Each orientation could be composed by elementary rotations of the object frame with respect to the reference frame.
- Successive rotations of an object about the object frame is obtained by ==premultiplication== of rotation matrices.
- Successive rotations of an object about the reference frame is obtained by ==postmultiplication== of rotation matrices.
Where premultiplication and postmultiplication only mean when the elementary rotation matrix is multiplied (if at the beginning or at the end).
NOTE: The object frame is referenced to the reference frame
The composition of various elementary rotation matrices gives form to a complete rotation matrix
We need also to define ==how the elementary rotation are composed==, to do this we use the rotation matrix descriptors.