Lines in space-combinators, algorithms and applications

  • Authors:
  • B. Chazelle;H. Edelsbrunner;L. Guibas;M. Sharir

  • Affiliations:
  • Princeton University;University of Illinois at Urbana-Champaign;Stanford University and DEC Systems Research Center;New York University and Tel Aviv University

  • Venue:
  • STOC '89 Proceedings of the twenty-first annual ACM symposium on Theory of computing
  • Year:
  • 1989

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Abstract

We study combinatorial and algorithmic problems involving arrangements of n lines in 3-dimensional space, and then present applications of our results to a variety of problems on polyhedral terrains. Our main results include:A tight &THgr;(n2) bound on the complexity of the space of all lines passing above all the n given lines (their “upper envelope”) and satisfying a certain orientation consistency constraint.A preprocessing procedure using near-quadratic time and storage that builds a structure supporting &Ogr;(log n) time queries for testing if a line lies above all the given lines.An &Ogr;(n4/3+&egr;) randomized expected time algorithm, for any fixed &egr; 0, that tests the “towering property”: do n given red lines lie all above n given blue lines?A preprocessing procedure for a polyhedral terrain &Sgr; with n edges, that uses near-quadratic time and storage and builds a structure supporting &Ogr;(log2 n) time rayshooting queries for computing the first intersection of an arbitrary query ray with &Sgr;.Finding the smallest vertical distance between two disjoint polyhedral terrains with a total of n edges, in time &Ogr;(n4/3+&egr;), for any &egr; 0.Computing the upper envelope (pointwise maximum) of two polyhedral terrains with a total of n edges, in time &Ogr;(n1.5+&egr; + klog2 n), for any &egr; 0, where &kgr; is the size of the output envelope.The tools used to obtain these results include Plücker coordinates for lines in space, random sampling in geometric problems, and a new variant of segment trees.