Virtual Reality - What it is and How it Works

Imagine being able to point into the sky and fly. Or

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perhaps walk through space and connect molecules together.

These are some of the dreams that have come with the

invention of virtual reality. With the introduction of

computers, numerous applications have been enhanced or

created. The newest technology that is being tapped is that

of artificial reality, or "virtual reality" (VR). When

Morton Heilig first got a patent for his "Sensorama

Simulator" in 1962, he had no idea that 30 years later

people would still be trying to simulate reality and that

they would be doing it so effectively. Jaron Lanier first

coined the phrase "virtual reality" around 1989, and it has

stuck ever since. Unfortunately, this catchy name has

caused people to dream up incredible uses for this

technology including using it as a sort of drug. This became

evident when, among other people, Timothy Leary became

interested in VR. This has also worried some of the

researchers who are trying to create very real applications

for medical, space, physical, chemical, and entertainment

uses among other things.

In order to create this alternate reality, however, you

need to find ways to create the illusion of reality with a

piece of machinery known as the computer. This is done with

several computer-user interfaces used to simulate the

senses. Among these, are stereoscopic glasses to make the

simulated world look real, a 3D auditory display to give

depth to sound, sensor lined gloves to simulate tactile

feedback, and head-trackers to follow the orientation of the

head. Since the technology is fairly young, these

interfaces have not been perfected, making for a somewhat

cartoonish simulated reality.

Stereoscopic vision is probably the most important

feature of VR because in real life, people rely mainly on

vision to get places and do things. The eyes are

approximately 6.5 centimeters apart, and allow you to have a

full-colour, three-dimensional view of the world.

Stereoscopy, in itself, is not a very new idea, but the new

twist is trying to generate completely new images in real-

time. In 1933, Sir Charles Wheatstone invented the first

stereoscope with the same basic principle being used in

today's head-mounted displays. Presenting different views

to each eye gives the illusion of three dimensions. The

glasses that are used today work by using what is called an

"electronic shutter". The lenses of the glasses interleaveOh)0*0*0*A‚A°A‚A°O?the left-eye and right-eye views every thirtieth of a

second. The shutters selectively block and admit views of

the screen in sync with the interleaving, allowing the

proper views to go into each eye. The problem with this

method though is that you have to wear special glasses.

Most VR researchers use complicated headsets, but it is

possible to create stereoscopic three-dimensional images

without them. One such way is through the use of lenticular

lenses. These lenses, known since Herman Ives experimented

with them in 1930, allow one to take two images, cut them

into thin vertical slices and interleave them in precise

order (also called multiplexing) and put cylinder shaped

lenses in front of them so that when you look into them

directly, the images correspond with each eye. This

illusion of depth is based on what is called binocular

parallax. Another problem that is solved is that which

occurs when one turns their head. Nearby objects appear to

move more than distant objects. This is called motion

parallax. Lenticular screens can show users the proper

stereo images when moving their heads well when a head-

motion sensor is used to adjust the effect.

Sound is another important part of daily life, and thus

must be simulated well in order to create artificial

reality. Many scientists including Dr. Elizabeth Wenzel, a

researcher at NASA, are convinced the 3D audio will be

useful for scientific visualization and space applications

in the ways the 3D video is somewhat limited. She has come

up with an interesting use for virtual sound that would

allow an astronaut to hear the state of their oxygen, or

have an acoustical beacon that directs one to a trouble spot

on a satellite. The "Convolvotron" is one such device that

simulates the location of up to four audio channels with a

sort of imaginary sphere surrounding the listener. This

device takes into account that each person has specialized

auditory signal processing, and personalizes what each

person hears.

Using a position sensor from Polhemus, another VR

research company, it is possible to move the position of

sound by simply moving a small cube around in your hand.

The key to the Convolvotron is something called the "Head-

Related Transfer Function (HRTF)", which is a set of

mathematically modelable responses that our ears impose on

the signals they get from the air. In order to develop the

HRTF, researchers had to sit people in an anechoic room

surrounded with 144 different speakers to measure the

effects of hearing precise sounds from every direction by

using tiny microphone probes placed near the eardrums of the

listener. The way in which those microphones distorted the

sound from all directions was a specific model of the way

that person's ears impose a complex signal on incoming sound

waves in order to encode it in their spatial environment.Oh)0*0*0*A‚A°A‚A°O?The map of the results is then converted to numbers and a

computer performs about 300 million operations per second

(MIPS) to create a numerical model based on the HRTF which

makes it possible to reconfigure any sound source so that it

appears to be coming from any number of different points

within the acoustic sphere.

