Add HandmadeMath.

Add simple morphing code.

examples/common/matrix.cc

@@ -99,6 +99,28 @@ void Matrix::LookAt(float m[4][4], float eye[3], float lookat[3],
 #endif
 }
 
+void Matrix::Identity(float m[4][4]) {
+  m[0][0] = 1.0f;
+  m[0][1] = 0.0f;
+  m[0][2] = 0.0f;
+  m[0][3] = 0.0f;
+
+  m[1][0] = 0.0f;
+  m[1][1] = 1.0f;
+  m[1][2] = 0.0f;
+  m[1][3] = 0.0f;
+
+  m[2][0] = 0.0f;
+  m[2][1] = 0.0f;
+  m[2][2] = 1.0f;
+  m[2][3] = 0.0f;
+
+  m[3][0] = 0.0f;
+  m[3][1] = 0.0f;
+  m[3][2] = 0.0f;
+  m[3][3] = 1.0f;
+}
+
 void Matrix::Inverse(float m[4][4]) {
   /*
    * codes from intel web
@@ -195,7 +217,16 @@ void Matrix::Inverse(float m[4][4]) {
   }
 }
 
-void Matrix::Mult(float dst[4][4], float m0[4][4], float m1[4][4]) {
+void Matrix::Add(float dst[4][4], const float m0[4][4], const float m1[4][4]) {
+  for (int i = 0; i < 4; ++i) {
+    for (int j = 0; j < 4; ++j) {
+      dst[i][j] += m0[i][j] + m1[i][j];
+    }
+  }
+}
+
+
+void Matrix::Mult(float dst[4][4], const float m0[4][4], const float m1[4][4]) {
   for (int i = 0; i < 4; ++i) {
     for (int j = 0; j < 4; ++j) {
       dst[i][j] = 0;
@@ -206,7 +237,7 @@ void Matrix::Mult(float dst[4][4], float m0[4][4], float m1[4][4]) {
   }
 }
 
-void Matrix::MultV(float dst[3], float m[4][4], float v[3]) {
+void Matrix::MultV(float dst[3], const float m[4][4], const float v[3]) {
   // printf("v = %f, %f, %f\n", v[0], v[1], v[2]);
   dst[0] = m[0][0] * v[0] + m[1][0] * v[1] + m[2][0] * v[2] + m[3][0];
   dst[1] = m[0][1] * v[0] + m[1][1] * v[1] + m[2][1] * v[2] + m[3][1];
@@ -214,3 +245,10 @@ void Matrix::MultV(float dst[3], float m[4][4], float v[3]) {
   // printf("m = %f, %f, %f\n", m[3][0], m[3][1], m[3][2]);
   // printf("dst = %f, %f, %f\n", dst[0], dst[1], dst[2]);
 }
+
+void Matrix::MultV4(float dst[4], const float m[4][4], const float v[4]) {
+  dst[0] = m[0][0] * v[0] + m[1][0] * v[1] + m[2][0] * v[2] + m[3][0] * v[3];
+  dst[1] = m[0][1] * v[0] + m[1][1] * v[1] + m[2][1] * v[2] + m[3][1] * v[3];
+  dst[2] = m[0][2] * v[0] + m[1][2] * v[1] + m[2][2] * v[2] + m[3][2] * v[3];
+  dst[3] = m[0][3] * v[0] + m[1][3] * v[1] + m[2][3] * v[2] + m[3][3] * v[3];
+}

examples/common/matrix.h

@@ -10,8 +10,11 @@ public:
   static void LookAt(float m[4][4], float eye[3], float lookat[3],
                      float up[3]);
   static void Inverse(float m[4][4]);
-  static void Mult(float dst[4][4], float m0[4][4], float m1[4][4]);
-  static void MultV(float dst[3], float m[4][4], float v[3]);
+  static void Identity(float m[4][4]);
+  static void Add(float dst[4][4], const float m0[4][4], const float m1[4][4]);
+  static void Mult(float dst[4][4], const float m0[4][4], const float m1[4][4]);
+  static void MultV(float dst[3], const float m[4][4], const float v[3]);
+  static void MultV4(float dst[4], const float m[4][4], const float v[4]);
 };
 
 #endif  // 

examples/common/trackball.cc

@@ -52,11 +52,6 @@
 #include <math.h>
 #include "trackball.h"
 
