Foreword	5
	Contents	9
	Part I Perception	11
	1 Sensory Contributions to Spatial Knowledge of Real and Virtual Environments	12
	1.1 External Sensory Information	14
	1.2 Internal Sensory Information	16
	1.3 Efferent Sources of Information	17
	1.4 Relative Influence of External and Internal Sensory Information	19
	1.4.1 Sensory Contributions in the Real World	19
	1.4.2 Sensory Contributions in Virtual Environments	21
	1.5 Conclusion	30
	References	31
	2 Perceptual and Cognitive Factors for Self-Motion Simulation in Virtual Environments: How Can Self-Motion Illusions (``Vection'') Be Utilized?	36
	2.1 Introduction: The Challenge of Walking in VR	36
	2.2 Visually Induced Self-Motion Illusions	38
	2.2.1 Circular Vection	39
	2.2.2 Linear Vection	40
	2.3 Self-Motion Sensation from Walking	41
	2.4 Interaction of Walking and Other Modalities for Vection	42
	2.4.1 Walking and Auditory Cues	42
	2.4.2 Walking and Visual Cues	42
	2.5 Further Cross-Modal Effects on Self-Motion Perception in VR	45
	2.6 Simulator Sickness and Vection in VR	47
	2.7 Perceptual Versus Cognitive Contributions to Vection	47
	2.7.1 Lower-Level and Bottom-Up Contributions to Vection	47
	2.7.2 Cognitive and Top-Down Contributions to Vection	49
	2.8 Does Vection Improve Spatial Updating and Perspective Switches?	52
	2.9 Conclusions and Conceptual Framework	53
	2.10 Outlook	56
	References	57
	3 Biomechanics of Walking in Real World: Naturalness we Wish to Reach in Virtual Reality	64
	3.1 Introduction	64
	3.2 Kinematics of Human Walking	65
	3.2.1 Global Description	66
	3.2.2 Joint Kinematics	71
	3.3 Dynamics of Human Walking	73
	3.3.1 Forces and Torques Description	74
	3.3.2 Energetics of Human Walking	76
	3.3.3 Balance	78
	3.4 Comparison Between Ground and Treadmill Walking	80
	3.5 Conclusion	81
	References	82
	4 Affordance Perception and the Visual Control of Locomotion	87
	4.1 Introduction	87
	4.2 Taking Body Dimensions and Movement Capabilities into Account	88
	4.2.1 Theoretical Approach	88
	4.2.2 Affordance Perception and the Control of Locomotion	89
	4.2.3 Eyeheight-Scaled Information	89
	4.3 Perceiving Body-Scaled Affordances	91
	4.4 Perceiving Action-Scaled Affordances	94
	4.4.1 The Information-Based Approach	94
	4.5 Testing the Information-Based Approach	95
	4.5.1 An Alternative Account	97
	4.6 Testing the Affordance-Based Approach	99
	4.7 Extensions of the Affordance-Based Approach	101
	4.8 Affordance Perception and the Continuous Control of Locomotion	102
	4.9 Conclusions	103
	References	105
	5 The Effect of Translational and Rotational Body-Based Information on Navigation	107
	5.1 Introduction	107
	5.2 Applications of Virtual Environments	108
	5.3 Ecological Validity	109
	5.4 The Effect of Body-Based Information	110
	5.4.1 Review Framework	111
	5.4.2 Studies Investigating the Effect of Body-Based Information	113
	5.5 Summary and Conclusions for VE Applications	116
	5.5.1 Model-Scale Environments	116
	5.5.2 Small-Scale Environments	117
	5.5.3 Large-Scale Environments	118
	5.5.4 Further Research	118
	References	119
	6 Enabling Unconstrained Omnidirectional Walking Through Virtual Environments: An Overview of the CyberWalk Project	121
	6.1 Introduction	122
	6.2 Gait and Biomechanics	124
	6.2.1 Natural Unconstrained Walking	124
	6.2.2 Overground Versus Treadmill Walking	128
	6.2.3 Potential Implications for CyberWalk	132
	6.3 Multisensory Self-Motion Perception	132
	6.3.1 Multisensory Nature of Walking	133
