material light groups

This is a feature of Goo Engine which is very lacking in Blender.

You can set active light groups on any light. And you can per material, set active light groups. (as well as within a material using nodes)

And this all works in real-time, without needing to hook up render passes in the compositor.

And i think it's a much more straightforward workflow (it should work for both eevee and cycles ideally)