Complex barycentric coordinates with applications to planar shape deformation

Ofir Weber, Mirela Ben-Chen, Craig Gotsman

Research output: Contribution to journalArticlepeer-review

83 Scopus citations

Abstract

Barycentric coordinates are heavily used in computer graphics applications to generalize a set of given data values. Traditionally, the coordinates are required to satisfy a number of key properties, the first being that they are real and positive. In this paper we relax this requirement, allowing the barycentric coordinates to be complex numbers. This allows us to generate new families of barycentric coordinates, which have some powerful advantages over traditional ones. Applying complex barycentric coordinates to data which is itself complex-valued allows to manipulate functions from the complex plane to itself, which may be interpreted as planar mappings. These mappings are useful in shape and image deformation applications. We use Cauchy's theorem from complex analysis to construct complex barycentric coordinates on (not necessarily convex) polygons, which are shown to be equivalent to planar Green coordinates. These generate conformal mappings from a given source region to a given target region, such that the image of the source region is close to the target region. We then show how to improve the Green coordinates in two ways. The first provides a much better fit to the polygonal target region, and the second allows to generate deformations based on positional constraints, which provide a more intuitive user interface than the conventional cage-based approach. These define two new types of complex barycentric coordinates, which are shown to be very effective in interactive deformation and animation scenarios.

Original languageEnglish (US)
Pages (from-to)587-597
Number of pages11
JournalComputer Graphics Forum
Volume28
Issue number2
DOIs
StatePublished - Apr 2009
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Computer Graphics and Computer-Aided Design

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