Physics-Based Motion Retiming

James McCann, Nancy Pollard, and Siddhartha Srinivasa
Eurographics/ ACM SIGGRAPH Symposium on Computer Animation, September, 2006.


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Abstract
By changing only the playback time of a motion sequence, an animator can achieve a variety of effects that can change our perception of an event. In some scenarios, it may be possible to consider physical properties of motion when retiming (eg. to preserve physical plausibility). However, existing retiming solutions can be quite time consuming when physical parameters are considered. This paper presents an interactive method for optimal motion retimings that takes into account physically based constraints and objective functions. We achieve fast performance through a precomputation phase where constraints are projected into the two-dimensional space of velocities and accelerations along the input motion path. Unlike previous approaches, our precomputation technique allows for rapid computation of plausible contact forces that result from retiming, and it also accomodates changing physical parameters. We demonstrate our approach by creating physically plausible results for changes in motion duration, manipulations of the gravity vector, and modifications of character limb masses.

Keywords
graphics, retiming, human motion, motion capture

Notes
Associated Center(s) / Consortia: Quality of Life Technology Center, National Robotics Engineering Center, and Center for the Foundations of Robotics
Associated Lab(s) / Group(s): Personal Robotics and Manipulation Lab
Number of pages: 10

Text Reference
James McCann, Nancy Pollard, and Siddhartha Srinivasa, "Physics-Based Motion Retiming," Eurographics/ ACM SIGGRAPH Symposium on Computer Animation, September, 2006.

BibTeX Reference
@inproceedings{Pollard_2006_5495,
   author = "James McCann and Nancy Pollard and Siddhartha Srinivasa",
   editor = "M-P. Cani, J. O'Brien",
   title = "Physics-Based Motion Retiming",
   booktitle = "Eurographics/ ACM SIGGRAPH Symposium on Computer Animation",
   month = "September",
   year = "2006",
}