The Computing behind Motion (Pictures)

Jun 05 2017 | By Ann Rae Jonas | Image courtesy of Disney.

Walt Disney Animation Studios recently used Eitan Grinspun’s technology on its live-action remake of The Jungle Book to depict the motion of plants and trees—trees reacting to the wind, monkeys swinging on branches. Grinspun says he himself felt he was watching real vegetation when he saw the movie.

Most of Grinspun’s animation technology is used for supporting roles—and that’s fine with him. In Tangled, for example, Rapunzel’s hair was an important character in its own right. Disney used Grinspun’s technology for the clothes, to depict how fabrics draped and flowed—freeing up the artists to work on the hair. Grinspun’s technology was also used to model realistic hair and its motion for the hero characters in Disney’s forthcoming animated adventure, Moana.

“You don’t want the motion of the fabric to draw too much attention to itself,” says Grinspun, associate professor of computer science and director of the Columbia Computer Graphics Group. “Yet it needs to be responsive, realistic, and supportive of the artistic vision. If you can compute motion that’s realistic, and you can render it realistically, you can help the audience to become immersed in the world of the story, and that makes the experience all the more believable!”

Grinspun’s algorithms, which are based on the field of mathematics called “discrete differential geometry,” not only can simulate how materials bend and move, but also predict it. Working with Pedro Reis of MIT, Grinspun adapted code developed for animation to predict the coiling patterns of fiber-optic cables laid on the ocean floor. The computer code worked so well that it predicted things the scientists hadn’t even considered—which they then confirmed in the lab.

All of his work, says Grinspun, grows out of his interest in the geometry of physics. “That is what fascinates me,” he remarks. “Anything that is a geometric approach to physics—the intersection of geometry, physics, and computation.”

“I pursue this stuff for the beauty of the geometry and the physics,” says Grinspun, “but the larger fulfillment for me is in knowing that our code is being used on the big screen, by doctors in medical simulations, by biologists studying the motion of bacteria flagella.”


A scene from The Jungle Book © 2016 Disney

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