_TYPE_VEC3) {
+          elem_size = 3;
+        } else if (accessor.type == TINYGLTF_TYPE_VEC4) {
+          elem_size = 4;
+        } else {
+          std::cerr << "Invalid or unsupported accessor type: "
+                    << PrintType(accessor.type) << "\n";
+          return false;
+        }
+
+        std::cout << PrintComponentType(accessor.componentType) << "\n";
+
+        size_t byte_stride = ComponentTypeByteSize(accessor.componentType);
+
+        std::cout << "attribute: " << it->first << "\n";
+        // if (gGLProgramState.attribs[it->first] >= 0) {
+        // Compute byteStride from Accessor + BufferView combination.
+        int byteStride =
+            accessor.ByteStride(model.bufferViews[size_t(accessor.bufferView)]);
+        assert(byteStride != -1);
+
+        std::cout << "byteOffset: " << accessor.byteOffset << "\n";
+
+        const tinygltf::BufferView &bufferView =
+            model.bufferViews[size_t(accessor.bufferView)];
+        const tinygltf::Buffer &buffer =
+            model.buffers[size_t(bufferView.buffer)];
+
+        size_t num_elems = accessor.count * elem_size;
+
+        example::VertexAttrib attrib;
+        for (size_t k = 0; k < num_elems; k++) {
+          // TODO(syoyo): out-of-bounds check.
+          const unsigned char *ptr = buffer.data.data() +
+                                     bufferView.byteOffset + (k * byte_stride) +
+                                     accessor.byteOffset;
+          float value = Unpack(ptr, accessor.componentType);
+          if (verbose) {
+            std::cout << "[" << k << "] value = " << value << "\n";
+          }
+          attrib.data.push_back(value);
+        }
+        attrib.component_type = accessor.componentType;
+        attrib.data_type = accessor.type;
+        attrib.name = it->first;
+
+        if (attrib.name.compare("POSITION") == 0) {
+          out_prim.position = attrib;
+        } else if (attrib.name.compare("NORMAL") == 0) {
+          out_prim.normal = attrib;
+        } else if (attrib.name.compare("TANGENT") == 0) {
+          out_prim.tangent = attrib;
+        } else if (attrib.name.rfind("TEXCOORD_", 0) == 0) {
+          int id = GetSlotId(attrib.name);
+          std::cout << "texcoord[" << id << "]\n";
+          out_prim.texcoords[id] = attrib;
+        } else if (attrib.name.rfind("JOINTS_", 0) == 0) {
+          int id = GetSlotId(attrib.name);
+          std::cout << "joints[" << id << "]\n";
+          out_prim.joints[id] = attrib;
+        } else if (attrib.name.rfind("WEIGHTS_", 0) == 0) {
+          int id = GetSlotId(attrib.name);
+          std::cout << "weights[" << id << "]\n";
+          out_prim.weights[id] = attrib;
+        } else {
+          std::cerr << "???: attrib.name = " << attrib.name << "\n";
+          return false;
+        }
+      }
+    }
+
+    const tinygltf::Accessor &indexAccessor =
+        model.accessors[size_t(primitive.indices)];
+    (void)indexAccessor;
+    PrintMode(primitive.mode);
+    if (primitive.mode != TINYGLTF_MODE_TRIANGLES) {
+      std::cerr << "Supported Primitive mode is TRIANGLES only at the moment\n";
+      return false;
+    }
+
+    out_prim.mode = primitive.mode;
+
