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Wh would you use a shadow bias higher than 0.0?

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  • Wh would you use a shadow bias higher than 0.0?

    I've noticed some weird shadows in some scenes I've been rendering lately, for example when using a scene bought from evermotion, and I discovered that for some reason the v-ray sun had a shadow bias of a few maybe 0.2 cm, and in other cases more (maybe due to rescaling a scene. This is creating a weird effect where the shadow was further away from the casting object. Why would you need a shadow bias higher than 0.0?

  • #2
    0.0 is bad as you may get disappearing shadows altogether.
    It's not as bad, however, as the state of the shadow bias section of the docs as it is right now, so sorry about that.

    In general, Shadow Bias is a dark art, as it depends on distances and scene sizes.
    A low, non-zero value is generally fine (type 0.02 in the box, provided your units are sensible, ofc, like Cm, or mm, and not meters or kilometers.).
    Lele
    Trouble Stirrer in RnD @ Chaos
    ----------------------
    emanuele.lecchi@chaos.com

    Disclaimer:
    The views and opinions expressed here are my own and do not represent those of Chaos Group, unless otherwise stated.

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    • #3
      in centimeters in Maya, I usually set all of my lights to .001 if I'm doing shots of anything medium range and especially for close up shots. For wide shots or shots not close up it usually doesn't seem to make a difference.

      I've tried putting it to zero and I don't remember having any issues, but I've been warned that there could potentially be issues. So I leave it at .001 usually
      Last edited by Buck; 11-12-2017, 11:50 AM.
      www.DanielBuck.net - www.My46Willys.com - www.33Chevy.net - www.DNSFail.com

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      • #4
        Thanks for the feedback! I tried setting it to 0.0 and didn?t have any problems. Maybe there is something going on under the hood that converts it to a very low value, like 0.001 without telling the user (if 0.0 is not a good value)? Anyways, thanks for the info!

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        • #5
          Originally posted by ^Lele^ View Post
          0.0 is bad as you may get disappearing shadows altogether.
          It's not as bad, however, as the state of the shadow bias section of the docs as it is right now, so sorry about that.

          In general, Shadow Bias is a dark art, as it depends on distances and scene sizes.
          A low, non-zero value is generally fine (type 0.02 in the box, provided your units are sensible, ofc, like Cm, or mm, and not meters or kilometers.).

          On that note, the default bias for the VRaySun is 0.2. That is huge. I have run into issues with this (forgetting that this was 0.2 and not the default 0.02 as everywhere else) often times, and I have to remember to set it correctly and I can't use the defaults here.
          It would be really good if the VRaySun defaults to 0.01 or 0.02 instead of 0.2
          Software:
          Windows 7 Ultimate x64 SP1
          3ds Max 2016 SP4
          V-Ray Adv 3.60.04


          Hardware:
          Intel Core i7-4930K @ 3.40 GHz
          NVIDIA GeForce GTX 780 (4096MB RAM)
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          • #6
            This is one of those annoying 'defaults' that needs more intelligence. Our scenes are always (well, 99% of the time) in meters, and if we don't forget to change the value (we typically always use 0.0 and it hasn't ever given us a problem) shadows on 'normal' sized objects (curbs, bris soleil etc) do not work properly. Why can't these defaults have a bit more intelligence so that they respect the scene units?

            It's like with the default physical camera setup: why oh why would anyone want those default settings???
            Kind Regards,
            Richard Birket
            ----------------------------------->
            http://www.blinkimage.com

            ----------------------------------->

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            • #7
              Originally posted by tricky View Post
              This is one of those annoying 'defaults' that needs more intelligence. Our scenes are always (well, 99% of the time) in meters, and if we don't forget to change the value (we typically always use 0.0 and it hasn't ever given us a problem) shadows on 'normal' sized objects (curbs, bris soleil etc) do not work properly. Why can't these defaults have a bit more intelligence so that they respect the scene units?

              It's like with the default physical camera setup: why oh why would anyone want those default settings???
              this is something I've never really thought about, do you have any examples of the difference you could post, showing where you've had it misbehave?

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              • #8
                Next time it crops up I will post it.
                Kind Regards,
                Richard Birket
                ----------------------------------->
                http://www.blinkimage.com

                ----------------------------------->

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                • #9
                  I hope this value will soon be removed and handled internally. I don't think shadow bias is something an end user should come in contact with.

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                  • #10
                    Originally posted by LudvikKoutny View Post
                    I hope this value will soon be removed and handled internally. I don't think shadow bias is something an end user should come in contact with.
                    I'm all ears for suggestions, personally.
                    Lele
                    Trouble Stirrer in RnD @ Chaos
                    ----------------------
                    emanuele.lecchi@chaos.com

                    Disclaimer:
                    The views and opinions expressed here are my own and do not represent those of Chaos Group, unless otherwise stated.

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