Rotation matrix R1 w.r.t to another matrix, say R2

Question

I have two camera rotation matrices R1 and R2. Both of them are calculated w.r.t. a reference frame.

My ultimate goal is to perform stereo 3D triangulation using the corresponding features from these two images.

My question, given two rotation matrices R1 & R2 w.r.t some reference frame, how can I calculate the matrix 'R' which represents the rotation between first and second frame?

Thanks

Answer 1

If R1 is a rotation component of the first camera matrix and R2 - of the second, then the second camera frame is rotated by R2*inv(R1) with respect to the first camera frame. I.e, given a point X in a first frame, it will be R2*inv(R1)*X in the second frame.