Ive got a strange problem with my shadowvolumes:
Small cracks appear in the volume, depending on my position/where I look at. ( This can not be solved with glPolygonOffset, Ive been playing around with all kinds of values. ).
If I render the volume in wireframe, I can see that the lines that intersect the surface, on which the shadow is supposed to be visible, move slightly around as I change my position.
At first I guessed this is caused by the extrusion ( setting w=0 ), but then I just rendered a normal line with 2 vectors that have w=1 and I can still see the line move when I get really close.
Tough being able to see the lines moving can only be seen at a very low distance to the line, the cracks in the volume are visible across a high distance and it simply looks ugly
I started thinking about the projection matrix, but since the effect occurs with both, my infinite frustum and gluLookAt, I dont really think that this can be the problem.