This portion of a VR system can really enhance the visual

and tactile responses. Imagine hearing the sound of

footsteps behind you in a dark alley late at night. That is

how important 3D sound really is.

The third important sense that we use in everyday life is

that of touch. There is no way of avoiding the feeling of

touch, and thus this is one of the technologies that is

being researched upon most feverishly. The two main types

of feedback that are being researched are that of force-

reflection feedback and tactile feedback. Force feedback

devices exert a force against the user when they try to push

something in a virtual world that is 'heavy'. Tactile

feedback is the sensation of feeling an object such as the

texture of sandpaper. Both are equally important in the

development of VR.

Currently, the most successful development in force-

reflective feedback is that of the Argonne Remote

Manipulator (ARM). It consists of a group of articulated

joints, encoiled by long bunches of electrical cables. The

ARM allows for six degrees of movement (position and

orientation) to give a true feel of movement. Suspended

from the ceiling and connected by a wire to the computer,

this machine grants a user the power to reach out and

manipulate 3D objects that are not real. As is the case at

the University of North Carolina, it is possible to "dock

molecules" using VR. Simulating molecular forces and

translating them into physical forces allows the ARM to push

back at the user if he tries to dock the molecules

incorrectly.

Tactile feedback is just as important as force feedback

in allowing the user to "feel" computer-generated objects.

There are several methods for providing tactile feedback.

Some of these include inflating air bladders in a glove,

arrays of tiny pins moved by shape memory wires, and even

fingertip piezoelectric vibrotactile actuators. The latter

method uses tiny crystals that vibrate when an electric

current stimulates them. This design has not really taken

off however, but the other two methods are being more

actively researched. According to a report called "Tactile

Sensing in Humans and Robots," distortions inside the skins

cause mechanosensitive nerve terminals to respond with

electrical impulses. Each impulse is approximately 50 to

100mV in magnitude and 1 ms in duration. However, the

frequency of the impulses (up to a maximum of 500/s) dependsOh)0*0*0*A‚A°A‚A°O?on the intensity of the combination of the stresses in the

area near the receptor which is responsive. In other words,

the sensors which affect pressure in the skin are all

basically the same, but can convey a message over and over

to give the feeling of pressure. Therefore, in order to

have any kind of tactile response system, there must be a

frequency of about 500 Hz in order to simulate the tactile

accuracy of the human.

Right now however, the gloves being used are used as

input devices. One such device is that called the

DataGlove. This well-fitting glove has bundles of optic

fibers attached at the knuckles and joints. Light is passed

through these optic fibers at one end of the glove. When a

finger is bent, the fibers also bend, and the amount of

light that is allowed through the fiber can be converted to

determine the location at which the user is. The type of

glove that is wanted is one that can be used as an input and

output device. Jim Hennequin has worked on an "Air Muscle"

that inflates and deflates parts of a glove to allow the

feeling of various kinds of pressure. Unfortunately at this

time, the feel it creates is somewhat crude. The company

TiNi is exploring the possibility of using "shape memory

alloys" to create tactile response devices. TiNi uses an

alloy called nitinol as the basis for a small grid of what

look like ballpoint-pen tips. Nitinol can take the shape of

whatever it is cast in, and can be reshaped. Then when it

is electrically stimulated, the alloy it can return to its

original cast shape. The hope is that in the future some of

these techniques will be used to form a complete body suit

that can simulate tactile sensation.

Being able to determine where in the virtual world means

you need to have orientation and position trackers to follow

the movements of the head and other parts of the body that

are interfacing with the computer. Many companies have

developed successful methods of allowing six degrees of

freedom including Polhemus Research, and Shooting Star

Technology. Six degrees of freedom refers to a combination

cartesian coordinate system and an orientation system with

rotation angles called roll, pitch and yaw. The ADL-1 from

Shooting Star is a sophisticated and inexpensive (relative

to other trackers) 6D tracking system which is mounted on

the head, and converts position and orientation information

into a readable form for the computer. The machine

calculates head/object position by the use of a lightweight,

multiply-jointed arm. Sensors mounted on this arm measure

the angles of the joints. The computer-based control unit

uses these angles to compute position-orientation

information so that the user can manipulate a virtual world.

