Introduction to Virtual Environments Simon Julier, William Steptoe - - PowerPoint PPT Presentation

Introduction to Virtual Environments

Simon Julier, William Steptoe

Department of Computer Science University College London http://www.cs.ucl.ac.uk/teaching/VE

Outline

• Defining Virtual Environments
• Immersion, Virtualisation and Presence
• Components of a Virtual Environment
• Components of a Virtual Environment System

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Defining Virtual Environments

• Defining Virtual Environments
• Immersion, Virtualisation and Presence
• Components of a Virtual Environment
• Components of a Virtual Environment System

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Some Definitions….

• “Virtual Reality is electronic simulations of

environments experienced via head mounted eye goggles and wired clothing enabling the end user to interact in realistic three-dimensional situations.” (Coates, 1992)

• “Virtual Reality is an alternate world filled with

computer-generated images that respond to human

• movements. These simulated environments are usually

visited with the aid of an expensive data suit which features stereophonic video goggles and fiber-optic data gloves.” (Greenbaum, 1992)

Device-Driven Definitions of Virtual Environments

User Interface Devices Computer Synthetic Environment Real Environment This is what makes this a VE

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User

Virtual Reality in the Early 90s

NASA Ames Photo Archive

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Limitations of Device-Driven Definition

• “VR” and “not-VR” systems are defined by

presence / absence of hardware alone

– Does not uniquely describe the VE experience

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A Head-Mounted Media Display

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my.vu Personal Media Viewer

Improving User’s Experience at the Dentist

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Limitations of Device-Driven Definition

• “VR” and “not-VR” systems are defined by

presence / absence of hardware alone

– Does not uniquely describe the VE experience – Does not say if the VE experience works

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User

Stimulating the Senses is Not Enough

Virtual Reality Real World

Limitations of Device-Driven Definition

• ““VR” and “not-VR” systems are defined by

presence / absence of hardware alone

– Does not uniquely describe the VE experience – Does not say if the VE experience works

• Lack of theoretical dimensions for parameterising

characteristics of VR

– How can different VR systems be compared? – How can VR be compared with different media?

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Assess Appearance vs. Behaviour?

“An eye gaze model for dyadic interaction in an immersive virtual environment: Practice and experience”, Vinayagamoorthy et al., 2004

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A VE System is Defined by Presence

• “The subjective experience of being

in one place or environment, even when one is physically situated in another.”

• “A perceptual illusion of

nonmediation.”

• “The sense of ‘being there’.”

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The Pit

"Physiological Measures of Presence in Stressful Virtual Environments," Meehan, et al., 2002

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The Pit in Action

Immersion, Virtualisation and Presence

• Defining Virtual Environments
• Immersion, Virtualisation and Presence
• Components of a Virtual Environment
• Components of a Virtual Environment System

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Achieving Presence

• Presence is achieved in several steps:

Immersion Virtualisation Presence

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Immerson

• Immersion is a description of the technology

– Inclusive – sensory experience from VE only – Extensive – more sensory modalities – Surrounding – from all directions – Vivid – high fidelity – Egocentric – first person point of view – Plot – things are happening and the VE responds to the user – Proprioceptive match – between sensory data and proprioception

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Virtualisation

• “the process by which a viewer interprets

patterned sensory impressions to represent

• bjects in an environment other than that from

which the impressions originate”.

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“Nature and Origin of Virtual Environments: A Bibliographical Essay”, S. Ellis, 1991

Levels of Virtualisation

• Virtualisation consists of three levels:

– Virtual Space – Virtual Image – Virtual Environment

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Virtual Space

• “… the process by which a viewer perceives a

three-dimensional layout of objects in space when viewing a flat surface presenting the pictorial cues to space, that is, perspective, shading, occlusion, and texture gradients…. Since scaling does not affect the relative position of the features of the

• ptic array, perceived size or scale is not

intrinsically defined in the virtual space.”

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Example of a Virtual Space

Half-Life 2, Valve Software

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Virtual Spaces can be Non-Photorealistic

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“Non-Photorealistic Virtual Environments,” Klein et al, 2000

Virtual Image

• “… it is the perception of an object in depth in

which accommodative, vergence, and (optionally) stereoscopic disparity cues are present, though not necessarily consistent. Since, virtual images can incorporate stereoscopic and vergence cues, the actual perceptual scaling of the constructed space is not arbitrary but, somewhat surprisingly, not simply related to viewing geometry”

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Virtual Image

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Xinerama OpenGL Stereo render test, http://www.tevs.eu/blog_7.html

Virtual Environment

• “… the key added sources of information are
• bserver-slaved motion parallax, depth-of-focus

variation, and wide field-of-view without a prominent frame. If properly implemented, these additional features can be consistently synthesized to provide stimulation of major physiological reflexes such as accommodative vergence,… and the vestibular-ocular reflex.”

