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– 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 visual-vestibular 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
– 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!
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