The joint angle transducers use conductive plastic

potentiometers and ball bearings so that this machine is

heavy duty. Time-lag is eliminated by the direct-reading

transducers and high speed microprocessor, allowing for a

maximum update rate of approximately 300Oh)0*0*0*A‚A°A‚A°O?measurements/second.

Another system developed by Ascension Technology does

basically the same thing as the ADL-1, but the sensor is in

the form of a small cube which can fit in the users hand or

in a computer mouse specially developed to encase it. The

Ascension Bird is the first system that generates and senses

DC magnetic fields. The Ascension Bird first measures the

earth's magnetic field and then the steady magnetic field

generated by the transmitter. The earth's field is then

subtracted from the total, which allows one to yield true

position and orientation measurements. The existing

electromagnetic systems transmit a rapidly varying AC field.

As this field varies, eddy currents are induced in nearby

metals which causes the metals to become electromagnets

which distort the measurements. The Ascension Bird uses a

steady DC magnetic filed which does not create an eddy

current. The update rate of the Bird is 100

measurements/second. However, the Bird has a small lag of

about 1/60th of a second which is noticeable.

Researchers have also thought about supporting the other

senses such as taste and smell, but have decided that it is

unfeasible to do. Smell would be possible, and would

enhance reality, but there is a certain problem with the

fact that there is only a limited spectrum of smells that

could be simulated. Taste is basically a disgusting premise

from most standpoints. It might be useful for entertainment

purposes, but has almost no purpose for researchers or

developers. For one thing, people would have to put some

kind of receptors in their mouths and it would be very

unsanitary. Thus, the main senses that are relied on in a

virtual reality are sight, touch, and hearing.

Applications of Virtual Reality

Virtual Reality has promise for nearly every industry

ranging from architecture and design to movies and

entertainment, but the real industry to gain from this

technology is science, in general. The money that can be

saved examining the feasibility of experiments in an

artificial world before they are done could be great, and

the money saved on energy used to operate such things as

wind tunnels quite large.

The best example of how VR can help science is that of

the "molecular docking" experiments being done in Chapel

Hill, North Carolina. Scientists at the University of North

Carolina have developed a system that simulated the bonding

of molecules. But instead of using complicated formulas to

determine bonding energy, or illegible stick drawings, the

potential chemist can don a high-tech head-mounted display,

attach themselves to an artificial arm from the ceiling andOh)0*0*0*A‚A°A‚A°O?actually push the molecules together to determine whether or

not they can be connected. The chemical bonding process

takes on a sort of puzzle-like quality, in which even

children could learn to form bonds using a trial and error

method.

Architectural designers have also found that VR can be

useful in visualizing what their buildings will look like

when they are put together. Often, using a 2D diagram to

represent a 3D home is confusing, and the people that fund

large projects would like to be able to see what they are

paying for before it is constructed. An example which is

fascinating would be that of designing an elementary school.

Designers could walk in the school from a child's

perspective to gain insight on how high that water fountain

is, or how narrow the halls are. Product designers could

also use VR in similar ways to test their products.

NASA and other aerospace facilities are concentrating

research on such things as human factors engineering,

virtual prototyping of buildings and military devices,

aerodynamic analysis, flight simulation, 3D data

visualization, satellite position fixing, and planetary

exploration simulations. Such things as virtual wind

tunnels have been in development for a couple years and

could save money and energy for aerospace companies.

Medical researchers have been using VR techniques to

synthesize diagnostic images of a patient's body to do

"predictive" modeling of radiation treatment using images

created by ultrasound, magnetic resonance imaging, and X-

ray. A radiation therapist in a virtual would could view

and expose a tumour at any angle and then model specific

doses and configurations of radiation beams to aim at the

tumour more effectively. Since radiation destroys human

tissue easily, there is no allowance for error.

Also, doctors could use "virtual cadavers" to practice

rare operations which are tough to perform. This is an

excellent use because one could perform the operation over

and over without the worry of hurting any human life.

However, this sort of practice may have it's limitations

because of the fact that it is only a virtual world. As

well, at this time, the computer-user interfaces are not

well enough developed and it is estimated that it will take

5 to 10 years to develop this technology.

In Japan, a company called Matsushita Electric World Ltd.

is using VR to sell their products. They employ a VPL

Research head-mounted display linked to a high-powered

computer to help prospective customers design their own

kitchens. Being able to see what your kitchen will look

like before you actually refurnish could help you save from

costly mistakes in the future.

