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 2
Defining Virtual Environments • Defining Virtual Environments • Immersion, Virtualisation and Presence • Components of a Virtual Environment • Components of a Virtual Environment System 3
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 Synthetic User Environment Computer Interface Devices This is what makes Real this a VE 5 Environment
Virtual Reality in the Early 90s NASA Ames Photo Archive 6
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 7
A Head-Mounted Media Display my.vu Personal Media Viewer 8
Improving User’s Experience at the Dentist 9
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 10
Stimulating the Senses is Not Enough Real World Virtual Reality User
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? 12
Assess Appearance vs. Behaviour? “An eye gaze model for dyadic interaction in an immersive virtual environment: Practice and experience”, Vinayagamoorthy et al., 2004 13
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’.” 14
The Pit "Physiological Measures of Presence in Stressful Virtual Environments," Meehan, et al., 2002 15
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 17
Achieving Presence • Presence is achieved in several steps: Immersion Virtualisation Presence 18
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 19
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”. “Nature and Origin of Virtual Environments: A Bibliographical Essay”, S. Ellis, 1991 20
Levels of Virtualisation • Virtualisation consists of three levels: – Virtual Space – Virtual Image – Virtual Environment 21
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 optic array, perceived size or scale is not intrinsically defined in the virtual space.” 22
Example of a Virtual Space Half-Life 2, Valve Software 23
Virtual Spaces can be Non-Photorealistic “Non-Photorealistic Virtual Environments,” Klein et al, 2000 24
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” 25
Virtual Image Xinerama OpenGL Stereo render test, http://www.tevs.eu/blog_7.html 26
Virtual Environment • “… the key added sources of information are observer-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.” 27
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 28
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’.” 29
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 30
Another Example of Presence 31
Components of a Virtual Environment • Defining Virtual Environments • Immersion, Virtualisation and Presence • Components of a Virtual Environment • Components of a Virtual Environment System 32
The Components of the Environment Geometry: Contents: Dimensions, Actors and Metrics and Objects Extent Dynamics: Interaction Rules Environment “Nature and Origins of Virtual Environments: A Bibliographical 33 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 34
A Heavily-Populated VE Environment SecondLife – not used by VE researchers as much as you’d think 35
Geometry • Description of the environmental field of action • Contains: – Dimensionality: The degree of freedom of the position “vector” 36
Rigid Objects Are Low-Dimensional Darwin Oil Refinery by Bechtel National Inc. 37 from http://www.okino.com/mainpic13.htm
Flexible Object Are High-Dimensional Vikramvr's Punk character [3D] 38 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. 39
Metric “Special Relativity in Virtual Reality”, Rau et al. 40
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 41
Extent 42
Dynamics • These are the rules of interaction among the contents • These can be: – Differential equations of Newtonian dynamics to describe kinematic and dynamic relationships 43
Newtonian Dynamics in Action 44
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 45
Console-Based Interaction 46
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, r elationship between proprioceptive information and sensory data requires consistency, predictability, and completeness 47
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