Virtual reality (VR) is a technology which allows a user to interact with a
computer-simulated environment, whether that environment is a simulation of the real
world or an imaginary world. Most current virtual reality environments are primarily
visual experiences, displayed either on a computer screen or through special or
stereoscopic displays, but some simulations include additional sensory information, such
as sound through speakers or headphones. Some advanced, hepatic systems now include
tactile information, generally known as force feedback, in medical and gaming
applications. Users can interact with a virtual environment or a virtual artifact (VA) either
through the use of standard input devices such as a keyboard and mouse, or through
multimodal devices such as a wired glove, the boom arm, and Omni directional treadmill.
The simulated environment can be similar to the real world, for example, simulations for
pilot or combat training, or it can differ significantly from reality, as in VR games.
Virtual reality can be divided into:
The simulation of a real environment for training and education.
The development of an imagined environment for a game or interactive story.
1.2 TERMS OF VIRTUAL REALITY:
"Virtual" refers to its computer-generated existence; some prefer the term "cyber" to
reinforce the world.
"Reality" is the more controversial term. Realism debates whirl around what levels of
realistic detail are needed and affordable. Practitioners can choose types and amounts
of reality varying from "objective" to "novel" and from specific to variable, or
VR has five main components which are variable according per the instructional context
motion or animation,
viewpoint or frame of reference, and
Immersion, or embodiment, through enhanced multisensory experiences.
1.3 WHY IS VR USEFUL?
VR technologies address a wide range of interaction and immersion capabilities.
Interaction varies learner control during the VR experience. Immersion varies from first-,
second-, or third-person experiences and in physical, perceptual, and psychological
The concept of virtual reality has been around for decades, even though the public
really only became aware of it in the early 1990s. In the mid 1950s, a
cinematographer named Morton Heilig envisioned a theatre experience that would
stimulate all his audiences’ senses, drawing them in to the stories more effectively.
He built a single user console in 1960 called the Sensorama that included a
stereoscopic display, fans, odor emitters, stereo speakers and a moving chair. He also
invented a head mounted television display designed to let a user watch television in
3-D. Users were passive audiences for the films, but many of Heilig’s concepts would
find their way into the VR field.
Philco Corporation engineers developed the first HMD in 1961, called the Head sight.
The helmet included a video screen and tracking system, which the engineers linked
to a closed circuit camera system. They intended the HMD for use in dangerous
situations -- a user could observe a real environment remotely, adjusting the camera
angle by turning his head. Bell Laboratories used a similar HMD for helicopter pilots.
They linked HMDs to infrared cameras attached to the bottom of helicopters, which
allowed pilots to have a clear field of view while flying in the dark.
In 1965, a computer scientist named Ivan Sutherland envisioned what he called the
“Ultimate Display.” Using this display, a person could look into a virtual world that
would appear as real as the physical world the user lived in. This vision guided almost all
the developments within the field of virtual reality. Sutherland’s concept included:
A virtual world that appears real to any observer, seen through an HMD and
augmented through three-dimensional sound and tactile stimuli
A computer that maintains the world model in real time
The ability for users to manipulate virtual objects in a realistic, intuitive way
In 1966, Sutherland built an HMD that was tethered to a computer system. The computer
provided all the graphics for the display.
Although it is difficult to categorize all VR systems, most configurations fall into
three main categories and each category can be ranked by the sense of immersion, or
degree of presence it provides. Immersion or presence can be regarded as how powerfully
the attention of the user is focused on the task in hand. Immersion presence is generally
believed to be the product of several parameters including level of interactivity, image
complexity, stereoscopic view, and field of regard and the update rate of the display. For
example, providing a stereoscopic rather than monoscopic view of the virtual
environment will increase the sense of immersion experienced by the user. It must be
stressed that no one parameter is effective in isolation and the level of immersion
achieved is due to the complex interaction of the many factors involved.
3.1 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."
Telepresence is a variation on visualizing complete computer generated worlds.
