Virtual Reality (VR)

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14 Νοε 2013 (πριν από 3 χρόνια και 6 μήνες)

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Virtual Reality (VR)


Kyle Maitland

Department of Computer Science

University of Wisconsin Platteville

Platteville WI, 53818

maitlandk@uwplatt.edu




Abstract


The current level of
virtual reality systems is not as advanced as it is portrayed by movies.
However, virtual reality systems are more widely used than thought. A VR system is simpl
y

a
three
-
dimensional image or environment that can be interacted with, whether it is a simple
3
D
game or an interactive simulator. VR systems can be described by their system type, hardware,
and hardware level. Their systems


type describes the kind of environment; the hardware is how
the VR is interacted with by a user stand
-
point; its hardware le
vel describes the degree to which
the hardware is implemented. VR systems can be
a useful tool

in a learning environment, for
example a VR system was used in the teaching and training of med school students to practice a
simple surgery routine with a head
-
mounted simulator.




Introduction


This paper will identify and explain the different types of 3 categories that make a VR
-
System
(system type, hardware, hardware levels). A good
,

yet simple definition of a VR is any
c
omputer
generated simulation of a
three
-
dimensional image or environment that can be interacted in a
seemingly real or physical way by a person

or computer.



System Types


Window on world systems

(W
o
W) uses the monitor to display the visual environment, and is
sometimes referred to as
Desktop VR. The main challenge to windows on worlds is making the
environment look real, sound real and have the objects act real.

Video mapping

is a variation of the windows on worlds system. It merges the video input of the
user with 2D computer graphics
. The user will watch a monitor that will show their body’s
interaction with the VR environment. A good example would be the early
Kinect

for the Xbox
360. It simpl
y

mirrored your body movements on the screen

with a motion sensor for video
input
.

The
immer
sive system

completely immerses the user’s personal sight within the virtual
environment. The simplest way to utilize the immersive system is with the use of a head
mounted display, such as a helmet or face mask that can be free ranging, tethered, or even
2


attached to some stand. The HUD will have a form of a visual and audio display so as to bring
out the full effect of the VR system. A nice immersive system set up is called the “cave”, which
consists of multiple large projecting displays set up around a ro
om so as to create the VR
environment.

(
Fig
. 1)


Telepresence

is a visualizing complete computer generated world. The world is created using
remote sensors in the real world on a form of a human operator and/or robot, and even in some
cases, on the ends of a tool. This kind of VR system is used a lot of times in the

movie world
when
animating

CG environments around actors

on a green screen
. This type of VR system is
useful with surgeons using small instruments on cables to perform detailed surgeries without
cutting too major of a hole in a patient. With the use of te
lepresence on robots, deep sea and
volcanic exploration can be achieved much easier and safer by simply sending in the robot with a
camera attached.

Mixed reality

is a form of mixing telepresence and other VR systems,
such as

immersive
systems. Using the
generated input of the telepresence system, mixed reality systems will
generate a VR environment in which a user can then interact with. A good example of this would
be a fighter pilot using previously record flights to test a new jet’s capabilities in a V
R
environment.

3




Hardware


Image generators


The most time consuming task of any VR system is the creation of the 3D environment. A
computer with faster graphic generating is ideal when working with VR systems. Because of
this, image generating cards, most of which are based on the Intel i860 process
or, is the first item
to be taken into effect when working on a set budget. Image generating cards can cost up to
10,000$, and on much more advance VR systems can even end up costing around
$
100,000.



Position tracking


Ultrasonic sensors can be used to t
rack position and orientation. A set of emitters are pulsed in
sequence and the time lag to the receiver is then measured. Once data is collect
ed
, triangulation
allows us to calculate positions. A problem with ultrasonic sensors is interference from echoes

or
other devices
,

which can lead to un
-
accurate data collection resulting in poor 3D environment
creation.

Magnetic trackers use sets of coils to pulse
magnetic fields,
which allow

magnetic sensors
to

determine the strength and angle of the pulse fields. The drawback to magnetic tracking is
possible interference with ferrous materials in the fields, the range limits on the magnetics, and
high latency for the processing. Even with the drawbacks
,

magneti
c tracking is the preferred
method.

Optical position tracking systems uses grid LEDs and a head mounted camera. The LEDs are
pulsed in a sequence with the cameras image to detect the flashes so as to project the
environment. Optical positioning is limited

to spacing with the LED grid set up and the limit of
rotation on the head mounted camera. Another method of optical positioning is using a number
of cameras to capture images of an environment simultaneously to track objects.



Stereo vision


Stereo visio
n is the process of creating two different images of an environment, one image for
each “eye”. The images are computed with the viewpoints offset by the equivalent distance
between the eyes. The two images can be displayed sequentially on a conventional mo
nitor or
projection display. The user’s brain then receive
s

the images in a rapid succession
.
It

will fuse
the images together into a single image with a perceive
d

depth. This method is dependent on a
higher display swap rate.

Another method to stereo vis
ion is to use computer screens to split an image. The image will be
divided into two parts and displayed on the monitor at the same time. One way to do this is to
place the split image side by side
or
conventionally

oriented
(one above and one below)
. The
image splitting may not take up the whole screen or it may alter the display ratio.


4



Head Mounted Displayed (HMD)


As is sounds
,

HMD is the use of some kind of helmet, goggle, or other mounted device to place a
small display in front of the user’s sight. Most HMD’s use two displays
,

so as to provide
stereoscopic imaging; however some HMD’s will only use one display
,

so as to displa
y a higher
resolution. Most HMD devices require a position tracker in addition to the helmet or goggle.


