numpy - Compute absolute rotaion matrix from relative rotation matrix

Question

Using a homography matrix, I am able to find a mapping from one image to another. From this matrix I can also compute a relative rotation matrix between the two images. How can I then compute an absolute rotation matrix? And what are the differences between these two matrices?

question from:https://stackoverflow.com/questions/66055768/compute-absolute-rotaion-matrix-from-relative-rotation-matrix

Answer 1

General points:

• A general homography between images does not imply a camera motion that is a pure rotation.
• However, camera motion that is a pure rotation, or one whose translation is very small compared to the distance from the camera and the scene, is well modeled by a homography.

Specifically to your question:

• A "relative" rotation is just that, a motion from the orientation of the first camera to the one of the second camera.
• An "absolute" rotation, or orientation, describes a motion with respect to a specified "reference" coordinate frame that is constant and independent of the camera motion.
• As a special case, if you have only two camera poses, and you use the first one as the reference, then the relative pose of the second one is also its absolute pose.