Computing the Penetration Depth of Two Convex Polytopes in 3D

  • Authors:
  • Pankaj K. Agarwal;Leonidas J. Guibas;Sariel Har-Peled;Alexander Rabinovitch;Micha Sharir

  • Affiliations:
  • -;-;-;-;-

  • Venue:
  • SWAT '00 Proceedings of the 7th Scandinavian Workshop on Algorithm Theory
  • Year:
  • 2000

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Abstract

Let A and B be two convex polytopes in R3 with m and n facets, respectively. The penetration depth of A and B, denoted as π(A, B), is the minimum distance by which A has to be translated so that A and B do not intersect. We present a randomized algorithm that computes π(A, B) in O(m3/4+Ɛn3/4+Ɛ + m1+Ɛ + n1+Ɛ) expected time, for any constant Ɛ 0. It also computes a vector t such that ∥t∥ = π(A, B) and int(A + t) ∩ B = θ. We show that if the Minkowski sum B⊕(-A) has K facets, then the expected running time of our algorithm is O(K1/2+Ɛm1/4n1/4+m1+Ɛ+n1+Ɛ), for any Ɛ 0. We also present an approximation algorithm for computing π(A, B). For any δ 0, we can compute, in time O(m+n+(log2(m+n))/δ), a vector t such that ∥t∥ ≤ (1 + δ)π(A, B) and int(A + t) ∩ B = θ. Our result also gives a δ-approximation algorithm for computing the width of A in time O(n + (log2 n)/δ), which is simpler and slightly faster than the recent algorithm by Chan [4].