Glitches in rendering using grouped objects

[nubo]

Hi,

We've encountered a problem while rendering a scene with FP using grouped objects.
There are some strange glitches and artifacts mostly visible in the shadows.
We've tested this scene with Vray LightCache+BruteForce, LightCache+IrradianceMap, Progressive Image Sampler, Bucket Image Sampler, all with the same result.
The only thing that resolves the problem is instantiating the Forest Pack hence our suspicion where the problem lies.
Any ideas how to fix this without giving up on FP scattering?


3DSMax 2023.3.4
Vray 6
ForestPack 8.2.2, 8.2.4

[RealViz]

Rendering via DR? If so, is FP the same version everywhere?

[nubo]

Rendering via DR? If so, is FP the same version everywhere?

Nope, no Distributed Rendering here.
I know that it looks like a bucket inconsistency problem but, believe it or not, this preview was made with progressive image sampler.
What's interesting during the light cache prepass the shadows look normal.

Another weird observation:
With global material override turned on (default gray VrMtl) everything renders fine. The same override with "Preserve original: reflections, refractions" turned on - the problem is back.

Another thing worth noting is that within the scattered group there are some instances of CAD Vizblock objects, but I don't know if it's relevant.

[RealViz]

Aaaa... try to set the "secondary ray bias" in the renderer to a value greater than zero e.g. 0.02.

[nubo]

Aaaa... try to set the "secondary ray bias" in the renderer to a value greater than zero e.g. 0.02.

Thanks for the advice but we always keep it at 0,001, I've tried it with 0,02 and it's the same.
I think it's neither Vray nor scene setup problem, since after instantiating the Forest Pack (meaning replacing the scattered geometry with actual geometry via Forest Tools) everything renders fine.

[nubo]

UPDATE:

It turns out that part of the problem lies in 'Adaptive Lights' in render setup.
Switching to 'Full Light Evaluation' gets rid of the artifacts which is strange, because there's only VraySun + VraySky in the scene, so there should be no approximating down of the lights.
Again, the problem does not occur with regular instances of the model (also grouped), only while scattered via ForestPack, so there must be something wrong with how the grouped scattering behaves combined with Adaptive Lights.

[Michal Karmazín]

Hi,

If possible, please feel free to send us your scene (ideally simplified and containing just this problematic object(s)). Thanks in advance.

Best regards,

[nubo]

Hi,

If possible, please feel free to send us your scene (ideally simplified and containing just this problematic object(s)). Thanks in advance.

Best regards,

Thanks, scene sent.