This technology links remote sensors in the real world with the senses of a human
operator. The remote sensors might be located on a robot, or they might be on the ends of
WALDO like tools. Fire fighters use remotely operated vehicles to handle some
dangerous conditions. Surgeons are using very small instruments on cables to do surgery
without cutting a major hole in their patients. The instruments have a small video camera
at the business end. Robots equipped with Telepresence systems have already changed
the way deep sea and volcanic exploration is done. NASA plans to use telerobotics for
space exploration. There is currently a joint US/Russian project researching Telepresence
for space rover exploration.
3.3 Mixed Reality
Merging the Telepresence and Virtual Reality systems gives the Mixed Reality or
Seamless Simulation systems. Here the computer generated inputs are merged with
Telepresence inputs and/or the users view of the real world. A surgeon's view of a
brain surgery is overlaid with images from earlier CAT scans and real-time
ultrasound. A fighter pilot sees computer generated maps and data displays inside his
fancy helmet visor or on cockpit displays.
The phrase "fish tank virtual reality" was used to describe a Canadian VR system
reported in the 1993 InterCHI proceedings. It combines a stereoscopic monitor
display using liquid crystal shutter glasses with a mechanical head tracker. The
resulting system is superior to simple stereo-WoW systems due to the motion parallax
effects introduced by the head tracker.
3.4 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. The Holodeck used in the television
series "Star Trek: The Next Generation" is afar term extrapolation of this technology.
3.5 Non-Immersive Systems
Non-immersive systems, as the name suggests, are the least immersive
implementation of VR techniques. Using the desktop system, the virtual environment
is viewed through a portal or window by utilizing a standard high resolution monitor.
Interaction with the virtual environment can occur by conventional means such as
keyboards, mice and trackballs or may be enhanced by using 3D interaction devices
such as a Space Ball; or Data Glove.
The non-immersive system has advantages in that they do not require the highest
level of graphics performance, no special hardware and can be implemented on high
specification PC clones. This means that these systems can be regarded as the lowest
cost VR solution which can be used for many applications. However, this low cost
means that these systems will always be outperformed by more sophisticated
implementations, provide almost no sense of immersion and are limited to a certain
extent by current 2D interaction devices.
3.6 Semi-Immersive Systems
Semi-immersive systems are a relatively new implementation of VR technology and
borrow considerably from technologies developed in the flight simulation field. A semiimmersive system will comprise of a relatively high performance graphics computing
system which can be coupled with either:
A large screen monitor
A large screen projector system
Multiple television projection systems
In many ways, these projection systems are similar to the IMAX theatres. Using a
wide field of view, these systems increase the feeling of immersion or presence
experienced by the user. However, the quality of the projected image is an important
consideration. It is important to calibrate the geometry of the projected image to the
shape of the screen to prevent distortions and the resolution will determine the quality of
textures, colors, the ability of define shapes and the ability of the user to read text onscreen. The resolutions of projection systems range from 1000 - 3000 lines but to achieve
the highest levels it may be necessary to use multiple projection systems which are more
3.7 Fully Immersive Systems
The most direct experience of virtual environments is provided by fully
immersive VR systems. These systems are probably the most widely known VR
implementation where the user either wears an HMD or uses some form of head-coupled
display such as a Binocular Omni-Orientation Monitor or BOOM. Fully immersive VR
systems tend to be the most demanding in terms of the computing power and level of
technology required achieving a satisfactory level of realism and development is
constantly underway to improve the technologies. Major areas of research and
development include field of view vs. resolution trade-offs, reducing the size and weight
of HMDs and reducing system lag times.
A good comparison between the various VR implementations is shown below. It
is also important that these implementations are not regarded as distinct boundaries for
implementations. For example, it is possible to turn a desktop system into a semiimmersive system by simply adding shutter glasses and the appropriate software, or a
fully immersive system by connecting an HMD.
Low - Medium
Medium - High
Sense of situational Low
Field of regard
Medium - High
Medium - High
Medium - High
of None - low
There are a number of specialized types of hardware devices that have been developed or
used for Virtual Reality applications.
5.1 Head Mounted Display (HMD)
One hardware device closely associated with VR is the Head Mounted Device
(HMD). These use some sort of helmet or goggles to place small video displays in
front of each eye, with special optics to focus and stretch the perceived field of view.
