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Thread: Specular indirect

  1. #16
    www.Digitawn.co.uk rustythe1's Avatar
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    are you using brute force, you say you have 20 gi, but if using interporlated that setting is meaningless, if using brute force, that's where your problem lies, bring the camera aa back to 4 and reflection samples back to 8 or so, then keep upping the brute force gi (you will probably find 100 to 200 it will start to clean up)
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  2. #17
    Super Member kolby's Avatar
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    Quote Originally Posted by Mats Andersen View Post
    Turning off the affect specual on the distant light of course remove the fireflies - but I would not loose the specualar!
    What is the Angle value of the distant light ?
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  3. #18
    Hmm from this i suspect the main culprit is probably the sun light it's self and that's damn hard to actually fix, other than using some clever node tricks. Work out which objects are causing bright secondary reflections of the sun, and use the ray type switch to swap out for a non glossy material for reflections, which should help kill some of the worst offenders.

  4. #19
    Not so newbie member lardbros's Avatar
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    Ah... Just thought. Was this scene brought over from an old LW scene?

    Even if it wasn't, check the lights, falloff nodal stuff. Importing old lights
    from 2015 scenes into LW 2018 attempts to recreate the falloff, or no falloff that was used in the old LW.

    Basically, go to all of your lights and untick the node stuff, and then make sure the falloff is set to inverse.
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  5. #20
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    Cool

    Thanks for the input guys.

    No GI is used in order to isolate the problem.
    Distant light has about 0.5 degrees

    Ill have to look more.

    Again it would be awesome if there in future version of LW was a way to fake/predict added samples in this specular indirect so that very high AA and sample settings could be avoided.
    Like interpolation.
    GI interpolation in the new lightwave I have stopped using as I dont undertstand it anymore, hehe. Seems to not be as efficient in creating a smooth interpolation as before.The new interpolation smoothness setting only goes half the way.
    Only brute force now. :-)

    M

  6. #21
    Yes typically i only use brute force now, as while it's slow it's predictable, and less prone to issues, if slower. I struggle with interpolated too tbh. yes, theoretically brute force can result in noisy indirect specular, it's mostly the reflections of reflections, from very bright (necessarily) light sources, which causes fireflies, which is why i was establishing if you had used old-standard, as that can magnify and make fireflies so much worse!

    There's a few paths to solving indirect specular, from using bi-directional path tracing, and VCM, which resolve causicts much better than MC, raytracing, to simply clamping indirect specular, which produces less realistic but normalised results, which are easier to clean. TBH if you look into it every single PBR based renderer which handles indirect specular (and indirect diffuse to an extent) suffers from fireflies, because you cannot multiple importance sample indirect, and either clamp indirect rays or filter the fireflies post-render, neither of which are ideal. Using more modern techniques such as VCM PTC can solve the issue, at the cost of render time, in general.

  7. #22
    Super Member kolby's Avatar
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    Lot of the fireflies comes from very bright and small light sources. Try simulate distant light with the use of area light. It could help in some cases.
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  8. #23
    Super Member Kryslin's Avatar
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    You can also increase the angle of the distant light to 20° or so. Someone mentioned that this helped them with fireflies.
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  9. #24
    Well it would because that would decrease the intensity of the light by several orders of magnitude. It's not a good fix.

  10. #25
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    Quote Originally Posted by Tobian View Post
    Yes typically i only use brute force now, as while it's slow it's predictable, and less prone to issues, if slower. I struggle with interpolated too tbh. yes, theoretically brute force can result in noisy indirect specular, it's mostly the reflections of reflections, from very bright (necessarily) light sources, which causes fireflies, which is why i was establishing if you had used old-standard, as that can magnify and make fireflies so much worse!

    There's a few paths to solving indirect specular, from using bi-directional path tracing, and VCM, which resolve causicts much better than MC, raytracing, to simply clamping indirect specular, which produces less realistic but normalised results, which are easier to clean. TBH if you look into it every single PBR based renderer which handles indirect specular (and indirect diffuse to an extent) suffers from fireflies, because you cannot multiple importance sample indirect, and either clamp indirect rays or filter the fireflies post-render, neither of which are ideal. Using more modern techniques such as VCM PTC can solve the issue, at the cost of render time, in general.
    Thanks guys! How to I approach such a solution? Is this built in options in LW?

    Mats

  11. #26
    Sadly we don't yet have pathtracing in LW, or indirect clamping.

    The only thing we have is ray type switches, to swap out materials to specific rays

    https://docs.lightwave3d.com/display...ay+Type+Switch

  12. #27
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    Quote Originally Posted by Tobian View Post
    Sadly we don't yet have pathtracing in LW, or indirect clamping.

    The only thing we have is ray type switches, to swap out materials to specific rays

    https://docs.lightwave3d.com/display...ay+Type+Switch
    Looks complex but thanks for all the help!

    M

  13. #28
    It's fiddly but once you get it, you'll be 'aha!'

  14. #29
    Hi, no time to read this all but:
    - never use an enviro for interior, use portals instead and set samples high (>20).
    - most of the issues you see are caused by materials having Glossy on AND Raytrace + backdrop, so check that every material in scene has Raytrace only in reflection.
    - A wrong glass can cause a noise feast. Try removing glass and let's see if this improves. If yes, i'll try to explain why and because.

    Best
    Paolo

  15. #30
    Not so newbie member lardbros's Avatar
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    Good advice Paolo
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