J.E. Boyd and J.J. Little
phase-based. We will consider only the first two categories since they are the
most popular.
Differential flow algorithms find solutions to a differential equation, the optical
flow constraint equation [26],
Ixu + Iyv + It = 0
where I is the spatiotemporal (x, y, and t) image sequence, Ix, Iy, It are the
partial derivatives of I with respect to space and time, and u and v are the
x and y image velocities, i.e., the optical flow. Fig. 4 shows a sample frame of
optical flow computed using the Lucas and Kanade [27] least-squares algorithm
for differential flow.