New Results on Visibility in Simple Polygons

  • Authors:
  • Alexander Gilbers;Rolf Klein

  • Affiliations:
  • Institute of Computer Science, University of Bonn, Bonn, Germany 53117;Institute of Computer Science, University of Bonn, Bonn, Germany 53117

  • Venue:
  • WADS '09 Proceedings of the 11th International Symposium on Algorithms and Data Structures
  • Year:
  • 2009

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Abstract

We show that (A), 14 points on the boundary of a Jordan curve, and (B), 16 points in convex position encircled by a Jordan curve, cannot be shattered by interior visibility domains. This means that there always exists a subset of the given points, for which no point of the curve's interior domain sees all points of the subset and no point of its complement. As a consequence, we obtain a new result on guarding art galleries. If each point of the art gallery sees at least an r -th part of the gallery's boundary, then the art gallery can be covered by 13 ·C ·r logr guards placed on the boundary. Here, C is the constant from the *** -net theorem.