Pixar

Hayley Iben

Mark Joseph Meyer

Michael Kass

Andrew Witkin

Lena Petrovic

Olivier Soares

Techniques are disclosed for stably simulating stylized curly hair that address artistic needs and performance demands, both found in the production of feature films. To satisfy the artistic requirement of maintaining a curl's helical shape during motion, a hair model is developed based upon an extensible elastic rod. A method is provided for stably computing a frame along a hair curve for stable simulation of curly hair. The hair model introduces a new type of spring for controlling the bending and twisting of a curl and another for maintaining the helical shape during extension. The disclosed techniques address performance concerns often associated with handling hair-hair contact interactions by efficiently parallelizing the simulation. A novel algorithm is presented for pruning both hair-hair contact pairs and hair particles. The method can be used on a full length feature film and has proven to be robust and stable over a wide range of animated motion and on a variety of hair styles, from straight to wavy to curly.

Artistic simulation of curly hair

A model is associated with a deep pose. When the model is changed from an attractor pose to a current pose, the current pose and the attractor pose are compared with the deep pose. If any portion of the current pose is more similar to the deep pose than the attractor pose, then the attractor pose is updated. A portion of the attractor pose may be set to the corresponding portion of the current pose. The attractor pose may be modified by a function. Pose attributes of each pose degrees of freedom for the attractor pose, the current pose, and the deep pose may be evaluated to potentially modify all or a portion of the attractor pose. The attractor pose and pose constraints are used to determine a pose of the model, for example by an optimization process based on the attractor pose while satisfying pose constraints.

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Fremont, CA, United States of America

Hayley Iben