CUDA renders darker in indirectly lit places compared to CPU

[Alex_M]

I'm using the same setting for both CPU and CUDA but CUDA renders darker in indirectly lit places. Areas that are more or less lit directly look pretty much the same. Can I make CUDA match the results of RT CPU in these indirectly lit areas of the image?

My settings are RT as Production Renderer, GI solution is BF+LC, Trace depth 20, Override depth in Global switches 20, Max ray intensity 20

Please check the screenshot below

[vlado]

Can you get us a scene for this so that we can check what's going on?

Best regards,
Vlado

[Alex_M]

Sure, should be in your inbox now.

I forgot to mention that during the light cache calculation, the indirectly lit areas look brighter and once RT CUDA starts rendering they are dark.

[Zdravko]

RT GPU does not support Compensate camera exposure option of the VRayLightMtl when using PhysicalCamera. We added the issue in our bug tracking system.

[Alex_M]

Hi Zdravko,

Thanks for the reply but I'm not sure I understand what you mean. How does that relate to the problem? The interior is lit by Vray lights, not geometry with VrayLightMtl (or am I missing something?). Can you clarify?

[Zdravko.Keremidchiev]

Apparently there are some other options that are not supported by the GPU. In example in that version 3.40.03 the Directional option of the lights is not supported, this is fixed in 3.5. The VRayMtl Fog color map is not supported, we are working on that. There seems to be other features that ore not supported by the RT GPU, we will continue investigating.

[Alex_M]

The screenshots in my first post was made with 3.5 Beta actually, not 3.4. I noticed that directionality indeed works with 3.5 so this doesn't seem to be the issue. I might do some more testing for example applying grey material to everything and adding simple glass material with no fog color to rule out shader incompatibility.

PS: I think I found where the difference comes from. I had to manually increase the reflection & refraction depth of the glass panels to 20 in the material itself and now it seems that it looks pretty much the same as the render made with Vray Adv. So it seems that Override depth in Global switches is not supported in RT CUDA.