Shape indexing was broken when TINYOBJ_FLAG_TRIANGULATE flag was present.

examples/viewer/viewer.c

@@ -41,12 +41,13 @@ static DrawObject gDrawObject;
 static int width = 768;
 static int height = 768;
 
-static bool use_colors = false;
+static enum { COLOR_FROM_NORMALS, COLOR_FROM_MATERIAL, COLOR_FROM_SHAPE, __COLOR_FROM_LAST } color_source = COLOR_FROM_NORMALS;
 static bool draw_wireframe = true;
 
 static const size_t OBJ_SIZE = sizeof(float) * 3 // pos
 	+ sizeof(float) * 3 // normal
 	+ sizeof(float) * 3 // color (based on normal)
+	+ sizeof(float) * 3 // color (based on shape)
 	+ sizeof(float) * 3; // color from material file.
 
 static float prevMouseX, prevMouseY;
@@ -364,6 +365,28 @@ static int LoadObjAndConvert(float bmin[3], float bmax[3],
       face_offset += (size_t)attrib.face_num_verts[i];
     }
 
+    face_offset = 0;
+    for (i = 0; i < num_shapes; i++)
+    {
+      /* Get unique color based on shape index */
+      float r = (cosf(6.283185f * ((float)i / num_shapes + 0.0f / 3.0f)) + 1.0f) / 2.0f;
+      float g = (cosf(6.283185f * ((float)i / num_shapes + 2.0f / 3.0f)) + 1.0f) / 2.0f;
+      float b = (cosf(6.283185f * ((float)i / num_shapes + 1.0f / 3.0f)) + 1.0f) / 2.0f;
+      size_t s;
+      for (s = 0; s < (size_t)shapes[i].length; s++)
+      {
+        size_t f = (size_t)shapes[i].face_offset + s;
+        size_t k;
+        for(k = 0; k < (size_t)attrib.face_num_verts[f]; k++)
+        {
+          vb[(face_offset + k) * stride + 12] = r;
+          vb[(face_offset + k) * stride + 13] = g;
+          vb[(face_offset + k) * stride + 14] = b;
+        }
+        face_offset += k;
+      }
+    }
+
     o.vb = 0;
     o.numTriangles = 0;
     if (num_triangles > 0) {
@@ -431,7 +454,8 @@ static void keyboardFunc(GLFWwindow* window, int key, int scancode, int action,
 
     if (key == GLFW_KEY_Q || key == GLFW_KEY_ESCAPE)
       glfwSetWindowShouldClose(window, GL_TRUE);
-    if (key == GLFW_KEY_C) use_colors = !use_colors;
+    if (key == GLFW_KEY_C && ++color_source >= __COLOR_FROM_LAST)
+      color_source = COLOR_FROM_NORMALS;
     if (key == GLFW_KEY_W) draw_wireframe = !draw_wireframe;
   }
 }
@@ -504,10 +528,10 @@ static void Draw(const DrawObject* draw_object) {
     glEnableClientState(GL_COLOR_ARRAY);
     glVertexPointer(3, GL_FLOAT, OBJ_SIZE, (const void*)0);
     glNormalPointer(GL_FLOAT, OBJ_SIZE, (const void*)(sizeof(float) * 3));
-    if (use_colors) {
-      glColorPointer(3, GL_FLOAT, OBJ_SIZE, (const void*)(sizeof(float) * 9));
-    } else {
-      glColorPointer(3, GL_FLOAT, OBJ_SIZE, (const void*)(sizeof(float) * 6));
+    switch (color_source) {
+      case COLOR_FROM_NORMALS: glColorPointer(3, GL_FLOAT, OBJ_SIZE, (const void*)(sizeof(float) * 6)); break;
+      case COLOR_FROM_MATERIAL: glColorPointer(3, GL_FLOAT, OBJ_SIZE, (const void*)(sizeof(float) * 9)); break;
+      case COLOR_FROM_SHAPE: glColorPointer(3, GL_FLOAT, OBJ_SIZE, (const void*)(sizeof(float) * 12)); break;
     }
     glDrawArrays(GL_TRIANGLES, 0, 3 * draw_object->numTriangles);
     CheckErrors("drawarrays");

