System Enables Remote Writing

Daniel S. Burgess

If researchers at Carnegie Mellon University in Pittsburgh have their way, tomorrow's desktop won't look much different from today's, but pen and paper will enable distant colleagues to collaborate on a project, and students and teachers to interact remotely. Called Tele-Graffiti, the system monitors what users write on a piece of paper and projects it onto that of their counterparts on the other end of the network.

Jianbo Shi, a research scientist at the university who helped develop Tele-Graffiti, explained that the ability to communicate with sketches can be essential to graphics designers and architects. It also is a natural part of the collaborative act in general.

"It is hard to describe things, sometimes," Shi said. "If you work with someone, you draw things -- on the blackboard, on paper."

As a user writes, the lamp-size input/output station on the desktop captures images of the paper, including of the writer's hand, and streams the information to projectors at the other stations. "You see someone's hand or pen writing on your paper," Shi said. "It gives physical realism and allows you to convey information with gestures."

The stations comprise a Sony CCD camera and a Panasonic XVGA liquid crystal display (LCD) projector, connected to a 400-MHz Pentium II computer. A frame grabber is not necessary. "It's outdated but works," Shi said, "showing that the system doesn't require a high-end PC."

The researchers developed an algorithm that identifies the paper and tracks its position, even when it's on a cluttered desk. The writing surface is attached to a clipboard with a thicker border on the top than on the bottom or sides. The border defines the edges of the paper and its orientation for image capture, and enables the system to orient the projected frame with the surfaces at the destinations.

'A question of timing'

Currently, Tele-Graffiti's older cameras limit the resolution of the system. Users can read each other's line drawings but not print. It is the price tag, however, and not the resolution, that is the impediment to the system's commercial realization. Each station costs approximately $5000 to build, largely because of the LCD projector.

Shi said that the team is in the process of patenting the Tele-Graffiti system but has no immediate plans to market it. "It's a question [of] timing, with the costs of the projectors and cameras."

At the 2001 International Conference on Computer Vision, held in July in Vancouver, British Columbia, Canada, the system's creators demonstrated Tele-Graffiti's other capability: playing paper games with a remote opponent. "We tell people, 'This is the most expensive tic-tac-toe game ever developed,' " Shi joked.