+    out->prims.push_back(out_prim);
+  }
+
+  out->name = mesh.name;
+
+  return true;
+}
+
+static bool ExtractMesh(const std::string &asset_path, tinygltf::Model &model,
+                        bool verbose, std::vector<example::MeshPrim> *outs) {
+  // Get .bin data
+  {
+    if (model.buffers.size() != 1) {
+      std::cerr << "Single element of `buffers` is supported at the moment.\n";
+      return false;
+    }
+
+    const tinygltf::Buffer &buffer = model.buffers[0];
+    if (buffer.uri.empty()) {
+      std::cerr << "buffer.uri must be a filepath.\n";
+      return false;
+    }
+
+    if (buffer.data.size() < 4) {
+      std::cerr << "Invalid buffer.byteLength.\n";
+      return false;
+    }
+
+    std::vector<std::string> search_paths;
+    search_paths.push_back(asset_path);
+
+    std::string abs_filepath = FindFile(search_paths, buffer.uri);
+    std::vector<uint8_t> bin = LoadBin(abs_filepath);
+    if (bin.size() != buffer.data.size()) {
+      std::cerr << "Byte size mismatch. Failed to load file: " << buffer.uri
+                << "\n";
+      std::cerr << "  Searched absolute file path: " << abs_filepath << "\n";
+      std::cerr << "  .bin size = " << bin.size()
+                << ", size in 'buffer.uri' = " << buffer.data.size() << "\n";
+      return false;
+    }
+  }
+
+  for (const auto &mesh : model.meshes) {
+    std::cout << "mesh.name: " << mesh.name << "\n";
+
+    example::MeshPrim output;
+    bool ret = DumpMesh(model, mesh, verbose, &output);
+    if (!ret) {
+      return false;
+    }
+
+    outs->push_back(output);
+  }
+
+  return true;
+}
+
+}  // namespace
+
+int main(int argc, char **argv) {
+  std::string op;
+  std::string input_filename;
+  std::string output_filename = "output.gltf";
+  int uvset = 0;
+  bool verbose = false;
+  bool export_skinweight = true;
+  bool no_flip_texcoord_y = false;
+
+  auto cli =
+      (clipp::required("-i", "--input") &
+           clipp::value("input filename", input_filename),
+       clipp::option("-o", "--outout") &
+           clipp::value("Output filename(obj2fltf)", output_filename),
+       clipp::option("-v", "--verbose").set(verbose).doc("Verbose output"),
+       clipp::option("--export_skinweight") &
+           clipp::value("Export skin weights(gltf2obj). default true.",
+                        export_skinweight),
+       clipp::option("--uvset").set(uvset).doc("UV set(TEXCOORD_N) to use"),
+       clipp::option("--op") &
+           clipp::value("operation mode(`gltf2obj`, `obj2gltf`", op),
+       clipp::option("--no-flip-texcoord-y")
+           .set(no_flip_texcoord_y)
+           .doc("Do not flip texcoord Y"));
+
+  if (!clipp::parse(argc, argv, cli)) {
+    std::cout << clipp::make_man_page(cli, argv[0]);
+    return EXIT_FAILURE;
+  }
+
+  if (op == "gltf2obj") {
+    tinygltf::Model model;
+    tinygltf::TinyGLTF loader;
+    std::string err;
+    std::string warn;
+
+    std::string ext = GetFilePathExtension(input_filename);
+
+    {
+      bool ret = false;
+      if (ext.compare("glb") == 0) {
+        // assume binary glTF.
+        ret = loader.LoadBinaryFromFile(&model, &err, &warn,
+                                        input_filename.c_str());
+      } else {
