Look-at quaternion using up vector

Question

I have a camera (in a custom 3D engine) that accepts a quaternion for the rotation transform. I have two 3D points representing a camera and an object to look at. I want to

Answer 1

lookAt sideaxis rotatedup

If you normalize this 3 vectors, it is a components of rotation matrix 3x3. So just convert this rotation matrix to quaternion.