Doug James built a tower of 3,601 plastic chairs a quarter-mile high, then knocked it down just to see what would happen. Fortunately for his neighbors, James wasn't testing real-world gravity, but an algorithm that detects how computer-generated objects collide. "In order to have a physically realistic virtual environment, you need to know when objects touch each other," says the Carnegie Mellon assistant prof and lead researcher on the project.
Collision detection sounds simple, but add deformation - the way objects bend and buckle when they bump - to the equation, and simultaneously tracking thousands of moving objects onscreen puts an incredible strain on processors. This is true for everything from the skidding hot rods in Grand Theft Auto to the shape-shifting molecules in a chemistry simulation. James' two-minute animation, premiering August 9 at the Siggraph computer graphics show in Los Angeles, demonstrates the efficiency of his new algorithm: The chairs' 1.6 billion collisions were calculated in about 14 hours. Considering that other computational methods can take more than two months, this code promises to have pixel jockeys sitting pretty.
- David Pescovitz
credit:
PLAY
>
It's Raining Chairs
