Ridge Curves and Shape Analysis

Ridge curves are important features in human vision (see Koenderink, 1990, p.295). In this paper we apply a simple algebraic criterion of Porteous (1994) to the problem of nding ridge curves in machine vision. This work provides a simpler approach than other existing methods (see for example, Thirion and Gourdon, 1992, and Hosaka, 1992). To identify ridge curves in practice on surface data it is necessary rst to smooth the data, which we do using thin-plate splines and related kriging procedures. After validating our methodology, we illustrate its use on a set of laser range data of the human head.