Most HMDs use two displays and can provide stereoscopic imaging. Others use a
single larger display to provide higher resolution, but without the stereoscopic vision.
An HMD uses small monitors placed in front of each eye which can provide stereo,
bi-ocular or monocular images. Stereo images are provided in a similar way to shutter
glasses, in that a slightly different image is presented to each eye. The major
difference is that the two screens are placed very close (50-70mm) to the eye,
although the image, which the wearer focuses on, will be much further away because
of the HMD optical system. Bi-ocular images can be provided by displaying identical
images on each screen and monocular images by using only one display screen.
5.2 Binocular Omni-Orientation Monitor
The human brain perceives depth only because it has two eyes for visual input. Each
eye sees a slightly different angle of the same scene. These two separate views are
combined in the brain to form a single, 3D image, with parts of the data from each
eye used to work out relative distances.
To replicate this effect in VR, you require a device that can do the same thing – give
each eye a separate view. Enter the BOOM or Binocular Omni Orientation Monitor.
The Binocular Omni Orientation Monitor or BOOM is one of the oldest VR displays,
and direct ancestor to the HMD. It consists of a 3-D display device suspended from a
weighted boom that can swivel freely. Sometimes this boom is mounted on a trolley,
sometimes affixed to the ceiling.
BOOMs typically communicate the user’s point of view to the computer system by
the position and orientation of the view port. Typical BOOM configurations will
swivel in six degrees of freedom, moving up and down and swiveling on the boom as
well as rotating about an axis point, to closely replicate head movements without
being attached to the head.
5.3 Cave Automatic Virtual Environment
A Cave Automatic Virtual Environment is an immersive virtual reality environment
where projectors are directed to three, four, five or six of the walls of a room-sized
cube. The name is also a reference to the allegory of the Cave in Plato's Republic
where a philosopher contemplates perception, reality and illusion.
The CAVE is a 10’ X 10’ X 9’ theatre that sits in a larger room measured to be
around 35’ X 25’ X 13’. The walls of the CAVE are made up of rear-projection
screens, and the floor is made of a down-projection screen. High-resolution projectors
(the University of Illinois uses an Electro home Marquee 8000) display images on
each of the screens by projecting the images onto mirrors which reflect the images
onto the projection screens.
5.4 Data Gloves
One common VR device is the instrumented glove. The use of a glove to manipulate
objects in a computer is covered by a basic patent in the USA. Such a glove is
outfitted with sensors on the fingers as well as an overall position/orientation tracker.
There are a number of different types of sensors that can be used. This device is
easily adapted to interface to a personal computer. It provides some limited hand
location and finger position data using strain gauges for finger bends and ultrasonic
5.5 Control Devices
One key element for interaction with a virtual world
is a means of tracking the position of a real world
object, such as a head or hand. There are numerous
methods for position tracking and control. Ideally a
position(X, Y, Z) and 3 measures of orientation
(roll, pitch, and yaw). One of the biggest problems
for position tracking is latency, or the time required
to make the measurements and preprocess them
before input to the simulation engine.
The simplest control hardware is a conventional mouse, trackball or joystick. While these
are two dimensional devices, creative programming can use them for 6D controls. There
are a number of 3 and 6 dimensional mice/trackball/joystick devices being introduced to
the market at this time. These add some extra buttons and wheels that are used to control
not just the XY translation of a cursor, but its Z dimension and rotations in all three
directions. The Global Devices 6D Controllers is one such 6D joystick it looks like a
racket ball mounted on a short stick. You can pull and twist the ball in addition to the
left/right & forward/back of a normal joystick. Other 3D and 6D mice, joystick and force
balls are available from Logitech, Mouse System Corp. among others.
There are two major categories for the available VR software: toolkits and
authoring systems. Toolkits are programming libraries, generally for C or C++ that
provides a set of functions with which a skilled programmer can create VR applications.
