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Thread: Suspecting bug in clearcoat

  1. #1
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    Suspecting bug in clearcoat

    I have 2 images. One has clearcoat all the way off. The other had clearcoat at 1 percent. That's the only change between the 2 images. The first has minimal to no fireflies. The second has a big problem that aa is unable to mitigate.
    At one percent, I would expect any fireflies from clearcoat to resolve out after a few passes, but here's 400 aa passes, and they only get worse and worse with aa passes.


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  2. #2
    skeptic lertola2's Avatar
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    If you turn on Limit Dynamic Range on the Effects - Processing tab does that help?

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    Yes, but that doesn't keep it from being a bug.

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    After some more testing, I'm convinced this is a clearcoat bug. Perhaps clearcoat is not energy preserving. Anyone else having this problem.
    Do I need to provide a scene, or is this clear enough?

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    Here's a scene demonstrating the problem
    http://squirreldome.com/Download/LWO.zip

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    scene after 1000 aa passesClick image for larger version. 

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  7. #7
    Electron wrangler jwiede's Avatar
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    It definitely looks like an issue. There seem to be significant issues regarding interactions where even small pBSDF "Roughness" term values combined with any specular/reflective-type term values yield "fireflies" in quantity. There may also be an AA issue, as it seems to identify these "fireflies" as fine details meriting preservation or similar, instead of trying to mitigate their contrast.
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  8. #8
    www.Digitawn.co.uk rustythe1's Avatar
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    Jason posted on FB that the problem goes away if you enable mipmapping, however not sure you are using a BG image, which I would say is usually the main culprit for creating fireflies in gloss/conductor
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  9. #9
    skeptic lertola2's Avatar
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    I think the fire flys are some kind of reflection artifact. I turned off the light and set a gray background and set roughness to zero. Interestingly the fire flys only show up where the object self reflects. There is nothing in the scene that could yield a bright reflection as far as I can see. Turning on limit dynamic range gets rid of the fire flys. I think that means that the fire flys are so bright that antialiasing cant correct them. So I hope this is a bug that can be fixed. For the moment it seems like we should not use clear coat and metallic setting together unless we are willing to turn on limited dynamic range.

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  10. #10
    Super Member omichon's Avatar
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    Quote Originally Posted by Dan Ritchie View Post
    After some more testing, I'm convinced this is a clearcoat bug. Perhaps clearcoat is not energy preserving. Anyone else having this problem.
    Same conclusion here too. Most of my fireflies issues are gone since I avoid using clearcoat.
    www.oliviermichon.fr | 3D Animation, Motion Graphics and Broadcast Design.

  11. #11
    Curmudgeon in Training Ma3rk's Avatar
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    Uncheck the Glossy Reflections option for the surface. You have that enabled plus Affect Specular for the light. You'll need to tweek other surface settings but gloss & sheen will behave more predictably, but that'll get rid of the fireflys.

    You should probably set the scene up with an enviro sphere & enviro light rather than just a distant to test correctly.
    Last edited by Ma3rk; 12-06-2018 at 09:58 AM.
    "Never be a cat in a cartoon. Never." Chief Wiggum

  12. #12
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    There's fireflies, and there's incorrect fireflies, and that seems to be what we have here with clearcoat.

  13. #13
    skeptic lertola2's Avatar
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    I put in a bug report for this yesterday. Today I got a message from Lightwave Customer Support: "This has been fixed internally. This should not be reproducible in the next available version."

    Yes!

  14. #14
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    Quote Originally Posted by jwiede View Post
    It definitely looks like an issue. There seem to be significant issues regarding interactions where even small pBSDF "Roughness" term values combined with any specular/reflective-type term values yield "fireflies" in quantity. There may also be an AA issue, as it seems to identify these "fireflies" as fine details meriting preservation or similar, instead of trying to mitigate their contrast.
    Admittedly, I'm not a programmer, but I don't understand why the renderer can't have a sanity-check of some sort. If it gets a result on a single pass (or even every pass!) of a single pixel that's a hundred or a thousand times brighter than the other passes, and the surrounding pixels, it's far more likely that the value is an error than that there's one impossibly-bright object in the scene that's smaller than a single pixel in the render (well, hundreds of such objects scattered around the frame). I basically do it manually to clean up fireflies in my stills, cranking down the exposure of an exr render until the fireflies are all that's left, and then using that as a mask and using content-aware fill on my main layer.

  15. #15
    Curmudgeon in Training Ma3rk's Avatar
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    Mmmm, well, just sayin'...

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    Last edited by Ma3rk; 12-07-2018 at 01:00 AM.
    "Never be a cat in a cartoon. Never." Chief Wiggum

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