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Physics Professor Lays Down the Law for Animators

May 21, 2008

The Incredible Hulk makes a terrific leap, and physicist Alejandro Garcia cringes.

It’s not because Bruce Banner’s alter ego is angry and green, but because the ground underneath stood still. Newton’s laws say that the force of the jump should have destroyed the launch site.

“You can tell when something isn’t quite there,” Garcia said. “Often the audience doesn’t like it, and they can’t quite put their finger on it.”

So the San Jose State University professor is trying to bring the rules of Newton and Einstein to Shrek’s swamp and Ratatouille’s kitchen. He recently won a National Science Foundation grant to develop a course called Physics of Animation.

To Garcia’s knowledge, the university will be the only place in the nation where animators get formal training in physics, learning how to make a leaf flutter to the ground and a character walk with the right spring in his step.

As technology allows moviemakers to create more sophisticated scenes inside a computer, the laws of physics are key to making those scenes realistic.

“Understanding the basic physics, forces and mass and inertia and momentum and all that, are really important for making believable characters,” said Rex Grignon, a DreamWorks animator who worked on punches, kicks and leaps for the upcoming film “Kung Fu Panda.” Grignon is also an adviser for the new course at San Jose State.

A chubby panda wouldn’t normally do karate, of course. But, Grignon said, if he

did, he’d take time to get up to full speed because his massive body would have inertia.

The role of physics is not limited to animated pandas and computer-generated ogres. Live-action blockbusters animate many special effects that used to be done with stunt men. Experts in the physics of fluids won a 2008 technical Oscar for making the whirlpool battle in the third “Pirates of the Caribbean” spin realistically.

Physics is also making its way into computer games. Nvidia, a Santa Clara company, markets a physics chip. When a player blasts a wall into bits, the physics chip ensures they fall to the ground in an accurate trajectory, instead of merely dissolving.

At San Jose State, art students study light and shadow, and view autopsy videos to understand anatomy and get a firm grounding in classic drawing techniques.

But Alice Carter, co-director of the animation and illustration program, noticed that some students were getting basic motions wrong. For example, they might draw a ball that bounces higher on the second bounce, when it should reach lower and lower peaks.

Carter met Garcia when, just for fun, he signed up for her painting class in 2002. (In fact, she said she’s still waiting for him to turn in his final project.) She invited the physicist to be a guest lecturer in the animation course.

Garcia’s lectures were a hit, both informative and entertaining. Garcia leaves out the equations and uses live demonstrations of principles that are useful to art students. For one lesson, he lies bare-chested on a bed of nails to teach them how his weight, when distributed over a large area, doesn’t exert enough pressure to pierce his skin. That means that if a heavy creature like the Hulk has big enough feet, he can stand on a rooftop without breaking through.

“I’m not a science person, but after having his lectures, I really changed my perspective of it,” said student Priscilla Wong. “I think it’s necessary.”

Inspired by the success of these lectures, Garcia teamed up with animation instructors at San Jose State and De Anza College to design a semester-long course. The professors expect to offer one-day master classes this summer, and hope the full course will be available to students in fall 2009.

Once students understand his rules, Garcia realizes they may have to break them. After all, Wile E. Coyote’s animators knew about gravity, but when the coyote walked off a cliff, they still let him hover until he realized his mistake. Physics shouldn’t get in the way of a good joke.

Ultimately, Garcia said, “It’s all about the story.”




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