+        // assume ascii glTF.
+        ret = loader.LoadASCIIFromFile(&model, &err, &warn,
+                                       input_filename.c_str());
+      }
+
+      if (!warn.empty()) {
+        printf("Warn: %s\n", warn.c_str());
+      }
+
+      if (!err.empty()) {
+        printf("ERR: %s\n", err.c_str());
+      }
+      if (!ret) {
+        printf("Failed to load .glTF : %s\n", argv[1]);
+        exit(-1);
+      }
+    }
+
+#if 0
+    json j;
+    {
+      std::ifstream i(input_filename);
+      i >> j;
+    }
+    std::cout << "j = " << j << "\n";
+
+    json j_patch = R"([
+      { "op": "add", "path": "/buffers/-", "value": {
+              "name": "plane/data",
+              "byteLength": 480,
+              "uri": "plane1.bin"
+          } }
+    ])"_json;
+
+    // a JSON value
+    json j_original = R"({
+      "baz": ["one", "two", "three"],
+      "foo": "bar"
+  })"_json;
+
+    //json j_patch = R"([
+    //  { "op": "remove", "path": "/buffers" }
+    //])"_json;
+
+    std::cout << "patch = " << j_patch.dump(2) << "\n";
+
+  json j_ret = j.patch(j_patch);
+  std::cout << "patched = " << j_ret.dump(2) << "\n";
+#endif
+
+    std::string basedir = GetBaseDir(input_filename);
+    std::vector<example::MeshPrim> meshes;
+    bool ret = ExtractMesh(basedir, model, verbose, &meshes);
+
+    size_t n = 0;
+    for (const auto &mesh : meshes) {
+      // Assume no duplicated name in .glTF data
+      std::string basename;
+      if (mesh.name.empty()) {
+        basename = "untitled-" + std::to_string(n);
+      } else {
+        basename = mesh.name;
+      }
+
+
+      for (size_t primid = 0; primid < mesh.prims.size(); primid++) {
+        example::ObjExportOption options;
+        options.primid = int(primid);
+        options.export_skinweights = export_skinweight;
+        options.uvset = uvset;
+        options.flip_texcoord_y = !no_flip_texcoord_y;
+
+        bool ok = example::SaveAsObjMesh(basename, mesh, options);
+        if (!ok) {
+          std::cout << "Failed to export mesh[" << mesh.name << "].primitives["
+                    << primid << "]\n";
+          // may ok;
+        }
+      }
+      n++;
+    }
+
+    return ret ? EXIT_SUCCESS : EXIT_FAILURE;
+  } else if (op == "obj2gltf") {
+    // Require facevarying layout?
+    // facevarying representation is required if a vertex can have multiple
+    // normal/uv value. drawback of facevarying is mesh data increases. false =
+    // try to keep shared vertex representation as much as possible. true =
+    // reorder vertex data and re-assign vertex indices for facevarying data
+    // layout.
+    bool facevarying = false;
+
+    example::MeshPrim mesh;
+    bool ok = example::LoadObjMesh(input_filename, facevarying, &mesh);
+    if (!ok) {
+      return EXIT_FAILURE;
+    }
+
+    if (verbose) {
+      PrintMeshPrim(mesh);
+    }
+
+    ok = example::SaveAsGLTFMesh(output_filename, mesh);
+    if (!ok) {
+      std::cerr << "Failed to save mesh as glTF\n";
+      return EXIT_FAILURE;
+    }
+    std::cout << "Write glTF: " << output_filename << "\n";
+    return EXIT_SUCCESS;
+  } else {
+    std::cerr << "Unknown operation: " << op << "\n";
+    return EXIT_FAILURE;
+  }
+}

