message: fix getInstanceIndex()
  it would be initialized after user material code was called.
diff: */
  void main() {
  +#if defined(TARGET_METAL_ENVIRONMENT) || defined(TARGET_VULKAN_ENVIRONMENT)
  + instance_index = gl_InstanceIndex;
  +#else
  + instance_index = gl_InstanceID;
  +#endif
  +
  // Initialize the inputs to sensible default values, see material_inputs.vs
  #if defined(USE_OPTIMIZED_DEPTH_VERTEX_SHADER)
  @@ -179,12 +185,6 @@ void main() {
  vertex_worldPosition.w = depth;
  #endif
  -#if defined(TARGET_METAL_ENVIRONMENT) || defined(TARGET_VULKAN_ENVIRONMENT)
  - instance_index = gl_InstanceIndex;
  -#else
  - instance_index = gl_InstanceID;
  -#endif
  -
  // this must happen before we compensate for vulkan below
  vertex_position = gl_Position;
  