Origins of Virtual Environments
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Transcript Origins of Virtual Environments
Origins of Virtual Environments
S.R. Ellis, Origins and Elements of Virtual
Environments, in Virtual Environments and
Advanced Interface Design, Barfield and Furness,
Oxford University Press, 1995, pp. 14-57
Summarized by Geb Thomas
Learning Objectives
1. Learn what VR is and how it works as a form of
communication.
2. Understand the concept of virtualization including the
differences between virtual space, a virtual image and a
virtual environment.
3. Learn about the history of virtual environments and the
important pioneers and forces that shaped its creation.
4. Understand the variety and types of hardware used in
VR.
5. Learn about the types of tradeoffs that VR technology
requires, particularly cost versus performance, mass of
gear to be worn, and resolution versus field of view.
Communications and
Environments
VE’s are media, like books, movies or radio
Task of scientists is to make interaction with
the media efficient and effortless -- reduce
the adaptation period
VE extends the desktop metaphor to 3D.
Historically this uses physical constraints
from simulator and telerobotics fields
Components of VE
Content
Geometry
Dynamics
Content
Objects and actors described by
characteristic vectors (a total description of
each element) and position vectors (a subset
of character vectors).
Self is a special actor representing point of
view
Geometry
Dimensionality
– Number of independent descriptive terms
needd to specify the position vector
Metrics
– Rules applied to the position vector to establish
order
Extent
– The range of possible values for the position
vector
Dynamics
Rules of interaction of the content elements
Example, the differential equations of
Newtonian dynamics.
Our Sense of Physical Reality
We construct reality from symbolic,
geometric and dynamic information directly
presented to our senses
Generally we see only a small part of the
whole.
We rely on a priori knowledge
We are predisposed to certain arrangements
of information -- we resonate with some
more than others.
Virtualization
The process by which a human viewer
interprets a patterned sensory impression to
represent an extended object in a n
environment other than that in which it
physically exists.
Three levels:
– Virtual space
– Virtual image
– Virtual Environment
Virtual Space
Perceived 3D layout of objects in space when
viewing a flat screen
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perspective
shading
occlusion
texture gradients
This must be learned! False cues
Perceived size or scale is not inherent in
media
Virtual Image
The perception of an object in depth with
accommodative, vergence and (optionally)
stereoscopic disparity cues are present.
Scale not arbitrary
Virtual Environment
Add observer-slaved motion parallax, depth
of focus variation and wide field-of-view
without visible restriction of the field of
view
vergence
accommodative vergence - reflective
change in vergence caused by focus adjust.
optokinetic reflex - eye tracking objects
vestibular-ocular reflex - eye tracking head
Virtual Environments (cont)
“Measurements of the degree to which a VE
display convinces its users that they are
present in the synthetic world can be made
by measuring the degree to which these
responses can be triggered in it.”
Device calibration and timing are critical.
The sensory systems can often adjust to
systematic distortion, but not to time lags.
Viewpoints
Egocentric -- see the world from viewer’s
point of view
Exocentric -- see the user acting in the
world
Similar to inside-out and outside-in frames
in aviation literature
Origins of VE
Human fascination with vicarious
experience
–
–
–
–
cave art
Through the looking glass
Computer games
Neuromancer (Gibson)
Ivan Sutherland stereo display
Myron Krueger’s VIDEOPLACE
U. of Illinois’ CAVE
Vehicle Simulation
Much VE derived from aircraft and ship
simulators
Development of special purpose machines:
matrix multipliers -- graphic pipelines,
graphic engines
Moving Simulators
Motion sickness
Subthreshold visual-vestibular mismatches
to produce illusions of greater freedom of
movement “washout”
Understand dynamic limits of visualvestibular miscorrelation
Cartography
Controlled information distortion
– spherical projection
– vertical scale exaggeration
VE’s can enhance presentation with
graticules to help avoid effects of distortion.
Combine images to make virtual maps
Applications
Scientific and medical visualization
– multiple time functions of force and torque on
manipulator or limb joints
– Volumetric medical data
– Electronic dissection
– Architectural Walk-throughs
Telerobotics
Predated many VR technology
Spurred position tracking
technology
–
–
–
–
–
Polhemus system
accelerometers
optical tracking
acoustic systems
mechanical systems
Telerobotics II
Input devices
– Isotonic (significant travel)
– Isometric (sense force and torque)
Force feedback devices
– high electro-mechanical bandwidth
– Can create instabilities
– Utah/MIT Hand
Photography, cinematography,
viceo technology
The LEEP optical system,
originally for stereo video used in
VR stereo viewers
Sensorama, Morton Heilig (1955)
Interactive video map (MIT 1980)
Engineering Models
Tendency to overplay successes and suggest
greater generality than exists
Most helmet-mounted displays make users legally
blind
We need to understand characteristics of
–
–
–
–
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human movement
visual tracking
vestibular responses
grasp
manual track
time lags
VE: Performance and Trade-Offs
Performance Advances
Stereoscopic visual strain
Resolution/field-of-view tradeoff
Appropriate application areas:
– multiple, simultaneous, coordinated, real-time foci of
control
– Manipulation of objects in complex visual
environments and require frequent, concurrent changes
in viewing position
Learning Objectives
1. Learn what VR is and how it works as a form of
communication.
2. Understand the concept of virtualization including the
differences between virtual space, a virtual image and a
virtual environment.
3. Learn about the history of virtual environments and the
important pioneers and forces that shaped its creation.
4. Understand the variety and types of hardware used in
VR.
5. Learn about the types of tradeoffs that VR technology
requires, particularly cost versus performance, mass of
gear to be worn, and resolution versus field of view.
For Friday
Read the NRC Report, especially 13-24 and 35-
66. Skim the rest
Personally, I think the recommendations are very
interesting, because they reveal how a panel of
scientists think of what research is important.
Depending on where you are in your career,
however this may not be so key.
Start drafting your essay. I want to see complete,
supported ideas, not stream-of-consciousness!