Technologies. Philippe Fuchs Ecole des Mines, ParisTech, Paris, France. Virtual Reality: Concepts and. Guillaume Moreau.

Transcription

1 Virtual Reality: Concepts and Technologies Editors Philippe Fuchs Ecole des Mines, ParisTech, Paris, France Guillaume Moreau Ecole Centrale de Nantes, CERMA, Nantes, France Pascal Guitton INRIA, University of Bordeaux I, Bordeaux, France CRC Press >V J Taylor 8k Francis Group Boca Raton London NewYork Leiden CRC Press is an imprint of the Taylor & Francis Croup, an informa business A BALKEMA BOOK

2 Table of Contents Preface About the editors List of authors The French Association for Virtual Reality and Mixed Reality xv xvii xix xxi SECTION I Introduction 1 Introduction to virtual reality Foundation of virtual reality Introduction Definitions of virtual reality Origin and simplistic image of virtual reality Purpose of virtual reality Functional definition A Technical definition Book outline 9 Bibliographic references 10 2 Theoretical and pragmatic approach to virtual reality Human behaviour in a real environment Behavioural interfaces Hardware design Transparency of an interface Commercial interfaces and custom interfaces "Instrumental" approach for immersion and interaction Fundamental concepts of behavioural interfacing Behavioural interfaces, schema and metaphors Concept of schema Use of schemas, metaphors or sensorimotor substitutions Consistency and discrepancy of virtual environment Interface and multimodality Method of designing and assessing a virtual reality environment VR reference model Virtual behavioural primitives 26

3 vi Table of Contents Behavioural Software Aids Sensorimotor Software Aids Cognitive Software Aids Design approach Assessment approach Examples of designing and a assessing virtual reality environment Virtual shop for experimentation Introduction Analysis of the problem based on our general diagram of VR Visual observation of products Natural handling of 3D products with 6DOF Navigation in the shop Training on railway infrastructure using virtual reality Analysis of the problem on the basis of our general VR diagram D movement on railway tracks Orientation on tracks Visual immersion Natural handling of objects in 3D with 3DOF Discussion on our approach for the subject's immersion and interaction Perspectives and conclusions 44 Bibliographic references 44 SECTION II The human being in virtual environments 3 Human senses 3.1 Introduction Vision The human visual system The entire visual system The eye Accommodation and convergence The retina The concept of spatial frequency Visual perception of depth Cognitive perception by monocular cues Convergence and retinal disparity Binocular vision and diplopia Neurophysiological mechanisms of the perception of depth Psychophysical characteristics of vision Light sensitivity Frequency sensitivities Visual acuity Field of vision 67 49

4 Table of Contents vii Maximum temporal frequency in vision Psychophysical characteristics of stereoscopic vision Colour discrimination Field dependence-independence Cutaneous sensitivity The skin Classification of biological sensors Nociceptors Thermoreceptors Mechanoreceptors Proprioception Introduction Physics of gravity and accelerations Vestibular apparatus and kinaesthetic canals 76 Bibliographic references 79 4 Interaction between virtual reality and behavioural sciences Introduction Contribution of virtual reality to behavioural sciences Basic research Applied research Training, learning and simulation Therapy and rehabilitation Visualization in scientific computing Contribution of behavioural sciences to virtual reality What are the correct parameters? Realism The concept of "real time" Conclusion 89 Bibliographic references 90 5 Immersion and presence Introduction Immersion Sensory richness Interaction Structural factors of immersion Coherence Mapping Presence Questionnaires and subjective measurements Physiological measurements Behavioural measurements Performance Reflex actions Sensorimotor control 99

5 viii Table of Contents yy 5.4 Conclusion Bibliographic references 100 SECTION III 6 Location sensors 6.1 Introduction Behavioural interfaces Spatial location Location sensor and command interface Mechanical trackers Mechanical trackers measuring distances Mechanical trackers determining an orientation, speed or acceleration Inclinometers Gyroscopes and rate gyros Accelerometers Electromagnetic trackers Electromagnetic trackers using alternating magnetic field Electromagnetic trackers using impulsive field Characteristics of electromagnetic trackers Compass Optical trackers Introduction Principle Classification of trackers Some recently launched systems Conclusion 120 Bibliographic references Manual motor interfaces Introduction Location sensor and dataglove Location sensor and command interface Data gloves Fibre optic gloves Detection of hand movements by cameras Resistance variation gloves Hall effect gloves Special case: binary command glove Conclusion Command interfaces D Mouse D Mouse with force feedback Six degrees of freedom command interface for a large screen Non-manual command interfaces 135 Bibliographic references 136

6 Table of Contents ix Hardware devices of force feedback interfaces Introduction Problems and classification of force feedback interfaces Design of the force feedback interfaces Performance criteria and specifications Concept of transparency Necessity of specifications Posture and type of grip Work space and position resolution Static capacity and force resolution Dynamics, stiffness, inertia and bandwidth Report Modelling and dimensioning Problem Methods and tools Optimisation Technical constraints Mechanical architecture of the force feedback interface Motorisation Reduction stages Transmissions Balancing The different force feedback interfaces External reaction force feedback interfaces The fixed interfaces with serial structure The parallel structure fixed interfaces Fixed interfaces with tight ropes Fixed interfaces with magnetic levitation Internal reaction force feedback interfaces Generic portable interfaces Portable interfaces for hand Exoskeletons for the hand Exoskeletons for the arm Report 172 Bibliographic references 173 Control of a force feedback interface Introduction Intuitive description of the haptic coupling Modelling of the haptic command by a network formalism Passivity Stability Application to the single degree of freedom problem Conclusion Annexe; Elements of network theory 188 Bibliographic references 190