	6.3.2 Integration of Vestibular and Proprioceptive Information in Human Locomotion	135
	6.3.3 ``Vection'' from Walking	139
	6.3.4 Potential Implications for CyberWalk	140
	6.4 Large Scale Navigation	141
	6.4.1 Potential Implications for CyberWalk	144
	6.5 Putting it All Together: The CyberWalk Platform	144
	References	147
	Part II Technologies	153
	7 Displays and Interaction for Virtual Travel	154
	7.1 Introduction	154
	7.2 Display Systems	156
	7.3 Interaction Devices	161
	7.4 Travel Techniques	173
	7.4.1 Travel as a Control Task	173
	7.4.2 Direct Self Motion Control Techniques	177
	7.4.3 Indirect Self Motion Control Techniques	178
	7.4.4 Scene Motion Techniques	178
	7.4.5 Other Control Inputs	179
	7.5 Conclusion	179
	References	180
	8 Sensing Human Walking: Algorithms and Techniques for Extracting and Modeling Locomotion	183
	8.1 Introduction	183
	8.2 Sensing and Interpreting Global Gait Parameters	184
	8.2.1 Step Length and Frequency	184
	8.2.2 Curvature and Non-linear Walking	185
	8.2.3 Gait Asymmetry and Regularity	189
	8.3 Joint Angles, Torques and Muscle Activity	189
	8.3.1 Measuring Joint Displacements	189
	8.3.2 Measuring Joint Angles	192
	8.3.3 Estimating Joint Torques with Inverse Dynamics	194
	8.4 Isolated Segments	194
	8.5 Global System and Controllers	195
	8.6 Conclusion About Inverse Dynamic Approaches	196
	8.6.1 Measuring or Estimating Muscle Activities	197
	8.7 Conclusion	201
	References	201
	9 Locomotion Interfaces	204
	9.1 Introduction	204
	9.2 Sliding Shoes	206
	9.2.1 Virtual Perambulator	206
	9.2.2 Powered Shoes	207
	9.2.3 String Walker	208
	9.2.4 Evacuation Simulator Using the Virtual Perambulator	209
	9.3 Treadmills	210
	9.3.1 Related Works in Treadmill-Based Locomotion Interface	210
	9.3.2 Torus Treadmill	211
	9.3.3 Control Algorithm of the Torus Treadmill	213
	9.3.4 Effects of Walking on the Torus Treadmill	214
	9.3.5 Limitation of Torus Treadmill	214
	9.4 Foot Pad	215
	9.4.1 Related Works in Foot-Pad-Based Locomotion Interface	215
	9.4.2 Gait Master	215
	9.4.3 Control Algorithm of the GaitMaster	218
	9.4.4 GaitMater for Walking Rehabilitation	219
	9.5 Robotic Tiles	220
	9.5.1 The CirculaFloor	220
	9.5.2 User Study of the Robot Tile Approach	220
	9.6 Conclusion	223
	References	223
	10 Implementing Walking in Virtual Environments	225
	10.1 Introduction	225
	10.2 Virtual Reality Workspaces	227
	10.3 Isometric Virtual Walking	229
	10.3.1 One-to-One Mappings	229
	10.3.2 Reference Coordinates	230
	10.3.3 Virtual Traveling	231
	10.4 Nonisometric Virtual Walking	231
	10.4.1 User-Centric Coordinates	232
	10.4.2 Scaling Self-Motions	234
	10.4.3 Redirected Walking	237
	10.5 Conclusion	241
	References	242
	11 Stepping-Driven Locomotion Interfaces	245
	11.1 Designing Stepping-Driven Locomotion for Virtual Environment Systems	245
	11.2 Walking-in-Place Interfaces	248
	11.2.1 Setting Speed: Interpreting Stepping Gestures	248
	11.2.2 Setting Direction for Walking-in-Place	253
	11.2.3 The Future for Walking-in-Place Interfaces	255
	11.3 Real-Walking Interfaces	256
	11.3.1 Manipulating Speed	256
	11.3.2 Manipulating Direction	258
	11.3.3 Reorientation Techniques	262
	11.3.4 The Future for Real-Walking Interfaces for IVE Systems	264
	References	264
	12 Multimodal Rendering of Walking Over Virtual Grounds	267
	12.1 Introduction	268
	12.2 Auditory Rendering	269
	12.2.1 Introduction	269
	12.2.2 Footstep Sound Synthesis	271
	12.2.3 Walking Sounds and Soundscape Reproduction	276
