Andrew Fitzgibbon, Principal Researcher for Microsoft Research, told the crowd: “What Natal does, is it evaluates effectively trillions of body configurations every frame. We’ve made it do that 30 times a second.”
This, according to IGN, is done through a combination of software and a camera that tracks the body’s motion in three dimensions.
As IGN notes, though Natal will evaluate the room you’re playing in 30 times a second, this doesn’t necessarily mean games will also run at that rate. That will be the effective number of times the game can receive new input from the user, however.
Microsoft confirmed a 2010 release date for Natal in Vegas last night.