I worked really hard to make ColorSource work, but sadly we need color to be instanceable and making it optional would add too much complexity. Maybe at some point in the future we can add it back. On the plus side, albedo color now modulates the albedo texture
Must follow VertexBufferDescriptorName_AttributeName format
I_VertexBufferDescriptorName_AttributeName indicates that an attribute is instanced
Currently all attributes must be defined in shaders or offsets will be incorrect.
