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Light Select and SSS problem

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  • Light Select and SSS problem

    The Light Select RE does not seem to play nice with SSS materials.

    Here's the simple setup:
    A sphere with the SSS2 material. One directional light with ray traced shadows on. GI is off.

    These passes build together to create the beauty
    lighting + SSS + specular + reflection = beauty

    Now if I instead make a Light Select RE set to "diffuse" what I get is not the same as the lighting pass, but rather the same as the Total Light pass.
    Light Select "diffuse" = Total Light. I have no idea how to comp that together. The problem is that I cannot add the SSS to it because the SSS is already added where the direct light hits it, but it is not added in the indirect part (the forward scattering). This is easy to replicate with the test I describe above.

    The behavior I'd like to have is
    1) Light Select "diffuse" gives the same result as the Lighting pass, not the same as Total Light.
    2) There would be a SSS option in the Light Select "type" dropdown menu.

    Then it would build properly:Light Select "diffuse" (=lighting) + Light Select "SSS" (=SSS) + specular + reflection = beauty

    Any chance of getting this in a future release/update?

    The only workaround I know is using Render Layers with a particular light to make "do-it-yourself light select passes." But as it is, since pretty much everything we do will have an SSS material somewhere in the shot the Light Select pass itself -- which in theory is super awesome -- is pretty much unusable. So it would be really great if we could get this addressed.

    thanks!

  • #2
    Clarification:
    On an SSS2 material a Total Light pass and a Light Select pass set to "diffuse" are the same if GI is off.
    When GI is on, the Total Light pass includes the GI, while the Light Select pass set to "diffuse" does not.
    Both a Total Light pass and a Light Select pass set to "diffuse" contain the SSS contribution in the lit area (back scatter), but not in the unlit area (forward scatter). This means that a Total Light pass cannot be combined with an SSS pass.

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    • #3
      We can only fix this for raytraced SSS. If this is ok, let me know and we'll work on it.

      Best regards,
      Vlado
      I only act like I know everything, Rogers.

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      • #4
        Originally posted by vlado View Post
        We can only fix this for raytraced SSS. If this is ok, let me know and we'll work on it.

        Best regards,
        Vlado

        Thinking out loud here: the SSS2 material does not use raytraced SSS by default (it uses "simple"). Last time I tried it was super slow in raytrace mode so I don't think that would be viable. However, I think the new Skin material for Vray 3.0 uses raytracing mode by default and is pretty fast at this. So for that I think it would be good to have the Light Select fixed for Vray 3.0.

        That's my 2 cents.

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