-#ifdef _MSC_VER
-#pragma warning(disable : 4244)
-#pragma warning(disable : 4305)
-#endif
-
 /*
  * This size should really be based on the distance from the center of
  * rotation to the point on the object underneath the mouse.  That
@@ -173,11 +168,11 @@ void trackball(float q[4], float p1x, float p1y, float p2x, float p2y) {
   /*
    * Avoid problems with out-of-control values...
    */
-  if (t > 1.0f)
-    t = 1.0f;
-  if (t < -1.0f)
-    t = -1.0f;
-  phi = 2.0f * asinf(t);
+  if (t > 1.0)
+    t = 1.0;
+  if (t < -1.0)
+    t = -1.0;
+  phi = 2.0 * asin(t);
 
   axis_to_quat(a, phi, q);
 }

examples/glview/glview.cc

@@ -19,7 +19,8 @@
 #define STB_IMAGE_WRITE_IMPLEMENTATION
 #include "tiny_gltf.h"
 
-#define BUFFER_OFFSET(i) ((char *)NULL + (i))
+//#define BUFFER_OFFSET(i) ((char *)NULL + (i))
+#define BUFFER_OFFSET(i) (reinterpret_cast<void *>(i))
 
 #define CheckGLErrors(desc)                                                   \
   {                                                                           \
@@ -251,7 +252,7 @@ static void SetupMeshState(tinygltf::Model &model, GLuint progId) {
       const tinygltf::BufferView &bufferView = model.bufferViews[i];
       if (bufferView.target == 0) {
         std::cout << "WARN: bufferView.target is zero" << std::endl;
-        continue;  // Unsupported bufferView.
+        continue;  // Unsupported or not directly used bufferView.
       }
 
       const tinygltf::Buffer &buffer = model.buffers[bufferView.buffer];
@@ -528,6 +529,13 @@ static void DrawMesh(tinygltf::Model &model, const tinygltf::Mesh &mesh) {
     for (; it != itEnd; it++) {
       assert(it->second >= 0);
       const tinygltf::Accessor &accessor = model.accessors[it->second];
+      const tinygltf::BufferView &bufferView = model.bufferViews[accessor.bufferView];
+
+      if (bufferView.target == 0) {
+        // Unsupported or not directly used buffer
+        continue;
+      }
+
       glBindBuffer(GL_ARRAY_BUFFER, gBufferState[accessor.bufferView].vb);
       CheckErrors("bind buffer");
       int size = 1;
@@ -667,7 +675,10 @@ static void DrawNode(tinygltf::Model &model, const tinygltf::Node &node) {
   // std::cout << it->first << std::endl;
   // FIXME(syoyo): Refactor.
   // DrawCurves(scene, it->second);
-  DrawMesh(model, model.meshes[node.mesh]);
+
+  if ((node.mesh >= 0) && (node.mesh < int(model.meshes.size()))) {
+    DrawMesh(model, model.meshes[node.mesh]);
+  }
 
   // Draw child nodes.
   for (size_t i = 0; i < node.children.size(); i++) {
@@ -677,7 +688,7 @@ static void DrawNode(tinygltf::Model &model, const tinygltf::Node &node) {
   glPopMatrix();
 }
 
-static void DrawModel(tinygltf::Model &model) {
+static void DrawModel(tinygltf::Model &model, size_t scene_idx) {
 #if 0
   std::map<std::string, tinygltf::Mesh>::const_iterator it(scene.meshes.begin());
   std::map<std::string, tinygltf::Mesh>::const_iterator itEnd(scene.meshes.end());
@@ -688,9 +699,8 @@ static void DrawModel(tinygltf::Model &model) {
   }
 #else
 
-  // TODO(syoyo): Support non-default scenes.
-  assert(model.defaultScene >= 0);
-  const tinygltf::Scene &scene = model.scenes[model.defaultScene];
+  assert(scene_idx < model.scenes.size());
+  const tinygltf::Scene &scene = model.scenes[scene_idx];
   for (size_t i = 0; i < scene.nodes.size(); i++) {
     DrawNode(model, model.nodes[scene.nodes[i]]);
   }
@@ -760,8 +770,18 @@ int main(int argc, char **argv) {
 
   Init();
 
+  if (model.scenes.empty()) {
+    std::cerr << "glTF model does not have scenes" << std::endl;
+    return EXIT_FAILURE;
+  }
+
   // DBG
-  PrintNodes(model.scenes[model.defaultScene]);
+  size_t scene_idx = size_t(model.defaultScene);
+  if (model.defaultScene == -1) {
+    scene_idx = 0;
+  }
+
+  PrintNodes(model.scenes[scene_idx]);
 
   if (!glfwInit()) {
     std::cerr << "Failed to initialize GLFW." << std::endl;
@@ -853,7 +873,7 @@ int main(int argc, char **argv) {
 
     glScalef(scale, scale, scale);
 
