Communications of the ACM
Microsoft's Body-Sensing, Button-Busting Controller
A LONG-lived videogaming skill could be on the way out this year as Microsoft hones an add-on to its Xbox 360 console aimed at making button-studded games controllers obsolete. The device, called Natal after the city in northern Brazil, allows players to control a game using only their body movements and voice. Robbie Bach, Microsoft's president of entertainment and devices, announced at the CES show in Las Vegas, Arizona, this week that Natal would go on sale in November.
Microsoft unveiled Natal in June 2009 at the E3 games industry expo in Los Angeles, but revealed little about how it works. Now the company has allowed New Scientist access to the device and its creators to discover more details.
A player standing anywhere between 0.8 and 4 metres from Natal is illuminated with infrared light. A monochrome video camera records how much of that light they reflect, using the brightness of the signal to approximate their distance from the device and capture their movements in 3D.
This means Natal doesn't require users to wear markers on their body - unlike the technology used by movie studios to animate CGI figures.
Motion capture normally requires massive processing power, and paring down the software to run on an everyday games console was a serious challenge, says Natal's lead developer, Alex Kipman. "Natal has to work on the existing hardware without taking too much hardware processing away from the games developers."
Microsoft collected "terabytes" of data of people in poses likely to crop up during game play, both in motion capture studios and their own homes. Frames from the home videos were manually labelled to identify key body parts, and the data was then fed into "expert system" software running on a powerful cluster of computers. The result was a 50-megabyte software package that can recognise 31 different body parts in any video frame.
From New Scientst
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