The entertainment industry stands to gain a lot from VR.Oh)0*0*0*A‚A°A‚A°O?With the video game revolution of bigger and better games

coming out all the time, this could be the biggest

breakthrough ever. It would be fantastic to have sword

fights which actually feel real. As well, virtual movies

(also called vroomies) are being developed with allow the

viewer to interact with the characters in the movie.

Universal Studios among others is developing a virtual

reality amusement park which will incorporate these games

and vroomies.

As it stands, almost every industry has something to gain

from VR and in the years to comes, it appears that the

possibilities are endless.

The Future of Virtual Reality

In the coming years, as more research is done we are

bound to see VR become as mainstay in our homes and at work.

As the computers become faster, they will be able to create

more realistic graphic images to simulate reality better.

As well, new interfaces will be developed which will

simulate force and tactile feedback more effectively to

enhance artificial reality that much more. This is the

birth of a new technology and it will be interesting to see

how it develops in the years to come. However, it may take

longer than people think for it to come into the mainstream.

Millions of dollars in research must be done, and only

select industries can afford to pay for this. Hopefully, it

will be sooner than later though.

It is very possible that in the future we will be

communicating with virtual phones. Nippon Telephone and

Telegraph (NTT) in Japan is developing a system which will

allow one person to see a 3D image of the other using VR

techniques. In the future, it is conceivable that

businessmen may hold conferences in a virtual meeting hall

when they are actually at each ends of the world. NTT is

developing a new method of telephone transmission using

fiber optics which will allow for much larger amounts of

information to be passed through the phone lines. This

system is called the Integrated Services Digital Network

(ISDN) which will help allow VR to be used in conjunction

with other communication methods.

Right now, it is very expensive to purchase, with the

head-mounted display costing anywhere from about $20,000 to

$1,000,000 for NASA's Super Cockpit. In the future, VR will

be available to the end-user at home for under $1000 and

will be of better quality than that being developed today.

The support for it will be about as good as it is currently

for plain computers, and it is possible that VR could become

a very useful teaching tool.

Oh)0*0*0*A‚A°A‚A°O?A?"zA?

Virtual Reality - What it is and How it Works

Imagine being able to point into the sky and fly. Or

perhaps walk through space and connect molecules together.

These are some of the dreams that have come with the

invention of virtual reality. With the introduction of

computers, numerous applications have been enhanced or

created. The newest technology that is being tapped is that

of artificial reality, or "virtual reality" (VR). When

Morton Heilig first got a patent for his "Sensorama

Simulator" in 1962, he had no idea that 30 years later

people would still be trying to simulate reality and that

they would be doing it so effectively. Jaron Lanier first

coined the phrase "virtual reality" around 1989, and it has

stuck ever since. Unfortunately, this catchy name has

caused people to dream up incredible uses for this

technology including using it as a sort of drug. This became

evident when, among other people, Timothy Leary became

interested in VR. This has also worried some of the

researchers who are trying to create very real applications

for medical, space, physical, chemical, and entertainment

uses among other things.

In order to create this alternate reality, however, you

need to find ways to create the illusion of reality with a

piece of machinery known as the computer. This is done with

several computer-user interfaces used to simulate the

senses. Among these, are stereoscopic glasses to make the

simulated world look real, a 3D auditory display to give

depth to sound, sensor lined gloves to simulate tactile

feedback, and head-trackers to follow the orientation of the

head. Since the technology is fairly young, these

interfaces have not been perfected, making for a somewhat

cartoonish simulated reality.

Stereoscopic vision is probably the most important

feature of VR because in real life, people rely mainly on

vision to get places and do things. The eyes are

approximately 6.5 centimeters apart, and allow you to have a

full-colour, three-dimensional view of the world.

Stereoscopy, in itself, is not a very new idea, but the new

twist is trying to generate completely new images in real-

time. In 1933, Sir Charles Wheatstone invented the first

stereoscope with the same basic principle being used in

today's head-mounted displays. Presenting different views

to each eye gives the illusion of three dimensions. The

glasses that are used today work by using what is called an

"electronic shutter". The lenses of the glasses interleaveOh)0*0*0*A‚A°A‚A°O?the left-eye and right-eye views every thirtieth of a

second. The shutters selectively block and admit views of

the screen in sync with the interleaving, allowing the

proper views to go into each eye. The problem with this

method though is that you have to wear special glasses.

