LOS ANGELES — Bloodied by Nintendo's runaway success, the other major gamemakers are attempting to leapfrog the Wii's innovative motion-sensitive controller with camera-based hardware that let players interact with games using nothing but their bodies.

"Camera" is the unlikely buzzword at this year's Electronic Entertainment Expo videogame trade show: The industry's biggest players unveiled no fewer than three advanced, camera-based controllers designed to let gamers manipulate directly with videogame consoles, ushering in the next phase in the war for the living room.

On Monday, Microsoft showed its Project Natal, a controller that uses two cameras to track a player's body movements in 3-D space, allowing them to play games without holding a controller. Later that day, game publisher Ubisoft said it would release a camera for its latest fitness game on Wii. And Sony unveiled a work-in-progress device Tuesday that uses a Wii-style motion-sensing wand controller that is tracked by a camera.

All of this is in direct response to Nintendo's massive success with the Wii's motion-sensing controller, an innovative piece of technology that helped catapult the gaming console to the top of the heap. Not to be outdone, Nintendo made its new Wii MotionPlus attachment — which adds similar positional sensing capabilities, but without a camera — the focus of its E3 show.

What's all the fuss about? Camera controls that sense a game player's full body position are the next big thing in game control, says Ubisoft CEO Yves Guillemot.

"The enormous advantage of the 3-D camera is that, if it's powerful enough, it can give you the feeling that it's you that's on the screen," he says.

If they work as advertised, these next-gen interfaces will do more than make videogames more engaging and fun to play. By turning body movements into computer commands, camera-based sensor systems could revolutionize the way humans interact with machines.

"It’s not about reinventing the wheel," said movie-making legend Steven Spielberg, who took the stage Monday to throw his support behind Microsoft's Project Natal as a key component that could transform the Xbox 360 into an interactive entertainment hub. "It’s about no wheel at all."

Each of the company's camera-based controllers offers a different experience. Microsoft's Natal is an effort to completely remove the physical controller from gameplay. In the demonstration pictured above, players can bounce balls back at the screen, playing a wild game of handball just by swinging their arms, legs, torso — whatever. The device has two cameras: a standard RGB camera that tracks your body's movements and an infrared camera that watches your distance from the screen. Using these two in combination lets games tell where you are in 3-D space, not just on a flat plane.

The effect, at least in the brief hands-on demo Wired.com received at E3, is both seamless and natural. (Read our report: "Hands On: Milo and Kate, and Other Project Natal Games.)

Sony achieves similar effects with a different solution. Its camera is already available — it's a straightforward webcam-style accessory called PlayStation Eye. The new wrinkle, as shown at Tuesday's briefing, is an unnamed controller add-on that in its current prototype form looks like a Wii remote with a big glowing colored ball on the end.

The camera can track the position of the ball in 3-D space, but it can also display an image of the player on the screen. Since it knows exactly where the wand is, it can for example replace the image of the wand with anything else. So you're watching yourself on your TV screen, but where the wand should be, the PS3 is replacing it with a baseball bat, or a whip, or a sword, and it reacts according to your movements.

Microsoft did not give a date for Project Natal's release; we expect to see it next year. Sony said it plans to release its controller in the spring. Ubisoft, at its Monday briefing, said its camera would be the first to release, although that's mostly because it's a straightforward 2-D camera, much like Sony's existing Eye.

However, Ubisoft's Guillemot said that his company has been hard at work for more than a year creating games and experiments that use 3-D camera controls like Microsoft's and Sony's. In fact, even prior to learning about these projects, Ubisoft has been anticipating the release of 3-D camera controllers for some time, he said.

"We wanted to be in advance of other publishers in understanding what that technology would bring, when Microsoft, Sony or Nintendo came out with one," he said. "We worked a lot with the manufacturers of those types of cameras to learn what to do with them."

Improving interfaces is key to getting more players involved in games, says Guillemot: "Everybody has the right to play."

Giving gamers a deeper level of immersion with realistic body movements isn't just confined to cameras. At Activision's booth, pro skateboarder Tony Hawk was demonstrating Tony Hawk: Ride, a game that you control by pushing, kicking and leaning on a skateboard-shaped controller.

Hawk said that although the game's designers had looked at using cameras for its control scheme, they decided having a physical board was important for a more realistic experience.

Although Microsoft is hoping the absence of a physical controller will appeal to those who are intimidated by gaming, longtime gamers seem reluctant to give up their controllers. Neal Ronaghan, 21, a college student from New Jersey, said he prefers Sony's controller to Microsoft's because of the physical interface.

"It's all very cool, but I don't know where the actual application for a game would work," he says. "(Sony's) sounds like it could go somewhere."

Guillemot says that hard-core gamers will want the comfort of physical control. Gamemakers won't be able to make hard-core experiences that use the camera all the time, he says, because gamers "don't have a problem with (traditional) interfaces. They are excellent at using the pad. (Cameras) could give them an option to be more in the action, moving around from time to time, but it should be 20 percent camera, 80 percent control pad."

Indeed, between Microsoft and Sony, the only game (as opposed to a technical demonstration) announced at E3 that will use either controller was Milo and Kate, a game in which you interact with a lifelike 10-year-old boy, talking to him via Project Natal's microphone and playing catch with him using gestures. (Lionhead Studios' Peter Molyneux told Wired.com about this project in vague terms more than a year ago, calling it a "significant scientific achievement.")

Having turned the gaming world on its head with the 2006 introduction of the original Wii remote control, Nintendo attempted to defend its position as the innovation leader with the $20 Wii MotionPlus, which adds position tracking (the standard Wii remote can only measure its rotation, not position in space). At E3, Nintendo said it would push MotionPlus with a variety of major games, including the sequel to its hit Wii Sports as well as the next game in its epic Legend of Zelda series.

As for other games that will track every movement, every position of your body? Well, you'll just have to wait for next year's E3.