	12.2.4 Footstep Sound Design Toolkits	278
	12.3 From Haptic to Multimodal Rendering	279
	12.3.1 Introduction	279
	12.3.2 Touch Sensation in the Feet	282
	12.3.3 Multimodal Displays	285
	12.3.4 Display Configurations	286
	12.3.5 Interactive Scenarios	290
	12.4 Conclusion	294
	References	294
	Part III Applications and Interactive Techniques	300
	13 Displacements in Virtual Reality for Sports Performance Analysis	301
	13.1 Introduction	301
	13.1.1 Why Virtual Reality for Sports?	302
	13.1.2 Requirements for Using Virtual Reality for Sports	306
	13.1.3 Some Applications of Virtual Reality for Sports	307
	13.2 Case Study 1: Deceptive Movements in Rugby	308
	13.2.1 Setup	308
	13.2.2 Method	309
	13.2.3 Results	310
	13.2.4 Discussion	310
	13.3 Case Study 2: Wall Configuration for Soccer Free Kicks	312
	13.3.1 Setup	313
	13.3.2 Methods	314
	13.3.3 Results	315
	13.3.4 Discussion	316
	13.4 Conclusion	316
	References	317
	14 Redirected Walking in Mixed Reality Training Applications	321
	14.1 Locomotion in Virtual Environments	322
	14.2 Redirected Walking	323
	14.3 Practical Considerations for Training Environments	324
	14.3.1 Impact of Redirection on Spatial Orientation	324
	14.3.2 Augmenting Effectiveness of Redirected Walking	325
	14.3.3 Designing Experiences for Redirected Walking	327
	14.4 Redirection in Mixed Reality Environments	328
	14.5 Challenges and Future Directions	330
	References	331
	15 VR-Based Assessment and Rehabilitation of Functional Mobility	334
	15.1 VR-Based Assessment and Rehabilitation to Promote Functional Mobility	337
	15.1.1 VR-Based Assessment and Rehabilitation Following Motor Dysfunction	337
	15.1.2 VR-Based Assessment and Rehabilitation Following Visual Dysfunction	340
	15.2 Dynamical Disease and VR-Based Assessment	342
	15.2.1 Dynamic Measures for Assessing Local Functional Mobility Using VR	343
	15.2.2 Dynamic Measures for Assessing Global Functional Mobility Using VR	345
	15.3 Conclusion	347
	References	348
	16 Full Body Locomotion with Video Game Motion Controllers	352
	16.1 Introduction	352
	16.2 Video Game Motion Controllers	353
	16.2.1 Wiimote	354
	16.2.2 Playstation Move	358
	16.2.3 Microsoft Kinect	360
	16.3 Dealing with the Data	363
	16.3.1 Understanding the Data Coming from the Device	364
	16.3.2 Research the Algorithm Options Suited for the Data	365
	16.3.3 Modifying the Models to Address Error and Uncertainty	369
	16.3.4 Applying All the Data Toward a Solution	370
	16.4 Creating an Interface	371
	16.4.1 Challenges	371
	16.4.2 Controlling Travel	372
	16.4.3 Understand Your Design Tradeoffs and Users	373
	16.4.4 Find How People Want to Interact	374
	16.4.5 Compensate For Technology Limitations	374
	16.5 Conclusion	376
	References	376
	17 Interacting with Augmented Floor Surfaces	378
	17.1 Introduction	378
	17.2 Background	379
	17.2.1 Input from the Foot in Human-Computer Interaction	381
	17.2.2 Relevance to Virtual Reality	382
	17.3 Techniques and Technologies	383
	17.3.1 Indirect Optical Sensing	383
	17.3.2 Contact Sensing	384
	17.3.3 Usability	385
	17.4 Case Study: A Distributed, Multimodal Floor Interface	388
	17.4.1 Contact Localization	388
	17.4.2 Virtual Walking on Natural Materials	391
	17.4.3 Floor Touch-Surface Interaction Techniques	391
	17.4.4 Usability of Foot-Floor Touch-Surface Interfaces	392
	17.4.5 Application: Geospatial Data Navigation	394
	17.4.6 Foot-Based Gestures for Geospatial Navigation	394
	17.5 Conclusions	398
	References	398
	Index	401