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Space-time sketching of character animation

Martin Guay 1 Rémi Ronfard 1 Michael Gleicher 2 Marie-Paule Cani 1
1 IMAGINE - Intuitive Modeling and Animation for Interactive Graphics & Narrative Environments
Grenoble INP [2007-2019] - Institut polytechnique de Grenoble - Grenoble Institute of Technology [2007-2019], LJK - Laboratoire Jean Kuntzmann, Inria Grenoble - Rhône-Alpes
Abstract : We present a space-time abstraction for the sketch-based design of character animation. It allows animators to draft a full coordinated motion using a single stroke called the space-time curve (STC). From the STC we compute a dynamic line of action (DLOA) that drives the motion of a 3D character through projective constraints. Our dynamic models for the line's motion are entirely geometric, require no pre-existing data, and allow full artistic control. The resulting DLOA can be refined by over-sketching strokes along the space-time curve, or by composing another DLOA on top leading to control over complex motions with few strokes. Additionally , the resulting dynamic line of action can be applied to arbitrary body parts or characters. To match a 3D character to the 2D line over time, we introduce a robust matching algorithm based on closed-form solutions, yielding a tight match while allowing squash and stretch of the character's skeleton. Our experiments show that space-time sketching has the potential of bringing animation design within the reach of beginners while saving time for skilled artists.
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Submitted on : Tuesday, December 22, 2015 - 9:24:03 PM
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Martin Guay, Rémi Ronfard, Michael Gleicher, Marie-Paule Cani. Space-time sketching of character animation. ACM Transactions on Graphics, Association for Computing Machinery, 2015, Proceedings of ACM SIGGRAPH 2015, 34 (4), pp.Article No. 118. ⟨10.1145/2766893⟩. ⟨hal-01153763⟩



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