Virtual reality (VR) is the ultimate simulator. The user can see and hear in an artificial realm called a virtual universe or VR universe. In the most sophisticated VR systems, other senses are replicated as well. Hardware and software developers in several countries, particularly the United States and Japan, are actively involved in VR technology.

Forms of VR

There are three degrees, or types, of VR. They are categorized according to the extent to which the operator participates in the experience. The first two forms are sometimes called virtual virtual reality (VVR). Passive VR is, in effect, a movie with enhanced graphics and sound. You can watch, listen, and feel the show, but you have no control over what happens, nor on the general contents of the show. An example of passive VR is a ride in a virtual submarine, a small room with windows through which you can look at a rendition of the undersea world. Exploratory VR is like a movie over which you have some control of the contents. You can choose scenes to see, hear, and feel, but you cannot participate fully in the experience.An example of exploratory VR is a ride in a tour bus on an alien planet, in which you get to choose the planet. Interactive VR is what most people imagine when they think of true VR.You have nearly as much control over the virtual environment as you would have if you were really there.Your surroundings react directly to your actions. If you reach out and push a virtual object, it moves. If you speak to virtual people, they respond.


The program, or set of programs, containing all the particulars for each VR session is called the simulation manager. The complexity of the simulation manager depends on the level of VR.

One dimension: In passive VR, the simulation manager consists of a large number of frames, one representing each moment in time. The frames lend together into a space-time experience path. This can be imagined, in simplified form, as a set of points strung out along a straight line in one geometric dimension (Fig. 1). Each point represents data for one instant of time in the VR session. This is similar to the way frames exist in a movie or a videotape.

Two dimensions: In exploratory VR, there are several different sets of frames, from among which you can choose to construct the experience path. Imagine each set of frames as lying along its own individual line, as shown in Fig. 2. You choose the line through space-time along which you want to travel. (Again, this is a simplistic rendition; there are far more points in an actual exploratory VR session than are shown here.) This is similar to having a selection of movies or videotapes from which to choose.

Three dimensions: In interactive VR, the sequence of frames depends on your input from moment to moment, adding another dimension to the programming. This can be rendered as a three-dimensional space (Fig. 3). The drawing shows only a few points along one path. There can be millions upon millions of points in the interactive experience space. The number of possible experience paths is vastly larger than the number of points themselves. It is impossible to make a good analogy with movies or videotapes in this case. The software, and the required computer hardware, for interactive VR is far more powerful than that in the passive or exploratory VR experiences.


Several hardware items, in addition to the programming, are required for VR.

Computer: For VR to be possible, even in the simplest form, a computer is necessary. The amount of computer power required depends on the sophistication of the VR session. Passive VR requires the least computer power, while exploratory VR needs more, and interactive VR takes even more. A high-end personal computer can provide passive and exploratory VR with moderate image resolution and speed. Larger computers, such as those used in file servers or that employ parallel processing (more than one microprocessor operating on a given task), are necessary for highresolution,
high-speed, and vivid interactive VR. The best interactive VR equipment is too expensive for most personal-computer users.

Robot: If the VR is intended to portray and facilitate the operation of a remotely controlled robot or telechir, that robot must have certain characteristics. In low-level VR, the telechir can be a simple vehicle that rolls on wheels or a track drive. In the most sophisticated VR telepresence systems, the telechir must be an android (humanoid robot).

Video system: This can be a simple monitor, a big screen, a set of several monitors, or a head-mounted display (HMD). The HMD gives a spectacular show, with binocular vision and sharp colors. Some HMDs shut out the operator’s view of the real world; others let the operator see the virtual universe superimposed on the real one. The HMD uses small liquid-crystal display (LCD) screens, whose images are magnified by lenses and/or reflected by mirrors to obtain the desired effects.

