Virtual Environments: Introduction

Anthony Steed, Simon JulierDepartment of Computer Science

University College London

http://www.cs.ucl.ac.uk/teaching/VE

Outline

• What are Virtual Environments?– Working definition– Constituents of the environment

• Technologies for VEs– What are the toolbox of parts?

• Describing and Measuring a VE– Immersiveness– Levels of virtualisation– Presence

Defining Virtual Environments

• What are Virtual Environments?– Working definition– Constituents of the environment

• Technologies for VEs– What are the toolbox of parts?

• Describing and Measuring a VE– Immersiveness– Levels of virtualisation– Presence

Virtual Reality in the Early 90s

NASA Ames Photo Archive

Device-Driven Definitions of Virtual Environments• 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)

• The terms virtual worlds, virtual cockpits, and virtual workstations were used to describe specific projects.... In 1989, Jaron Lanier, CEO of VPL, coined the term virtual reality to bring all of the virtual projects under a single rubric. The term therefore typically refers to three-dimensional realities implemented with stereo viewing goggles and reality gloves. (Krueger, 1991, p. xiii)

“Defining Virtual Reality: Dimensions Determining Telepresence”, Steueur, 1992

Device-Driven Definitions of Virtual Environments

User

Interface Devices

Computer

User

Synthetic Environment

Real Environment

This is what makes this a VE

Limitations of Device-Driven Definition

• “VR” and “not-VR” systems are defined by presence / absence of hardware alone– Previous definitions highly image oriented

• Lack of theoretical dimensions for parameterising characteristics of VR– How can different VR systems be compared?– How can VR be compared with different media?

A VE is an Immersive, Mediated Communication Medium

User

Interface Devices

Environment

User

Synthetic Environment

Real Environment

Mediated Medium

Components of the Environment

Contents:Actors and

Objects

Geometry:Dimensions, Metrics and

Extent

Dynamics:Interaction Rules

“Virtual Environments and Environmental Instruments”, S. Ellis, 1996

Environment

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• The self is a special kind of actor with a point-of-

view

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

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

VE Technologies

• What are Virtual Environments?– Working definition– Constituents of the environment

• Technologies for VEs– What are the toolbox of parts?

• Describing and Measuring a VE– Immersiveness– Levels of virtualisation– Presence

Components of a VE System

• Display / Rendering System• User Input• Tracking• Database - no time to talk about this

Visual Display Systems

FishTankVR: VR on a Monitor

Headmounted Display

Headmounted Display

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

Audio Display Systems

Spatialised AudioHeadphones

Haptic Display Systems

Phantom

CyberGrasp

Tactors

Olfactory Display Systems

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

Galvanic Vestibular Response System

User Input Devices

Cubic Mouse

Wand

CyberGlove

Tracking Systems

Inside-Out hybrid camera inertial system

Outside-In camera-based tracking system

Describing and Measuring VEs

• What are Virtual Environments?– Working definition

– Constituents of the environment

• Technologies for VEs– What are the toolbox of parts?

• Describing and Measuring a VE– Immersiveness

– Levels of virtualisation

– Presence

Why Study VEs?

• VEs are tools to try to maximise information between the computer and user

• Input – Responds to the user through 3D controls– Possibly speech controlled

• Output– High-fidelity surrounding graphics– High quality spatialised sound

• The input / output configuration needs to maximise the information flow

Optimising the Performance of a VE

• “I define a virtual reality experience as any in which the user is effectively immersed in a responsive virtual world. This implies user dynamic control of viewpoint.” - Professor Fred Brooks, UNC Chapel Hill, USA

• But what does “effectively immersed” mean?

Optimising the Performance of a VE

• The best performance occurs when:– the user loses awareness of the real world props that

support the perceptual illusions; and– Actions are successfully supported in the environment

• In other words, the user experiences presence• Presence is achieved in several steps:

Immersion Virtualisation Presence

Immersion

• 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

Virtualisation

• Immersion supports the process of virtualisation

• Virtualisation – “the process by which a viewer interprets patterned sensory impressions to represent objects in an environment other than that from which the impressions originate”.

Levels of Virtualisation

• Virtual Space – see a 3D object when looking at something inscribed on a flat sheet– Perspective cues, lighting, shading

• Virtual Image – perception of an object with depth– Stereo disparity

• Virtual Environment – perception of a surrounding environment– head-slaved parallax, accommodation and

vergence, surrounding display

Virtual Space

Half-Life 2, Valve Software

Virtual Image

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

Some Presence Definitions

• ‘The sense of “being there”’ (Held & Durlach, Sheridan, Zeltzer: premier issue of PRESENCE, 1992)

• ‘A perceptual illusion of nonmediation’ (Lombard and Ditton, 1997)

• ‘A mental state in which a user feels physically present within the computer-mediated environment’ (Draper & Kaber, 1998)

• ‘The subjective experience of being in one place or environment, even when one is physically situated in another’ (Witmer & Singer, 1998)

Presence Operationally

• 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

Impact of Virtual Environments

• Meehan, M., B. Insko, M. Whitton and F. P. Brooks Jr. (2002). "Physiological Measures of Presence in Stressful Virtual Environments." ACM Transactions on Graphics 21(3): 645-652. (Proceedings of ACM SIGGRAPH 2002, San Antonio , Texas ).

Summary

• A working definition of VEs– Mediated communication environments

• A very brief overview of the technology behind virtual environments

• Levels of virtualisation • Critical role of immersion in affording

proprioceptively correct changes in sensors data

• Presence as the human response