THE UPPER ENVELOPE OF VORONOI SURFACES AND ITS APPLICATIONS

Given a set S of sources (points or segments) in R(d), we consider the surface in R(d+1) that is the graph of the function d(x) = min(p is-a n-element-of s) rho(x, p) for some metric rho. This surface is closely related to the Voronoi diagram, Vor(S), of S under the metric rho. Th e upper envelope of a set of these Voronoi surfaces, each defined for a different set of sources, can be used to solve the problem of findin g the minimum Hausdorff distance between two sets of points or line se gments under translation. We derive bounds on the number of vertices o n the upper envelope of a collection of Voronoi surfaces, and provide efficient algorithms to calculate these vertices. We then discuss appl ications of the methods to the problems of finding the minimum Hausdor ff distance under translation, between sets of points and segments.