odd artefacts in VrayRawLighting Shadow and Reflection

[dose]

We've been seeing these odd artefacts for a while now, and finally thought i'd put a post on here to see if there's any solution.


We seem to usually see it somewhere in the middle of glass windows, and often on the side of cars in scenes.. It is mostly obvious in the VrayRawLighting pass, but also visible in the RawReflection and RawShadow passes..

Any help/thoughts or suggestions welcome..

Donal

[vlado]

Since the glass windows have no diffuse components and those areas are dark in your RGB render, V-Ray samples them (way) less than the rest of the image.

Best regards,
Vlado

[dose]

Thanks for swift response vlado..

Is there a way to avoid this issue then? Maybe custom samples on the glass materials??

D

[joconnell]

No, when you combine the raw passes with their companion pass which make up the final amount of reflection, refraction or diffuse, the problem areas you see are reduced to 0 anyway. Vray won't sample things that don't get used so for example a non reflective surface won't get any information in the raw reflection pass, likewise a totally see through glass object lets pretty much all light through so you won't get any shading information for it. The raw passes can sometimes be a bit misleading looking, you'll see some bad sampling in there which gets totally removed when you use it with it's filter pass.

[dose]

Ah ok, that's fine.

It'd be nice to be able to use ALL of hte lighting pass as an additional AO type of layer in photoshop. Just working on top of the RGB pass, not rebuilding the render from scratch...

D

[joconnell]

Sure. In some cases I do worse renders to force more data into all of the channels. What you'd have to do is make your glass material less than 100% refractive and this would give the glass some solidity for light to fall on. If part of a material like reflection, refraction or specular doesn't contribute anything to the beauty, vray won't sample it at all for speed reasons.