test/fixtures/shapes-triangulation.obj

@@ -0,0 +1,47 @@
+# OBJ File: 'house'
+# for tinyobjloader-c project
+
+o house
+v -1.0000  0.0000 -1.0000
+v  1.0000  0.0000 -1.0000
+v  1.0000  0.0000  1.0000
+v -1.0000  0.0000  1.0000
+v -1.0000  1.0000 -1.0000
+v  1.0000  1.0000 -1.0000
+v  1.0000  1.0000  1.0000
+v -1.0000  1.0000  1.0000
+v  0.0000  2.0000 -1.0000
+v  0.0000  2.0000  1.0000
+vn  0.0000 -1.0000  0.0000
+vn  0.0000  0.0000 -1.0000
+vn -1.0000  0.0000  0.0000
+vn  0.0000  0.0000  1.0000
+vn  1.0000  0.0000  0.0000
+vn  0.0000  1.0000  0.0000
+vn -0.7071  0.7071  0.0000
+vn  0.7071  0.7071  0.0000
+
+s off
+g base
+f 1//1 2//1 3//1 4//1
+g facade
+f 1//2 2//2 6//2 5//2
+f 5//2 6//2 9//2
+g left_wall
+f 4//3 1//3 5//3 8//3
+g back_wall
+f 3//4 4//4 8//4 7//4
+g back_roof_wall
+f 7//4 8//4 10//4
+g right_wall
+f 2//5 3//5 7//5 6//5
+g floor
+f 5//6 6//6 7//6
+f 5//6 7//6 8//6
+g left_roof
+f 8//7 5//7 9//7 10//7
+g right_roof
+f 6//8 7//8 10//8 9//8
+
+# TODO: Remove extra content at the end of the file when
+# https://github.com/syoyo/tinyobjloader-c/issues/12 is fixed

test/tinyobj_regression_tests.c

@@ -83,3 +83,44 @@ void test_tinyobj_negative_exponent(void)
         TEST_CHECK(float_equals(attrib.vertices[2], 2.0e-0f));
     }
 }
+
+void test_tinyobj_shapes_triangulation(void)
+{
+    {
+        const char * filename = "fixtures/shapes-triangulation.obj";
+
+        tinyobj_shape_t * shape = NULL;
+        tinyobj_material_t * material = NULL;
+        tinyobj_attrib_t attrib;
+
+        unsigned long num_shapes;
+        unsigned long num_materials;
+
+        tinyobj_attrib_init(&attrib);
+
+        int result = tinyobj_parse_obj(&attrib, &shape, &num_shapes, &material, &num_materials, filename, loadFile, NULL, TINYOBJ_FLAG_TRIANGULATE);
+
+        TEST_CHECK(result == TINYOBJ_SUCCESS);
+
+        TEST_CHECK(num_shapes == 9);
+
+        TEST_CHECK(shape[0].face_offset == 0);
+        TEST_CHECK(shape[0].length == 2);
+        TEST_CHECK(shape[1].face_offset == 2);
+        TEST_CHECK(shape[1].length == 3);
+        TEST_CHECK(shape[2].face_offset == 5);
+        TEST_CHECK(shape[2].length == 2);
+        TEST_CHECK(shape[3].face_offset == 7);
+        TEST_CHECK(shape[3].length == 2);
+        TEST_CHECK(shape[4].face_offset == 9);
+        TEST_CHECK(shape[4].length == 1);
+        TEST_CHECK(shape[5].face_offset == 10);
+        TEST_CHECK(shape[5].length == 2);
+        TEST_CHECK(shape[6].face_offset == 12);
+        TEST_CHECK(shape[6].length == 2);
+        TEST_CHECK(shape[7].face_offset == 14);
+        TEST_CHECK(shape[7].length == 2);
+        TEST_CHECK(shape[8].face_offset == 16);
+        TEST_CHECK(shape[8].length == 2);
+    }
+}

test/tinyobj_regression_tests.h

@@ -3,5 +3,6 @@
 
 void test_tinyobj_crlf_string(void);
 void test_tinyobj_negative_exponent(void);
+void test_tinyobj_shapes_triangulation(void);
 
 #endif

test/tinyobj_tests.c

@@ -34,6 +34,7 @@ TEST_LIST = {
 
     { "crlf_string",  test_tinyobj_crlf_string },
     { "negative_exponent_issue26",  test_tinyobj_negative_exponent },
+    { "shapes_triangulation",  test_tinyobj_shapes_triangulation },
 
     { 0 } // required by acutest
 };

tinyobj_loader_c.h

@@ -1647,7 +1647,11 @@ int tinyobj_parse_obj(tinyobj_attrib_t *attrib, tinyobj_shape_t **shapes,
         }
       }
       if (commands[i].type == COMMAND_F) {
-        face_count++;
+        if (flags & TINYOBJ_FLAG_TRIANGULATE) {
+          face_count += commands[i].num_f_num_verts;
+        } else {
+          face_count++;
+        }
       }
     }