-    DrawModel(model);
+    DrawModel(model, scene_idx);
 
     glMatrixMode(GL_PROJECTION);
     glPopMatrix();

examples/glview/premake5.lua

@@ -1,10 +1,20 @@
+newoption {
+   trigger = "asan",
+   description = "Enable Address Sanitizer(gcc5+ ang clang only)"
+}
+
 solution "glview"
    -- location ( "build" )
    configurations { "Debug", "Release" }
    platforms {"native", "x64", "x32"}
-   
+
    project "glview"
 
+      -- Use clang for better asan expericen
+      if _OPTIONS["asan"] then
+         toolset "clang"
+      end
+
       kind "ConsoleApp"
       language "C++"
 	  cppdialect "C++11"
@@ -13,6 +23,12 @@ solution "glview"
       includedirs { "../../" }
 
       configuration { "linux" }
+
+         if _OPTIONS["asan"] then
+            buildoptions { "-fsanitize=address,undefined" }
+            linkoptions { "-fsanitize=address,undefined" }
+         end
+
          linkoptions { "`pkg-config --libs glfw3`" }
          links { "GL", "GLU", "m", "GLEW", "X11", "Xrandr", "Xinerama", "Xi", "Xxf86vm", "Xcursor", "dl" }
 

examples/glview/trackball.cc

@@ -86,7 +86,7 @@ static void vsub(const float *src1, const float *src2, float *dst) {
 }
 
 static void vcopy(const float *v1, float *v2) {
-  register int i;
+  int i;
   for (i = 0; i < 3; i++)
     v2[i] = v1[i];
 }

examples/skinning/README.md

@@ -0,0 +1,19 @@
+# Simple glTF skinning sample with CPU skinning implementation.
+
+Example use CPU implementation of skinning for the explanation of how to process skin property in glTF format.
+
+Animation and skinning code is based on SacchaWillems' Vulkan-glTF-PBR: https://github.com/SaschaWillems/Vulkan-glTF-PBR
+
+OpenGL is still used to display renderings.
+
+## Build on Linux and macOS
+
+```
+$ premake5 gmake
+$ make
+$ ./bin/native/Debug/skinning simple-skin.gltf
+```
+
+## Note on asset
+
+`simple-skin.gltf` is grabbed from gltfTutorial https://github.com/KhronosGroup/glTF-Tutorials/blob/master/gltfTutorial/gltfTutorial_019_SimpleSkin.md

examples/skinning/morph-targets.cc

@@ -0,0 +1,22 @@
+#include <vector>
+#include <cstdlib>
+#include <cassert>
+
+void MorthTargets(std::vector<float> &weights,
+  std::vector<std::vector<float>> &targets,
+  std::vector<float> *output)
+{
+  assert(weights.size() > 0);
+  assert(targets.size() > 0);
+  assert(weights.size() == targets.size());
+
+  // Assume all position has same number of vertices;
+
+  // TODO(parallelize)
+  for (size_t v = 0; v < targets[0].size(); v++) { // for each vertex
+    (*output)[v] = 0.0f;  
+    for (size_t i = 0; i < weights.size(); i++) {
+      (*output)[v] += weights[i] * targets[i][v];
+    }
+  }
+}

examples/skinning/premake5.lua

@@ -0,0 +1,59 @@
+newoption {
+   trigger = "asan",
+   description = "Enable Address Sanitizer(gcc5+ ang clang only)"
+}
+
+solution "skinning"
+   -- location ( "build" )
+   configurations { "Debug", "Release" }
+   platforms {"native", "x64", "x32"}
+   
+   project "skinning"
+
+      -- Use clang for better asan expericen
+      if _OPTIONS["asan"] then
+         toolset "clang"
+      end
+
+      kind "ConsoleApp"
+      language "C++"
+	  cppdialect "C++11"
+      files { "main.cc", "skinning.cc", "morph-targets.cc", "../common/trackball.cc", "../common/matrix.cc" }
+      includedirs { "./" }
+      includedirs { "../../" }
+
+      configuration { "linux" }
+
+         if _OPTIONS["asan"] then
+            buildoptions { "-fsanitize=address" }
+            linkoptions { "-fsanitize=address" }
+         end
+
+         linkoptions { "`pkg-config --libs glfw3`" }
+         links { "GL", "GLU", "m", "GLEW", "X11", "Xrandr", "Xinerama", "Xi", "Xxf86vm", "Xcursor", "dl" }
+
+      configuration { "windows" }
+         -- Edit path to glew and GLFW3 fit to your environment.
+         includedirs { "../../../../local/glew-1.13.0/include/" }
+         includedirs { "../../../../local/glfw-3.2.bin.WIN32/include/" }
+         libdirs { "../../../../local/glew-1.13.0/lib/Release/Win32/" }
+         libdirs { "../../../../local/glfw-3.2.bin.WIN32/lib-vc2013/" }
+         links { "glfw3", "gdi32", "winmm", "user32", "glew32", "glu32","opengl32", "kernel32" }
+         defines { "_CRT_SECURE_NO_WARNINGS" }
+
+      configuration { "macosx" }
+         includedirs { "/usr/local/include" }
+         buildoptions { "-Wno-deprecated-declarations" }
+         libdirs { "/usr/local/lib" }
+         links { "glfw", "GLEW" }
+         linkoptions { "-framework OpenGL", "-framework Cocoa", "-framework IOKit", "-framework CoreVideo" }
+
+      configuration "Debug"
+         defines { "DEBUG" }
+		 symbols "On"
+		 warnings "Extra"
+
+      configuration "Release"
+         defines { "NDEBUG" }
+		 optimize "On"
+		 warnings "Extra"

