When constructing an orientation matrix, are the rows of the matrix the axis?
The matrix is row-major and I'm multiplying vectors on the right (Mv). So, the matrix looks like
r0c0 r0c1 r0c2 r1c0 r1c1 r1c2 r2c0 r2c1 r2c2
From a mathematical point of view, it depends on in which order you are multiplying the vectors with the matrix.
That depends, if it is in row major form then yes, for column major form no.
Where does this matrix come from?