Authoring systems are complete programs with graphical interfaces for creating worlds
without resorting to detailed programming. These usually include some sort of scripting
language in which to describe complex actions, so they are not really non-programming,
just much simpler programming. The programming libraries are generally more flexible
and have faster renders than the authoring systems, but you must be a very skilled
programmer to use them.
Multiverse is a freeware UNIX based client/server system written by Robert Grant. It
is a multi-user, non-immersive; X-Windows based Virtual Reality system, primarily
focused on entertainment/research. It includes capabilities for setting up multi-person
worlds and a client/server type world simulation over a local or long haul network.
Multiverse source and binaries for several flavors of UNIX are available via
anonymous ftp from medg.lcs.mit.edu in the directory pub/multiverse
6.2 Virtual Reality Studio
Virtual Reality Studio (or VR Studio, VRS) is a very low cost VR authoring system
that does allow the user to define their own virtual worlds. This program is also
known as "3D Construction Kit" in Europe. The program has a fairly nice graphical
interface and includes a simple scripting language. It is available for about $100 from
Domark for PC and Amiga systems. Worlds created with the program can be freely
distributed with a player program. There are a quite number of these worlds available
from the BBSes, and other sources. Compuserve's Cyber forum has several in its
libraries, like the company provided demo VRSDMO.ZIP (VRS.TXT gives a solution
to the demo game). Version 2 of VR Studio was released in early 1993. It has many
new features including a much enhanced scripting language and editor, but also an
annoying number of bugs. The developers of VRS (Dimension International) are
working hard to correct these.
6.3 Sense8 World Tool Kit
Sense 8 has announced a $795 programming library for Windows called World Tool
Kit for Windows. This will be released late in 1993 as DLL for Windows systems. It
will work directly with standard SVGA displays and show worlds with texture
mapping either within a window or allow full screen display. The programming
library will support DDE so a virtual world can be controlled from a spreadsheet,
database or other program.
The Sense8 World Tool Kit (WTK) is probably the most widely used product of this
type. It runs on a wide variety of platforms from i860 assisted PCs to high end SGI
boxes. It has won several awards for excellence.
6.4 Autodesk Cyberspace Development Kit
The Autodesk Cyberspace Development kit is another product in this range. It is a
C++ library for MSDOS systems using the Metaware HighC/C++ compiler and Pharlap
DOS 32bit extender. It supports VESA displays as well as several rendering accelerator
boards (SPEA Fireboard, FVS Sapphire, Division's dView). I used this system for a few
months and found it requires a strong background in C++ and a rendering accelerator
card. VESA speeds were about 4 frames per second.
The basic parts of the system can be broken down into an Input Processor, a Simulation
Processor, a Rendering Process, and a World Database. All these parts must consider the
time required for processing. Every delay in response time degrades the feeling of
'presence' and reality of the simulation.
7.1 Input Processor
The Input Processes of a VR program control the devices used to input
information to the computer. There are a wide variety of possible input devices:
keyboard, mouse, trackball, joystick, 3D & 6D position trackers (glove, wand, head
tracker, body suit, etc.). A networked VR system would add inputs received from net. A
voice recognition system is also a good augmentation for VR, especially if the user's
hands are being used for other tasks. Generally, the input processing of a VR system is
kept simple. The object is to get the coordinate data to the rest of the system with
minimal lag time. Some position sensor systems add some filtering and data smoothing
processing. Some glove systems add gesture recognition. This processing step examines
the glove inputs and determines when a specific gesture has been made. Thus it can
provide a higher level of input to the simulation.
7.2 Simulation Processor
The core of a VR program is the simulation system. This is the process that knows
about the objects and the various inputs. It handles the interactions, the scripted object
actions, simulations of physical laws (real or imaginary) and determines the world
status. This simulation is basically a discrete process that is iterated once for each
time step or frame. A networked VR application may have multiple simulations
running on different machines, each with a different time step. Coordination of these
can be a complex task.
It is the simulation engine that takes the user inputs along with any tasks programmed
into the world such as collision detection, scripts, etc. and determines the actions that
will take place in the virtual world.
