I'm having some incredible trouble building transformation matrices to simulate a camera. This is for OpenGL specifically, but since I'm doing it by hand it doesn't matter. Here's what's going on, I store the camera's position vector and orientation vectors, left/up/forward. Every frame I do as follows, check for button presses, for left/right I yaw by some small increment, for up/down I pitch. Currently I pitch by the camera's left vector (creating a rotation matrix out of the left vector and applying it to the 3x3 matrix [L|U|F], and yaw by the up vector similarly. Then I build a view matrix out of the inverse orientation/position vectors and load it as the current modelview matrix. I don't load the identity matrix at all, since it makes no sense to load it then replace it. The problem is that yaw + pitch isn't properly represented. For example if I yaw by 90, then pitch, i get a roll. I've calculated all this out by hand and it seems that the view matrix I load as the current modelview matrix isn't composed of the proper rotations. Here is an example. Pos = 0,0,0; L = 1,0,0; U = 0,1,0; F = 0,0,1; R = [L|U|T] T = -Rt*P The resulting 4x4 view matrix is: Rt|P 0001 Now, if I rotate R through L and build a new view matrix and load that all my geometry after that is rotated in the opposite direction, which is good. Now, if I take the newly rotated R and rotate through U and build a view matrix out of that the new view matrix doesn't represent represent a yaw, then a pitch, like I said, I get a yaw then a roll. Can anyone point out my error to me? I'm really having a hard time here... ------------ - outRider - Edited by - outRider on February 10, 2002 12:04:22 AM

Nobody has any ideas?

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- outRider -

I''m not quite sure but do OpenGL rowmajor matrices. You said you do i all by hand but do you glLoadMatrix that matrix?

Yes I load it every frame. I know OpenGL orients matrices differently, column major, but I declare my 4x4 matrices as float[16], so it shouldn''t matter.

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- outRider -

"but I declare my 4x4 matrices as float[16], so it shouldn''t matter."

I matters still.

> ... For example if I yaw by 90, then pitch, i get a roll ...

This sounds to me like a Gimbal lock problem.