7 x Table of Contents 10 Tactile feedback interfaces Introduction Advantage of tactile feedback interfaces in virtual reality Designing basics for a tactile interface State of the art of the tactile interfaces Tactile stimulation technologies Classification of tactile interfaces according to the domain of application Tactile interfaces for teleoperation and telepresence Tactile interfaces dedicated to the studies of tactile perception Tactile interfaces for sensory substitution Tactile interfaces for the generation of a 3D surface Braille interfaces for the visually impaired State-of-the-art summary Conclusion 205 Bibliographic references Visual interfaces Introduction to visual interfaces Visual interfaces with fixed support Monoscopic computer screens Display of stereoscopic images on a single plane Separation at the screen level Separation by eyeglasses Large screen projection systems Multiple projector architecture Distribution of rendering from multiple PCs Calibration Stereoscopy Multi-user stereoscopy Different types of projectors Passive screens for video projection Stereoscopic flat screens Connected hardware motor interfaces Examples of large screen projection systems Visiodesks or immersive desks Human scale visual interfaces: visioroom (immersive room) and visiocube Portable visual interfaces Architecture of a head-mounted display Head-mounted displays with cathode tube screens Head-mounted displays with liquid crystal screens Optical model of a head-mounted display and related problems 237

8 Table of Contents xi Problems in the visual quality of a head-mounted display Video eyeglasses Video-eyeglasses with LCD screen Head-mounted display and semi-transparent device Conclusion Annexe Restitution by volumetric images 242 Bibliographic references Interaction techniques for virtual behavioural primitives Introduction Reminder of our approach on virtual reality Interaction Virtual behavioural primitives of observation Classification Visual observation Acoustic observation Tactile observation Wayfinding Introduction Theoretical foundations Cognitive map Egocentric and exocentric strategies Decision-making Wayfinding in a virtual environment Characteristics of the virtual world Copying the real world Addition of software aids Conclusion Movement Introduction Continuous control Movement of the person in the world Movement of the world in relation to the person Movement of the viewpoint Discrete control Programmed control Evaluations Conclusion Selection and manipulation Introduction Interaction techniques Accuracy Virtual object positioning Rotation of a virtual object Conclusion 278

9 xii Table of Contents 12.6 Application control and text input Application control Text input Keyboard Conclusion 287 Bibliographic references Stereoscopic restitution of vision Creation of stereoscopic images Principle Choice of stereoscopic parameters Creation of 3D images for teleoperation Stereoscopic visual telepresence Study of stereoscopic vision Deductions of constraints Limitation of stereoscopic vision Limitation of visual strain in stereoscopic vision Problem of visual strain Frequency filtering method Experimental results Conclusion Creation of images in orthoscopic vision for a design review Evaluation of stereoscopic techniques Advantages of stereoscopic vision Choice of parameters of stereoscopic vision Conclusion Annexe D Perception on a sheet 309 Bibliographic references 309 SECTION IV Tools and models for virtual environments 14 Geometric models of virtual environments Introduction Types of objects Properties of models Solid models Spatial enumeration Constructive solid geometry Surface models Using plane surfaces Using non-planar surfaces Nurbs surfaces Algorithmic geometry Transformation of a volume into surface 327

10 Table of Contents xiii Polygonal meshing of a scatter plot Methods of spatial subdivision Distance function methods Deformation methods Surface expansion methods Decimation of meshes Incremental algorithms Operators Error metrics Optimisation of models for virtual reality Texturing Introduction Advantages and disadvantages of textures Levels of details Transition command Generating the levels of detail 337 Bibliographic references Models for visual rendering Rendering for virtual reality Introduction Real-time rendering Quality and perception Lighting and shading models Modelling the appearance Bidirectional reflectance distribution function Textures and bidirectional texture functions Modelling the lighting Global illumination and virtual reality Local illumination and virtual reality Rendering and perception Vision models and rendering calculations Vision models Algorithms of perceptual rendering Tone mapping Introduction 359 Bibliographic references Models for haptic rendering Haptic simulation/device coupling Calculation of haptic rendering Rendering by impedance patterns: calculation of forces Rendering by admittance patterns: calculations of constraints Models primitive to object models (PROXY) Principle 372

11 xiv Table of Contents Implementation Benefits of virtual proxy Modelling the environment for haptic rendering Frequency adaptation Intermediate representations Haptic libraries Conclusion 380 Bibliographic references Collision detection Detection of collision between primitives Definition of collision Spatial detection between convex polyhedrons Spatial detection between any polyhedrons Temporal approaches Discrete temporal methods Continuous temporal detection Assessment of detection of collision between objects and open problems Detection pipeline Problem Proximity search (broad-phase) Strategies of detection by division of the space Strategies of detection by topology and kinematics Approximate detection (narrow-phase) Strategies of detection by bounding volumes Strategies using graphic hardware Continuous temporal acceleration Summary of acceleration Processing the collision Conclusion 405 Bibliographic references 405