A SEMIAUTOMATIC SYSTEM FOR EDGE TRACKING WITH SNAKES

Active contour models, or ''snakes,'' developed in (Kass et al. 1988), use a simple physical model to track edges in image sequences. Snakes as originally defined however, tend to shrink, stretch and slide back and forth in unwanted ways along a tracked edge and are also confused by multiple edges, always grabbing the nearest one. In this paper a s emi-automatic system is presented that combines motion estimation tech niques with snakes to overcome these problems. An algorithm is present ed that uses a block matching technique to guide the endpoints of the snake, optical flow to push the snake in the direction of the underlyi ng motion, followed by the traditional snake edge-fitting minimization process. We use this technique for tracking facial features of an act or for driving computer animated characters.