examples/mesh-conv/mesh-util.hh

@@ -0,0 +1,95 @@
+#pragma once
+
+#include <vector>
+#include <map>
+
+namespace example {
+
+// TODO(syoyo): Support sparse accessor(sparse vertex attribute).
+// TODO(syoyo): Support more data type
+struct VertexAttrib {
+  std::string name;
+
+  // Value are converted to float type.
+  std::vector<float> data;
+
+  // Corresponding info in binary data
+  int data_type;       // e.g. TINYGLTF_TYPE_VEC2
+  int component_type;  // storage type. e.g.
+                       // TINYGLTF_COMPONENT_TYPE_UNSIGNED_INT
+  uint64_t buffer_offset{0};
+  size_t buffer_length{0};
+
+  // Optional.
+  std::vector<double> minValues;
+  std::vector<double> maxValues;
+
+  size_t numElements() const;
+
+};
+
+struct PrimSet {
+
+  int mode; // e.g. TRIANGLES
+
+  VertexAttrib position;                  // vec3
+  VertexAttrib normal;                    // vec3
+  VertexAttrib tangent;                   // vec4
+  VertexAttrib color;                     // vec3 or vec4
+  std::map<int, VertexAttrib> texcoords;  // <slot, attrib>  vec2
+  std::map<int, VertexAttrib> weights;    // <slot, attrib>  vec4
+  std::map<int, VertexAttrib>
+      joints;  // <slot, attrib> store data as float type
+
+
+  // min/max of index value. -1 = undef
+  int indices_min{-1};
+  int indices_max{-1};
+  int indices_type{-1}; // storage type(componentType) of `indices`.
+  std::vector<uint32_t> indices; // vertex indices
+
+};
+
+struct MeshPrim {
+  std::string name;
+  int32_t id{-1};
+
+  std::vector<PrimSet> prims;
+
+};
+
+struct ObjExportOption
+{
+  bool export_skinweights{true};
+  int primid{0}; /// Primitive id to export(default 0).
+  int uvset{0}; /// Tex coord ID to export(default 0).
+  bool flip_texcoord_y{true}; /// Flip texture coordinate V?(default true).
+};
+
+///
+/// Save MeshPrim as wavefront .obj
+///
+/// @param[in] basename Base filename. ".obj" will be appended.
+/// @param[in] mesh MeshPrim.
+/// @param[in] option Export options
+///
+bool SaveAsObjMesh(const std::string &basename, const MeshPrim &mesh, const ObjExportOption &option);
+
+//
+/// Save MeshPrim as glTF mesh
+///
+bool SaveAsGLTFMesh(const std::string &filename, const MeshPrim &mesh);
+
+///
+/// Loads .obj and convert to MeshPrim
+///
+/// @param[in] facevarying Construct mesh with facevarying vertex layout(default false)
+///
+bool LoadObjMesh(const std::string &filename, bool facevarying, MeshPrim *mesh);
+
+///
+/// Print MeshPrim datra
+///
+void PrintMeshPrim(const MeshPrim &mesh);
+
+} // namespace example

examples/mesh-conv/meson.build

@@ -0,0 +1,7 @@
+project('mesh-conv', 'cpp', default_options : ['cpp_std=c++11'])
+
+thread_dep = dependency('threads')
+
+incdir = include_directories(['../../', '../common'])
+
+executable('mesh-conv', ['mesh-conv.cc', 'mesh-util.cc', 'tinygltf_impl.cc'], include_directories : incdir, dependencies : thread_dep)

examples/mesh-conv/sandbox/README.md

@@ -0,0 +1,27 @@
+# concat_mesh.py
+
+Append(merge) mesh of glTF A to glTF B.
+
+`meshes`, `accessors`, `bufferViews`, `materials` of glTF A is appended to glTF B(index to accessor, bufferViews, etc will be recomputed).
+
+`skin`, `nodes`, etc are not appended(to be merged).
+
+## Usage
+
+concatenate sourceN.gltf to target.gltf and save it to merged.gltf
+
+```
+$ python concat_mesh.py source0.gltf <source1.gltf source2.gltf ...> target.gltf merged.gltf
+```
+
+## TODO
+
+* [x] Support multiple glTFs to merge(concat)
+* [ ] Support merging skin
+* [ ] Support merging different node hierarchies
+* [x] Support `images`, `textures`, `materials`, `samplers`
+* [ ] Support other glTF info
+
+# replace_attrib.py
+
+Replace the accessor id of specified attribute.

