Photos: How to animate 10,000 digital balloons

In Pixar's new film, "Up," the studio faced the challenge of how to animate more than 10,000 interdependent balloons. In the film, Pixar's tenth feature, the balloons needed to behave realistically, which meant that if one bumped into another, the second one would move.

And this interdependence had to include all 10,000 in the cluster. The studio couldn't hand-animate the balloons, nor would traditional computer animation work. Instead, Pixar's animation and computer experts crafted a procedural animation technique that let them achieve the look they wanted.