Level set methods: An overview and some recent results

The level set method was devised by S. Osher and J. A. Sethian (1988, J. Co mput, Phys. 79, 12-49) as a simple and versatile method for computing and a nalyzing the motion of an interface Gamma in two or three dimensions, Gamma bounds a (possibly multiply connected) region Omega. The goal is to comput e and analyze the subsequent motion of Gamma under a velocity field v. This velocity can depend on position, time. the geometry of the interface, and the external physics. The interface is captured for later time as the zero level set of a smooth (at least Lipschitz continuous) function phi (x. t); i.e., Gamma (t) = {x \ phi (x, t) = 0}. phi is positive inside Omega, negat ive outside Omega. and is zero on Gamma (t). Topological merging and breaki ng are well defined and easily performed. In this review article we discuss recent variants and extensions, including the motion of curves in three di mensions, the dynamic surface extension method. fast methods for steady sta te problems, diffusion generated motion, and the variational level set appr oach. We also give a user's guide to the level set dictionary and technolog y and couple the method to a wide variety of problems involving external ph ysics, such as compressible and incompressible (possibly reacting) flow, St efan problems. kinetic crystal growth, epitaxial growth of thin films, vort ex-dominated flows, and extensions to multiphase motion, We conclude with a discussion of applications to computer vision and image processing. (C) 20 01 Academic Press.