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Virtual Environment

• Requires (almost) full immersion because of the

requirements for head-related and egocentric display

• At this point, user can actively explore the (visual)

environment by moving naturally

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Recall the Definition of Presence

• “The subjective experience of being

in one place or environment, even when one is physically situated in another.”

• “A perceptual illusion of

nonmediation.”

• “The sense of ‘being there’.”

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Operational Definition

• Successful substitution of real sense data by

computer generated sense data

• ‘Successful’ – response is similar to expected

response in everyday reality

• ‘Response’ –

– Low level physiological →high level cognitive and emotional – Includes verbal responses about ‘being there’ – Response includes potential for interaction

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Another Example of Presence

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Components of a Virtual Environment

• Defining Virtual Environments
• Immersion, Virtualisation and Presence
• Components of a Virtual Environment
• Components of a Virtual Environment System

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The Components of the Environment

Contents: Actors and Objects Geometry: Dimensions, Metrics and Extent Dynamics: Interaction Rules Environment

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“Nature and Origins of Virtual Environments: A Bibliographical Essay”, S. R. Ellis, 1991

Contents

• Environment is made up of discrete items known

as objects and actors

• Objects

– Discrete and identifiable – Described by property vectors

• Actors are objects that initiate interactions

– Interactions involve energy or information – The self is a special kind of actor with a point-of-view

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A Heavily-Populated VE Environment

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SecondLife – not used by VE researchers as much as you’d think

Geometry

• Description of the environmental field of action
• Contains:

– Dimensionality: The degree of freedom of the position “vector”

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Rigid Objects Are Low-Dimensional

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Darwin Oil Refinery by Bechtel National Inc. from http://www.okino.com/mainpic13.htm

Flexible Object Are High-Dimensional

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Vikramvr's Punk character [3D] from http://www.cgtantra.com/forums/showthread.php?t=20890

Geometry

• Description of the environmental field of action
• Contains:

– Dimensionality: The degree of freedom of the position vector – Metric: The basic mathematical rules for defining order, distance, etc.

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Metric

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“Special Relativity in Virtual Reality”, Rau et al.

Geometry

• Description of the environmental field of action
• Contains:

– Dimensionality: The degree of freedom of the position vector – Metric: The basic mathematical rules for defining order, distance, etc. – Extent: The range of possible values of the position vector

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Extent

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Dynamics

• These are the rules of interaction among the

contents

• These can be:

– Differential equations of Newtonian dynamics to describe kinematic and dynamic relationships

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Newtonian Dynamics in Action

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Dynamics

• These are the rules of interaction among the

contents

• These can be:

– Differential equations of Newtonian dynamics to describe kinematic and dynamic relationships – Grammatical rules for pattern-matched triggered actions

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Console-Based Interaction

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Dynamics

• These are the rules of interaction among the

contents

• These can be:

– Differential equations of Newtonian dynamics to describe kinematic and dynamic relationships – Grammatical rules for pattern-matched triggered actions

• For comfortable use, relationship between

proprioceptive information and sensory data requires consistency, predictability, and completeness

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A Virtual Environment System

• Defining Virtual Environments
• Immersion, Virtualisation and Presence
• Components of a Virtual Environment
• Components of a Virtual Environment System

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Components of a VE System

• Display / Rendering Systems

– Stimulate immersion

• User Input

– Support interaction

• Tracking

– Supports proprioceptive match

• System Architecture

– Manages everything together

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Sight

Cruz-Neira, C., Sandin, D.J., DeFanti, T.A. (1993) Surround-Screen Projection- Based Virtual Reality: The Design and Implementation of the CAVE, Computer Graphics (SIGGRAPH) Proceedings, Annual Conference Series, 135-142.

CAVE = Cave Automatic Virtual Environment

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Sound

Spatialised Audio Headphones

Touch

Taste

Olfactory Display Systems

“Projection-Based Olfactory Display with Nose Tracking” Y. Yanagida, S. Kawato, H. Noma, A., and N. Tetsutani, IEEE VR 2004, Chicago

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Galvanic Vestibular Response System

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User Input Devices

Cubic Mouse Wand CyberGlove

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Tracking Systems

Inside-Out hybrid camera inertial system Outside-In camera- based tracking system

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System Architecture

Graphics Rendering Audio Rendering Haptic Scene-Graph Network Master Environment Input Devices External Databases Graphics Scene-Graph Interaction Processing Audio Scene-Graph

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Haptic Rendering User Application

Summary

• VEs are defined by Presence
• Presence is the human response
• We get it via immersion and virtualisation
• To create it:

– We define an environment with contents, metric and dynamics – We use various bits of hardware and software to implement it

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