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Color Stepping when using Refraction/Transparency

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  • Color Stepping when using Refraction/Transparency

    Ok, bit of a strange issue here.

    I'm dealing with some very small objects in a maya scene. They're smaller than 1cm in some cases.

    If I use a translucent Vray material on an object, with another object behind it, vray will render it as if they were clipping (like the object behind the translucent object is protruding into the translucent object). This doesn't happen at larger scales. I only actually noticed it because the issue is made much worse if the refraction color is anything near orange. It also doesn't occur if the inner object has no diffuse color (i.e. chrome).

    I've attached images showing the Scene view, the rendered view, and my material settings. the scene has a hollow sphere (double walled) with a translucent vray material on it, and a beveled cube with a plain white vray material on it.

    I'm using Maya 2015 Extension 1 + SP5 and Vray 2.4 on Mac OS 10.10.2

    this is messing up a project with a looming deadline so any tips would be appreciated!
    Attached Files
    Last edited by isoparmesan; 11-03-2015, 02:02 PM.

  • #2
    I did sort of find a workaround. If I disable shadows on the transparent object the issue goes away, but then I don't get shadows. In my particular case this should be fine, but that could be a bigger compromise in the future.

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    • #3
      Hi,

      Can you post this scene file to take a look at it?
      Tashko Zashev | chaos.com
      Chaos Support Representative | contact us

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      • #4
        Took me a while to get to it, but I've attached a scene that exhibits the issue. Thanks for your help.

        RefractionProblem.ma.zip

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        • #5
          Hello,

          This is just intersection according to my test. When you make the cube smaller, the issue look like to be fixed.
          Tsvetan Geshev
          Technical Support Representative

          Chaos Group

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          • #6
            Right, it looks like intersection, but if you look at the geometry, there's no actual clipping. If you make both the cube and the sphere uniformly larger (like if you grouped them and scaled the group up) the problem also goes away.

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            • #7
              The Default value of the Shadow Bias parameter in Dome Light is too high for this scene.
              Set its value to 0.001 or 0.000 and the issue will go away:
              Click image for larger version

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              Svetlozar Draganov | Senior Manager 3D Support | contact us
              Chaos & Enscape & Cylindo are now one!

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