Complete subdivision algorithms, II: Isotopic meshing of singular algebraic curves

  • Authors:
  • Michael Burr;Sung Woo Choi;Ben Galehouse;Chee K. Yap

  • Affiliations:
  • Courant Institute, NYU, 251 Mercer Street, New York, NY 10012, United States;Department of Mathematics, Duksung Womens University, Seoul 132-714, Republic of Korea;Courant Institute, NYU, 251 Mercer Street, New York, NY 10012, United States;Courant Institute, NYU, 251 Mercer Street, New York, NY 10012, United States and Korea Institute of Advanced Study, 85 Hoegiro (Cheongnyangni-dong 207-43), Dongdaemun-gu, Seoul 130-722, Republic o ...

  • Venue:
  • Journal of Symbolic Computation
  • Year:
  • 2012

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Abstract

Given a real valued function f(X,Y), a box region B"0@?R^2 and @e0, we want to compute an @e-isotopic polygonal approximation to the restriction of the curve S=f^-^1(0)={p@?R^2:f(p)=0} to B"0. We focus on subdivision algorithms because of their adaptive complexity and ease of implementation. Plantinga & Vegter gave a numerical subdivision algorithm that is exact when the curve S is bounded and non-singular. They used a computational model that relied only on function evaluation and interval arithmetic. We generalize their algorithm to any bounded (but possibly non-simply connected) region that does not contain singularities of S. With this generalization as a subroutine, we provide a method to detect isolated algebraic singularities and their branching degree. This appears to be the first complete purely numerical method to compute isotopic approximations of algebraic curves with isolated singularities.