Shapes, shocks and wiggles

Abstract We earlier introduced an approach to categorical shape description based on the singularities (shocks) of curve evolution equations. The approach relates to many techniques in computer vision, such as Blum's grass re transform, but since the motivation was abstract, it is not clear that it should also relate to human perception. We now report that this shock-based computational model can account for recent psychophysical data collected by Christina Burbeck and Steve Pizer. In these experiments subjects were asked to estimate the local centers of stimuli consisting of rectangles with \wiggles" (sides modulated by sinusoids). Since the experiments were motivated by their \core" model, in which the scale at which boundary detail is represented is proportional to object width, we conclude that such properties are also implicit in shock-based shape descriptions.