Using signature sequences to classify intersection curves of two quadrics

  • Authors:
  • Changhe Tu;Wenping Wang;Bernard Mourrain;Jiaye Wang

  • Affiliations:
  • Shandong University;University of Hong Kong;INRIA;Shandong University

  • Venue:
  • Computer Aided Geometric Design
  • Year:
  • 2009

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Abstract

We present a method that uses signature sequences to classify the intersection curve of two quadrics (QSIC) or, equivalently, quadric pencils in PR^3 (3D real projective space), in terms of the shape, topological properties, and algebraic properties of the QSIC. Specifically, for a QSIC we consider its singularity, reducibility, the number of its components, and the degree of each irreducible component, etc. There are in total 35 different types of non-degenerate quadric pencils. For each of the 35 types of QSICs given by these non-degenerate pencils, through a detailed study of the eigenvalue curve and the index function jump we establish a characterizing algebraic condition expressed in terms of the Segre characteristics and the signature sequence of the quadric pencil. We show how to compute a signature sequence with rational arithmetic and use it to determine the type of the intersection curve of any two quadrics which form a non-degenerate pencil. As an example of application, we discuss how to apply our results to collision detection of cones in 3D affine space.