tquack

01-03-2003, 03:44 AM

We get from another application a Projection Matrix of dimension 3x4, which maps 3d points (homogeneous coordinates) to the image plane (2d points, homogeneous coordinates).

Now we want to use this matrix in opengl.

The problems we encounter are

1) There seems to be no direct access to the "final" projection matrix, which consists of modelview-matrix, projection-matrix, viewport in terms of opengl naming.

2) Our Matrix is of dimension 3x4 (which is mathematically correct if you project from 3d to 2d environment) - matrix dimensions in opengl (for modelview matrix, projection matrix) are 4x4!!

a) How does opengl achieve 3d to 2d projection (with 2d meaning the screen) using 4x4 matrices???

b) How can we use our matrix in opengl under these circumstances?

Thanks for any hints!

Now we want to use this matrix in opengl.

The problems we encounter are

1) There seems to be no direct access to the "final" projection matrix, which consists of modelview-matrix, projection-matrix, viewport in terms of opengl naming.

2) Our Matrix is of dimension 3x4 (which is mathematically correct if you project from 3d to 2d environment) - matrix dimensions in opengl (for modelview matrix, projection matrix) are 4x4!!

a) How does opengl achieve 3d to 2d projection (with 2d meaning the screen) using 4x4 matrices???

b) How can we use our matrix in opengl under these circumstances?

Thanks for any hints!