Raytracing Problem

# 1 18-02-2011 , 08:23 AM

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Join Date: Feb 2011

Posts: 2

I thought it was an issue with final gather, but it's a problem with the raytracing itself. light will pass through "cracks" that aren't there at all and on models that have smoothed normals, and create streaks or blotches of light. I've been playing around wit the normals and think that might be the issue, but I've redone the normals every way I can think of..

here are some screenshots:
https://dl.dropbox.com/u/21092303/ren..._issues/1.jpeg
https://dl.dropbox.com/u/21092303/ren..._issues/2.jpeg
https://dl.dropbox.com/u/21092303/ren..._issues/3.jpeg
https://dl.dropbox.com/u/21092303/ren..._issues/4.jpeg

same thing happens when I export the same models as OBJ (only happens with the sofas) without the normals information even and reimport it into a totally new scene. I'm using directional light.

here's the chair OBJ:
https://dl.dropbox.com/u/21092303/ren...sues/chair.obj

I can't see any hidden faces or double edges. what is going on? I have a good amount of experience with Maya, but I'm stumped by such a simple problem..

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# 2 18-02-2011 , 12:54 PM

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Posts: 1,889

I'm guessing you've already considered near camera clipping? If I set my near camera clipping too high, I get similar results. Not that that's the issue though.

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# 3 18-02-2011 , 02:59 PM

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Join Date: Oct 2007

Location: London

Posts: 2,381

i can't even tell what i'm looking at tbh.

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# 4 19-02-2011 , 02:14 AM

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Join Date: Feb 2011

Posts: 2

basically in areas that are supposed to be in complete shadow (such as the curve where the back of the chair and base connect in the third image) there will be a strange sliver or area of light that does not make sense. Same with a similar object in picture 4 where the arm rest connects to the base there is a triangle of light that is supposed to be in shadow.

both objects are fairly simple meshes that only consist of a single mesh and should not have any problems. near clipping isn't the problem.

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# 5 23-02-2011 , 05:43 PM

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Join Date: Nov 2002

Location: USA

Posts: 1,170

could that be just a reflection of something else in the scene? the chair object you attached has a lambert shading group - but the material is of type phong with 0.5 reflectivity ??? but that is me beeing stupid - you probably did that on purpose ....

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# 6 23-02-2011 , 08:28 PM

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Join Date: Dec 2006

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Posts: 3,522

I took a look at the model, I noticed the problem went away when the model is smoothed (which also got rid of those tris in there). Which leaves me to believe it may be caused by the low poly count. You're ending up with some seriously non planar faces and there could be some trouble deciding if they should be illuminated or not. I ditched the phong shader because the highlights and reflections were just getting in the way.

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