examples/skinning/shader.frag

@@ -0,0 +1,16 @@
+uniform sampler2D diffuseTex;
+uniform int uIsCurve;
+
+varying vec3 normal;
+varying vec2 texcoord;
+
+void main(void)
+{
+    //gl_FragColor = vec4(0.5 * normalize(normal) + 0.5, 1.0);
+    //gl_FragColor = vec4(texcoord, 0.0, 1.0);
+    if (uIsCurve > 0) {
+        gl_FragColor = texture2D(diffuseTex, texcoord);
+    } else {
+        gl_FragColor = vec4(0.5 * normalize(normal) + 0.5, 1.0);
+    }
+}

examples/skinning/shader.vert

@@ -0,0 +1,16 @@
+attribute vec3    in_vertex;
+attribute vec3    in_normal;
+attribute vec2    in_texcoord;
+
+varying vec3      normal;
+varying vec2      texcoord;
+
+void main(void)
+{
+	vec4 p = gl_ModelViewProjectionMatrix * vec4(in_vertex, 1);
+	gl_Position = p;
+	vec4 nn = gl_ModelViewMatrixInverseTranspose * vec4(normalize(in_normal), 0);
+	normal = nn.xyz;
+
+	texcoord = in_texcoord;
+}

examples/skinning/simple-skin.gltf

@@ -0,0 +1,148 @@
+{
+  "scenes" : [ {
+    "nodes" : [ 0 ]
+  } ],
+  
+  "nodes" : [ {
+    "skin" : 0,
+    "mesh" : 0,
+    "children" : [ 1 ]
+  }, {
+    "children" : [ 2 ],
+    "translation" : [ 0.0, 1.0, 0.0 ]
+  }, {
+    "rotation" : [ 0.0, 0.0, 0.0, 1.0 ]
+  } ],
+  
+  "meshes" : [ {
+    "primitives" : [ {
+      "attributes" : {
+        "POSITION" : 1,
+        "JOINTS_0" : 2,
+        "WEIGHTS_0" : 3
+      },
+      "indices" : 0
+    } ]
+  } ],
+
+  "skins" : [ {
+    "inverseBindMatrices" : 4,
+    "joints" : [ 1, 2 ]
+  } ],
+  
+  "animations" : [ {
+    "channels" : [ {
+      "sampler" : 0,
+      "target" : {
+        "node" : 2,
+        "path" : "rotation"
+      }
+    } ],
+    "samplers" : [ {
+      "input" : 5,
+      "interpolation" : "LINEAR",
+      "output" : 6
+    } ]
+  } ],
+  
+  "buffers" : [ {
+    "uri" : "data:application/gltf-buffer;base64,AAABAAMAAAADAAIAAgADAAUAAgAFAAQABAAFAAcABAAHAAYABgAHAAkABgAJAAgAAAAAAAAAAAAAAAAAAACAPwAAAAAAAAAAAAAAAAAAAD8AAAAAAACAPwAAAD8AAAAAAAAAAAAAgD8AAAAAAACAPwAAgD8AAAAAAAAAAAAAwD8AAAAAAACAPwAAwD8AAAAAAAAAAAAAAEAAAAAAAACAPwAAAEAAAAAA",
+    "byteLength" : 168
+  }, {
+    "uri" : "data:application/gltf-buffer;base64,AAABAAAAAAAAAAAAAAAAAAAAAQAAAAAAAAAAAAAAAAAAAAEAAAAAAAAAAAAAAAAAAAABAAAAAAAAAAAAAAAAAAAAAQAAAAAAAAAAAAAAAAAAAAEAAAAAAAAAAAAAAAAAAAABAAAAAAAAAAAAAAAAAAAAAQAAAAAAAAAAAAAAAAAAAAEAAAAAAAAAAAAAAAAAAAABAAAAAAAAAAAAAAAAAAAAgD8AAAAAAAAAAAAAAAAAAIA/AAAAAAAAAAAAAAAAAABAPwAAgD4AAAAAAAAAAAAAQD8AAIA+AAAAAAAAAAAAAAA/AAAAPwAAAAAAAAAAAAAAPwAAAD8AAAAAAAAAAAAAgD4AAEA/AAAAAAAAAAAAAIA+AABAPwAAAAAAAAAAAAAAAAAAgD8AAAAAAAAAAAAAAAAAAIA/AAAAAAAAAAA=",
+    "byteLength" : 320
+  }, {
