Fast Planar Harmonic Deformations with Alternating Tangential Projections

Eden Fedida Hefetz, Edward Chien, Ofir Weber

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


We present a planar harmonic cage-based deformation method with local injectivity and bounded distortion guarantees, that is significantly faster than state-of-the-art methods with similar guarantees, and allows for real-time interaction. With a convex proxy for a near-convex characterization of the bounded distortion harmonic mapping space from [LW16], we utilize a modified alternating projection method (referred to as ATP) to project to this proxy. ATP draws inspiration from [KABL15] and restricts every other projection to lie in a tangential hyperplane. In contrast to [KABL15], our convex setting allows us to show that ATP is provably convergent (and is locally injective). Compared to the standard alternating projection method, it demonstrates superior convergence in fewer iterations, and it is also embarrassingly parallel, allowing for straightforward GPU implementation. Both of these factors combine to result in unprecedented speed. The convergence proof generalizes to arbitrary pairs of intersecting convex sets, suggesting potential use in other applications. Additional theoretical results sharpen the near-convex characterization that we use and demonstrate that it is homeomorphic to the bounded distortion harmonic mapping space (instead of merely being bijective).

Original languageEnglish
Pages (from-to)175-188
Number of pages14
JournalComputer Graphics Forum
Issue number5
StatePublished - Aug 2017

Bibliographical note

Publisher Copyright:
© 2017 The Author(s) Computer Graphics Forum © 2017 The Eurographics Association and John Wiley & Sons Ltd. Published by John Wiley & Sons Ltd.


  • Categories and Subject Descriptors (according to ACM CCS)
  • G.1.6 [Numerical Analysis]: Optimization—Convex programming
  • I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling—Geometric algorithms, languages, and systems; Hierarchy and geometric transformations
  • I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism—Animation


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