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Feature

By Stuart Ralston

Imagine strolling through a building before it is constructed; dancing with a twelve-foot purple lobster; playing tennis with a friend 800 kilometres away; or travelling through your own bloodstream.

You can do all these things using the new interactive computer technology of virtual reality (VR) which creates the illusion of being immersed in an artificial world. Visitors to that world perceive it as a physically real environment.

While fast developing overseas, in New Zealand virtual reality technology has only really been seen on science television programmes like Beyond 2000 and in movies like The Lawnmower Man. Now there is a chance to experience it in a new exhibit currently under development at the Science Alive! centre in Christchurch.

The exhibit -- known as JIVE for Juggling In a Virtual Environment -- uses conventional technology at low cost to introduce VR as an exciting learning tool. Its development has involved students and researchers from a diverse range of departments at the University of Canterbury, including Computer Science, Electrical Engineering and Psychology.

JIVE offers visitors the chance to try their hand at juggling virtual balls through the use of a virtual reality glove hooked up to a large-screen computer display. After donning the glove, the would-be juggler then sees a display of a computer-generated hand, in a textured, perspective virtual environment, that moves and imitates their own hand movements. They can reach out and "pick up" from the "floor" such objects as a fir tree, a giant donut or, of course, a ball to juggle with.

Graphical feedback windows display the user's gravity level --  initially set at half Earth's -- and their error-rate of drops per throw as they learn to juggle in virtual space. The system will adapt automatically to the user's ability, based on their error-rate, reducing the virtual gravity if necessary to make juggling easier, or increasing it as their skill improves. The user can also manually alter gravity with a simple gesture, setting it to that of a different planet, or reversing it so that things float to the ceiling.

Virtual Technology

The exhibit currently uses a modified Nintendo PowerGlove with an ultrasonic tracking device. This is interfaced to an IBM-compatible 486 personal computer and a thin film transistor (TFT) data projector which enables the large-screen projection of the computer display.

Full VR systems often use a head-mounted display to provide sensory feedback, and a hand measuring device and a three-dimensional position tracking device to register movements. The science centre display is simpler in operation, as there are no regular suppliers of VR components in New Zealand. This means that components need to be assembled locally or sent from overseas. The busy nature of an exhibit and the predicted breakage rates of the VR components -- especially the glove -- dictated using the former option. All equipment has to be robust, durable and replaceable.

The expense and fragility of a head-mounted display ruled it out. Possible visual options have included 3D-glasses using the traditional red/blue cellophane glasses, or high-speed LCD shutters where each eye is alternately blacked out as a stereo pair of images is displayed.

The large 1.5-metre-square data projector display was chosen as the best option to give the user the perception of being surrounded by their virtual world. It is important in real juggling to rely on peripheral vision, since the user cannot look directly at all the balls at once. The projector back-projects a computer-generated image to the large screen, and its active matrix ensures that it is quick to respond to change. It is also far more easily accessible than a head-mounted display and allows onlookers to share in the virtual world.

At just over $200, the Nintendo PowerGlove provided a relatively cheap and robust input unit. The glove straps to the back of the hand, with finger guides and straps that go around the wrist, extending up the forearm. To detect finger flexion, strong polyester strain gauges are used in the finger guides, giving four detectable positions for each finger. Tracking uses inexpensive ultrasonic technology that detects the position of the glove, and an 8-bit processor watches the fingers, communicates with the host computer, and handles the ultrasonics. The nearest comparable VR glove costs over $8,000, and is too fragile for public use.

The way the juggling "feels" to the user is an important factor. The largest single on-going problem is the time lag between the user's movements and the computer's response, since timing in the real world is crucial to a few milliseconds.

On-going monitoring of reactions to the exhibit are providing information on how well it is working as a learning tool. The results may indicate whether this concept can expand the application of computers into teaching a difficult perceptual-motor skill -- does experience with virtual juggling help to learn the real thing? There are some skills that some people simply cannot learn in the real world and VR may be able to teach them.

The JIVE exhibit demonstrates the power, flexibility and possibilities for VR to be used as a real-world skill-teacher, as opposed to just a computer game. Virtual Reality could be the most important development since humans first chipped flint, and is likely to revolutionise human-computer interaction in our future.

Stuart Ralston is a Masters student in Computer Science at Canterbury University, working in conjunction with the Christchurch Science Alive! centre.