Virtual Reality

I. What is Virtual Reality

The term Virtual Reality (VR) is used by many different people with many meanings. There are some people to whom VR is a
specific collection of technologies, that is a Head Mounted Display, Glove Input Device and Audio. Some other people stretch
the term to include conventional books, movies or pure fantasy and imagination. The NSF taxonomy mentioned in the
introduction can cover these as well. However, my personal preference, and for purposes of this paper, we restrict VR to
computer mediated systems. The best definition of Virtual Reality I have seen to date comes from the book "The Silicon
Mirage" (see section on VR Books):

"Virtual Reality is a way for humans to visualize, manipulate and interact with computers and extremely complex data"

The visualization part refers to the computer generating visual, auditory or other sensual outputs to the user of a world within the
computer. This world may be a CAD model, a scientific simulation, or a view into a database. The user can interact with the
world and directly manipulate objects within the world. Some worlds are animated by other processes, perhaps physical
simulations, or simple animation scripts. Interaction with the virtual world, at least with near real time control of the viewpoint, in
my opinion, is a critical test for a \'virtual reality\'.

Some people object to the term "Virtual Reality", saying it is an oxymoron. Other terms that have been used are Synthetic
Environments, Cyberspace, Artificial Reality, Simulator Technology, etc. VR is the most common and sexiest. It has caught the
attention of the media.

The applications being developed for VR run a wide spectrum, from games to architectural and business planning. Many
applications are worlds that are very similar to our own, like CAD or architectural modeling. Some applications provide ways
of viewing from an advantageous perspective not possible with the real world, like scientific simulators and telepresense
systems, air traffic control systems. Other applications are much different from anything we have ever directly experienced
before. These latter applications may be the hardest, and most interesting systems. Visualizing the ebb and flow of the world\'s
financial markets. Navigating a large corporate information base, etc.

I.1. Types of VR Systems

A major distinction of VR systems is the mode with which they interface to the user. This section describes some of the
common modes used in VR systems.

I.1.1. Window on World Systems (WoW)

Some systems use a conventional computer monitor to display the visual world. This sometimes called Desktop VR or a
Window on a World (WoW). This concept traces its lineage back through the entire history of computer graphics. In 1965,
Ivan Sutherland laid out a research program for computer graphics in a paper called "The Ultimate Display" that has driven the
field for the past nearly thirty years.

"One must look at a display screen," he said, "as a window through which one beholds a virtual world. The challenge to
computer graphics is to make the picture in the window look real, sound real and the objects act real." [quoted from Computer
Graphics V26#3]

I.1.2. Video Mapping

A variation of the WoW approach merges a video input of the user\'s silhouette with a 2D computer graphic. The user watches
a monitor that shows his body\'s interaction with the world. Myron Kruger has been a champion of this form of VR since the
late 60\'s. He has published two books on the subject: "Artificial Reality" and "Artificial Reality II". At least one commercial
system uses this approach, the Mandala system. This system is based on a Commodore Amiga with some added hardware and
software. A version of the Mandala is used by the cable TV channel Nickelodeon for a game show (Nick Arcade) to put the
contestants into what appears to be a large video game.

I.1.3. Immersive Systems

The ultimate VR systems completely immerse the user\'s personal viewpoint inside the virtual world. These "immersive" VR
systems are often equipped with a Head Mounted Display (HMD). This is a helmet or a face mask that holds the visual and
auditory displays. The helmet may be free ranging, tethered, or it might be attached to some sort of a boom armature.

A nice variation of the immersive systems use multiple large projection displays to create a \'Cave\' or room in which the
viewer(s) stand. An early implementation was called "The Closet Cathedral" for the ability to create the impression of an
immense environment. within a small physical space.