Computation of optimal composite re-parameterizations

  • Authors:
  • Paolo Costantini;Rida T. Farouki;Carla Manni;Alessandra Sestini

  • Affiliations:
  • Dipartimento di Matematica, Università di Siena Via del Capitano 15, 53100 Siena, Italy;Department of Mechanical and Aeronautical Engineering, University of California, Davis, CA 95616, USA;Dipartimento di Matematica, Università di Torino, Via Carlo Alberto 10, 10123 Torino, Italy;Dipartimento di Energetica, Università di Firenze, Via Lombroso 6/17, 50134 Firenze, Italy

  • Venue:
  • Computer Aided Geometric Design
  • Year:
  • 2001

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Abstract

Rational re-parameterizations of a polynomial curve that preserve the curve degree and [0,1] parameter domain are characterized by a single degree of freedom. The ''optimal'' re-parameterization in this family (that comes closest under the L"2 norm to arc-length parameterization) can be identified by solving a quadratic equation, but may exhibit too much residual parametric speed variation for motion control and other applications. Closer approximations to arc-length parameterizations require more flexible re-parameterization functions, such as piecewise-polynomial/rational forms. We show that, for fixed nodes, the optimal piecewise-rational parameterization of the same degree is defined by a simple recursion relation, and we analyze its convergence to the arc-length parameterization. With respect to the new curve parameter, this representation is only of C^0 continuity, although the smoothness and geometry of the curve are unchanged. A C^1 parameterization can be obtained by using continuity conditions, rather than optimization, to fix certain free parameters, but the objective function is then highly non-linear and does not admit a closed-form optimization. Empirical results from implementations of these methods are presented.