Yes, I was talking about the different render layers that one can extract separately when making a render in Blender, Maya, Lightwave, Max, Renderman, etc.
I understand that Indigo computes the information all together and offers the render at once in just one image, isn't it?
It's not possible to separate color, from reflection, from shadows, etc, isn't it?
Rendering passes... it's just a different philosophy as to what Indigo was primarily designed AFAIK (not that this can't change).
First I think that the concept of masks (matte, alpha, whatever) must be generalized, but that's a minor thing compared to the changes necessited in the rendering engine itself, to dispatch the relevant data to designed layer. Just a guess here.
The reasons they can get those layers its that they are a bi-product of scanline based renderers. It will require alot of overhead to produce those for indigo.