Non-Photorealistic Computer Graphics Library

Methods for Exploring Expressive Stance

Author(s): Michael Neff, Eugene L. Fiume.
Proceedings: Eurographics Symposium on Computer Animation, 2004.
[BibTeX]

Abstract:
The postures a character adopts over time are a key expressive aspect of her movement. While IK tools help a character achieve positioning constraints, there are few tools that help an animator with the expressive aspects of a character's poses. Three aspects are combined in good pose design: achieving a set of world space constraints, finding a body shape that reflects the character's inner state and personality, and making adjustments to balance that act to strengthen the pose and also maintain realism. This is routinely done in the performing arts, but is uncommon in computer graphics. Our system combines all three components within a single body shape solver. The system combines feedback based balance control with a hybrid IK system that utilizes optimization and analytic IK components. The IK system has been carefully designed to allow direct control over various aesthetically important aspects of body shape, such as the type of curve in the spine and the relationship between the collar bones. The system allows for both low-level control and for higher level shape sets to be defined and used. Shape sets allow an animator to use a single scalar to vary a character's pose within a specified shape class, providing an intuitive parameterization of a posture. Changing shape sets allows an animator to quickly experiment with different posture options for a movement sequence, supporting rapid exploration of the aesthetic space.