parsing gltf file

[sancelot]

Hi,
I am trying to decode triangles from gltf file.
Unfortunately, I don't manage to reach vertex data , what may be wrong ?

for (int m=0;m < mesh->primitives_count;m++)
  {
    cgltf_primitive *primitive = &mesh->primitives[m];

      if (primitive->type == cgltf_primitive_type_triangles)
      {
      index_accessor = primitive->indices;
      for (int i = 0; i < primitive->attributes_count; i++) {
                cgltf_attribute attr = primitive->attributes[i];
                switch (attr.type) {
                case cgltf_attribute_type_position:
                        { 
                        position_accessor = attr.data;
                        const float* position_data = (float *)position_accessor->buffer_view->buffer->data;

                        if (index_accessor->component_type == cgltf_component_type_r_16u)
                        {
                          for (int indice=0;indice <index_accessor->count ;indice  ++)
                          {                         
                            unsigned short t_indice = cgltf_accessor_read_index(index_accessor,indice);
                             std::cout << "vertex1 " << *(position_data+t_indice) << " / " << *(position_data+t_indice+1) << " / " <<  *(position_data+t_indice+2) << std::endl;
                          }
                        }
                        break;
                case cgltf_attribute_type_normal:
                        normal_accessor = attr.data;
                        break;
                case cgltf_attribute_type_texcoord:
                        uv_accessor = attr.data;
                        break;
                }
        }
 
        if (index_accessor == nullptr || position_accessor == nullptr || normal_accessor == nullptr)
                throw std::runtime_error("Gltf model invalid or unsupported");
 
      }  
  }
    }

[LxLasso]

I would open the glTF file in a text editor and step through the code in a debugger until I discover what is not happening as I had expected. Are there triangles in the glTF? 16-bit indexed? Has the buffer been loaded?

[zeux]

                    const float* position_data = (float *)position_accessor->buffer_view->buffer->data;

This ignores any type of offset that might apply to the accessor. I would recommend using cgltf_accessor_read_float or cgltf_accessor_unpack_floats helpers to read any attribute data.

                    if (index_accessor->component_type == cgltf_component_type_r_16u)

Note that you don't actually need this if you use cgltf_accessor_read_index since that function will handle different types transparently.

[jkuhlmann]

@sancelot Did the comments here help?

[sancelot]

I was trying To decode the blender cube at first before a bigger file ..I have not had time to continue. I will retry it very soon. I want to load the file in ordre To display it and have thé scenegraph available.

[ghost]

@jkuhlmann could the code above maybe get worked into an example? with incorporated use of cgltf_accessor_read_index as you mentioned