I never knew the meaning of "pleonasm" until I recently listened to a lecture by Mike Hammer (not the detective, but the world's leading "re-engineer"). In his typically animated fashion, Hammer presented "corporate change" as an oxymoron on its way to becoming a pleonasm. Basically, a pleonasm is a redundant expression like "in one's own mind." It is the opposite of an oxymoron, which is an apparent contradiction like "artificial intelligence" or "airplane food." If prizes were awarded for the best oxymorons, "virtual reality" would certainly be a winner. Freshman physics teaches us about real versus virtual images. Classicists get a more complex dose of the same in their reading of Plato. But virtual reality - or VR - is becoming a pleonasm.

If the words "virtual reality" are seen not as noun and adjective but as "equal halves," the logic of calling VR a pleonasm is more palatable. Basically, VR makes the artificial as realistic as the real. In flight simulation, its most sophisticated and longest-standing application, VR is more realistic than the real. Pilots are able to take the controls of fully loaded passenger planes for their first flight because they have learned more in the simulator than they could in a real plane. In the simulator, a pilot can be subjected to rare situations that, in the real world, would require more than a near miss.

I have often thought that one of the most socially responsible applications of VR would be its required use in driving schools. Virtual reality can place drivers in perilous predicaments - on a slippery road, a child darts out from between two cars - that they may encounter in their cars. All of us hope we are never faced with such situations, and none of us knows how we might react. VR allows one to experience a situation "with one's own eyes" (another pleonasm). As the French journalist Rene Doutard wrote, "Courage is having done it before."

VR Then and Now
Neophytes have a mistaken sense that VR is very new because the press just learned about it. It is not. Almost 25 years ago, Ivan Sutherland developed, with support from ARPA, the first surprisingly advanced VR system. This may not be astonishing to old-timers, because Ivan seems to have had half the good ideas in computer science. However, Ivan's idea is now very affordable. One company, whose name I am obliged to omit, will soon introduce a VR display system with a parts cost of less than US$25.

The dress code for VR is a head-tracking helmet with goggle displays. The principle is simple: Put data where the person is looking and nowhere else. In donning such a display, the general locale of your gaze is a given and elementary optics can move an image from the tip of your nose to infinity.

For a computer-graphics jock, the measures of reality are the numbers of polygons and/or edges a given image has, and the ability to apply textures to those images (considered cheating by some). Should you ask yourself, "What is the optimum number of edges and display resolution needed for photo-realistic imaging?" the answer is probably near you as you read this. Look out a window and imagine that window is a display.

The argument will be made that head-mounted displays are not acceptable because people feel silly wearing them. The same was once said about stereo headphones. If Sony's Akio Morita had not insisted on marketing the damn things, we might not have the Walkman today. I expect that within the next five years more than one in ten people will wear head-mounted computer displays while traveling in buses, trains, and planes. That number could include pilots -who could be landing planes in low visibility wearing goggles that subtract the real fog.

By the way, don't believe for a moment that all of our perceptions are derived from what we see. One of the most frequently cited studies conducted at the Media Lab was authored by Professor Russ Neuman, who proved that people saw a better picture when sound quality was improved. This observation extends to all of our senses as they work cooperatively. Some Department of Defense prototypes have shown that minor and random vibrations of a tank simulator platform induce an uncanny sense of extra visual realism.

The Couch Commando
The real issue and challenge in VR today is not the display, but how to reconcile a person's expectations of reality with what current systems deliver in terms of response time. In fact, all commercial systems, including those that will soon be brought to you by the major video game manufacturers, have a terrible lag. As you move your head, the image before you changes rapidly, but not rapidly enough. Even sophisticated flight simulators are lacking in this regard.

When you look out that window, you take for granted that the mullions won't alias and jerk as you move your head from left to right. We grow up in a world that fosters immediacy in action and reaction. In fact, young children find it almost impossible to steer a motor boat because its response time is just too long.

I played with VR systems fifteen or twenty years ago. With head-mounted glasses that were either piezo-ceramic shutters or polarized lenses, we could display images in stereo, squirting the proper view into each eye and thereby giving a sense of depth through binocular parallax. This is commonplace today.

But what I remember so vividly is that everyone - not most people, but literally everyone - would, after putting these glasses on for the first time, immediately move their heads from side to side, looking for the images before them to reflect their expectations of realistic motion parallax. Usually the system did not perform.

That human response, the "neck jerk" reaction, says it all. In VR, the frequency response of the system will be almost all that counts. While I am not aware of any such studies that would support the claim, I suspect that rapid response can be traded for resolution. If you look to the right or the left, you will be very dissatisfied if the landscape moves along jerkily, with spatial and temporal aliasing, because aliased VR is the oxymoron while VR itself will be the pleonasm, whether we like the ring of the words or not.

Next Issue: Aliasing: The Technical Blindspot of the Computer Industry

[Copyright 1993, WIRED Ventures Ltd. All Rights Reserved. Issue 1.06 November 1993.]