home *** CD-ROM | disk | FTP | other *** search
- 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 interleave╘ h) 0*0*0*░░ ╘îthe 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.╘ h) 0*0*0*░░ ╘îThe 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) depends╘ h) 0*0*0*░░ ╘îon 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 300╘ h) 0*0*0*░░ ╘îmeasurements/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 and╘ h) 0*0*0*░░ ╘îactually 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.╘ h) 0*0*0*░░ ╘îWith 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.
-
- ╘ h) 0*0*0*░░ ╘îÖ
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- 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.
-
- Emmett, Arielle. "Down to Earth: Practical Applications of
- Virtual Reality Find Commercial Uses."
-
- Computer Graphics World, March 1992, pp. 46-54.
-
- Peterson, Ivars. "Recipes for Artificial Realities."
- Science News, 24 Nov. 1990, pp. 328-329.
-
- Peterson, Ivars. "Looking-Glass Worlds." Science News,
- 4 Jan 1992, pp. 8-15.
-
- Porter, Stephen. "Virtual Reality." Computer Graphics
- World, March 1992, pp. 42-43.
- ╘ h) 0*0*0*░░ ╘îRheingold, Howard. Virtual Reality. Toronto: Summit Books,
- 1991.
-
- Tisdale, Sallie. "It's Been Real." Esquire, April 1991,
- pp. 36-40.
-
- Various. Virtual Reality Special Report. San Francisco:
- Meckler Publishing, 1992.
-
-
- Companies Contacted:
-
- Ascension Technology Corp.
- P.O Box 527
- Burlington, VT 05402
- (802)655-7879
-
- Polhemus Inc.
- P.O Box 560
- Colchester, VT 05446
- (802)655-3159
-
- Shooting Star Technology
- 1921 Holdom Ave.
-
-
-
-
-
-
-
-
-
-
-
-
- Burnaby, BC V5B 3W4
- (604)298-8574
-
- Virtual Technologies
- P.O. Box 5984
- Stanford, CA 94309
- (415)599-2331
-
- VPL Research Inc.
- 656 Bair Island Rd. Third Floor
- Redwood City, CA 94063
- (415)361-1710
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-