Augmented Reality and its contrast to Virtual Reality

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					  Augmented Reality and its contrast to Virtual Reality
                             S.M.Rezaul Hoque, smrhoque<a>
                                   Ubiquitous Computing

Abstract                                         than the traditional approach. He
                                                 complements     his   saying   with   the
Augmented Reality and Virtual Reality is         following statement; “Machines that fit
very closely related to each other, yet          the human environment, instead of
each faces different challenges of its own       forcing humans to enter theirs, will make
and has its own area of usage. In this           using a computer as refreshing as taking
paper we try to highlight the concepts,          a walk in the woods” [3].
their usage domains and technical
barriers. We focused on augmented                One of the main goals of ubiquitous
reality and its contrast to virtual reality.     computing is to enable devices to sense
                                                 changes in their environment and to
                                                 automatically adapt and act based on
                                                 these changes which in turn are
                                                 dependent      on   user   needs     and
Chapter1                                         preferences. The growth of such system
Introduction to characters of                    is highly catalyzed by the advent of
                                                 cheap, low-power computers that include
Ubiquitous                                       equally convenient displays, networks
                                                 that tie them all together and software
Computing                                        systems       implementing    ubiquitous
                                                 applications. [2]

Introduction                                     One important aspect which comes into
                                                 consideration while studying Ubiquitous
Ubiquitous computing is a paradigm shift         computing is Calm Computing. It refers
where technology becomes virtually               to the idea of computers fading into the
invisible in our lives.                          background while allowing us to focus on
                                                 our kernel and normal activities with a
Mark Weiser, who is considered as the            high degree of fluency and not hampering
father of Ubiquitous computing, defined it       with    defocusing   tools.   With    this
as the effort to integrate computation           technology the artifacts are intelligent,
into the environment rather than having          but do not require focused interaction—
computers which are distinct objects.            we just live with them and they work
Doing so will enable people to move              unobtrusively to make our lives simpler.
around and interact with information and
computing more naturally and casually

Let’s look at an example where we             in virtual reality research. The world
assume Aura as the pervasive computing        environment around us provides a wealth
system.                                       of information that is difficult to duplicate
                                              in a computer. This is evidenced by the
Jane is at Gate 23 in the Pittsburgh          world’s used in virtual environments.
airport, waiting for her connecting flight.   Either these worlds are very simplistic
She has edited any large documents, and       such as the environments created for
would like to use her wireless connection     immersive entertainment and games, or
to e-mail them. Unfortunately, bandwidth      the system that can create a more
is miserable because many passengers at       realistic environment has a million dollar
Gates 22 and 23 are surfing the web.          price tag such as flight simulators.

Aura observes that at the current             An augmented reality system generates a
bandwidth Jane won’t be able to finish        composite view for the user. It is a
sending her documents before her flight       combination of the real scene viewed by
departs. Consulting the airport’s network     the user and a virtual scene generated by
weather service and flight schedule           the computer that augments the scene
service, Aura discovers that wireless         with additional information.
bandwidth is excellent at Gate 15,and
that there are no departing or arriving       Augmentation can take on a number of
flights at nearby gates for half an hour. A   different forms. In all those applications
dialog box pops up on Jane’s screen           the augmented reality presented to the
suggesting that she go to Gate 15, which      user enhances that person's performance
is only three minutes away. It also asks      in and perception of the world. The
her to prioritize her e-mail, so that the     ultimate goal is to create a system such
most critical messages are transmitted        that the user cannot tell the difference
first. Jane accepts Aura’s advice and         between the real world and the virtual
walks to Gate 15. She watches CNN on          augmentation of it. To the user of this
the TV there unti lAura informs her that it   ultimate system it would appear that he
is close to being done with her messages,     is looking at a single real scene. An
and that she can start walking back. The      example is how a user might see from an
last message is transmitted during her        augmented reality a system in the
walk, and she is back at Gate 23 in time      medical domain. It depicts the merging
for her boarding call [4]                     and correct registration of data from a
                                              pre-operative imaging study onto the
                                              patient's head. Providing this view to a
                                              surgeon in the operating theater would
                                              enhance their performance and possibly
                                              eliminate the need for any other
Chapter2                                      calibration fixtures during the procedure.
                                              Augmented reality adds graphics, sounds
Augmented Reality                             and smell to the natural world as it

2.1 Introduction
                                              2.2 How Augmented Reality works
Augmented Reality (AR) is a growing area
                                              One   way    to   implement     Augmented

Reality is with an optical see-through        Augmented reality systems are expected
Head-Mounted Display. This device places      to run in real-time so that a user will be
optical combiners in front of the user's      able to move about freely within the
eyes.                                         scene and see a properly rendered
The combiners let light in from the real      augmented image. In order to achieve
world, and they also reflect light from       such a system there are two performance
monitors displaying graphic images.           criteria which are as follows:

                                              1. Update rate : The rate by which a new
                                                 augmenting       image   is   generated

                                              2. Accuracy : How close the real world is
                                                 pictured in the virtual image.

