# Origins of Virtual Environments

AI and Robotics

Nov 14, 2013 (4 years and 8 months ago)

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Origins of Virtual Environments

S.R. Ellis, Origins and Elements of Virtual
Environments, in
Virtual Environments and
, 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.

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
--

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

occlusion

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

-
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
-

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

-
Offs

Stereoscopic visual strain

Resolution/field
-
of
-

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.

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!