Researchers working on cheap motion sensors for games

Their new motion capture sensors works even while a person is driving or skiing (see video, top right). It could make computer animation or movie effects more lifelike, the researchers say, and perhaps even help doctors analyse movements of patients going through physical therapy.

Several sensors measuring about 2.5 centimetres on each side are attached to a person's legs and arms. The sensors detect movement in two different ways: accelerometers and gyroscopes measure motion, but ultrasonic beeps are also emitted.

Tiny microphones mounted on the torso pick up these beeps, allowing a laptop computer, carried in a backpack, to calculate the distance to the sensor. The system is similar to, albeit much simpler than, bats' ultrasonic echolocation, and together with the motion sensors provides a more accurate overall picture of body movement. The small backpack also holds the batteries that power the system.

"The sensors are all off-the-shelf parts," Adelsberger says, making the system much cheaper than other motion-capture technology. It cost about $3,000 currently, but this could come down to a few hundred dollars, he says, if the sensors are mass-produced.