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OpenGL Retrieving lookat vector from matrix.

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Fase    133
Hello all, After many hours of searching the www about opengl camera methods, I've become none the wiser. Many tutorials provide examples with magic code that don't make sense to me. Finally I've decided to take the following approach: - Use CML to take care of math. - Use euler angles (no banking) to construct quaternion, so I can map mouseX to heading, and mouseY to pitch. - Use CML math to calculate a rotation matrix from quaternion. - Extract lookatvector and right vector from matrix and calculate new camera position. My(limited) understanding of OpenGl Matrices tells me that the given rotation matrix contains the following:
m(0,0) = rv.x ,  m(0,1) = rv.y ,  m(0,2) = rv.z, m(0,3) = 0
m(1,0) = uv.x ,  m(1,1) = uv.y ,  m(1,2) = uv.z, m(1,3) = 0
m(2,0) = fv.x ,  m(2,1) = fv.y ,  m(2,2) = fv.z, m(2,3) = 0
m(3,0) = 0    ,  m(3,1) = 0    ,  m(3,2) = 0   , m(3,3) = 1
where r is the right vector, u is the up vector and f is the forward(lookat) vector. Now I want to calculate my new camera position like this:
position.x += (lookAtVector.x * forward) + (upVector.x * up) + (rightVector.x * right);
position.y += (lookAtVector.y * forward) + (upVector.y * up) + (rightVector.y * right);
position.z += (lookAtVector.z * forward) + (upVector.z * up) + (rightVector.z * right);
The problem with the code above is that the lookatvector and rightvector make absolutely no sense at all. The rotation is perfectly fine though. Can anyone give me a clue about what I'm doing wrong here? Thanks in advance

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KulSeran    3267
A 4x4 matrix transforms you to another coordinate system.
if your origional system is [x y z pos] then the matrix to your new
system takes the form of
[at up left pos] now been forever since i looked at opengl, so it could be
[at up left pos]'
so each column(or row, i forget) of your camera matrix should be one of the directions you are looking for.

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V-man    813
If you want, download
I think the function name is glhExtractLookAt
Source code is available.

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Fase    133
Thanks for the quick replies, much apreciated.

I will take a look at your library V-man. It looks interesting.

However I managed to solve the problem.
All I needed to do was to transpose the rotation matrix and retrieve the corresponding vectors.
Actualy I now do this at the quaternion stage using cml::quaternion_get_basis_vectors() after taking the conjugate of the rotation quaternion.

Thanks again for the reply's!

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