examples/mesh-conv/sandbox/concat_mesh.py

@@ -0,0 +1,272 @@
+# concat mesh to glTF
+# support multiple source glTF to me concatenated to target.gltf
+
+# TODO: skins, nodes, scenes
+
+import json
+import sys, os
+
+g_prefix = "added/"
+
+def adjustMaterialTextureIndex(mat, texture_index_offset):
+    # Args: mat(dict)
+    # texture_index_offset(int) Index offset
+
+    if "normalTexture" in mat:
+        if "index" in mat["normalTexture"]:
+            mat["normalTexture"]["index"] += texture_index_offset
+
+    if "occlusionTexture" in mat:
+        if "index" in mat["occlusionTexture"]:
+            mat["occlusionTexture"]["index"] += texture_index_offset
+
+    if "emissiveTexture" in mat:
+        if "index" in mat["emissiveTexture"]:
+            mat["emissiveTexture"]["index"] += texture_index_offset
+
+    if "pbrMetallicRoughness" in mat:
+        if "baseColorTexture" in mat["pbrMetallicRoughness"]:
+            if "index" in mat["pbrMetallicRoughness"]["baseColorTexture"]:
+                mat["pbrMetallicRoughness"]["baseColorTexture"]["index"] += texture_index_offset
+
+        if "metallicRoughnessTexture" in mat["pbrMetallicRoughness"]:
+            if "index" in mat["pbrMetallicRoughness"]["metallicRoughnessTexture"]:
+                mat["pbrMetallicRoughness"]["metallicRoughnessTexture"]["index"] += texture_index_offset
+
+    return mat
+
+
+def concat(source, target, offsets, prefix, extraInfo):
+    # Args:
+    # source: dict(modified), target: dict(modified),
+    # offsets: dict(modified). contains offset table.
+    # prefix: str
+    # extraInfo: dict(inout)
+
+    num_source_meshes = len(source["meshes"])
+    num_source_buffers = len(source["buffers"])
+    num_source_bufferViews = len(source["bufferViews"])
+    num_source_accessors = len(source["accessors"])
+    num_source_materials = len(source["materials"]) if "materials" in source else 0
+    num_source_samplers = len(source["samplers"]) if "samplers" in source else 0
+    num_source_images = len(source["images"]) if "images" in source else 0
+    num_source_textures = len(source["textures"]) if "textures" in source else 0
+    print("src =====")
+    print("num_src_meshes: ", num_source_meshes)
+    print("num_src_buffers: ", num_source_buffers)
+    print("num_src_bufferViews: ", num_source_bufferViews)
+    print("num_src_accessors: ", num_source_accessors)
+    print("num_src_materials: ", num_source_materials)
+    print("num_src_textures: ", num_source_textures)
+    print("num_src_images: ", num_source_images)
+    print("num_src_samplers: ", num_source_samplers)
+
+
+    #
+    # Modify name and adjust index offset
+    #
+    for i in range(len(source["buffers"])):
+        if "name" in source["buffers"][i]:
+            source["buffers"][i]["name"] = prefix + source["buffers"][i]["name"]
+
+    for i in range(len(source["bufferViews"])):
+        if "name" in source["bufferViews"][i]:
+            source["bufferViews"][i]["name"] = prefix + source["bufferViews"][i]["name"]
+
+        source["bufferViews"][i]["buffer"] += offsets["buffers"]
+
+    for i in range(len(source["accessors"])):
+        if "name" in source["accessors"][i]:
+            source["accessors"][i]["name"] = prefix + source["accessors"][i]["name"]
+
+        source["accessors"][i]["bufferView"] += offsets["bufferViews"]
+
+    for i in range(len(source["meshes"])):
+        mesh = source["meshes"][i]
+
+        if "name" in mesh:
+            source["meshes"][i]["name"] = prefix + source["meshes"][i]["name"]
+
+        for primid in range(len(mesh["primitives"])):
+            for attrib in mesh["primitives"][primid]["attributes"]:
