[osg-users] strange ShadowMap behavior

Ben Axelrod baxelrod at coroware.com
Mon Sep 22 13:05:29 PDT 2008


I am seeing strange shadow artifacts on my model when I use a ShadowMap.  The artifacts get worse as I increase the size of my ground plane.  You can see the artifacts get progressively worse in these images:

http://www.benaxelrod.com/temp/3x3.png
http://www.benaxelrod.com/temp/5x5.png
http://www.benaxelrod.com/temp/7x7.png
http://www.benaxelrod.com/temp/10x10.png <- this is the desired size of ground plane
http://www.benaxelrod.com/temp/12x12.png

You can see strange gradients on the humanoid's hands and feet.  And the shadow gets more and more pixilated.

I am using OSG 2.6 on Debian Etch with a NVidia 7300 LE graphics card.

This is how I configure the ShadowMap:

shadowmap->setTextureSize(osg::Vec2s(1024, 1024));
shadowmap->setPolygonOffset(osg::Vec2(1.1f, 4.0f));

Do I need to tune these parameters?  If so, how?  Are there more parameters I need?  And what do these parameters control exactly?

Thanks,
-Ben
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