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Alpha Contribution Limitation (?)

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  • Alpha Contribution Limitation (?)

    I'm just wondering if this is a GPU limitation when it comes to Alpha Contribtion. Usually when using the default shadow-catcher workflow, alpha contribution is set to -1 and the alpha is as expected (however it takes rather long until the alpha gets completely noisefree, therefore I'm usually setting the Alpha Contribution to 0 instead when using CPU rendering and I get the identical beauty-render and a nice alpha to knockout all the elements from the shadow-catcher and in post I can set the background to multiply and have the shadow applied to the background then. Alpha Contribution set to 0 on GPU gives a quite different result and I'm wondering if this is a technical limitation of V-Ray RT GPU
    Volker Troy


    www.pixelwerk.at

    +43 (0) 664 / 3 820 810
    Radetzkystrasse 102 a
    A-6845 Hohenems
    Austria

  • #2
    Here you can see the difference between alpha contribution set to 0 or -1 on V-Ray GPU and CPU. While -1 works like expected. 0 doesn't seem to work on GPU
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    Volker Troy


    www.pixelwerk.at

    +43 (0) 664 / 3 820 810
    Radetzkystrasse 102 a
    A-6845 Hohenems
    Austria

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    • #3
      We are aware of this limitation, sorry for the inconvenience. The problem with the noisy alpha and matte is resolved in V-Ray Next.
      If it was that easy, it would have already been done

      Peter Matanov
      Chaos

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