Mirroring Dome Light with Finite Dome causes excessive noise

[kosso_olli]

Hey guys,
it seems something weird is going on when dome lights with finite dome feature and HDRi in the texture slot are mirrored along the Y-axis. The result is excessive noise which is very hard to clean and therefore leads to very high render times.
If the dome light is not mirrored, but instead the values in the HDRi texture are flipped to get the same effect, the result is as expected: Clean and fast.
It almost seems as if the dome light loses the MIS after mirroring.
The problem is not related to the material, it will also happen with a simple grey VrayMtl.

The first image is rendered with the dome light itself mirrored along the Y-Axis, and the second image is the non-mirrored dome light with the mirroring applied to the HDRi texture itself using its mapping coordinates. Render time is 12:01 minutes versus 2:04 minutes.





Max 2023, V-Ray 6.00.20

Regards

Oliver

[Philip Shounev]

Hello,

Thanks for the report. I can confirm that noise levels seem visibly increased when mirroring the dome light. For the time being I would suggest using the VRayBitmap's own UV settings to mirror the texture instead of mirroring the whole dome light. Other than that, I've logged the issue in our internal bug-tracker under VMAX-13257 for our developers to look into.

Best regards,
Philip