Finding point correspondences and determining motion of a rigid object from two weak perspective views

The authors present a method which reduces an n-point problem to a set of four-point problems. The effort of reduction takes O(n) steps and it also takes O(n) steps to construct all possible mappings of an n-point set from the solution to a four-problem. Other results include (1) coplanarity condition of four points in two views, (2) recovering the tilt direction of the rotational axis using four points in two views, and (3) recovering the scaling factor