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
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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
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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
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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!