Another Virtual Reality

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 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