Method Init

teapots/image-decoder/src/main/cpp/ImageDecoderRender.cpp:65–137

* Init: Initialize the GL with needed data. We add on the things * needed for textures * - load image data into generated glBuffers * - configure samplerObj in fragment shader * @param assetMgr android assetManager from java side */

 * @param assetMgr android assetManager from java side
 */
void ImageDecoderRender::Init(AAssetManager* assetMgr) {
  // initialize the basic things from TeapotRenderer, no change
  TeapotRenderer::Init();

  GLint type = GetTextureType();
  if (type == GL_INVALID_VALUE) {
    // Plain teapot no texture
    return;
  }

  // load texture coordinator for 2D texture. Cubemap texture uses world space
  // normal to sample cubemap.
  if (type == GL_TEXTURE_2D) {
    // do Texture related initializations...
    glGenBuffers(1, &texVbo_);
    assert(texVbo_ != GL_INVALID_VALUE);

    /*
     * Loading Texture coord directly from data declared in model file
     *   teapot.inl
     * which is 3 floats/vertex.
     */
    glBindBuffer(GL_ARRAY_BUFFER, texVbo_);

#if (TILED_TEXTURE)
    glBufferData(GL_ARRAY_BUFFER,
                 kCoordElementCount * sizeof(float) * num_vertices_,
                 teapotTexCoords, GL_STATIC_DRAW);
#else
    std::vector<float> coords;
    for (int32_t idx = 0; idx < num_vertices_; idx++) {
      coords.push_back(teapotTexCoords[3 * idx] / 2);
      coords.push_back(teapotTexCoords[3 * idx + 1] / 2);
    }
    glBufferData(GL_ARRAY_BUFFER,
                 kCoordElementCount * sizeof(float) * num_vertices_,
                 coords.data(), GL_STATIC_DRAW);
#endif
    glVertexAttribPointer(ATTRIB_UV, 2, GL_FLOAT, GL_FALSE,
                          kCoordElementCount * sizeof(float), nullptr);
    glEnableVertexAttribArray(ATTRIB_UV);

    glBindBuffer(GL_ARRAY_BUFFER, 0);
  }

  // Need flip Y, so as top/bottom image
  std::vector<std::string> textures{
      std::string("Textures/right.png"),   // GL_TEXTURE_CUBE_MAP_POSITIVE_X
      std::string("Textures/left.png"),    // GL_TEXTURE_CUBE_MAP_NEGATIVE_X
      std::string("Textures/top.png"),     // GL_TEXTURE_CUBE_MAP_POSITIVE_Y
      std::string("Textures/bottom.png"),  // GL_TEXTURE_CUBE_MAP_NEGATIVE_Y
      std::string("Textures/front.png"),   // GL_TEXTURE_CUBE_MAP_POSITIVE_Z
      std::string("Textures/back.png")     // GL_TEXTURE_CUBE_MAP_NEGATIVE_Z
  };

  if (type == GL_TEXTURE_2D) {
    textures[0] = std::string("Textures/front.png");
  }