Hardware Levels


The entry level VR system is just a simple stock computer or workstation set and will normally
implement a window on worlds system. Th
e next level up is the basic level
,

and will have some
system add on such as a basic interaction device and display device. An example of an
interaction device would be a power glove or multidimensional mouse.

The next level up is the
advance VR level, whi
ch will add on a rendering accelerator for input handling. With the adding
of an accelerator card, the system can improve dramatically in the rendering process. The
advance level could also have a sound card added to improve audio output and/or voice
recog
nition.

The next level up is the immersion level. At this level
,

a VR system will have added
some type of immersive display system, such as a head mount display, or large projection
displays (much like the “cav
e” set up I mentioned earlier).
One of the hig
hest hardware levels is
the cockpit simulator. In this level the VR system uses a form of Cab or compartment the user
may enter to experience the 3D environment. The 3D environment is viewed thr
o
u
gh

some kind
of screen display. The cockpit simulator is mos
t often used in aircraft simulators for training
pilots, and to give the best training experience the cockpit will be placed on a motion platform to
give a better sense of the environment.



Main Functional Module of a Virtual Reality Substation
Simulation

(
fig.2
)




Before any VR system can be created, it must first have a design. The main design of a VR
system is the
Virtual Reality Substation Simulation

(VRSS)
.
The
da
ta acquisition

module is to
acquire the original

si
mulation parameters.

Next
,

we have the
Communication module to
transmit

the

orders and messages between the
different functional

models.

The
s
imulation
5


calculation module is
used

to calculate the

simulation results
according to preset mathematical
model.

The d
isplay module is for h
ighly visible display of

simulatio
n processes and results
vividly
and directly by fully

employing VR models of electrical devices, substation

virtual
scenes, 3D geometric graphs, data etc.

VRS
-
engine is the basis kernel of the Virtual Reality
Substation
Simulation system,

integrating different key VR technologies to provide

technical
support in the pattern of Application Program

Interface

(API)

for the whole Virtual Reality
Substation Simulation system.



The Kernel of

a

VRS
-
Engine (
fig 3
.)


The kernel is

the most important part of VRS
-
engine,

and provides the
basic handling functions
for VRS
-
engine.

Components of the kernel can be classified as the following

o
nes
:





Objects Management

is

the inter
-
bus of VRS
-
engine;

it manages all the

things in
VRS
-
engine
and regards them as objects.

Environment Modeling

can set up a corresponding VR environment
model for
Virtual Reality Substation
Simulation

and then submit to View Prejudgment
component.

View Prejudgment

can prejudge (judge before having good ev
idence) the visible
6


parts of VR environment

model observed by normal human sight and then submit to

Scene
Rendering
component.

Scene Rendering

is responsible for depicting the basic 3D models and

de
aling with light and texture in
the current and visible VR

environment model and then
generating VR environment. As one of

the most important components in VRS
-
engine, it
determines

the performance of Virtual Reality Substation Simulation

based on VRS
-
engine to a
large extent.

Collision Detection

is an inevitable

element of VRS
-
engine. It can catch

the
interaction
-
events triggered in the VR scene, and greatly

determine the interactive ability of
Virtual Reality Substation Simulation.

Events Transaction

can send different messages to the
corresponding

components ac
cording to different interaction
-
event.

Script
Compilation

is data
construction or language which can depict

behavior of objects. Script in VRS
-
engine can be
divided

into 3 types:


A
)
Action Script
, for modifying the location, direction

and related
attributes of objects;


B
)
Trigger Script
, on an occurrence of interaction
-
events

such as approach and touch,
the script will trigger the

relevant messages to deal with the event;


C
)
Connection Script
, for the connection between

output/input
equipment

and objects. It
is much e
asier

to

control the electrical devices in VR scene with the help of

these three
scripts. This component compiles all the scripts

for their exact execution.



Other Components

of VR Kernel


Virtual Devices

component provides many VR models
with

electrical devices. As an imp
ortant
segment
of Virtual Reality Substation Simulation,
Virtual Devices

component
is in charge of
carrying and
displaying messages in

the process of simulation.

However,
this
component

is

not a
pure but

compound

(consisting of multiple devices)
, including:


A
)
Electric Model
, receiving and storing simulation data

and reflecting the main
parameters of electrical devices such

as voltage, power;


B
)
Geometric Model
, displaying simulation
messages

and reflecting the appearance of
electrical devices;


C
)
Behavioral Model
, referring to the relevant

interactive mechanism and the
coordinating rules.


The
Sound Effect

component
deals

with the sound of VRS
-
engine
such as
sound effect
s

of stereo
to enhance

the reality
-
sense of VR environments.

Auxiliary Tools

mainly include editors of
electrical devices
,

VR

model
,

and substation VR environments. They can edit virtual

module
visually and store its

results in the data bank with the

usage
of editing instrument.

I/O Interface

is
responsible for receiving control
-
orders from input

equipment
s such as keyboard, mouse,

joy
stick or

data glove,

and in charge of administering input/output functions such as

printing,
import/export data
,

etc.

Intern
et Communication

provides such functions as data transmission for VRS
-
engine.

7




Conclusion

VR systems are very detailed and versatile, with many different useful applications. However,
even with everything described in this paper, VR systems are always changing and improving for
the better. As technology continues to advance so will the uses of
VR systems and the degree to
which they are implemented. In time, even the average person will benefit from VR and all we
can do is look forward to
results of
i
mprovement
.






























8



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