+                #print(source["meshes"][i]["primitives"][primid]["attributes"][attrib])
+                source["meshes"][i]["primitives"][primid]["attributes"][attrib] += offsets["accessors"]
+
+
+            source["meshes"][i]["primitives"][primid]["indices"] += offsets["accessors"]
+            if "material" in source["meshes"][i]["primitives"][primid]:
+                source["meshes"][i]["primitives"][primid]["material"] += offsets["materials"]
+
+
+    if "materials" in source:
+        for i in range(len(source["materials"])):
+            if "name" in source["materials"][i]:
+                source["materials"][i]["name"] = prefix + source["materials"][i]["name"]
+            source["materials"][i] = adjustMaterialTextureIndex(source["materials"][i], offsets["textures"])
+
+    if "images" in source:
+        for i in range(len(source["images"])):
+            if "name" in source["images"][i]:
+                source["images"][i]["name"] = prefix + source["images"][i]["name"]
+
+    if "samplers" in source:
+        for i in range(len(source["samplers"])):
+            if "name" in source["samplers"][i]:
+                source["samplers"][i]["name"] = prefix + source["samplers"][i]["name"]
+
+    if "textures" in source:
+        for i in range(len(source["textures"])):
+            if "name" in source["textures"][i]:
+                source["textures"][i]["name"] = prefix + source["textures"][i]["name"]
+            source["textures"][i]["sampler"] += offsets["samplers"]
+            source["textures"][i]["source"] += offsets["images"]
+
+    #
+    # Append mesh info
+    #
+    target["buffers"] += source["buffers"]
+    target["bufferViews"] += source["bufferViews"]
+    target["meshes"] += source["meshes"]
+    target["accessors"] += source["accessors"]
+    if "materials" in source:
+        if "materials" in target:
+            target["materials"] += source["materials"]
+        else:
+            target["materials"] = source["materials"]
+    if "images" in source:
+        if "images" in target:
+            target["images"] += source["images"]
+        else:
+            target["images"] = source["images"]
+    if "textures" in source:
+        if "textures" in target:
+            target["textures"] += source["textures"]
+        else:
+            target["textures"] = source["textures"]
+    if "samplers" in source:
+        if "samplers" in target:
+            target["samplers"] += source["samplers"]
+        else:
+            target["samplers"] = source["samplers"]
+
+    # assume `prefix` is unique
+    extraInfo["num_{}_meshes".format(prefix)] = num_source_meshes
+    extraInfo["num_{}_buffers".format(prefix)] = num_source_buffers
+    extraInfo["num_{}_bufferViews".format(prefix)] = num_source_bufferViews
+    extraInfo["num_{}_accessors".format(prefix)] = num_source_accessors
+    extraInfo["num_{}_materials".format(prefix)] = num_source_materials
+    extraInfo["num_{}_images".format(prefix)] = num_source_images
+    extraInfo["num_{}_samplers".format(prefix)] = num_source_samplers
+    extraInfo["num_{}_textures".format(prefix)] = num_source_textures
+
+    # update offsets
+    offsets["meshes"] += num_source_meshes
+    offsets["buffers"] += num_source_buffers
+    offsets["bufferViews"] += num_source_bufferViews
+    offsets["accessors"] += num_source_accessors
+    offsets["materials"] += num_source_materials
+    offsets["textures"] += num_source_textures
+    offsets["images"] += num_source_images
+    offsets["samplers"] += num_source_samplers
+
+
+def main():
+    if len(sys.argv) < 4:
