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Thread: This has got to be a render bug.

  1. #1
    Super Member Snosrap's Avatar
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    This has got to be a render bug.

    Ok, there has been a lot of buzz about 2018 PBR and noise and fireflies. And I get it, but this has got to be a bug. There is no reason there should be random white fireflies on very matte surfaces as shown in the attached render. I'm rendering @5K and VPR does not reveal these issues prior to rendering.

    Render @ 25% of 4992 x 4992
    Click image for larger version. 

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    Render @ 100% showing clearly the issue.
    Click image for larger version. 

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    Sure I can PS these out, but there is no way AS should miss these pixels.
    Click image for larger version. 

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    What's going on?
    Was the noise filter a late addition as a band aid to help correct the issue with the render engine?

  2. #2
    TrueArt Support
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    Programmers/electricians method of detecting cause: disable feature one by one, until wrong effect disappears.
    Start from disabling Adaptive AA, disabling GI, disabling multi-threading, Polygon Intersection Mode, etc. etc.

    After you will identify source, you will have to prepare test scene for NT developers..

  3. #3
    Super Member CaptainMarlowe's Avatar
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    You can also check the polygon intersection mode. There can be artefacts between tiles if set on fastest. You should get a try with watertight and double precision, it can help.
    https://docs.lightwave3d.com/plugins...t/view/1860271

  4. #4
    Check your scene for a light in front of the camera.
    That is to say, does a light cross the camera's plane, is the camera looking through a light?

    This is a theory I'm working on about some of the fireflies: if your camera goes through a light, fireflies are created.
    You can vary this by making the light bigger, and thus less fireflies. To that end, some of the fireflies can be somewhat controlled.

    Or so show my tests.
    Robert

  5. #5
    I saw that in surfaces that have Principal BSDF material.
    I think is the specular option, I will check later.


    Edit.
    I checked, but I'm not sure, sometimes appear and others times disappear
    Last edited by aperezg; 02-07-2018 at 07:11 AM.

  6. #6
    I make simple test I think this hot pixels might be reflections of another reflections of light and something more in BSDF.
    Scene with one distant light, 16 AA

    Standars shader, no GI:
    Click image for larger version. 

Name:	LW 2018 reflection of reflection standrad no GI.png 
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    Principled BSDF, with GI, reflection and recurion sampling on 1:
    Click image for larger version. 

Name:	LW 2018 reflection of reflection BSDF with GI.png 
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    Principled BSDF, with GI, reflection and recurion sampling on 4:
    Click image for larger version. 

Name:	LW 2018 reflection of reflection BSDF with GI RS 4 RS 4.png 
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    Last edited by MarcusM; 02-07-2018 at 08:04 AM.

  7. #7
    Super Member Snosrap's Avatar
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    Quote Originally Posted by Sensei View Post
    Programmers/electricians method of detecting cause: disable feature one by one, until wrong effect disappears.
    Start from disabling Adaptive AA, disabling GI, disabling multi-threading, Polygon Intersection Mode, etc. etc.
    I don't have time for that. I've bugged this with NT.

    Quote Originally Posted by CaptainMarlowe View Post
    You can also check the polygon intersection mode. There can be artefacts between tiles if set on fastest. You should get a try with watertight and double precision, it can help.
    https://docs.lightwave3d.com/plugins...t/view/1860271
    Yeah I looked at that but I though that was just where polygons come together. This is one big polygon therefore the tiles are not intersecting any.

    Quote Originally Posted by UnCommonGrafx View Post
    Check your scene for a light in front of the camera.
    That is to say, does a light cross the camera's plane, is the camera looking through a light?

    This is a theory I'm working on about some of the fireflies: if your camera goes through a light, fireflies are created.
    You can vary this by making the light bigger, and thus less fireflies. To that end, some of the fireflies can be somewhat controlled.

    Or so show my tests.
    Robert
    Yes I do have lights in front of the camera. But that is a huge advantage of 3D graphics!

    For now I'll fix this in post.

