non-perpendicular viewing plane

hey all,

i need to figure out some perspective projection matrix math ...

i project onto two walls that stand forming a 90degree angle. each wall has its own projector, and the projectors are placed so they project at the typical perpendicular angle onto the wall.

now imagine standing facing the corner, that is formed by these two walls.

my first try at achieving the right perspective, was to move both camera lookat-values towards that corner. which assumes a viewing plane perpendicular to that viewing angle. and then i changed the frustum values accordingly. this makes the perspective look right, if you look at both screens next to each other (in the software), but gives distortions when looked at on the walls.

i need either another matrix transformation to transform the values i achieved through the lookat-frustum correction further, or a different approach that allows me to project onto a non-perpendicular viewing plane from the start ...

any ideas?

eva

here a patch that should demonstrate the problem:
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