BIT Numerical Mathematics

, Volume 27, Issue 4, pp 458–473 | Cite as

Corrections to Lee's visibility polygon algorithm

  • B. Joe
  • R. B. Simpson
Part I Computer Science


We present a modification and extension of the (linear time) visibility polygon algorithm of Lee. The algorithm computes the visibility polygon of a simple polygon from a viewpoint that is either interior to the polygon, or in its blocked exterior (the cases of viewpoints on the boundary or in the free exterior being simple extensions of the interior case). We show by example that the original algorithm by Lee, and a more complex algorithm by El Gindy and Avis, can fail for polygons that wind sufficiently. We present a second version of the algorithm, which does not extend to the blocked exterior case.

CR Categories



computational geometry visibility 


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Copyright information

© BIT Foundations 1987

Authors and Affiliations

  • B. Joe
    • 1
    • 2
  • R. B. Simpson
    • 1
    • 2
  1. 1.Dept. of Computing ScienceUniversity of AlbertaEdmontonCanada
  2. 2.Dept. of Computer ScienceUniversity of WaterlooWaterlooCanada

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