Finding shadows among disks

N. Jovanovic, J.H.M. Korst, Z. Aleksovski, W.P.A.J. Michiels, J.J. Lukkien, E.H.L. Aarts

Research output: Other contribution

1 Citation (Scopus)


Given a set of n non-overlapping unit disks in the plane, a line l is called blocked if it intersects at least one of the disks and a point p is called a shadow point if all lines containing p are blocked. In addition, a maximal closed set of shadow points is called a shadow region. We derive properties of shadow regions, and present an O(n^4) algorithm that outputs all shadow regions. We prove that the number of shadow regions is O(n^4) for some instances, which implies that the worst-case time complexity of the presented algorithm is optimal.
Original languageEnglish
Number of pages6
Publication statusPublished - 2012
Externally publishedYes


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