Consider a set of n points in the Euclidean plane each of which is continuously moving along a given trajectory. At each instant in time, the points define a Voronoi diagram. As the points move, the Voronoi diagram changes continuously, but at certain critical instants in time, topological events occur that cause a change in the Delaunay diagram. In this paper, we present a method of maintaining the Voronoi diagram over time, while showing that the number of topological events has a nearly cubic upper bound of O(n2λ3(n)), where λ3,(n) is the maximum length of an (n, s)-Davenport-Schinzel sequence and s is a constant depending on the motions of the point sites. In the special case of points moving at constant speed along straight lines, we get s = 4, implying an upper bound of O(n32α(n)), where α(n) is the extremely slowly-growing inverse of Ackermann’s function. Our results are a linear-factor improvement over the naive quartic bound on the number of topological events. In addition, we show that if only k points are moving (while leaving the other n - k points fixed), there is an upper bound of O(kn λs(n) + (n - k)2 λs,(k)) on the number of topological events, which is nearly quadratic if k is constant. We give a numerically stable algorithm for the update of the topological structure of the Voronoi diagram, using only O(log n) time per event (which is worst-case optimal per event).
CITATION STYLE
Guibas, L. J., Mitchell, J. S. B., & Roos, T. (1992). Voronoi diagrams of moving points in the plane. In Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) (Vol. 570 LNCS, pp. 113–125). Springer Verlag. https://doi.org/10.1007/3-540-55121-2_11
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