Sound system: Stereo, high-fidelity sound is the norm in all VR universes. Loudspeakers can be used for low-level, group VR experiences. In an individual system, a set of headphones is included in the HMD. The sound programming is synchronized with the visual programming. Speech recognition and speech synthesis can be used so that virtual people, virtual robots, or virtual space aliens can communicate their virtual thoughts and feelings to the user.

Input devices: Passive and exploratory VR systems do not need input devices, except for the media that contain the programming. Interactive systems can make use of a variety of mechanical equipment. The nature of the input device(s) depends on the VR universe. For example, driving a car requires a steering wheel, gas pedal, and brake (at least). Games need a joystick or mouse. Devices called bats and birds resemble computer mice, but are movable in three dimensions rather than only two. Levers, handles, treadmills, stationary bicycles, pulley weights, and other devices
allow for real physical activities on the part of the operator. For complete hand control, special gloves can be used. These have air bladders built in, providing a sense of touch and physical resistance, so objects seem to have substance and heft. The computer can be equipped with speech recognition and speech synthesis so that the user can talk to virtual creatures. This requires at least one sound transducer at the operating location.

A complete system: Figure 4 is a block diagram showing the hardware for a typical interactive VR system, in which the user gets the impression of riding a bicycle down a street. This can be used for exercise as well as for entertainment. The system provides sights, sounds, and variable pedal resistance as the user negotiates hills and encounters wind. If a teleoperated android is put on a real bicycle, the VR system can be used to control that robot and bicycle remotely. This would involve the addition of two wireless transceivers (one for the computer and the other for the telechir), along with modems and antennas.


Virtual reality has been used as an entertainment and excitement medium.It also has practical applications.

Instruction: Virtual reality can be used in computer-assisted instruction (CAI). For example, a person can be trained to fly an aircraft, pilot a submarine, or operate complex and dangerous machinery,without any danger of being injured or killed during training. This form of CAI has been used by the military for some time. It has also been used for training medical personnel, particularly surgeons, who can operate on “virtual patients” while they perfect their skills.

Group VR: Passive and exploratory VR can be provided to groups of people. Several theme parks in the United States and Japan have already installed equipment of this type. People sit in chairs while they watch, and listen to, the portrayal of an intergalactic journey, a submarine ride, or a trip through time. The main limitation is that everyone has the same virtual experience.

Individual VR: Interactive VR, intended for individual users, is also found in theme parks. These sessions are expensive and generally last only a few minutes. You might walk on an alien planet inhabited by robots, ride in a Moon buggy, or swim with porpoises. The environment reacts to your input from moment to moment. You might go through the same 10-min “show” 100 times and have 100 different VR experiences. Hostile environments: In conjunction with robotics,VR facilitates remote control using telepresence. This allows a human operator to safely operate machines located in dangerous places. People using such a system get illusions similar to those in theme parks, except that a robot, at some distance, follows the operator’s movements.Teleoperated robots have been
used for rescue operations, for disarming bombs, and for maintaining nuclear reactors.

Warfare: Teleoperated robot tanks, aircraft, boats, and androids (humanoid robots) can be used in combat. One person can operate a “super android”with the strength of 100 fighting men and the endurance of a well-engineered machine. Such robots are immune to deadly radiation and chemicals. They have no mortal fear, which sometimes causes human soldiers to freeze up at critical moments in combat. Exercise:Walking, jogging, riding a bike, skiing, playing golf, and playing handball are examples of virtual activities that can provide most of the benefits of the real experience. The user might not really be doing the thing, but calories are burned, and aerobic benefits are realized. There is no danger of getting maimed by a car while cycling on a virtual street, or breaking a leg while skiing down a virtual mountain. (However, outdoor people will doubtless prefer the real activity to the virtual one, no matter how realistic VR becomes.)

Escape: Another possible, but not yet widely tested, use for virtual reality is as an escape from boredom and frustration in the real world. You can put on an HMD and romp in a jungle with dinosaurs. If the monsters try to eat you, you can take the helmet off. You can walk on some unknown planet, or under the sea.You can fly high above clouds or tunnel through the center of the earth.

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