[osg-users] normal vectors aren't causing culling

Paul Martz pmartz at skew-matrix.com
Sat Nov 28 08:32:36 PST 2009

Jim Brooks wrote:
> "normal vectors aren't causing culling"
> I had a misunderstanding that a scene-graph
> would do back-face culling by normal vectors.
> OSG does NOT.

Right. OSG does not do _face_ culling (culling of individual primitives) 
based on the normal.

However, OSG can do _Drawable_ culling based on a normal. This is how 
VPB databases cull away the back half of the planet. There is a custom 
cull callback (in osgTerrain, I think) that does this. You need to 
explicitly attach it; OSG doesn't use it by default.

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