[PyOpenGL-Users] Shadowmapping Strangeness

[Ian M. <geo...@gm...>]

Hello,

I have a problem with shadowmapping in my shaders.  The occluder appears to
be casting a shadow correctly on other objects, but not correctly on
itself.  The effect is difficult to describe, but it looks sort of like the
shadowmap is rotating twice as fast as the object rotates and is flipped
(occluded not shadowed and vice-versa).

The following example program displays the effect:
geometrian.com/shadowmapping%20problem.zip.  The occluder is a spaceship
from turbosquid.com rendered with VBOs (thanks!) and the floor is a single
quad with a brick texture applied.  As you can see, the shadow on the floor
looks correct (see below), but the shadow on the spaceship is not.  Try
rotating the camera and the spaceship (left or right click + drag
respectively).

My *guess *is that the texture matrix is not being set up correctly.  The
floor may look fine, but the floor is 2D, so the "flipped" effect mentioned
earlier has no real effect.  Also, when the floor is rotated, the shadow
rotates with it, so the rotation problem is still there too.  The spaceship
shows these problems quite obviously.

I think I should be able to fix the "flipped" problem in the shader, but
what do I do about the shadow rotation problem?

Thanks a ton,
Ian