GPU Multi-Color Pixel Artifacts

[Jakazul]

When I try using CUDA or RTX (or using the GPU setting prior to the recent Update 2), I get these funky little rainbow pixels in my refractive surfaces. You can see them all over the center diamond in the attached image.
I was able to remove them by turning off "affect specular" in my dome light settings, but of course that also killed pretty much any semblance of life in the image; and even if it is a solution I'm not sure why it worked or how to compensate for it.

Anyone know what's causing this, or have a good way to fix it?

Running VRay Next on Rhino 6, Windows 10, NVIDIA GTX 2060 Super.

[kosso_olli]

There is dispersion activated for the gemstone material in the center. Disable the disperion-feature in that shader and the effect should be gone.This is not a render-artifact. See here: https://docs.chaosgroup.com/display/...c#Generic-Disp

[Jakazul]

Thanks, but I'm not sure you're seeing what I'm talking about. Here's another pic.
I want the dispersion, I don't want the random pixels. If I switch dispersion off, it's basically just black and white - which is no good.

[Jakazul]

Still looking for an answer, but here are a couple of updates:

1. If I turn dispersion off in my gem, the stray pixels still appear, just white instead of colored.
2. If I turn off my light dome, I can have dispersion on with absolutely no stray pixels. I even tried lowering the abbe to really crank up my dispersion, and it works fine as long as the dome is turned off.

I'm still not sure what's causing the issue, but guessing it is possibly related to light reflection rather than refraction?

[Micha]

Last I found that speculars are not right sampled after interreflection levels. Maybe speculars are also used for dispersion. Try to disable the speculars of the light sources or set the specular highlights of the materials at 1. Doe's it help?

[Jakazul]

Micha, yes and no. Disabling speculars in my HDRI does get rid of the pixes, but it causes a bunch of other weirdness.

These images are all rendered in RTX mode.
Dispersion & Light Dome both off gives me the grayscale look
Dispersion On & Light Dome off gives me a clean image, but a little dull
Dispersion On, Light Dome On with Affect Dispersion off gives me no pixels, but the weird black reflections
Dispersion & Light Dome both on gives me the best looking image, but the pixels are back (you can see them if you look close along the left side of the gem)

[chris_lang]

Has anyone been able to solve this yet? I've run into the same issue. When rendering the first few passes, sometimes I see the rainbow artifacts. To bypass this, I just restart the render and it usually fixes it after one or more tries. Not sure what the issue is here. Another thing I did was decrease the noise limit to something ridiculous like 0.001. I have an A6000 GPU and I'm using 3DS Max 2023 with V-Ray.