Most VR researchers use complicated headsets, but it is

possible to create stereoscopic three-dimensional images

without them. One such way is through the use of lenticular

lenses. These lenses, known since Herman Ives experimented

with them in 1930, allow one to take two images, cut them

into thin vertical slices and interleave them in precise

order (also called multiplexing) and put cylinder shaped

lenses in front of them so that when you look into them

directly, the images correspond with each eye. This

illusion of depth is based on what is called binocular

parallax. Another problem that is solved is that which

occurs when one turns their head. Nearby objects appear to

move more than distant objects. This is called motion

parallax. Lenticular screens can show users the proper

stereo images when moving their heads well when a head-

motion sensor is used to adjust the effect.

Sound is another important part of daily life, and thus

must be simulated well in order to create artificial

reality. Many scientists including Dr. Elizabeth Wenzel, a

researcher at NASA, are convinced the 3D audio will be

useful for scientific visualization and space applications

in the ways the 3D video is somewhat limited. She has come

up with an interesting use for virtual sound that would

allow an astronaut to hear the state of their oxygen, or

have an acoustical beacon that directs one to a trouble spot

on a satellite. The "Convolvotron" is one such device that

simulates the location of up to four audio channels with a

sort of imaginary sphere surrounding the listener. This

device takes into account that each person has specialized

auditory signal processing, and personalizes what each

person hears.

Using a position sensor from Polhemus, another VR

research company, it is possible to move the position of

sound by simply moving a small cube around in your hand.

The key to the Convolvotron is something called the "Head-

Related Transfer Function (HRTF)", which is a set of

mathematically modelable responses that our ears impose on

the signals they get from the air. In order to develop the

HRTF, researchers had to sit people in an anechoic room

surrounded with 144 different speakers to measure the

effects of hearing precise sounds from every direction by

using tiny microphone probes placed near the eardrums of the

listener. The way in which those microphones distorted the

sound from all directions was a specific model of the way

that person's ears impose a complex signal on incoming sound

waves in order to encode it in their spatial environment.Oh)0*0*0*A‚A°A‚A°O?The map of the results is then converted to numbers and a

computer performs about 300 million operations per second

(MIPS) to create a numerical model based on the HRTF which

makes it possible to reconfigure any sound source so that it

appears to be coming from any number of different points

within the acoustic sphere.

This portion of a VR system can really enhance the visual

and tactile responses. Imagine hearing the sound of

footsteps behind you in a dark alley late at night. That is

how important 3D sound really is.

The third important sense that we use in everyday life is

that of touch. There is no way of avoiding the feeling of

touch, and thus this is one of the technologies that is

being researched upon most feverishly. The two main types

of feedback that are being researched are that of force-

reflection feedback and tactile feedback. Force feedback

devices exert a force against the user when they try to push

something in a virtual world that is 'heavy'. Tactile

feedback is the sensation of feeling an object such as the

texture of sandpaper. Both are equally important in the

development of VR.

Currently, the most successful development in force-

reflective feedback is that of the Argonne Remote

Manipulator (ARM). It consists of a group of articulated

joints, encoiled by long bunches of electrical cables. The

ARM allows for six degrees of movement (position and

orientation) to give a true feel of movement. Suspended

from the ceiling and connected by a wire to the computer,

this machine grants a user the power to reach out and

manipulate 3D objects that are not real. As is the case at

the University of North Carolina, it is possible to "dock

molecules" using VR. Simulating molecular forces and

translating them into physical forces allows the ARM to push

back at the user if he tries to dock the molecules

incorrectly.

Tactile feedback is just as important as force feedback

in allowing the user to "feel" computer-generated objects.

There are several methods for providing tactile feedback.

Some of these include inflating air bladders in a glove,

arrays of tiny pins moved by shape memory wires, and even

fingertip piezoelectric vibrotactile actuators. The latter

method uses tiny crystals that vibrate when an electric

cu

Sources of Information

Books and Periodicals

Benningfield, Damond. "The Virtues of Virtual Reality."

Star Date, July/Aug. 1991, pp. 14-15.

Burrill, William. "Virtual Reality." Toronto Star, 13 July

1991, pp. J1-3.

Brill, Louis M. "Facing Interface Issues." Computer

Graphics World, April 1992, pp. 48-58.

Daviss, Bennett. "Grand Illusions." Discover, June 1990,

pp. 36-41.