Determining the visibility of a planar set of line segments in O(n log log n) time

  • Authors:
  • Frank Dévai;Marina L. Gavrilova

  • Affiliations:
  • London South Bank University, London, UK;Department of Computer Science, University of Calgary, Calgary, AB, Canada

  • Venue:
  • ICCSA'07 Proceedings of the 2007 international conference on Computational science and Its applications - Volume Part II
  • Year:
  • 2007

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Abstract

The visibility of a planar set of n disjoint line segments, arising from the scanline approach to rendering three-dimensional scenes, is one of the classic problems in computer graphics. In order to solve the problem quickly, many authors proposed binary space partitioning (BSP) as a preprocessing, possibly breaking up the input line segments so that visibility is determined in time linear in the number of resulting segments. Tóth [Discrete & Comput. Geometry 30, 1 pp. 3-16, 2003] demonstrated that a BSP may result in Ω(n log n/ log log n) line segments. We demonstrate that the time and space complexities of the problem are Θ(n log n) and Θ(n) respectively, under the algebraic RAM model of computation. Introducing a more realistic model, a RAM with arbitrary-precision rational arithmetics, a deterministic algorithm is given that solves the problem directly, without the need of preprocessing, in O(n log log n) time and O(n) space, regardless of the precision of the input data.