13-08-2014, 12:03 PM
AUGMENTED REALITY
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ABSTRACT
This paper surveys the field of Augmented Reality, in which 3-D virtual
objects are integrated into a 3-D real environment in real time. It describes the
medical, manufacturing, visualization, path planning, entertainment and military
applications that have been explored. This paper describes the characteristics of
Augmented Reality systems, including a detailed discussion of the tradeoffs between
optical and video blending approaches. Registration and sensing errors are two of the
biggest problems in building effective Augmented Reality systems, so this paper
summarizes current efforts to overcome these problems. Future directions and areas
requiring further research are discussed. This survey provides a starting point for
anyone interested in researching or using Augmented Reality.
. INTRODUCTION
Augmented reality (AR) refers to computer displays that add virtual
information to a user's sensory perceptions. Most AR research focuses on see-through
devices, usually worn on the head that overlay graphics and text on the user's view of
his or her surroundings. In general it superimposes graphics over a real world
environment in real time.
Getting the right information at the right time and the right place is key in all
these applications. Personal digital assistants such as the Palm and the Pocket PC can
provide timely information using wireless networking and Global Positioning System
(GPS) receivers that constantly track the handheld devices. But what makes
augmented reality different is how the information is presented: not on a separate
display but integrated with the user's perceptions. This kind of interface minimizes the
extra mental effort that a user has to expend when switching his or her attention back
and forth between real-world tasks and a computer screen. In augmented reality, the
user's view of the world and the computer interface literally become one.
WORKING
AR systems track the position and orientation of the user's head so that the
overlaid material can be aligned with the user's view of the world. Through this
process, known as registration, graphics software can place a three-dimensional image
of a teacup, for example, on top of a real saucer and keep the virtual cup fixed in that
position as the user moves about the room. AR systems employ some of the same
hardware technologies used in virtual-reality research, but there's a crucial difference:
whereas virtual reality brashly aims to replace the real world, augmented reality
respectfully supplements it.
INDOOR TRACKING:
Tracking is easier in small spaces than in large spaces. Trackers typically have
two parts: one worn by the tracked person or object and the other built into the
surrounding environment, usually within the same room. In optical trackers, the
targets--LEDs or reflectors, for instance--can be attached to the tracked person or
object, and an array of optical sensors can be embedded in the room's ceiling.
Alternatively, the tracked users can wear the sensors, and the targets can be fixed to
the ceiling. By calculating the distance to each visible target, the sensors can
determine the user's position and orientation.
7.APPLICATION DOMAINS
Only recently have the capabilities of real-time video image processing,
computer graphic systems and new display technologies converged to make possible
the display of a virtual graphical image correctly registered with a view of the 3D
environment surrounding the user. Researchers working with augmented reality
systems have proposed them as solutions in many domains. The areas that have been
discussed range from entertainment to military training. Many of the domains, such as
medical are also proposed for traditional virtual reality systems. This section will
highlight some of the proposed applications for augmented reality.
3 MILITARY TRAINING
The military has been using displays in cockpits that present information to the
pilot on the windshield of the cockpit or the visor of their flight helmet. This is a form
of augmented reality display. SIMNET, a distributed war games simulation system, is
also embracing augmented reality technology. By equipping military personnel with
helmet mounted visor displays or a special purpose rangefinder the activities of other
units participating in the exercise can be imaged. While looking at the horizon, for
example, the display equipped soldier could see a helicopter rising above the tree line.
This helicopter could be being flown in simulation by another participant. In wartime,
the display of the real battlefield scene could be augmented with annotation
information or highlighting to emphasize hidden enemy units.
.CONCLUSION
Augmented Reality is far behind Virtual Environments in maturity. Several
commercial vendors sell complete, turnkey Virtual Environment systems. However,
no commercial vendor currently sells an HMD-based Augmented Reality system. A
few monitor-based "virtual set" systems are available, but today AR systems are
primarily found in academic and industrial research laboratories. The first deployed
HMD-based AR systems will probably be in the application of aircraft manufacturing.
The former uses optical approaches, while the latter is pursuing video approaches.
Boeing has performed trial runs with workers using a prototype system but has not yet
made any deployment decisions. Annotation and visualization applications in
restricted, limited-range environments are deployable today, although much more
work needs to be done to make them cost effective and flexible. Applications in
medical visualization will take longer. Prototype visualization aids have been used on
an experimental basis, but the stringent registration requirements and ramifications of
mistakes will postpone common usage for many years. AR will probably be used for
medical training before it is commonly used in surgery. The next generation of
combat aircraft will have Helmet-Mounted Sights with graphics registered to targets
in the environment. These displays, combined with short-range steerable missiles that
can shoot at targets off-bore sight, give a tremendous combat advantage to pilots in
dogfights. Instead of having to be directly behind his target in order to shoot at it, a
pilot can now shoot at anything within a 60-90 degree cone of his aircraft's forward
centerline.
One area where a breakthrough is required is tracking an HMD outdoors at the
accuracy required by AR. If this is accomplished, several interesting applications will
become possible. Two examples are described here: navigation maps and
visualization of past and future environments. The first application is a navigation aid
to people walking outdoors. These individuals could be soldiers advancing upon their
objective, hikers lost in the woods, or tourists seeking directions to their intended
destination. Today, these individuals must pull out a physical map and associate what
they see in the real environment around them with the markings on the 2–D map. If
landmarks are not easily identifiable, this association can be difficult to perform, as
anyone lost in the woods can attest. An AR system makes navigation easier by
performing the association step automatically. If the user's position and orientation are
known, and the AR system has access to a digital map of the area, then the AR system
can draw the map in 3-D directly upon the user's view. Tourists and students walking
around the grounds with such AR displays would gain a much better understanding of
these historical sites and the important events that took place there. Similarly, AR
displays could show what proposed architectural changes would look like before they
are carried out. An urban designer could show clients and politicians what a new
stadium would look like as they walked around the adjoining neighborhood, to better
understand how the stadium project will affect nearby residents.
After the basic problems with AR are solved, the ultimate goal will be to
generate virtual objects that are so realistic that they are virtually indistinguishable
from the real environment. Photorealism has been demonstrated in feature films, but
accomplishing this in an interactive application will be much harder. Lighting
conditions, surface reflections, and other properties must be measured automatically,
in real time. More sophisticated lighting, texturing, and shading capabilities must run
at interactive rates in future scene generators. Registration must be nearly perfect,
without manual intervention or adjustments. While these are difficult problems, they
are probably not insurmountable. It took about 25 years to progress from drawing
stick figures on a screen to the photorealistic dinosaurs in "Jurassic Park." Within
another 25 years, we should be able to wear a pair of AR glasses outdoors to see and
interact with photorealistic dinosaurs eating a tree in our backyard.