Light emitting mesh with VRayMtl on it

[dgruwier]

I have a scene lit entirely by partially glowing metal objects, and I need a way to make them accurately illuminate the scene, while also being shaded and receiving illumination themselves.
I've tried with with VRayLightMtl and self-illumination in VRayMtl in a blend material, both of which let me have a shader on the illuminated object. But when using either of those, the rest of the scene scene doesn't seem to receive specular/reflections, and the illumination seems way too dark in general (no GI?).

The illumination on the environment looks perfect if I use a mesh light instead, but that replaces any shaders I have on the mesh.

The only way I can think of actually accomplishing what I need is a mess of render layers and material overrides. But even then, I can't get GI to bounce correctly back onto my glowing objects, and it feels wrong to have to dive into something like that for such a conceptually simple effect.

Any ideas?

[dgruwier]

Digging deeper in the documentation I found this regading the VRayLightMtl:

The direct illumination options currently only work properly if the VRayLightMtl material is the only material applied on the object. They will not work if the material is part of a complex material like a VRayBlendMtl material. This restriction will probably be removed in a future release.

Any chance that this is on the to-do for a release in the near future? This would solve all my problems and greatly simplify working with any self-illuminated object, since self-illumination would suddenly be as fast and painless as real lights.

[yolov]

I've bumped up our system records for that, but there's no guarantee when we'll get to it.
Btw, what exactly is your end goal with this setup, could you share some screenshots/renders? There might be an easier approach to cheat your way out of this.

[dgruwier]

Thanks!

Can't share pictures unfortunately, and I'm having trouble reproducing the issues I'm having with the self-illumination in other scenes.

I did manage to simplify my setup so that I have one render layer that only contains the environment lit up by the mesh lights (set to invisible), and one render layer that contains the objects themselves with a self-illuminated shader, and the environment as a matte. It's not perfect, but I can make it work with a bit of compositing.

I think some of the issues might have been due to the mesh lights not casting shadows from themselves, making the scene brighter than it should technically be. So the version using self-illumination might actually have been the most correctly ones, they just looked wrong because they were so much darker.
I'm still using the mesh light though, because that doesn't have any other problems and renders sooo much faster.