Secondary Ray bias not working on overlapping surfaces

[Daniel_Ray]

On newest version of Vray for modo, it doesn't work. I still see the dark artifacts in the area where it is overlapping.

Although when I uncheck shadows in global options - advanced , the artifact disappears.

Please help.

Thanks.

[Daniel_Ray]

Opps nevermind still there.

[vladimir.nedev]

There is also the Shadow Bias parameter that offsets the shadow rays.
You might need to increase that as well. It's per light.

Also note that the Secondary Ray Bias is not updated in RT, so you need to restart RT after changing it.

Greetings,
Vladimir Nedev

[vladimir.nedev]

Oh, and you should avoid creating overlapping faces, it could lead to all kinds of problems that are not solvable with the bias parameters.
There are no overlapping faces in the physical world.

Greetings,
Vladimir Nedev

[vladimir.nedev]

Also these bias parameters don't help with the camera (i.e. primary) rays, so you are probably seeing those rays randomly hitting one polygon or the other.

Greetings,
Vladimir Nedev

[Daniel_Ray]

Thanks but I was not having this issue before. Still not working.

Modo render and Octane render have no problems with this....

[Daniel_Ray]

Secondary Ray Bias is not working correctly. Would appreciate it being fixed.

[vladimir.nedev]

The polygons that overlap, do they have different materials ?

Greetings,
Vladimir Nedev

[Daniel_Ray]

No it doesn't have different materials.

So when I disabled environment importance sampling, the artifacts disappeared. Will disabling EIS cause any problems?

This was just a crude example to illustrate what the problem was.

Thanks,

Daniel

[boyan]

Hey, Daniel,

Thank you for the feedback, the most simple solution for this is to run mesh cleanup command (mesh.cleanup true) this should fix the overlapping polygons in geometry as well.

[Daniel_Ray]

Hey, Daniel,

Thank you for the feedback, the most simple solution for this is to run mesh cleanup command (mesh.cleanup true) this should fix the overlapping polygons in geometry as well.

That doesn't work. I always mesh clean up first.

Try creating a cube and duplicating it and then translate it in the y axis a little bit. There will be artifacts where they overlap in vray render but not modo or octane render.

[vladimir.nedev]

Without EIS, rendering HDR environments might be very noisy and slow.

I will add a note to add the "shadow bias" parameter to the EIS light as well.
Currently it's exported as 0 to V-Ray and you can't change it.

I think Modo/Octane always offset the rays by some amount, but we have specifically chosen not to do this (at least by default), I don't know the reason why.

Greetings,
Vladimir Nedev

[boyan]

Hey, Daniel,

That doesn't work. I always mesh clean up first.

Try creating a cube and duplicating it and then translate it in the y axis a little bit. There will be artifacts where they overlap in vray render but not modo or octane render.

Can you send me the specific scene file with, which one you've run the mesh clean command and still has an overlapping issue?

[vladimir.nedev]

I will add a note to add the "shadow bias" parameter to the EIS light as well.
Currently it's exported as 0 to V-Ray and you can't change it.

I've added this option for the 2019.10.26 nightly builds for V-Ray Next for Modo (versions 4.12.02 and 4.20.90).
It defaults to a slight shadow bias just like the other lights.
The option is hidden under the "advanced" version of the V-Ray GI tab.

Greetings,
Vladimir Nedev