reversing transformation


I’m writing an opengl application which i need to revert the geometric processing pipeline.
A two-dimensional screen location coud have originated from anywhere on an entire line in three-dimensional-space. if I use glUnproject i must specify a window deph coordinate (winz). winz=0.0 will request the world coordinate of the transformed point at the near clipping plane, while winz=1.0 will request the point at the far clipping planes.
I’m intersted to abtain a point at my plane for esample a z=0 plane (the plane xy) . For to do this I would use a my reversing transformation but i have big problems.
Can I help me?

Rino Billa.

I don’t know if i have understood your problem correctly, but to make a reverse transformation you can multiply with the inverted transformation matrix.