Extensions of the witness method to characterize under-, over- and well-constrained geometric constraint systems

  • Authors:
  • Simon E. B. Thierry;Pascal Schreck;Dominique Michelucci;Christoph FüNfzig;Jean-David GéNevaux

  • Affiliations:
  • LSIIT, UMR CNRS 7005, Université de Strasbourg, France;LSIIT, UMR CNRS 7005, Université de Strasbourg, France;LE21, UMR CNRS 5158, Université de Bourgogne, France;LE21, UMR CNRS 5158, Université de Bourgogne, France;LSIIT, UMR CNRS 7005, Université de Strasbourg, France

  • Venue:
  • Computer-Aided Design
  • Year:
  • 2011

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Abstract

This paper describes new ways to tackle several important problems encountered in geometric constraint solving, in the context of CAD, and which are linked to the handling of under- and over-constrained systems. It presents a powerful decomposition algorithm of such systems. Our methods are based on the witness principle whose theoretical background is recalled in a first step. A method to generate a witness is then explained. We show that having a witness can be used to incrementally detect over-constrainedness and thus to compute a well-constrained boundary system. An algorithm is introduced to check if anchoring a given subset of the coordinates brings the number of solutions to a finite number. An algorithm to efficiently identify all maximal well-constrained parts of a geometric constraint system is described. This allows us to design a powerful algorithm of decomposition, called W-decomposition, which is able to identify all well-constrained subsystems: it manages to decompose systems which were not decomposable by classic combinatorial methods.