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Bug with Filmic Tonemap and Unpremult Alpha channel

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  • Bug with Filmic Tonemap and Unpremult Alpha channel

    We've being having very ugly edges when rendering our 3d since we upgraded to Vray 5. We've came to the conclusion that it's being caused by the Filmic Tonemap, and it's specially noticeable when unpremulting the render in Nuke.

    Please have a look at the sample picture below.

    We've tried using all the Filmic nodes, but every setting is causing this same issue. Which makes it pretty much unusable when we're comping the 3d over real footage.

    Is this a known issue?
    Attached Files

  • #2
    Thanks for the report. The issue is reproducible. I've logged it (internal bug-tracker id: VMAX-10471) for developer investigation. We'll see what we can do.
    Aleksandar Hadzhiev | chaos.com
    Chaos Support Representative | contact us

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    • #3
      Thank you, please let us know when its fixed so we can use it again.

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      • #4
        From what I've tested on a simple scene, the Normal blending mode seems to eliminate the issue. I can't really tell from your attached image if that is so in your case, however. Could you share a comparison between the unpremultiplied normal blending mode image versus the original?
        Aleksandar Hadzhiev | chaos.com
        Chaos Support Representative | contact us

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        • #5
          After communicating with our developers, it seems there isn't anything wrong on our side - the result is based on the unpremult's dividing effect. The outline is evident even without filmic tonemapping; i.e. when using a lower value light which makes the background darker. Could you share what exactly are you trying by using this node? Also, to which file format are you outputting?

          EDIT: Attached screencap from Nuke result on the non-filmic mapped image with low lights. Download scene, nuke setup and .exr here.
          Attached Files
          Last edited by hermit.crab; 20-11-2020, 02:48 AM.
          Aleksandar Hadzhiev | chaos.com
          Chaos Support Representative | contact us

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          • #6
            Have not seen the specific issue, but for premultiplied renders you definitely need a pure black BG. Make sure there are no maps in the environment and that it is pure black. (Use VRay environment overrides in the render settings if you need something in the environment map. )

            But I am guessing you tried this, as this issue would manifest itself without tone mapping.

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