Origins of Virtual Environments

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14 Νοε 2013 (πριν από 4 χρόνια και 1 μήνα)

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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

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!