+    "uri" : "data:application/gltf-buffer;base64,AACAPwAAAAAAAAAAAAAAAAAAAAAAAIA/AAAAAAAAAAAAAAAAAAAAAAAAgD8AAAAAAAAAvwAAgL8AAAAAAACAPwAAgD8AAAAAAAAAAAAAAAAAAAAAAACAPwAAAAAAAAAAAAAAAAAAAAAAAIA/AAAAAAAAAL8AAIC/AAAAAAAAgD8=",
+    "byteLength" : 128
+  }, {
+    "uri" : "data:application/gltf-buffer;base64,AAAAAAAAAD8AAIA/AADAPwAAAEAAACBAAABAQAAAYEAAAIBAAACQQAAAoEAAALBAAAAAAAAAAAAAAAAAAACAPwAAAAAAAAAAkxjEPkSLbD8AAAAAAAAAAPT9ND/0/TQ/AAAAAAAAAAD0/TQ/9P00PwAAAAAAAAAAkxjEPkSLbD8AAAAAAAAAAAAAAAAAAIA/AAAAAAAAAAAAAAAAAACAPwAAAAAAAAAAkxjEvkSLbD8AAAAAAAAAAPT9NL/0/TQ/AAAAAAAAAAD0/TS/9P00PwAAAAAAAAAAkxjEvkSLbD8AAAAAAAAAAAAAAAAAAIA/",
+    "byteLength" : 240
+  } ],
+  
+  "bufferViews" : [ {
+    "buffer" : 0,
+    "byteOffset" : 0,
+    "byteLength" : 48,
+    "target" : 34963
+  }, {
+    "buffer" : 0,
+    "byteOffset" : 48,
+    "byteLength" : 120,
+    "target" : 34962
+  }, {
+    "buffer" : 1,
+    "byteOffset" : 0,
+    "byteLength" : 320,
+    "byteStride" : 16
+  }, {
+    "buffer" : 2,
+    "byteOffset" : 0,
+    "byteLength" : 128
+  }, {
+    "buffer" : 3,
+    "byteOffset" : 0,
+    "byteLength" : 240
+  } ],
+
+  "accessors" : [ {
+    "bufferView" : 0,
+    "byteOffset" : 0,
+    "componentType" : 5123,
+    "count" : 24,
+    "type" : "SCALAR",
+    "max" : [ 9 ],
+    "min" : [ 0 ]
+  }, {
+    "bufferView" : 1,
+    "byteOffset" : 0,
+    "componentType" : 5126,
+    "count" : 10,
+    "type" : "VEC3",
+    "max" : [ 1.0, 2.0, 0.0 ],
+    "min" : [ 0.0, 0.0, 0.0 ]
+  }, {
+    "bufferView" : 2,
+    "byteOffset" : 0,
+    "componentType" : 5123,
+    "count" : 10,
+    "type" : "VEC4",
+    "max" : [ 0, 1, 0, 0 ],
+    "min" : [ 0, 1, 0, 0 ]
+  }, {
+    "bufferView" : 2,
+    "byteOffset" : 160,
+    "componentType" : 5126,
+    "count" : 10,
+    "type" : "VEC4",
+    "max" : [ 1.0, 1.0, 0.0, 0.0 ],
+    "min" : [ 0.0, 0.0, 0.0, 0.0 ]
+  }, {
+    "bufferView" : 3,
+    "byteOffset" : 0,
+    "componentType" : 5126,
+    "count" : 2,
+    "type" : "MAT4",
+    "max" : [ 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, -0.5, -1.0, 0.0, 1.0 ],
+    "min" : [ 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, -0.5, -1.0, 0.0, 1.0 ]
+  }, {
+    "bufferView" : 4,
+    "byteOffset" : 0,
+    "componentType" : 5126,
+    "count" : 12,
+    "type" : "SCALAR",
+    "max" : [ 5.5 ],
+    "min" : [ 0.0 ]
+  }, {
+    "bufferView" : 4,
+    "byteOffset" : 48,
+    "componentType" : 5126,
+    "count" : 12,
+    "type" : "VEC4",
+    "max" : [ 0.0, 0.0, 0.707, 1.0 ],
+    "min" : [ 0.0, 0.0, -0.707, 0.707 ]
+  } ],
+  
+  "asset" : {
+    "version" : "2.0"
+  }
+}

