Transcript Document

Immersion, Prescence,
Distributed VR
Bob Hobbs
Staffordshire University
Computing School
• Outline
–
–
–
–
Context
Immersion
Presence
Shared Environments
Virtual Reality is a Tool
• What it is:
– Use of highly interactive real-time immersive
systems to convey information
• What it is not :
– Desktop graphics
– Text based
– Non-interactive
– Linear
Immersion: Realisation of an
Environment
• generates displays ideally in all sensory
systems;
• fully encloses the participant in those displays;
• tracks the body, limbs, head;
• determines the optical, auditory... arrays as a
function of head tracking
• Either:
– displays a Virtual Body with movements as function
of the tracking. (mainly with HMD)
– Participant can visualise self and world (CAVE)
Virtual Body
• At any moment there is a position in the
geometry with respect to which sensory data is
generated - the egocentric self-reference
position.
• This corresponds to the place occupied by the
human actor in the environment.
• At the self-reference position there is a
functioning VB represented by the displays.
Means of Immersion
•
•
•
•
Cave Environment
Boom-Mounted Display
Head-Mounted Display
ImmersaDesk
Cave
ImmersaDesk
(-3 3 0)
Boom
Stereo Displays
• Binocular vision considerably enhances visual depth perception.
• Stereo displays like StereoView option on SGI workstations may
provide high resolution stereo real-time interaction.
• StereoView consists of 2 items-specially designed eyewear and
infrar emitter.
• shutters alternately open and close every 120th of second in
conjunction with alternating display of left and right eye view on
display-presenting each eye with effective 60Hz refresh.
• Infrared emitter transmits left/right signal from IRIS
workstation to wireless eyewear so that shuttering of LCS locked
to alternating left/right image display.
• As result, each eye sees unique image and brain integrates 2 views
into stereo picture.
Head-Mounted Display
• EyePhone: head-mounted display system,
presents rich 3D cues of head-motion parallax
and stereopsis.
• designed to take advantage of human binocular
vision capabilities and presents general following
characteristics:
• headgear with 2 small LCD color screens, each
optically channelled to one eye, for binocular
vision.
• special optics in front of screens, for wide field of
view
• tracking system (Polhemus 3Space Isotrack) for
precise location of user's head in real time.
Position/orientation trackers
3 main ways of recording positions and orientations: magnetic,
ultrasonic and optical Magnetic tracking devices most
successful.
• Polhemus 3Space Isotrack and Ascension Birds (Flock of
Birds), not perfect but most common.
• Source generates low frequency magnetic field detected by
sensor.
• Second approach generally based on tripod consisting of 3
ultrasonic speakers set in triangular position that emits
ultrasonic sound signals from each of 3 transmitters.
• Optical uses light sources in similar way (InterSense)
• Eddy effect used to detect orientation, position by grid
reference
Electromagnetic Position Tracking
transmitter
receiver
driving
electronics
SP
electronics
computer
position, orientation
Electromagnetic Position Tracking
• Altering current (AC)
• (Direct current DC)
transmitter
X antenna
transmitter
X antenna
transmitter
Y antenna
transmitter
Y antenna
transmitter
Z antenna
transmitter
Z antenna
receiver
X antenna
receiver
X antenna
receiver
Y antenna
receiver
Y antenna
receiver
Z antenna
receiver
Z antenna
time
T0
T1
T2
T0
time
T0
T1
T2
T3
T0
Position Tracking Systems
• Polhemus Inc. (http://www.polhemus.com)
– 3Space ISOTRAK (1 sensor)
– 3Space FASTRAK (many sensors)
• Ascension Technology Corp.
(http://www.ascension-tech.com)
– Flock of Birds
– pcBIRD
– SpacePad
Trackers Calibration
• Dynamic errors
– caused by external electromagnetic fields
– can be corrected by increasing measurements
frequency, synchronizing the measurements with the
external field source, and filtering
• Static errors
– caused by the field distortions due to the surrounding
metal and external fields
– can be corrected via trackers calibration
Calibration Table
8.3°
7.9°
8.6°
10.3°
12.9°
16.5°
20.7°
5.3°
4.5°
6.3°
3.5°
1.4°
2.9°
4.9°
1.9°
6.8°
8.8°
12.2°
16.5°
9.0°
12.6°
17.4°
24.8°
5.5°
9.7°
15.3°
23.6°
1.6°
4.5°
8.3°
3.3°
3.0°
Z 4.3°
7.4°
12.5°
19.3°
5.7°
X 4.3°
5.1°
7.6°
12.2°
18.1°
8.7°
7.1°
7.0°
9.1°
13.0°
17.9°
10.5°
9.6°
11.5°
14.0°
19.3°
13.4°
14.0°
21.1°
true
tracked
Calibration Example
4.5
3.5
2.5
1.5
0.5
-4.5
-3.5
-2.5
-1.5
-0.5
-0.5
0.5
1.5
2.5
3.5
4.5
-1.5
-2.5
-3.5
4 feet from the floor
-4.5
TRUE
ISENSE
FOB
CAL FOB
• CAVE, FoB
• 4 feet from the
floor
• 1 foot grid
• 4th order
polynomial fit
Interpolation
• True space
q5
• Tracked space
v7
q5
v7
d8
d1
q3
v1
q3
v1
V. Kindratenko, A. Bennett, “Evaluation of Rotation Correction Techniques
for Electromagnetic Position Tracking Systems”, in Proc. VE 2000, pp. 13-22
Data Acquisition Techniques
• Size and type of a calibration table depends on
– Type of the calibration technique to be used
– Severity of the field distortions
– Required calibration quality
• Calibration table can be
– Irregular (for high-order polynomial fit)
– Regular in the true space (for interpolation)
– Regular in the tracked space (for tri-linear
interpolation)
Regular Grid in the True Space
An Immersive Participant
• A user will be head
tracked
• Have a ‘Wand’
• Stereo glasses in
CAVE
• HMD user may have
additional tracking
sensors – Data Glove
or Motion tracker
Data Glove
Hand measurement devices
must sense both flexing
angles of fingers and
position/orientation of
wrist in real-time.
typical example of hand
measurement device:
DataGlove from VPL
Research.