7.3 Rendering Processor
The Rendering Processes of a VR program are those that create the sensations that
are output to the user. A network VR program would also output data to other network
processes. There would be separate rendering processes for visual, auditory, haptic
(touch/force), and other sensory systems. Each renderer would take a description of the
world state from the simulation process or derive it directly from the World Database for
each time step.
7.4 World Database
The storage of information on objects and the world is a major part of the design of a
VR system. The primary things that are stored in the World Database are the objects
that inhabit the world, scripts that describe actions of those objects or the user,
lighting, program controls, and hardware device support.
There are a number of different ways the world information may be stored: a single
file, a collection of files, or a database. The multiple file method is one of the more
common approaches for VR development packages. Each object has one or more files
(geometry, scripts, etc.) and there is some overall 'world' file that causes the other
files to be loaded. Some systems also include a configuration file that defines the
hardware interface connections.
Sometimes the entire database is loaded during program startup; other systems only
read the currently needed files. A real database system helps tremendously with the
latter approach. An Object Oriented Database would be a great fit for a VR system,
but I am not aware of any projects currently using one.
Virtual Reality is well known for its use with flight simulators and games. However,
these are only two of the many ways virtual reality is being used today. This article will
summarize how virtual reality is used in medicine, architecture, weather simulation, and
Mark Billinghurst, at the Hit Lab in Washington, has developed a prototype surgical
assistant for simulation of paranasal surgery. During a simulated operation the system
provides vocal and visual feedback to the user, and warns the surgeon when a
dangerous action is about to take place. In addition to training, the expert assistant can
be used during the actual operation to provide feedback and guidance. This is very
useful when the surgeon's awareness of the situation is limited due to complex
Finally, Billinghurst and his associates are working at developing a toolkit for
physicians which will help them create their own expert assistants for other types of
The department of visualization and virtual reality at the IGD University in Germany
has developed a program that uses radiosity and ray tracing to simulate light. This
virtual reality program has applications in the area of architecture and light
With light simulation architects can examine how outdoor light will fall inside and
outside their building before it is built. If the lighting needs to be redesigned, the
architect can redesign the building on the computer and examine the new outdoor
In addition to outdoor light, lighting engineers use virtual reality to examine the
effects of point lights, spotlights and other indoor light sources. An interior designer
could examine how light will affect different room arrangements.
3. WEATHER SIMULATION:
It has developed a visualization system for weather forecasting called "TriVis".
TriVis accepts data from meteorological services such as satellite data, statistically
corrected forecast data, precipitation data and fronts information. It then analyzes this
data and uses fractal functions to create projections of storm systems. Using TriVis to
visualize artificial clouds, meteorologists can predict weather with increased
The data gathered and analyzed by the TriVis system is used by television weather
reporters to show their audiences storm systems. TriVis has been used in television
weather forecasts since 1993.
Real Mol is a program that uses virtual reality to show molecular models in an
interactive, immersive environment. The scientist who uses the program wears a
cyber glove and a head mounted display to interact with the molecular system. Using
Real Mol scientists can move molecules or protein chains to create new molecules.
This is useful in fields such as drug design.
Real Mol displays molecules in three ways: ball and stick model, stick model and
CPK model. The molecules are rendered through a molecular dynamics simulation
VR is imaginably more personal than electronic mail or instant messaging, or even a
letter or a telephone call.
VR is a great social leveler; it may find a common ground across differences in age,
culture, and linguistic orientation.
People will be drawn together by similar interests instead of purely by geographic
Communication will be challenging and rewarding, more effective and productive,
and thus more enjoyable.
A tremendous opportunity for every 'connected' person to find his or her field and/or
After using a medium that provides total freedom of expression face-to-face
communication may be found to be too confining.
An inescapable aspect of social life is the formation and maintenance of interpersonal
Interaction ought not to be substituted for community.
Separates the 'haves' from the 'have-nots', a technology of Information Age
VR will provide a communication environment in which the dangers of deception and
the benefits of creativity are amplified beyond the levels that humans currently
experience in their interpersonal interactions.
Could lead to low self-esteem, feelings of worthlessness and insignificance, even selfdestructive acts.