It is possible and useful to assign materials to lights, but currently:
- Rhino gives no indication (i.e. no material panel in light object properties, no highlighting of the assigned material in the material list, when a light is selected) that a material has been assigned.
- The ChangeQueue does not update upon assignment of material to lights, nor upon changes being made to materials assigned to lights (i.e. you must force an update some other way, by moving something, etc).
The former could be helped a bit by a plugin adding custom gui to light object properties, but since support for assignment already exists, I think it would be better for Rhino to just expose that, so the UX can be uniform across render engines.
As for why I think it should be done, I have now written plugins for two different engines, where the ability to use materials on lights would be useful and expected by users, and while the capability may have been an oddity 15 years ago, I’d be surprised to find that any render engine does not internally support it now.
(this topic did not seem to fit cleanly in any given category, so please move it as you see fit – I figured it is mostly Rhino devs who would know what I’m talking about)