                                              1.Update Rate Issues

                                              Today’s modern graphics cards are able
                                              to render images in a good update rate
     Figure 1: Head Mounted Display Design    for simple or moderate graphic scenes
                                              without much trouble. The standard
The result is a combination of the real       update rate is 10 times per second. But in
world and a virtual world drawn by the        order to make the virtual objects to
monitors.                                     realistically appear part of the scene
                                              more photorealistic graphics rendering is
                                              required. The current graphics system yet
                                              does not fully support lit, shaded and ray
                                              traced images of complex scenes, but the
                                              rate at which graphics card are pushing
                                              the boundaries we can expect to reach
                                              great heights of photorealism and virtual
                                              worlds soon.

                                              2.Accuracy Issues
        Figure 2: Head Mounded Display
                                              There are two possible reasons which
In figure 2 you can see the user is looking   holds back accuracy, first is miss
at a corner of a wooden frame, but he in      calculation of the real and virtual scene
addition sees the three colored virtual       because of the noise in the system. That
axes appearing on the frame corners.          is the position and pose of the camera
Augmented-reality displays will overlay       with respect to the real scene must be
computer-generated graphics onto the          sensed properly. Any noise in this
real world. Ideally, it would seem to the     measurement’s will extrapolate as an
user that the real and virtual objects co-    error between the real scene and the
existed.                                      virtual scene generated.

                                              Second reason is the time delays in the
2.3 Performance Issues                        system itself. As already mentioned that
                                              a system needs at least 10 frames per

second to be acceptable real time             to 30 meters away from what you were
performance, and if there are delays in       actually looking at.
calculating the camera position and other
calculations, it will cause the augmented     There are ways to increase tracking
objects to lag behind motions in the real     accuracy. For instance, the military uses
scene. The system is designed to              multiple GPS signals. There is also
minimize the delays as much as possible       differential GPS, which involves using an
and to keep the overall delay within the      area that has already been surveyed.
boundary requirements for a real-time         Then the system would use a GPS
performance.                                  receiver with an antenna that's location is
                                              known very precisely to track your
This is an ever going struggle to balance     location within that area. This will allow
the delay with the performance and            users to know exactly how inaccurate
posse’s huge challenges of making such a      their GPS receivers are, and can adjust
system come to life.                          an augmented-reality system accordingly.
                                              Differential GPS allows for submeter
                                              accuracy. A more accurate system being
2.4 Tracking in Augmented Reality             developed, known as real-time kinematic
                                              GPS,     can   achieve    centimeter-level
Tracking is a major challenge in              accuracy.
augmented reality. There is a need to
know where the user is located in
reference to his or her surroundings.         2.5 Application Domains
There's also the additional problem of
tracking the movement of users' eyes and      The research on Augmented Reality has
heads. A tracking system has to               come far and soon augmented reality will
recognize these movements and project         likely pervade in every corner of our
the graphics related to the real-world        lives. There are hundreds of other
environment the user is seeing at any         potential   applications for such     a
given moment. Currently, both video see-      technology, gaming and entertainment
through and optical see-through displays      being the most obvious ones.
typically have lag in the overlaid material
due to the tracking technologies currently
available.                                    2.5.1 Gaming

For augmented reality to reach its full       A game could be projected onto the real
potential, it must be usable both outdoors    world around you, and you could,
and indoors. Currently, the best tracking     literally, be in it as one of the characters.
technology available for large open areas     One Australian researcher has created a
is the Global Positioning System (GPS).       prototype game that combines Quake, a
However, GPS receivers have an accuracy       popular video game, with augmented
of about 10 to 30 meters, which is not        reality. He put a model of a university
bad in the grand scheme of things, but        campus into the game's software. Now,
isn't good enough for augmented reality,      when he uses this system, the game
which needs accuracy measured in              surrounds him as he walks across
millimeters or smaller. An augmented-         campus.
reality system would be worthless if the
graphics projected were of something 10

                                             SIMNET is another military training tool,
2.5.2 Entertainment                          which is a distributed war game
                                             simulations system. In this system the
A simple form of augmented reality has       military personnel are equipped with see
been in use in the entertainment and         through helmet mounted visor displays or
news business for quite some time.           special purpose rangefinder and the
Whenever you are watching the evening        activities of the other units participating
weather report the weather reporter is       in the exercise can be imaged [5]. The
shown standing in front of changing          display of the real battlefield scene could
weather maps. In the studio the reporter     be augmented as such that it could
is actually standing in front of a blue or   provide troops with vital information
green screen. This real image is             about their surroundings, such as
augmented with computer generated            showing where entrances are on the
maps using a technique called chroma-        opposite end of a building, somewhat like
keying.                                      X-ray vision. Augmented reality displays
                                             could also highlight troop movements,
                                             and give soldiers the ability to move to
                                             where the enemy can't see them.

