VrayLighMtl renders incorrectly if it's part of a Mutli/Sub-object material

[Alex_M]

I was trying out Vray GPU when I noticed that if VrayLighMtl is part of a Mutli/Sub-object material, it renders incorrectly. Please check the screenshot below.

Max 2018.4 + Vray Next Update 1

[savage309]

When it is part of Multi Sub, the sampling can not be that efficient. If you can, avoid that.
The result render here is caused by more noise, which the image sampler decides that might never clean up. Either raise up the Ray Per Pixel (to 32 or 64) or try using light cache.

Best,
Blago.

[Alex_M]

Thanks for the reply, Blago. Should I avoid doing this in the CPU renderer as well?

EDIT: Ok, I just tested this and appears that it happens with the CPU renderer as well. I'll try to remember this.

[savage309]

I am not sure to be honest. matanov ?

Best,
Blago.

[matanov]

Alex_M I guess you are using Direct Illumination ON ?

[Alex_M]

Yes, Direct Illumination is turned on.

[matanov]

This is expected. "DI on" converts the geometry that has VRayLightMtl to a regular VRayLight and that's not working when the material is part of a Multi/Sub-object. Making parts of the geometry to real lights depending on their face ID is not very trivial to do and it's pretty prone to errors. This is why in such scenarios DI is forced to be off.

[Alex_M]

Alright, thanks for the clarification, Peter. I'll make sure to detach the parts of geometry that have VrayLight materials applied and add their own separate material.