working with rotation matrices
I have a rotation matrices, and I have to do a few things with it.
If the matrix represents the rotations around three axis,
1) how do you apply the rotation around 1 axis to another matrix ?
for example : I want one matrix to have only the y-rotation of the other matrix. For example, when I want a 3rd person camera.
2) how do you set the rotation around a specific axis to a value. But without touching the rotations around the other axis ?
For example, when I want a camera to look at a specific height.
Thanks in advance.