examples/skinning/skinning.cc

@@ -0,0 +1,252 @@
+#include "skinning.h"
+
+#include "../common/matrix.h"
+#include "../common/trackball.h"  // for quaternion
+
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Weverything"
+#endif
+
+#define HANDMADE_MATH_IMPLEMENTATION
+#include "HandmadeMath.h"
+
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
+
+#include <cassert>
+#include <cstring>
+
+namespace example {
+
+struct Node {
+
+  float translation[3] = {0.0f, 0.0f, 0.0f};
+  float scale[4] = {1.0f, 1.0f, 1.0f};
+  float rotation[4] = {0.0f, 0.0f, 0.0f, 1.0f};
+
+
+  void update() {
+  }
+};
+
+static inline vec4 mix(vec4 x, vec4 y, float a) {
+  vec4 v;
+  v.f[0] = (1.0f - a) * x.f[0] + a * y.f[0];
+  v.f[1] = (1.0f - a) * x.f[1] + a * y.f[1];
+  v.f[2] = (1.0f - a) * x.f[2] + a * y.f[2];
+  v.f[3] = (1.0f - a) * x.f[3] + a * y.f[3];
+
+  return v;
+}
+
+void BuildTransofrmMatrix(const float translate[3],
+                          const float rotation[4],  // as quaternion in glTF
+                          const float scale[3], mat4 *transform_matrix) {
+  float T[4][4];
+  T[0][0] = 1.0f;
+  T[0][1] = 0.0f;
+  T[0][2] = 0.0f;
+  T[0][3] = 0.0f;
+
+  T[1][0] = 0.0f;
+  T[1][1] = 1.0f;
+  T[1][2] = 0.0f;
+  T[1][3] = 0.0f;
+
+  T[2][0] = 0.0f;
+  T[2][1] = 0.0f;
+  T[2][2] = 1.0f;
+  T[2][3] = 0.0f;
+
+  T[3][0] = translate[0];
+  T[3][1] = translate[1];
+  T[3][2] = translate[2];
+  T[3][3] = 1.0f;
+
+  float R[4][4];
+
+  build_rotmatrix(R, rotation);
+
+  float S[4][4];
+  S[0][0] = scale[0];
+  S[0][1] = 0.0f;
+  S[0][2] = 0.0f;
+  S[0][3] = 0.0f;
+
+  S[1][0] = 0.0f;
+  S[1][1] = scale[1];
+  S[1][2] = 0.0f;
+  S[1][3] = 0.0f;
+
+  S[2][0] = 0.0f;
+  S[2][1] = 0.0f;
+  S[2][2] = scale[2];
+  S[2][3] = 0.0f;
+
+  S[3][0] = 0.0f;
+  S[3][1] = 0.0f;
+  S[3][2] = 0.0f;
+  S[3][3] = 1.0f;
+
+  float RS[4][4];
+
+  Matrix::Mult(RS, R, S);
+
+  Matrix::Mult(transform_matrix->m, T, RS);
+}
+
+void ComputeJointMatrices(
+    const std::vector<mat4> global_transform_of_nodes,
+    const std::vector<mat4> global_transform_of_joint_nodes,
+    const std::vector<mat4> inverse_bind_matrix_for_joints,
+    std::vector<mat4> *output_joint_matrices) {
+  const size_t n = global_transform_of_nodes.size();
+
+  output_joint_matrices->resize(n);
+
+  for (size_t i = 0; i < n; i++) {
+    mat4 g_inv = global_transform_of_nodes[i];
+    Matrix::Inverse(g_inv.m);
+
+    mat4 g_joint = global_transform_of_joint_nodes[i];
+    mat4 inverse_bind_matrix = inverse_bind_matrix_for_joints[i];
+
+    float a[4][4];  // temp matrix
+    Matrix::Mult(a, g_joint.m, inverse_bind_matrix.m);
+
+    Matrix::Mult((*output_joint_matrices)[i].m, g_inv.m, a);
+  }
+}
+
+void Skining(const std::vector<float> vertices,
+             const std::vector<float> weights, const std::vector<size_t> joints,
+             const size_t num_skinning_weights,
+             const std::vector<mat4> joint_matrices, const float t,
+             std::vector<float> *skinned_vertices) {
+  assert((vertices.size() % 4) == 0);
+  const size_t num_vertices = vertices.size() / 4;
+
+  skinned_vertices->resize(vertices.size());
+
+  // TODO(syoyo): Ensure sum(weights) = 1.0;
+
+  for (size_t v = 0; v < num_vertices; v++) {
+    const float *w_p = weights.data() + v * num_skinning_weights;
+    const size_t *j_p = joints.data() + v * num_skinning_weights;
+
+    mat4 skin_mat;
+    memset(skin_mat.m, 0, sizeof(float) * 4 * 4);
+
+    for (size_t k = 0; k < num_skinning_weights; k++) {