  8. #8
    Super Member Snosrap's Avatar
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    Quote Originally Posted by MarcusM View Post
    I make simple test I think this hot pixels might be reflections of another reflections of light and something more in BSDF.
    Scene with one distant light, 16 AA

    Standars shader, no GI:
    Click image for larger version. 

Name:	LW 2018 reflection of reflection standrad no GI.png 
Views:	131 
Size:	144.3 KB 
ID:	139991

    Principled BSDF, with GI, reflection and recurion sampling on 1:
    Click image for larger version. 

Name:	LW 2018 reflection of reflection BSDF with GI.png 
Views:	147 
Size:	102.9 KB 
ID:	139989

    Principled BSDF, with GI, reflection and recurion sampling on 4:
    Click image for larger version. 

Name:	LW 2018 reflection of reflection BSDF with GI RS 4 RS 4.png 
Views:	154 
Size:	95.2 KB 
ID:	139990
    In my early testing with similar scene I did notice hot spots that looked like errors but on closer inspection they were very small reflections of other spec hits. (Which was cool!) What I'm dealing with here I think is a rendering artifact - error. And if AS is looking at adjacent pixels it should clean this pixel up IMO.

  9. #9
    Quote Originally Posted by Snosrap View Post
    ...And if AS is looking at adjacent pixels it should clean this pixel up IMO.
    After few tests in LW 2018 and LW 2015.3 it is clear to me this is fault of new shaders/renderer.
    In standard material specular reflections are pixelated, in BSDF hot pixels are in stnage places.

    In 2015.3 specular reflections are smooth and nice:
    Click image for larger version. 

Name:	LW 2015-3 reflection of reflection.png 
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    Last edited by MarcusM; 02-08-2018 at 03:40 AM.

  10. #10
    Super Member Snosrap's Avatar
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    Quote Originally Posted by MarcusM View Post
    After few tests in LW 2018 and LW 2015.3 it is clear to me this is fault of new shaders/renderer.
    I agree! In my case how can a bright white 1 pixel hotspot ever be generated in a tan matte wood finish?

  11. #11
    Quote Originally Posted by MarcusM View Post
    In standard material specular reflections are pixelated, in BSDF hot pixels are in stnage places.

    Click image for larger version. 

Name:	LW 2015-3 reflection of reflection.png 
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ID:	140014
    When I first started rendering reflective surfaces, I noticed that reflections that were image maps looked pixelated. If you go into the Image Editor > Source Tab > make sure Use MipMaps is checked. If not you will get pixelated image reflections.

    I have not noticed that ray-traced reflections look pixelated, though.

  12. #12
    Quote Originally Posted by Axis3d View Post
    When I first started rendering reflective surfaces, I noticed that reflections that were image maps looked pixelated. If you go into the Image Editor > Source Tab > make sure Use MipMaps is checked. If not you will get pixelated image reflections.

    I have not noticed that ray-traced reflections look pixelated, though.
    I have done exteremly simple examples showing problems. Good to look better on them... Your last quote is not full and can be misleading.

    Maybe in Snorsap case this have connection with mip maps.
    Last edited by MarcusM; 02-08-2018 at 10:59 AM.

  13. #13
    After made some test.
    I can't find how fix it.

    The white pixels continue existing.
    Click image for larger version. 

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    In standard materials like version 2015.3 the white pixel disappear.
    Click image for larger version. 

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    In BSDF material appear.
    Click image for larger version. 

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  14. #14
    Quote Originally Posted by aperezg View Post
    In BSDF material appear.
    If you render the exact same scene again (maybe as a limited region of only the floor inside the original image size), are the white pixels in the exact same locations or do they change?

  15. #15
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    Those fireflies (as they are called) are typically caused by caustics, or "hot" pixels. (It has many names )
    You can control it with limiting the dynamic range to some degree.

    RebelHill have made a good video about it here: https://www.youtube.com/watch?v=I5wC8xRrDBA
    Last edited by MichaelT; 02-08-2018 at 01:37 PM.

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