Reporting intersecting pairs of polytopes in two and three dimensions

Abstract

Let P = {P1,…, Pm} be a set of m convex polytopes in Rd, for d = 2, 3, with a total of n vertices. We present output-sensitive algorithms for reporting all k pairs of indices (i, j) such that Piintersects Pj. For the planar case we describe a simple algorithm with running time O(n4/3log n + k), and an improved randomized algorithm with expected running time O((n logm + k)α(n) log n) (which is faster for small values of k). For d = 3, we present an O(n8/5+ε+ k)-time algorithm, for any ε > 0. Our algorithms can be modified to count the number of intersecting pairs in O(n4/3logO(1) n) time for the planar case, and in O(n8/5+ε) time and R3.