+        print("Needs source0.gltf <source1.gltf, ...> target.gltf output.gltf")
+        sys.exit(-1)
+
+    num_args = len(sys.argv)
+    print("num_args = ", num_args)
+
+    source_filenames = []
+
+    num_srcs = num_args - 3
+
+    for i in range(num_srcs):
+        source_filenames.append(sys.argv[1+i])
+        print("source[{}] = {}".format(i, sys.argv[1+i]))
+
+    target_filename = sys.argv[num_args - 2]
+    output_filename = sys.argv[num_args - 1]
+    print("target = ", target_filename)
+    print("output = ", output_filename)
+
+    sources = []
+    for i in range(num_srcs):
+        sources.append(json.loads(open(source_filenames[i]).read()))
+    target = json.loads(open(target_filename).read())
+
+    num_target_meshes = len(target["meshes"])
+    num_target_buffers = len(target["buffers"])
+    num_target_bufferViews = len(target["bufferViews"])
+    num_target_accessors = len(target["accessors"])
+    num_target_materials = 0
+    if "materials" in target:
+        num_target_materials = len(target["materials"])
+
+    num_target_images = 0
+    if "images" in target:
+        num_target_images = len(target["images"])
+
+    num_target_samplers = 0
+    if "samplers" in target:
+        num_target_samplers = len(target["samplers"])
+
+    num_target_textures = 0
+    if "textures" in target:
+        num_target_textures = len(target["textures"])
+
+    print("num_target_meshes: ", num_target_meshes)
+    print("num_target_buffers: ", num_target_buffers)
+    print("num_target_bufferViews: ", num_target_bufferViews)
+    print("num_target_accessors: ", num_target_accessors)
+    print("num_target_materials: ", num_target_materials)
+    print("num_target_textures: ", num_target_textures)
+    print("num_target_images: ", num_target_images)
+    print("num_target_samplers: ", num_target_samplers)
+
+    #
+    # add some info to asset.extras
+    #
+    extraInfo = {}
+    extraInfo["num_target_meshes"] = num_target_meshes
+    extraInfo["num_target_buffers"] = num_target_buffers
+    extraInfo["num_target_bufferViews"] = num_target_bufferViews
+    extraInfo["num_target_accessors"] = num_target_accessors
+    extraInfo["num_target_materials"] = num_target_materials
+    extraInfo["num_target_textures"] = num_target_textures
+    extraInfo["num_target_images"] = num_target_images
+    extraInfo["num_target_samplers"] = num_target_samplers
+
+    offsets = {}
+    offsets["meshes"] = num_target_meshes
+    offsets["buffers"] = num_target_buffers
+    offsets["bufferViews"] = num_target_bufferViews
+    offsets["accessors"] = num_target_accessors
+    offsets["materials"] = num_target_materials
+    offsets["textures"] = num_target_textures
+    offsets["samplers"] = num_target_samplers
+    offsets["images"] = num_target_images
+
+    for i in range(num_srcs):
+        source = sources[i]
+
+        prefix = g_prefix + "{}/".format(source_filenames[i])
+        concat(source, target, offsets, prefix, extraInfo)
+
+    extraInfo["num_total_meshes"] = offsets["meshes"]
+    extraInfo["num_total_buffers"] = offsets["buffers"]
+    extraInfo["num_total_bufferViews"] = offsets["bufferViews"]
+    extraInfo["num_total_accessors"] = offsets["accessors"]
+    extraInfo["num_total_materials"] = offsets["materials"]
+    extraInfo["num_total_textures"] = offsets["textures"]
+    extraInfo["num_total_images"] = offsets["images"]
+    extraInfo["num_total_samplers"] = offsets["samplers"]
+
+    target["asset"]["extras"] = extraInfo
+
+    with open(output_filename, "w") as f:
+        f.write(json.dumps(target, indent=2))
+
+    print("Merged glTF was exported to : ", output_filename)
+main()

