Values for the projection matrix?

[lrianu]

The values used in MatrixState.set_projection_matrix() don't match fx, fy, cx, cy values from what I see in the calibration yaml. Where do they come from? I'm also curious why not use projection matrix functions already available in OpenGL, like Matrix.projectionM() and Matrix.frustrumM(). It looks like you tried but then created your own custom matrix. Did the OpenGL functions not work? Thanks, just trying to learn.