                                             2.5.4 Maintenance and Repair

                                             When    the   maintenance    technician
                                             approaches a new or unfamiliar piece of
                                             equipment instead of opening several
                                             repair manuals they could put on an
                                             augmented reality display.

          Figure 3: Chroma-keying

It is also possible to create a virtual
studio environment so that the actors can
appear to be positioned in a studio with
computer generated decorating.

2.5.3 Military Training
                                                 Figure 5 : Superimposition of instructional
The military has been using displays in         information over actual machine assemblies
cockpits that present information to the
pilot on the windshield of the cockpit.
This is a form of augmented reality          In this display the image of the
display.                                     equipment would be augmented with

annotations and information pertinent to
the repair [6]                               If a dress store does not have a particular
                                             style dress in your size an appropriate
                                             sized dress could be used to augment the
2.5.5 Medical Domain                         image of you. As you looked in the three
                                             sided mirror you would see the image of
Most of the medical applications deal with   the new dress on your body. Changes in
image guided surgery, or pre-operative       hem length, shoulder styles or other
imaging studies such as CT or MRI scans.     particulars of the design could be viewed
This scans provide necessary view of the     on you before you place the order. When
internal anatomy. From these images the      you head into some high-tech beauty
surgery is planned. For example a tumor      shops today you can see what a new hair
must be removed, thus first a 3D model       style would look like on a digitized image
from the multiple views is generated via     of yourself. But with an advanced
some systems which can process images        augmented reality system you would be
taken from different angle and as            able to see the view as you moved. If the
combination of those images produce a        dynamics of hair are included in the
3D model. Augmented reality can be           description of the virtual object you would
applied here so that the surgical team       also see the motion of your hair as your
can see the CT or MRI data correctly         head moved. [6]
registered on the patient in the operating
theater while the procedure is in
progress. This process is well known as
image guided surgery and has gained
quite popularity because of its success
rate.                                        Chapter3
                                             Virtual Reality
2.5.5 Tourism

A tourist can see information of buildings
as he walks.                                 3.1 Introduction

                                             Virtual Reality (VR) is a computer system
                                             used to create an artificial world in which
                                             the user has the impression of being in
                                             that world and with the ability to navigate
                                             through the world and manipulate objects
                                             in the world. [7]

        Figure 6: Info Guided Tourism
                                             3.2 How Virtual Reality Works
This is an experimental project developed
at Columbia University.                      Virtual Reality became a success with the
                                             development of a head-mounted display
                                             (HMD) with two tiny stereoscopic screens
2.5.6 Consumer Design                        positioned just a few inches in front of
                                             the eyes. Users also wear a Data Glove

that generates movement and interaction         the user "feels" the virtual object. The
in the virtual environment.                     user can pick up an object and do things
                                                with it just as he would do with a real

                                                3.4 Technologies needed

                                                Technologies that are core requirements of a
                                                Virtual Reality system are:

                                                      The visual (and aural and haptic)
                                                       displays that immerse the user in the
                                                       virtual world and that block out

            Figure 5: Virtual Reality                  contradictory sensory impressions from
                                                       the real world.
Movement in Virtual world is simulated by
shifting the optics in the field of vision in
direct response to movement of certain                The graphics rendering system that
body parts, such as the head or hand.
                                                       generates, at 20 to 30 frames per
Turn the head, and the scene shifts
accordingly. The sensation is like being               second, the ever-changing images.
inside an artificial world the computer has
                                                      The tracking system that continually
The HMD uses a set of wide-angle optics                reports the position and orientation of
that covers approximately 140 degrees,
                                                       the user’s head and limbs.
almost the entire horizontal field of view.
As the user moves his head to look
around, the images shift to create an                 The database construction and
illusion of movement. The user moves
                                                       maintenance system for building and
while the virtual world is standing still.
The glasses also sense the user's facial               maintaining detailed and realistic
expressions through embedded sensors,                  models of the virtual world.
and that information can control the
virtual version of the user's body.
                                                3.4 Applications of Virtual Reality
The Data Glove, a key interface device,
uses position tracking sensors and fiber
                                                In almost every domain virtual reality can
optic strands running down each finger,
                                                come into play. Here are a few
allowing the user to manipulate objects
                                                applications of virtual reality:
that exist only within the computer
simulated environment.
                                                3.4.1 Education
When the computer "senses" that the
user's hand is touching a virtual object,

