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From: Mousehunter
Subject: bright triangles in mesh2
Date: 14 Jan 2007 16:25:00
Message: <web.45aa9ea6d1d72407c32be1770@news.povray.org>
I'm having a problem with a smooth mesh2. For a face recognition project I
make smooth mesh2 objects from datasets. Each data set is a little
different, so is every mesh.

After solving the strange lighting problems with the double_illuminate, I
kept some strange bright triangles:

www.wattsup06.com/images/render.png

As I just said, every mesh2 is a little different; most parts of the renders
are smooth, except for 1 to 3 triangles which appear at different places for
slighty different meshes.

Help would be appreciated :)
Sid


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From: Warp
Subject: Re: bright triangles in mesh2
Date: 14 Jan 2007 17:40:20
Message: <45aab153@news.povray.org>
Mousehunter <svi### [at] click2cnet> wrote:
> After solving the strange lighting problems with the double_illuminate, I
> kept some strange bright triangles:

  This is most probably caused by the inverted normals problem described
here:

http://tag.povray.org/povQandT/SmoothTriangleArtifact/index.html

  Also this is good to know about smooth triangles:

http://tag.povray.org/povQandT/TheShadowLineArtifact/index.html

  Unfortunately there's no solution currently. If your objects cast
shadows then you may want to try making them closed so that they
will self-shadow. If they are shadowless, then the problem becomes
more difficult.

  Increasing the mesh resolution (ie. more triangles) might help
a bit (at least reduce the sice of the artifacts).

-- 
                                                          - Warp


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From: Mousehunter
Subject: Re: bright triangles in mesh2
Date: 14 Jan 2007 18:15:00
Message: <web.45aab8f22b4aaefbc32be1770@news.povray.org>
>
>   This is most probably caused by the inverted normals problem described
> here:
>
> http://tag.povray.org/povQandT/SmoothTriangleArtifact/index.html
>
>   Also this is good to know about smooth triangles:
>
> http://tag.povray.org/povQandT/TheShadowLineArtifact/index.html
>

I read those, but I found it strange that it all works for all the other
triangles. A small change in position or normal makes the artifact come or
disappear...


>   Increasing the mesh resolution (ie. more triangles) might help
> a bit (at least reduce the sice of the artifacts).
>

Indeed, but the data I have is on a 40x40 grid. And when the normals are
determined, the outer bounds are lost, so only 38x38 remains. Not really
fancy for face recognition...


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