"Shared Space" Allows Users To Meld Virtual Reality, Real World

Move two cards together and the images interact, combining and shifting, morphing into something new. A fourth architect can't make the session, but sends a card bearing his name. When it's turned over, his image appears, floating above the table, and he joins in the discussion from a remote location. At the end of the meeting, the architects simply pocket their cards and are on their way.

If you think that sounds like science fiction, you're half right. A group of researchers at the University of Washington's Human Interface Technology (HIT) Lab have taken the fiction out of the proposition with their latest project, called Shared Space, which moves virtual reality into the real world.

The UW group, in collaboration with ATR International of Japan, will demonstrate Shared Space in Los Angeles next week at the 1999 SIGGRAPH (Special Interest Group on GRAPHics) conference, the Association of Computing Machinery's annual international gathering that attracts more than 30,000 people from academia and industry. Shared Space was selected as one of 20 cutting-edge technologies to be showcased in the Millenium Motel section of SIGGRAPH. The conference will be Sunday through Aug. 13.

Shared Space is based on "augmented reality," a technology that combines real and digital views in a single display. The idea, according to Mark Billinghurst, project director and a UW doctoral student, is to integrate virtual reality into the everyday environment in such a way that it is natural and useful.

"If you look in movies like the original 'Star Wars,' you see what are supposed to be holographic images mixed with the real world in ways that allow the characters to see the images and interact with them in intuitive ways while still interacting with each other," he said. "That's basically what we're shooting for."

Most of the current software intended for collaboration uses a monitor interface, forcing users to view three-dimensional images on a two-dimensional screen. "That's not at all natural," Billinghurst said. And in the case of immersive virtual environments, which put the user into a three-dimensional virtual world, connections with colleagues and physical tools are lost.

"You couldn't have architects talking about 3D models and interacting with each other in an immersive environment, for example," Billinghurst said. "They also wouldn't be able to make notes on paper or refer to real plans." Shared Space, by comparison, melds the virtual and the physical, allowing users to see digital images as well as one another and the real world simultaneously. Here's how it works: Users don specialized goggles, known as see-through headmounted displays (HMDs). Mounted in the HMDs are small cameras, which provide continuous video feedback of what's being viewed to a computer. White cards bearing a unique pattern of felt strips can be recognized by the computer, which projects a corresponding virtual image onto the card.

"We essentially train our software to recognize the patterns," Billinghurst said.

The system software, developed in collaboration with Hirokazu Kato of Hiroshima City University in Japan, continuously calculates the position and orientation of the camera relative to the square, so the images appear to stay fixed in relation to their cards. When cards are rotated and tilted, the images move in sync. Since the software keeps tabs on the relative positions of the cards, it can also recognize when two cards are brought together and be programmed to cause the virtual images to interact.

In the demonstration at SIGGRAPH, users will be asked to find virtual images that appear to be related, then bring the image's corresponding cards together to see what happens. In one case, a solid-color tiger deftly leaps into its stripes. In another, a witch jumps onto her broom and begins flying around the room in large, looping circles.

"People are generally pretty amazed when they see what this can do," Billinghurst said. "We're looking forward to seeing what sort of reaction we get at the conference."

In Los Angeles, the HIT Lab team plans to give away the most time-consuming part of the project - the image-tracking and registration libraries that make Shared Space work.

"Our hope is that, by giving the code away free, other researchers will have more time to explore more possibilities and develop hundreds of intriguing applications," Billinghurst said.

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For more information, see the Shared Space Web site at http://www.hitl.washington.edu/research/shared_space/.