1. A method for determining motion vectors from one point in one image frame of a scene to corresponding points in at least two other image frames of the scene, wherein the frames are obtained in a capture process utilizing one or more cameras, said method comprising the steps of: providing first, second and third images of a scene under perspective projection with unconstrained motion of the camera, wherein points (x′,y′) and (x″,y″) in the second and third frames are projections of the same spatial points (x,y) in the first frame; specifying a system of trifocal tensors and optical flow equations that describe point correspondence across the three images; and applying both a geometric constraint of trilinearity and an appearance constraint of constant brightness, thereby utilizing a trilinear constraint and a constant brightness constraint to obtain the pointwise displacement between the three frames simultaneously.