DataGlove consists of
lightweight nylon glove
with optical sensors
mounted along fingers.
• Each sensor: short length of fiberoptic cable,
with light-emitting diode (LED) at one end and
phototransistor at other end.
• When cable flexed, some of LED's light lost, so
less light received by phototransistor.
• Attached to back: 3Space Isotrack system to
measure orientation/position of gloved hand.
Data Suit
• Much less popular than DataGlove: allows to
measure positions of body.
• typical example of use of datasuit:
• film of Fuji TV: the Dream of Mr. M.
• 3D character approximately performs same
motion as animator.
• Another way of measuring positions of body
just to use collection of sensors like Flock of
Birds.
• However, needs algorithms for calibration and
conversion (see paper by Molet et al.)
Sound
• Midi-equipment and workstation audio for
sound generation and effects, filter processors
and 3D-audio cards for spatial audio.
• Two categories of sound in VR can be identified:
– Simulation of real world acoustics: based on our
experiences in everyday life physical behavior of
sound can be modeled.
– comprises sound generation, e.g. caused by object
collision, sound propagation and auralization.
• Immersive user interfaces can be used to evaluate
simulation results.
– Sound at user interface: sound can be applied to
support user in current task or to provide information
about invisible proceedings.
Presence
• Presence is a state of consciousness where the
human actor has a sense of being in the location
specified by the displays.
• We take presence as the central feature of "virtual
reality":
• "A virtual reality is defined as a real or simulated
environment in which a perceiver experiences
telepresence" (Steuer).
• The unique feature of "virtual reality" systems is
that they are general purpose presence
transforming machines..
Meaning of Presence
• Presence is the psychological sense of being there in the
environment specified by the displays.
• a high degree of presence in the VE should lead to the
participant experiencing objects and processes in the virtual
world as (temporarily) more the presenting reality than the
real world in which the VE experience is actually embedded.
• A correlate of this is that the participant should exhibit
behaviours that are the same as those they would carry out in
similar circumstances in everyday reality.
• The VE experience - should be more like visiting a place,
rather than like seeing images designating a place
Design in Immersive VEs
With design in immersive virtual
environments...
• designer shares same space as objects;
• a degree of evaluation can take place in
the virtual space;
• presence leads to the designer behaving
in a manner appropriate to everyday
reality in similar circumstances.
• Special "interactive techniques" and
behaviours do not have to be learned...
Feedback
• Two forms of feedbaack
– Force Feedback
• Manipulating virtual objects
• Gravity
• Simulation
– Touch (tactile) Feedback
• Texture appreciation
• Navigation
• Sensitive
• Use Haptic Devices
What is a haptic interface?
• A haptic interface is a force reflecting
device which allows a user to touch, feel,
manipulate, create, and/or alter
simulated 3D-objects in a virtual
environment.
• Movement trackers do not provide
feedback
Usage
It could be used to
• train physical skills such as those jobs requiring
specialized hand-help tools (e.g. surgeons,
astronauts, mechanics),
• to provide haptic-feedback modeling of three
dimensional objects without a physical medium
(such as automobile body designers working with
clay models), or
• to mock-up developmental prototypes directly
from CAD databases (rather than in a machine
shop).
Phantom
Very common haptic device mainly used with
augmentation on desktop systems
Exoskeleton
Tactile Feedback
Presence in Multi-participant
Environments
• Sense of being in a place
• sense of sharing the same space as other
individuals
• Sense of belonging to a totality more than
just the sum of the individuals
• Awareness may be an important factor
enhancing shared presence.
• Shared presence may correspondingly
enhance awareness
Tele-Immersion
• Goal - not just
making these
collaborations
possible, but
making them
convenient
CAVERNsoft Application
Virtual Harlem
•
•
•
•
•
Bryan Carter, Bill Plummer – ATC
(Advanced Technology Center at Univ
of Missouri- Columbia )
SIGGRAPH 1999
Harlem is reconstructed for an African
American Literature course at MU.
Instead of just reading literary works
from this era, this prototype will allow
students to become immersed and
engaged in an interactive literature
course.
Jim Sosnoski, Jim Fletcher- English
Dept. Univ Illinois Chicago
Steve Jones- Communications Dept.
Univ Illinois Chicago
Elements of
Tele-Immersion
Avatars
• Tracking head and hand position and orientation give good
cues
• Extendable pointing rays can be useful in large spaces
• Exaggerated head and hand motions give better cues than
just hand
Business users
Augmentation
Shared Virtual Environments
in Europe
• Collaborative Virtual Environments (COVEN) ACTS
• Develops an integrated teleworking platform that
supports multi-sensory presence for collaboration in
shared virtual environments.
• Services:
• mechanisms to support the presence of users in shared
virtual environments.
• browsing and interaction facilities for large numbers of
users accessing enormous quantities of remote
information;
• synchronised multi-sensory interaction with dynamic
representations of three-dimensional objects and actors;
• support for collaborative tasks requiring complex motor
skills and shared information.
VR Applications
• Augmented Reality
– Placing data in the normal workspace
• Data Visualisation
– Explaining data through better representation
• Training
– For dangerous/expense procedures
• Conferencing
– Social context for telecommunication
• Health
– Treatment of phobias/psychological disorders
• Entertainment