Cutting hyperplane arrangements

  • Authors:
  • Jiří Matoušek

  • Affiliations:
  • -

  • Venue:
  • SCG '90 Proceedings of the sixth annual symposium on Computational geometry
  • Year:
  • 1990

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Abstract

We will consider an arrangement H of n hyperplanes in Ed (where the dimension d is fixed). An &egr;-cutting for H will be a collection of (possibly unbounded) d-dimensional simplices with disjoint interiors, which cover all Ed and such that the interior of any simplex is intersected by at most &egr;n hyperplanes of H. We give a deterministic algorithm, finding a (1/r)-cutting with &Ogr;(rd(log r)C) simplices in time &Ogr;(n(log n)Ard-1 (log r)B) (A,B,C are constants dependent on dimension). In a similar time bound (with an additional &Ogr;(r&Ogr;(1)) overhead) we can also find a (1/r)-net for the range space (X, H(X)), where X is a n-point set in Ed and H(X) denotes the set of all subsets of X which can be cut by a halfspace. This (1/r)-net has size &Ogr;(r log r), which matches the best known existence result; in fact, the method gives a constructive existence proof. In the plane, we can obtain a (1/r)-cutting of optimal size &Ogr;(r2) in time &Ogr;(nr) (which is optimal if we want to compute also the collection of lines intersecting each simplex of the cutting). This improves the result of Agarwal, and our algorithm is conceptually simpler.