Instead of communicating with a real
real-time teacher, the student can talk
with a virtual teacher. It remains
essential however that you as a student
can always feel as if you are in a learning
environment with feedback, explanations
and negotiation about meaning and
                                                         Figure 8: War simulation

3.4.2 Games                                   These types of simulation are used in
                                              many domains for training purposes.
Virtual Baseball is an example where the
user has a bat in his hand and the person
sees the ball coming and hits the ball with   3.4.4 Medical
his bat.
                                              Surgeons may use Virtual Reality to walk
                                              through the brain or rehearse a surgical
                                              operation on a virtual patient.

                                              3.4.5 Training

                                              Instead of working with a real machinery
                                              or expensive equipment, students may
                                              finally work with virtual ones. In case it
                                              concerns the training in an administrative
                                              environment, the fictitious office is the
                                              environment. The virtuality aspect should
                                              not only be seen as a compromise. It is
           Figure 7: Virtual baseball         also an advantage in order to regulate
                                              the level of complexity. Also, in case of
Upon     heating    the      ball feedback    mistakes, the damage and danger will be
mechanism is present to give the user a       reduced.
jerk back giving the feeling that he
actually hit an actual ball.
                                              3.5 Draw Backs

3.4.3 Simulations                             Despite enormous potential practical
                                              application, VR, in its current state, has
Virtual Reality is used in simulations. On    drawbacks. It is still extremely expensive,
the left of the picture you can see the       the graphics are still cartoonish, and
user wearing a Head mounted display and       there is still a slight, but perceptible time
on the right image is the image the user      lag between the user's body movements
is seeing.                                    and their translation in virtual world. The
                                              equipment the user must wear, such as
                                              head gear, gloves, and other devices,
                                              needs refinement.

At this early stage in the development of    AR allows a user to work with and
VR, no one knows what the long-term          examine real 3D objects, while receiving
effect of using head-mounted displays        additional    information   about    those
might be on human eyes or what the           objects or the task at hand. By exploiting
possible psychological effect might be       people's visual and spatial skills, AR
from spending too much time in               brings information into the user's real
Cyberspace. People using VR head gear        world. That is, AR allows the user to stay
sometimes       complain   about   chronic   in touch with the real environment. This
fatigue, a lack of initiative, drowsiness,   is in contrast to virtual reality (VR) in
irritability, or nausea after interacting    which the user is completely immersed in
with a virtual environment for a long        an artificial world and cut off from the
time. We do not know how much each of        real world.
these      symptoms    depends    on   the
characteristics of the       VR systems      In VR systems, there is no way for the
themselves, or on the characteristics of     user to interact with objects in the real
the individuals using the systems.           world. Using AR technology, users can
                                             thus interact with a mixed virtual and real
                                             world in a natural way. AR systems bring
                                             the computer to the user's real work
                                             environment, whereas VR systems try to
Chapter4                                     bring the world into the user's computer.
A contrast of Augmented Reality
                                             4.3 Conclusion
with Virtual Reality
                                             Virtual Reality provides virtual world
                                             imagery to totally replace the real world,
                                             where as augmented reality provides
4.1 Introduction                             virtual world imagery merged into the
                                             real world.
Virtual Reality focuses an enormous
apparatus on simulating the world rather
than on invisibly enhancing the world that
already exists, which is done in
augmented Reality.

4.2 AR in contrast with VR

As we already mentioned that Augmented
Reality (AR) is a technology in which a
user's view of the real world is enhanced
or augmented with additional information
generated from a computer model. The
enhancement may consist of virtual
artifacts  to    be    fitted   into  the
environment, or a display of non-
geometric information about existing real

                                                  Figure 6: Virtual Reality
References                                        Gallery/Virtual reality/Virtual_reality_6.JPG

[1] Designing Calm Technology by Mark
Weiser and John Seely Brown, Xerox PARC,
retrieved from

[2] The Computer for the 21st Century by
Mark Weiser retrieved from

[3] Calm Computing by Hari Khalsa
Presentation retrieved from

[4] Satyanarayanan, M.A Pervasive
Computing: Vision and Challenges, Carnegie
Mellon University.

[5] Urban, E. C. (1995). "The Information
Warrior." IEEE Spectrum 32 (11): 66-70.

[6] Introduction to Augmented Reality

[7] C. Manetta and R. Blade in "Glossary of
Virtual Reality Terminology" in the
International Journal of Virtual Reality, Vol.1
Nr.2 1995

Figure1: ChromaKey

Figure 2: Military Training cockpit

Figure 3: Head Mounted Display Design

Figure 4: Head Mounded Display


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