We reported recently that Microsoft was preparing to announce a gesture-control system for the Xbox 360 at the E3 show in Los Angeles starting Monday. Now we’ve peeled back another layer of the secret.

The motion-sensing control system that Microsoft is working on is key to its attempt to win back market share from Nintendo. We’ve heard that Microsoft is not only working with 3DV Systems on this but also one of 3DV’s competitors, Prime Sense.

Sony has its own effort in the works as well because everyone knows that gesture-control, or using your whole body to make things happen in a game, is important to making games more appealing to broader audiences. Controllers with lots of buttons and joysticks are passe.

We previously reported that Microsoft has a definitive agreement to buy Israel’s 3DV Systems. That company has been working on a gallium-arsenide-based 3-D depth camera that can detect motion and position in way that’s much more accurate than the Wii game controller. This tidbit has been known for a while.

Yet something is going on with another 3-D depth camera maker, Prime Sense. That’s a fresh piece of news that hasn’t been reported before. I don’t want to overstate what I know here, as I’m not sure why Microsoft has to rely on two different startups for what appears to be the same technology.

Microsoft has tied up PrimeSense in the console market as well. Perhaps it needs the patent protection. I don’t know if Microsoft has licensed or acquired the technology from Prime Sense. But Prime Sense has gone dark on its communications. Inon Beracha, chief executive of Prime Sense, says the company is in stealth mode. That’s unusual for a company that’s already come out of stealth mode once before. Microsoft declined to comment.

In any case, the Prime Sense move shows that Microsoft is willing to splurge on the gesture-control technology, perhaps just to keep it from falling into the hands of competitors. A source confirms that Microsoft has begun to show the gesture-control system to game publishers. And the system is expected to be shown at E3, but it won’t debut until the fall of 2010.

By that time, it will be cheaper. The ultimate goal is to create a depth camera that costs less than $20 to make. 3DV Systems won’t get there with its current gallium arsenide chips. But it could get there with its next-generation CMOS chips, which cost much less to make.

If Microsoft has locked up PrimeSense, that leaves one depth camera maker, Canesta, available in the market. Companies such as Electronic Arts could introduce games that use depth cameras and package them with the actual game. Sony might also be tempted to use cameras from Canesta for its rumored solution. Canesta already has a CMOS chip solution.

By no means is this kind of technology easy to develop. Microsoft had an internal team try to come up with its own solution, but it chose not to launch that solution.

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