+      const float w = w_p[k];
+      const mat4 &m = joint_matrices[j_p[k]];
+
+      for (size_t j = 0; j < 4; j++) {
+        for (size_t i = 0; i < 4; i++) {
+          skin_mat.m[j][i] += w * m.m[j][i];
+        }
+      }
+    }
+
+    // M = lerp I and skin_mat
+    mat4 M;
+
+    mat4 I;
+    Matrix::Identity(I.m);
+
+    for (size_t j = 0; j < 4; j++) {
+      for (size_t i = 0; i < 4; i++) {
+        M.m[j][i] = I.m[j][i] * t + (1.0f - t) * skin_mat.m[j][i];
+      }
+    }
+
+    float vtx[4];
+    vtx[0] = vertices[4 * v + 0];
+    vtx[1] = vertices[4 * v + 1];
+    vtx[2] = vertices[4 * v + 2];
+    vtx[3] = vertices[4 * v + 3];
+
+    float ret[4];
+    Matrix::MultV4(ret, M.m, vtx);
+  }
+}
+
+void UpdateAnimation(std::vector<Animation> &animations, uint32_t index,
+                     float time, std::vector<Node*> &nodes) {
+  if (index > uint32_t(animations.size() - 1)) {
+    return;
+  }
+
+  const Animation &animation = animations[index];
+
+  bool updated = false;
+  for (auto &channel : animation.channels) {
+    const AnimationSampler &sampler = animation.samplers[channel.samplerIndex];
+    if (sampler.inputs.size() > sampler.outputsVec4.size()) {
+      continue;
+    }
+
+    // TODO(LTE): support interpolation other than LINEAR
+    for (size_t i = 0; i < sampler.inputs.size() - 1; i++) {
+      if ((time >= sampler.inputs[i]) && (time <= sampler.inputs[i + 1])) {
+        float u = std::max(0.0f, time - sampler.inputs[i]) /
+                  (sampler.inputs[i + 1] - sampler.inputs[i]);
+        if (u <= 1.0f) {
+          switch (channel.path) {
+            case AnimationChannel::PathType::TRANSLATION: {
+              example::vec4 trans =
+                  mix(sampler.outputsVec4[i], sampler.outputsVec4[i + 1], u);
+              channel.node->translation[0] = trans.f[0];
+              channel.node->translation[1] = trans.f[1];
+              channel.node->translation[2] = trans.f[2];
+              // drop w
+              break;
+            }
+            case AnimationChannel::PathType::SCALE: {
+              example::vec4 scale =
+                  mix(sampler.outputsVec4[i], sampler.outputsVec4[i + 1], u);
+              channel.node->scale[0] = scale.f[0];
+              channel.node->scale[1] = scale.f[1];
+              channel.node->scale[2] = scale.f[2];
+              break;
+            }
+            case AnimationChannel::PathType::ROTATION: {
+
+              hmm_quaternion q1 = HMM_Quaternion(
+               sampler.outputsVec4[i].f[0],
+               sampler.outputsVec4[i].f[1],
+               sampler.outputsVec4[i].f[2],
+               sampler.outputsVec4[i].f[3]);
+
+              hmm_quaternion q2 = HMM_Quaternion(
+               sampler.outputsVec4[i + 1].f[0],
+               sampler.outputsVec4[i + 1].f[1],
+               sampler.outputsVec4[i + 1].f[2],
+               sampler.outputsVec4[i + 1].f[3]);
+
+              hmm_quaternion q = HMM_NormalizeQuaternion(HMM_Slerp(q1, u, q2));
+
+              channel.node->rotation[0] = q.Elements[0];
+              channel.node->rotation[1] = q.Elements[1];
+              channel.node->rotation[2] = q.Elements[2];
+              channel.node->rotation[3] = q.Elements[3];
+
+              break;
+            }
+          }
+          updated = true;
+        }
+      }
+    }
+  }
+
+  if (updated) {
+    for (auto &node : nodes) {
+      node->update();
+    }
+  }
+}
+
+}  // namespace example

