Object-image correspondence for curves under central and parallel projections

  • Authors:
  • Joseph M. Burdis;Irina A. Kogan

  • Affiliations:
  • North Carolina State University, Raleigh, NC, USA;North Carolina State University, Raleigh, NC, USA

  • Venue:
  • Proceedings of the twenty-eighth annual symposium on Computational geometry
  • Year:
  • 2012

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Abstract

We present a novel algorithm for deciding whether a given planar curve is an image of a given spatial curve, obtained by a central or a parallel projection with unknown parameters. A straightforward approach to this problem consists of setting up a system of conditions on the projection parameters and then checking whether or not this system has a solution. The computational advantage of the algorithm presented here, in comparison to algorithms based on the straightforward approach, lies in a significant reduction of a number of real parameters that need to be eliminated in order to establish existence or non-existence of a projection that maps a given spatial curve to a given planar curve. Our algorithm is based on projection criteria that reduce the projection problem to a certain modification of the equivalence problem of planar curves under affine and projective transformations. The latter problem is then solved using a separating set of rational differential invariants. A similar approach can be used to solve the projection problem for finite lists of points. The motivation comes from the problem of establishing a correspondence between an object and an image, taken by a camera with unknown position and parameters.