examples/mesh-conv/sandbox/replace_attrib.py

@@ -0,0 +1,107 @@
+# Replace accessor id of attributes for speicified mesh
+# Usually called after concat_mesh.py
+# Example usecase is to replace UV coordinate of a mesh.
+
+import json
+import sys, os
+
+replace_indices = False
+attrib_names = ["TEXCOORD_0"]
+
+def check_accessor(src, target):
+    if src["componentType"] != target["componentType"]:
+        print("componentType mismatch!")
+        return False
+
+    if src["count"] != target["count"]:
+        print("`count` mismatch!")
+        return False
+
+    if src["type"] != target["type"]:
+        print("`type` mismatch!")
+        return False
+
+    return True
+
+def main():
+    if len(sys.argv) < 5:
+        print("Needs input.gltf output.gltf source_mesh_name target_mesh_name <source_primid> <target_primid>")
+        sys.exit(-1)
+
+    input_filename = sys.argv[1]
+    output_filename = sys.argv[2]
+    source_mesh_name = sys.argv[3]
+    target_mesh_name = sys.argv[4]
+
+    source_primid = 0
+    target_primid = 0
+
+    if len(sys.argv) > 5:
+        source_primid = int(sys.argv[5])
+
+    if len(sys.argv) > 6:
+        target_primid = int(sys.argv[6])
+
+    gltf = json.loads(open(input_filename).read())
+
+    source_mesh_id = -1
+    target_mesh_id = -1
+
+    for i in range(len(gltf["meshes"])):
+        mesh = gltf["meshes"][i]
+        print("mesh[{}].name = {}".format(i, mesh["name"]))
+
+        if target_mesh_name == mesh["name"]:
+            target_mesh_id = i
+
+        if source_mesh_name == mesh["name"]:
+            source_mesh_id = i
+
+    if source_mesh_id == -1:
+        print("source mesh with name [{}] not found.".format(source_mesh_name))
+        sys.exit(-1)
+
+    if target_mesh_id == -1:
+        print("target mesh with name [{}] not found.".format(target_mesh_name))
+        sys.exit(-1)
+
+    print("target: name = {}, id = {}".format(target_mesh_name, target_mesh_id))
+    print("source: name = {}, id = {}".format(source_mesh_name, source_mesh_id))
+
+    source_mesh = gltf["meshes"][source_mesh_id]
+    target_mesh = gltf["meshes"][target_mesh_id]
+
+
+    source_prim = source_mesh["primitives"][source_primid]
+    target_prim = target_mesh["primitives"][target_primid]
+
+    if replace_indices:
+        target_indices_id = target_prim["indices"]
+        src_indices_id = source_prim["indices"]
+
+        print("Replace vertex indices from {} to {}".format(target_indices_id, src_indices_id))
+        gltf["meshes"][target_mesh_id]["primitives"][target_primid]["indices"] = gltf["meshes"][source_mesh_id]["primitives"][source_primid]["indices"]
+
+
+    for attrib in target_prim["attributes"]:
+        print("attrib ", attrib)
+        if attrib in attrib_names:
+            if attrib in source_prim["attributes"]:
+                target_accessor_id = target_prim["attributes"][attrib]
+                src_accessor_id = source_prim["attributes"][attrib]
+
+                if check_accessor(gltf["accessors"][src_accessor_id], gltf["accessors"][target_accessor_id]):
+                    gltf["meshes"][target_mesh_id]["primitives"][target_primid]["attributes"][attrib] = src_accessor_id
+                    print("Replaced accessor id for attrib {} from {} to {}".format(attrib, target_accessor_id, src_accessor_id))
+                else:
+                    print("Accessor type/format is not identical. Skip replace")
+                    print("  attrib {}".format(attrib))
+
+            else:
+                print("attribute[{}] not found in source primitive: mesh[{}].primitives[{}]".format(attrib, source_mesh_name, source_primid))
+
+    with open(output_filename, "w") as f:
+        f.write(json.dumps(gltf, indent=2))
+
+    print("Merged glTF was exported to : ", output_filename)
+main()

examples/mesh-conv/tinygltf_impl.cc

@@ -0,0 +1,9 @@
+#define TINYGLTF_IMPLEMENTATION
+#define STB_IMAGE_IMPLEMENTATION
+#define STB_IMAGE_WRITE_IMPLEMENTATION
+
+#ifdef _WIN32
+#include "../../tiny_gltf.h"
+#else
+#include "tiny_gltf.h"
+#endif

examples/raytrace/obj-loader.cc

@@ -150,6 +150,7 @@ bool LoadObj(const std::string &filename, float scale,
   tinyobj::attrib_t attrib;
   std::vector<tinyobj::shape_t> shapes;
   std::vector<tinyobj::material_t> materials;
+  std::string warn;
   std::string err;
 
   std::string basedir = GetBaseDir(filename) + "/";
@@ -158,12 +159,16 @@ bool LoadObj(const std::string &filename, float scale,
   // auto t_start = std::chrono::system_clock::now();
 
   bool ret =
-      tinyobj::LoadObj(&attrib, &shapes, &materials, &err, filename.c_str(),
+      tinyobj::LoadObj(&attrib, &shapes, &materials, &warn, &err, filename.c_str(),
                        basepath, /* triangulate */ true);
 
   // auto t_end = std::chrono::system_clock::now();
   // std::chrono::duration<double, std::milli> ms = t_end - t_start;
 
+  if (!warn.empty()) {
+    std::cout << warn << std::endl;
+  }
+
   if (!err.empty()) {
     std::cerr << err << std::endl;
   }