p389fig11.25 Boundaries are not just edge detectors.  If they were, a shaded ellipse would look flat, and uniformly gray.<BR>||  3D vision and figure-ground separation.  Multiple-scale, depth-selective boundary webs. [dark-light, light-dark] boundaries -> complex cells!  If boundaries were just edge detectors, there would be just a bounding edge of the ellipse.  After filling-in, it would look like this:.