Researchers are adding a third sensation to virtual reality's sights and sounds.
Drill in hand, the dentist pushes down on the tooth, feeling its firmness, its ridges, its curves. Then the dentist turns on the drill and ever so carefully starts chipping away the tooth decay.
That's how it usually goes. But in this instance, it is okay to push that drill into a perfectly healthy part of the tooth, sending pearly white chunks flying. Why? Because there is no real tooth, no drill, not even a patient; it is all a demonstration of a virtual reality known as haptics, or virtual touch.
Virtual touch relays tactile sensations to the body in computer-generated environments, allowing a dentist, for example, to feel a tooth that isn't there.
Those who experience virtual touch find the experience jarring at first. "If you haven't felt the sensation of touching something that isn't there, it has a strong psychological effect that you don't expect until you've done it," said Mike Bevan, managing editor of VR News, a trade magazine.
Bevan and about 400 other researchers, developers and students were in New Brunswick, N.J., recently to attend a conference and exhibition on virtual reality sponsored by the Institute of Electrical and Electronics Engineers.
The conference featured products that are on the market, including a virtual touch unit made by SensAble Technologies of Woburn, Mass., that consists of a stylus that hangs from a disc. In computer simulations, the stylus represents an object on a screen, like a drill or a screwdriver, that can be moved and rotated freely in open space.
But when the object hits a virtual barrier _ a tooth, for instance _ the stylus locks as if it were pushing against a hard surface. The stylus also can be moved, with resistance, to simulate an action such as pushing a knife through hard cheese.
Companies, including ReachIn Technologies of Sweden, have combined the stylus system with computer environments to enhance the effect. At the exhibition, ReachIn demonstrated a system in which a computer monitor is tilted down so that the image appears in a reflective panel. A user, wearing special 3-D glasses, manipulates the objects using the stylus.
Teneo Computing, of Princeton, Mass., developed dental training software using SensAble's system. Teneo and the Harvard School of Dental Medicine plan to build a virtual reality dental training system.
Another haptics tool, developed by Virtual Technologies, of Palo Alto, Calif., is Cyber-Glove, which can simulate the weight and basic texture of objects in a virtual environment.
Virtual touch is still in an early stage of development. Work on more advanced systems continues in universities and private companies.
"Up till now, we were using the visual and auditory channels" for virtual reality, said Grigore Burdea, a professor at Rutgers University and general chairman of the conference. Burdea also is developing a haptic glove. "Now people are realizing that if we open another communications channel, which is haptics, we can do it better and faster. It's not just fast, it's more natural."
Many applications of virtual reality, such as medical training and military applications, greatly benefit from a sense of touch, he said. "Think about a fighter pilot," Burdea said. "He's chasing somebody, and he's sensorially overloaded. All his normal communications are saturated. You can tell him anything, he won't hear. You can show him anything, he won't see. But if you can touch him, he'll respond."
In fact, the military has shown a major interest in haptics development. Air Force researcher Daniel Repperger presented the results of a study that showed that in simulated flight tests, haptic interfaces could reduce crash rates by as much as half in some cases. That bodes well for the military's research on remote-control aircraft; from safe locations, pilots will feel turbulence rather than just see it.
But for all their promise, haptic systems are relatively crude, especially when compared with the range of sensations a human body can feel.
"It's not easy," Burdea said. "The state of technology is so far behind what the human body needs and can do. The skin needs to be tickled hundreds of times per second" to create a continuous sensation. Motion, on the other hand, can be simulated by showing the eye as few as 15 or 20 picture frames per second.
And although advances in computer technology have allowed for the development of more complex visual virtual reality environments, haptic devices remain rudimentary.
"Interfaces tend to be too heavy, too encumbering, too fragile, too difficult to use or too restraining," Burdea said. "You lose your natural freedom of motion."
A solution may be to sidestep wearable contraptions and create a direct connection to the brain, allowing sensations of touch to be created without actual tactile stimulation.
"Directly tickling the brain," Burdea said. "It's something that has many issues. I think it's dangerous, and like any other technology could be used in the wrong way. If you were able to find a way to control a person through some kind of neural interface, then you can program the person and transfer him into a robot. The border between the person and the robot starts to melt."