examples/skinning/skinning.h

@@ -0,0 +1,95 @@
+#ifndef EXAMPLE_SKINNING_H_
+#define EXAMPLE_SKINNING_H_
+
+#include <vector>
+#include <cstddef>
+#include <cstdint>
+#include <string>
+#include <limits>
+
+namespace example {
+
+struct mat4 {
+  float m[4][4];
+};
+
+struct vec4 {
+  float f[4];
+};
+
+// glTF node
+struct Node;
+
+
+struct AnimationChannel {
+  enum PathType { TRANSLATION, ROTATION, SCALE };
+  PathType path;
+  Node *node;
+  uint32_t samplerIndex;
+};
+
+struct AnimationSampler {
+  enum InterpolationType { LINEAR, STEP, CUBICSPLINE };
+  InterpolationType interpolation;
+  std::vector<float> inputs;
+  std::vector<example::vec4> outputsVec4;
+};
+
+struct Animation {
+  std::string name;
+  std::vector<AnimationSampler> samplers;
+  std::vector<AnimationChannel> channels;
+  float start = std::numeric_limits<float>::max();
+  float end = std::numeric_limits<float>::min();
+};
+
+///
+/// Utility function to build transformation matrix from translate/rotation/scale
+///
+/// https://github.com/KhronosGroup/glTF-Tutorials/blob/master/gltfTutorial/gltfTutorial_004_ScenesNodes.md
+///
+/// M = T * R * S
+///
+void BuildTransofrmMatrix(
+  const float translate[3],
+  const float rotation[4], // as quaternion in glTF
+  const float scale[3],
+  mat4 *transform_matrix);
+  
+
+///
+/// Compute joint matrices.
+///
+/// jointMatrix(j) =
+///   globalTransformOfNodeThatTheMeshIsAttachedTo^-1 *
+///   globalTransformOfJointNode(j) *
+///   inverseBindMatrixForJoint(j);
+///
+
+void ComputeJointMatrices(
+  const std::vector<mat4> global_transform_of_nodes,
+  const std::vector<mat4> global_transform_of_joint_nodes,
+  const std::vector<mat4> inverse_bind_matrix_for_joints,
+  std::vector<mat4> output_joint_matrices);
+
+
+///
+///
+/// @param[in] vertices Input vertices(# of elements = num_vertices * 4(xyzw))
+/// @param[in] weights Linearized weights(# of elements = num_vertices * num_skinning_weights)
+/// @param[in] weights Linearized weights(# of elements = num_vertices * num_skinning_weights)
+/// @param[in] num_weights Linearized weights(# of elements = num_vertices * 
+/// @param[in] joint_matrices Array of joint matricies.
+/// @param[in] t Interpolator. [0.0, 1.0]
+/// @param[in] skinned_vertices Resulting skinned vertices
+///
+void Skining(const std::vector<float> vertices,
+             const std::vector<float> weights, const std::vector<size_t> joints,
+             const size_t num_skinning_weights,
+             const std::vector<mat4> joint_matrices,
+             const float t,
+             std::vector<float> *skinned_vertices);
+
+}  // namespace example
+
+#endif  // EXAMPLE_SKINNING_H_

loader_example.cc

@@ -30,7 +30,8 @@ static std::string PrintMode(int mode) {
   } else if (mode == TINYGLTF_MODE_TRIANGLE_STRIP) {
     return "TRIANGLE_STRIP";
   }
-  return "**UNKNOWN**";
+
+  return "**UNKNOWN**(" + std::to_string(mode) + ")";
 }
 
 static std::string PrintTarget(int target) {
@@ -39,7 +40,7 @@ static std::string PrintTarget(int target) {
   } else if (target == 34963) {
     return "GL_ELEMENT_ARRAY_BUFFER";
   } else {
-    return "**UNKNOWN**";
+    return "**UNKNOWN**(" + std::to_string(target) + ")";
   }
 }
 
@@ -63,7 +64,7 @@ static std::string PrintType(int ty) {
   } else if (ty == TINYGLTF_TYPE_MAT4) {
     return "MAT4";
   }
-  return "**UNKNOWN**";
+  return "**UNKNOWN**(" + std::to_string(ty) + ")";
 }
 
 static std::string PrintComponentType(int ty) {
@@ -85,7 +86,7 @@ static std::string PrintComponentType(int ty) {
     return "DOUBLE";
   }
 
-  return "**UNKNOWN**";
+  return "**UNKNOWN**(" + std::to_string(ty) + ")";
 }
 
 #if 0
@@ -147,7 +148,7 @@ static std::string PrintWrapMode(int mode) {
     return "MIRRORED_REPEAT";
   }
 
-  return "**UNKNOWN**";
+  return "**UNKNOWN**(" + std::to_string(mode) + ")";
 }
 
 static std::string PrintFilterMode(int mode) {
@@ -164,7 +165,7 @@ static std::string PrintFilterMode(int mode) {
   } else if (mode == TINYGLTF_TEXTURE_FILTER_LINEAR_MIPMAP_LINEAR) {
     return "LINEAR_MIPMAP_LINEAR";
   }
-  return "**UNKNOWN**";
+  return "**UNKNOWN**(" + std::to_string(mode) + ")";
 }
 
 static std::string PrintIntArray(const std::vector<int> &arr) {