Origins of Virtual Environments

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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

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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.

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Communications and Environments

• VEs 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

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Components of VE

• Content
• Geometry
• Dynamics

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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

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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

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Dynamics

• Rules of interaction of the content elements
• Example, the differential equations of Newtonian
  dynamics.

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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.

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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

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Virtual Space

• Perceived 3D layout of objects in space when
  viewing a flat screen
• perspective
• shading
• occlusion
• texture gradients
• This must be learned! False cues
• Perceived size or scale is not inherent in media

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Virtual Image

• The perception of an object in depth with
  accommodative, vergence and (optionally)
  stereoscopic disparity cues are present.
• Scale not arbitrary

12
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

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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.

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Viewpoints

• Egocentric -- see the world from viewers point
  of view
• Exocentric -- see the user acting in the world
• Similar to inside-out and outside-in frames in
  aviation literature

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Origins of VE

• Human fascination with vicarious experience
• cave art
• Through the looking glass
• Computer games
• Neuromancer (Gibson)
• Ivan Sutherland stereo display
• Myron Kruegers VIDEOPLACE
• U. of Illinois CAVE

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Vehicle Simulation

• Much VE derived from aircraft and ship simulators
• Development of special purpose machines matrix
  multipliers -- graphic pipelines, graphic engines

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Moving Simulators

• Motion sickness
• Subthreshold visual-vestibular mismatches to
  produce illusions of greater freedom of movement
  washout
• Understand dynamic limits of visual-vestibular
  miscorrelation

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Cartography

• Controlled information distortion
• spherical projection
• vertical scale exaggeration
• VEs can enhance presentation with graticules to
  help avoid effects of distortion.
• Combine images to make virtual maps

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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

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Telerobotics

• Predated many VR technology
• Spurred position tracking technology
• Polhemus system
• accelerometers
• optical tracking
• acoustic systems
• mechanical systems

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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

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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)

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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
• human movement
• visual tracking
• vestibular responses
• grasp
• manual track
• time lags

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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

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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.

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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-conscious
  ness!

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