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Poor light bounce results with Irradiance Map

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  • Poor light bounce results with Irradiance Map

    On a job I'm working on at the moment I noticed strange results when using IM for primary bounces. It looks like the light bounces just a few times so areas that are not directly lit by the lights look like they are rendered without GI. I made a quick test changing the IM engine with BF and the results are MUCH better. Please check the screenshot below. Why does this happen? Does IM cast less light bounces than BF? You can even notice that the super bright lampshade casts a very dark shadow on the wall as if there is no bright lamp there.

    Click image for larger version

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    Aleksandar Mitov
    www.renarvisuals.com
    office@renarvisuals.com

    3ds Max 2023.2.2 + Vray 6 Update 2.1
    AMD Ryzen 9 9950X 16-core
    64GB DDR5
    GeForce RTX 3090 24GB + GPU Driver 551.86

  • #2
    Which V-Ray version?

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

    Comment


    • #3
      Vray 3.20.03

      Originally posted by vlado View Post
      Which V-Ray version?

      Best regards,
      Vlado
      Aleksandar Mitov
      www.renarvisuals.com
      office@renarvisuals.com

      3ds Max 2023.2.2 + Vray 6 Update 2.1
      AMD Ryzen 9 9950X 16-core
      64GB DDR5
      GeForce RTX 3090 24GB + GPU Driver 551.86

      Comment


      • #4
        I know there was an issue with GI through irradiance map when there was a dome light with "affect alpha" disabled, but in that case the IM came out brighter, not the other way round.

        Is is possible to get us a part of the scene to support@chaosgroup.com so that we can check what's wrong?

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

        Comment


        • #5
          Ok, I will send the scene as soon as time allows.

          Originally posted by vlado View Post
          I know there was an issue with GI through irradiance map when there was a dome light with "affect alpha" disabled, but in that case the IM came out brighter, not the other way round.

          Is is possible to get us a part of the scene to support@chaosgroup.com so that we can check what's wrong?

          Best regards,
          Vlado
          Aleksandar Mitov
          www.renarvisuals.com
          office@renarvisuals.com

          3ds Max 2023.2.2 + Vray 6 Update 2.1
          AMD Ryzen 9 9950X 16-core
          64GB DDR5
          GeForce RTX 3090 24GB + GPU Driver 551.86

          Comment


          • #6
            Getting different bright GI between IM and brute-force here. BR gets brighter by around 10-20%.
            Indoor, no sun-/skylight or Dome light. Some lights, a lot of GI bounces. Secondary always flythrough-LC.
            Primary Single-frame IM or Brute force.
            Can't post scene, it's confidential. Vray 3.30.01 and max 2016.
            Will try to reproduce in small scene, no time now.
            Valentin

            ...forget Warp 9, engine-room please switch to Vray-speed...

            Comment


            • #7
              Make sure that Store with Irradiance Map option is deactivated for all the lights in the scene.
              Light with that option enabled will be calculated only when IM is being used, in most of the cases though the result should be brighter with IM and darker with other GI-engines.

              If possible please substitute the confidential information in the scene with simple primitives and materials and send it for investigation.
              Svetlozar Draganov | Senior Manager 3D Support | contact us
              Chaos & Enscape & Cylindo are now one!

              Comment


              • #8
                I just sent part of the scene to the support email for testing (the download link will be active for 5 days).

                Originally posted by svetlozar.draganov View Post
                Make sure that Store with Irradiance Map option is deactivated for all the lights in the scene.
                Light with that option enabled will be calculated only when IM is being used, in most of the cases though the result should be brighter with IM and darker with other GI-engines.

                If possible please substitute the confidential information in the scene with simple primitives and materials and send it for investigation.
                Aleksandar Mitov
                www.renarvisuals.com
                office@renarvisuals.com

                3ds Max 2023.2.2 + Vray 6 Update 2.1
                AMD Ryzen 9 9950X 16-core
                64GB DDR5
                GeForce RTX 3090 24GB + GPU Driver 551.86

                Comment


                • #9
                  The result with IM is incorrect since Min and Max rate parameter are not set properly, the Min value is supposed to be smaller than the Max value which is not the case in your scene.
                  A warning about that is printed in the log file:

                  Click image for larger version

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                  As soon as these values are set correctly the illumination between both engines becomes identical.
                  Svetlozar Draganov | Senior Manager 3D Support | contact us
                  Chaos & Enscape & Cylindo are now one!

                  Comment

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