Fig. 3.

Linear approximations of the optical flows.A–I show the vector fields obtained by linearly approximating the optical flows shown in the solid boxesin the corresponding panels of Figure 2. In each, the Xindicates the position of the singular point. The drawings of the segment annuli are the same as Figure 2. The agreement between the original optical flow (Fig. 2), and the linear approximation (Fig. 3) is good within the box and in the skin area mainly involved in the contraction and poor outside.