Query point visibility computation in polygons with holes

  • Authors:
  • Alireza Zarei;Mohammad Ghodsi

  • Affiliations:
  • Computer Engineering Department, Sharif University of Technology, Tehran, Iran;Computer Engineering Department, Sharif University of Technology, Tehran, Iran and IPM School of Computer Science, Niavaran, Tehran, Iran

  • Venue:
  • Computational Geometry: Theory and Applications
  • Year:
  • 2008

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Abstract

In this paper, we consider the problem of computing the visibility of a query point inside polygons with holes. The goal is to perform this computation efficiently per query considering the cost of the preprocessing phase. Our algorithm is based on solutions in [A.L.P. Bose, J.I. Munro, Efficient visibility queries in simple polygons, Computational Geometry: Theory and Applications 23 (3) (2002) 313-335] and [M.T.B. Aronov, L. Guibas, L. Zhang, Visibility queries and maintenance in simple polygons, Discrete and Computational Geometry 27 (4) (2002) 461-483] proposed for simple polygons. In our solution, the preprocessing is done in time O(n^3logn) to construct a data structure of size O(n^3). It is then possible to report the visibility polygon of any query point q in time O((1+h^')logn+|V(q)|), in which n and h are the number of the vertices and holes of the polygon respectively, |V(q)| is the size of the visibility polygon of q, and h^' is an output and preprocessing sensitive parameter of at most min(h,|V(q)|). This is claimed to be the best query-time result on this problem so far.