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Some GI thoughts and questions

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  • Some GI thoughts and questions

    Hi!

    I'm working on a architectural visualization project. Exterior and aerial, so its buildings, trees and vegetation. The camera will hover slowly around the buildings. The scene is static, so its great to have the feature to read the irradiance map and light cache from file. Sun and sky system. 720p.

    Some GI questions have popped up during this process and it would be great if someone could clarify.
    I create the IR and LCache files with "Don't render final image" checked.

    Regarding Irradience map:
    1. Does it matter what IR-setting I have while incrementally adding to current map (ex medium or high animation preset)? There is a lot of details to be captured in the trees.
    2. The camera move is almost a 360 degrees rotation around the building. The more increments/snapshots to the file the better I assume?
    3. I have the Irradience map multiplier set to 1.2 to get more boost from the GI. Is it important to keep it at 1.0 while creating the file?

    About Light Cache:
    1. One Fly-through pass is enough to get a proper file?
    2. Should 'Use light cache for glossy rays' and 'Use retrace threshold' always be checked? Any exceptions?
    3. What is a proper amount of Light cache subdivs? Its set to 1000 atm.

    One last thing thats outside GI:
    I'm getting a really hot, flickery specularity spot on one object. A metal object where the evening sun bounces almost right into the camera. I've tried to soften it and make it stable by raising the refl subdivs on the object, lowered the cutoff threshold, lowered the new Max ray intensity to 2.0, but it still vobbles around a bit. DMC Sampler is at min 3, max 16, thresh 0,01. Anything else I could try?

    Thanx a lot!
    Last edited by fasterG; 12-06-2014, 09:00 AM.

  • #2
    Originally posted by fasterG View Post
    1. Does it matter what IR-setting I have while incrementally adding to current map (ex medium or high animation preset)? There is a lot of details to be captured in the trees.
    The "high" preset should be enough.

    2. The camera move is almost a 360 degrees rotation around the building. The more increments/snapshots to the file the better I assume?
    Yes, though you can go every other frame, or every 4th frame to speed things up.

    3. I have the Irradience map multiplier set to 1.2 to get more boost from the GI. Is it important to keep it at 1.0 while creating the file?
    You can keep it to 1.2 while creating the file.

    1. One Fly-through pass is enough to get a proper file?
    Yes, just make sure you give it enough subdivs (you can do a few quick renders with the saved light cache as primary and secondary bounces to see how splotchy it is).

    2. Should 'Use light cache for glossy rays' and 'Use retrace threshold' always be checked? Any exceptions?
    It makes sense to generally keep them enabled, yes.

    3. What is a proper amount of Light cache subdivs? Its set to 1000 atm.
    Depends on how long the camera path is; 1000 will probably not be enough, but whether you need to go to 2000 or 3000 or more - you'll have to do a few tests.

    I'm getting a really hot, flickery specularity spot on one object. A metal object where the evening sun bounces almost right into the camera.
    Is the V-Ray sun "invisible" option on or off? Have you tried raising the sun subdivs a bit?

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

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    • #3
      Originally posted by vlado View Post
      The "high" preset should be enough.

      Yes, though you can go every other frame, or every 4th frame to speed things up.
      Thanx!
      The camera move is 1300 frames so I'm looking for a way to create the IR file by not having to choose frames manually to incrementally add.
      I'm not getting the IR incremental add to work when batch rendering (with Don't render final image, by 10th frame).
      Would be nice to batch render the full sequence at every Nth frame and have the IR file completed the next day. Is it possible?

      And I'm not sure how a good light cache is supposed to look. I gave it 7000 subdivs and hoping for the best (the time it takes to calculate is nothing compared to the rest anyway)!
      Last edited by fasterG; 14-06-2014, 07:15 AM.

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      • #4
        It is not necessary to manually add IM-caches - Vray will do that automatically for you.
        IR incremental add works fine with batch rendering.
        Yes it is possible to render every Nth frame with batch render resulting complete IM file for the entire animation.

        Please let us know what is the exact Vray version that you are using.
        May you send us a screen-shots of the settings you are using and let us know what steps did you take in order to pre-calculate IM?

        Thank you very much in advance.
        Last edited by Svetlozar Draganov; 16-06-2014, 12:15 AM.
        Svetlozar Draganov | Senior Manager 3D Support | contact us
        Chaos & Enscape & Cylindo are now one!

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        • #5
          I kept it at medium animation, since high would add a 4th pass and it would take too long
          You can see the result here:

          https://vimeo.com/99451372

          Regards,
          Peter

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          • #6
            The result is very nice - thats for sharing.
            Svetlozar Draganov | Senior Manager 3D Support | contact us
            Chaos & Enscape & Cylindo are now one!

            Comment

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