Hello,

I have noticed that the basic 3D rotation matrices in http://en.wikipedia.org/wiki/Rotation_matrix
rotate vectors clockwise and not counter-clockwise, when the axis about which they occur points toward me !

For example: the following operation yields the vector (0,1,0)

[1 0 0 ] [0]

[0 cos(90) sin(90) ] X [0]

[0 -sin(90) cos(90) ] [1]

Am I missing something ?

Thank you for your help

I think the problem is that the given matrix is a row-major matrix, which means row vectors. You're trying to use it as a column-major w/ column vector.

So the operation you want to do is really:

[0 0 1] X [1 0 0 ] = [0 -1 0]

[0 cos(90) sin(90) ]

[0 -sin(90) cos(90) ]

Remember when you look at a matrix it's very important if it's row-major or column-major and right-handed vs left-handed. The above matrix gives you the correct result if it's right-handed row-major.