Fireflies impossible to clean

[flaviuscristea]

Hi there,

As in my previous post I am looking into the possibility to switch to Vray GPU but I have a serious issue here which makes my life impossible at the moment. Those fireflies(RGB values over 35 or so) appear on the foam and there seems nothing I can do. I tried so far:

1.Unchecking affect specular from Vray Sun
2.Making the sun 100x size
3. Unchecking affect GI from phoenix fd shader -> vray properties
4. Trying bucket mode vs progressive mode
5. Tried rendering foam as Geometry or Atmospheric effect
6. Tried to change the maximum ray intensity from 20 to 5 (which kind of also darkened the foam a lot)
7. Set the Highlights strengths in the Phoenix Shader foam to 0
8. Set the Secondary Ray Bias to 0.001 0> I thought some overlapping bubbles do that.
10. Tried different filters.
11. Denoiser, I was very surprised to see, doesn't clear them. And it creates really weird big squares on the reflection of the ship (not visible here due to NDA of course)
12. Used a Vray Dome with HDRI and to my surprise the foam doesn't render AT ALL like that

Nothing worked I am getting desperate here. Is there any solution to this?

and I cannot clear it in post production because I need the denoiser to..denoise the ship, but the denoiser itself creates super weird artifacts from them.

is there anyway to just clamp the really absurd pixel values? Like..if a pixel value is above 10 or whatever value it should look to adjacent pixels and just average them out instead of the really high value... ? Is this hard to implement?

Thank you

[nikoleta.garkova]

Hi flaviuscristea,

Best would be to forward a sample scene with the issue reproducible to support@chaosgroup.com so we can investigate further, thanks.

[flaviuscristea]

Hi there!
I will arrange the scene and send it to support with explanations.

Thanks!

[seandunderdale]

Hi there,

12. Used a Vray Dome with HDRI and to my surprise the foam doesn't render AT ALL like that

Did you find it rendered better or worse? Ive been very surprised how different Vray Sun and Sky looks to a clear sky, unclamped hdri with the sun in a similar position. Totally different results.

[Xntric]

Have you tried lowering the max ray intensity?

[flaviuscristea]

Have you tried lowering the max ray intensity?

Hi,
Yes I've tried it. It doesn't fix them sadly. Those pixels values are insane. In a still it's not a problem I can fix them manually but in animations it is a nightmare I am desperate for a fix for this

[Paul Oblomov]

Clamp will work.

[flaviuscristea]

Hi Paul,

In the VFB I can see these white pixels, I assume they are NaN errors? But I see no way of clamping these. I am not very proficient in post production, I'll try to see if I can fix them in Fusion. I just need these pixels to be averaged by their surrounding pixels values. But of course, the ideal fix would be from Vray itself.

[flaviuscristea]

So "affect specular" on/off doesn't work with vray GPU - works fine with Vray CPU. The documentation says that Vray Specular is supported by Vray GPU so I assumed turning "affect specular" from the Vray sun works, but it doesn't.

I assume if this bug is fixed, there will be a workaround with 2 suns for my current scene and issue. Is this difficult to implement?

EDIT: Fireflies are still there. Include/exclude doesn't seem to work properly with Vray GPU. (tried 2 suns, one with specularity set to 0 for the foam only, other sun specularity set to 1 for the rest of the objects)
Thanks

[nikoleta.garkova]

Thanks for the provided scene files, flaviuscristea.

Using VRaySun will increase the contribution of very bright rays, hence the cause of such excessive noise. Unfortunately, for the time being, disabling the Sun's Affect Specular parameter will not produce the desired results in V-Ray GPU. This is a known issue (internal bug-tracker ID: VGPU-4753) and I'll make sure to bump its priority additionally.

What you can do in the meantime is:

1. Lower down the water material reflection glossiness a bit.
2. Decrease the Sun's intensity and play with the exposure settings
3. Use a Dome light instead of Sun, where you can also add a suitable HDRI map.

Note: In the Particle Shader's parameters, try to set the Highlights Width and Strength to 0 as this seems to improve the situation a bit.

[flaviuscristea]

Hi there Nikoleta,

I have tried everything you said but sadly I still get the fireflies, more or less but they are still there

This last image i posted is with a HDRI(I lowered the exposure a lot to see the fireflies better). As soon as I bring rotate the HDR in the position the Sun was (one i need) I get the fireflies. It's clearly related to specularity and the interaction with the water. I have tried water glossines to 0.8 but I can't go lower because it starts to look like a weird surface.

Will there be a future fix for this? Some internal clamping, similar to Corona's Highlight clamping? Or something else?

Thanks !