The huge number of balloons required to lift Carl’s house in “Up” presented some unique problems for the animation staff at Pixar.  Animating that huge number of balloons was a daunting tasks, and making them all react realistically was an impossible amount of work.  To solve it, Pixar developed a procedural animation and physics simulation tool to make it work.

“These are relatively simple physical equations, so you program them into the computer and therefore kind of let the computer animate things for you, using those physics,” said May. “So in every frame of the animation, (the computer can) literally compute the forces acting on those balloons, (so) that they’re buoyant, that their strings are attached, that wind is blowing through them. And based on those forces, we can compute how the balloon should move.”

Pixar’s “Up” opens this Friday.

via How technology lifts Pixar’s ‘Up’ | Geek Gestalt – CNET News.