1. Origins of Virtual Environments S.R. Ellis, Origins and Elements of Virtual Environments, in Virtual Environments and Advanced Interface Design, Barfield and Furness, Oxford University Press, 1995, pp. 14-57 Summarized by Geb Thomas

2. Learning Objectives 4 1. Learn what VR is and how it works as a form of communication. 4 2. Understand the concept of virtualization including the differences between virtual space, a virtual image and a virtual environment. 4 3. Learn about the history of virtual environments and the important pioneers and forces that shaped its creation. 4 4. Understand the variety and types of hardware used in VR. 4 5. Learn about the types of tradeoffs that VR technology requires, particularly cost versus performance, mass of gear to be worn, and resolution versus field of view.

3. Communications and Environments 4 VE’s are media, like books, movies or radio 4 Task of scientists is to make interaction with the media efficient and effortless -- reduce the adaptation period 4 VE extends the desktop metaphor to 3D. 4 Historically this uses physical constraints from simulator and telerobotics fields

4. Components of VE 4 Content 4 Geometry 4 Dynamics

5. Content 4 Objects and actors described by characteristic vectors (a total description of each element) and position vectors (a subset of character vectors). 4 Self is a special actor representing point of view

6. Geometry 4 Dimensionality –Number of independent descriptive terms needd to specify the position vector 4 Metrics –Rules applied to the position vector to establish order 4 Extent –The range of possible values for the position vector

7. Dynamics 4 Rules of interaction of the content elements 4 Example, the differential equations of Newtonian dynamics.

8. Our Sense of Physical Reality 4 We construct reality from symbolic, geometric and dynamic information directly presented to our senses 4 Generally we see only a small part of the whole. 4 We rely on a priori knowledge 4 We are predisposed to certain arrangements of information -- we resonate with some more than others.

9. Virtualization 4 The process by which a human viewer interprets a patterned sensory impression to represent an extended object in a n environment other than that in which it physically exists. 4 Three levels: –Virtual space –Virtual image –Virtual Environment

10. Virtual Space 4 Perceived 3D layout of objects in space when viewing a flat screen –perspective –shading –occlusion –texture gradients 4 This must be learned! False cues 4 Perceived size or scale is not inherent in media

11. Virtual Image 4 The perception of an object in depth with accommodative, vergence and (optionally) stereoscopic disparity cues are present. 4 Scale not arbitrary

12. Virtual Environment 4 Add observer-slaved motion parallax, depth of focus variation and wide field-of-view without visible restriction of the field of view 4 vergence 4 accommodative vergence - reflective change in vergence caused by focus adjust. 4 optokinetic reflex - eye tracking objects 4 vestibular-ocular reflex - eye tracking head

13. Virtual Environments (cont) 4 “Measurements of the degree to which a VE display convinces its users that they are present in the synthetic world can be made by measuring the degree to which these responses can be triggered in it.” 4 Device calibration and timing are critical. The sensory systems can often adjust to systematic distortion, but not to time lags.

14. Viewpoints 4 Egocentric -- see the world from viewer’s point of view 4 Exocentric -- see the user acting in the world 4 Similar to inside-out and outside-in frames in aviation literature

15. Origins of VE 4 Human fascination with vicarious experience –cave art –Through the looking glass –Computer games –Neuromancer (Gibson) 4 Ivan Sutherland stereo display 4 Myron Krueger’s VIDEOPLACE 4 U. of Illinois’ CAVE

16. Vehicle Simulation 4 Much VE derived from aircraft and ship simulators 4 Development of special purpose machines: matrix multipliers -- graphic pipelines, graphic engines

21. Moving Simulators 4 Motion sickness 4 Subthreshold visual-vestibular mismatches to produce illusions of greater freedom of movement “washout” 4 Understand dynamic limits of visual- vestibular miscorrelation

22. Cartography 4 Controlled information distortion –spherical projection –vertical scale exaggeration 4 VE’s can enhance presentation with graticules to help avoid effects of distortion. 4 Combine images to make virtual maps

23. Applications 4 Scientific and medical visualization –multiple time functions of force and torque on manipulator or limb joints –Volumetric medical data –Electronic dissection –Architectural Walk-throughs

24. Telerobotics 4 Predated many VR technology 4 Spurred position tracking technology –Polhemus system –accelerometers –optical tracking –acoustic systems –mechanical systems

25. Telerobotics II 4 Input devices –Isotonic (significant travel) –Isometric (sense force and torque) 4 Force feedback devices –high electro-mechanical bandwidth –Can create instabilities –Utah/MIT Hand

26. Photography, cinematography, viceo technology 4 The LEEP optical system, originally for stereo video used in VR stereo viewers 4 Sensorama, Morton Heilig (1955) 4 Interactive video map (MIT 1980)

27. Engineering Models 4 Tendency to overplay successes and suggest greater generality than exists 4 Most helmet-mounted displays make users legally blind 4 We need to understand characteristics of –human movement –visual tracking –vestibular responses –grasp –manual track –time lags

28. VE: Performance and Trade- Offs 4 Performance Advances 4 Stereoscopic visual strain 4 Resolution/field-of-view tradeoff 4 Appropriate application areas: –multiple, simultaneous, coordinated, real-time foci of control –Manipulation of objects in complex visual environments and require frequent, concurrent changes in viewing position

31. Learning Objectives 4 1. Learn what VR is and how it works as a form of communication. 4 2. Understand the concept of virtualization including the differences between virtual space, a virtual image and a virtual environment. 4 3. Learn about the history of virtual environments and the important pioneers and forces that shaped its creation. 4 4. Understand the variety and types of hardware used in VR. 4 5. Learn about the types of tradeoffs that VR technology requires, particularly cost versus performance, mass of gear to be worn, and resolution versus field of view.

32. For Friday 4 Read the NRC Report, especially 13-24 and 35- 66. Skim the rest 4 Personally, I think the recommendations are very interesting, because they reveal how a panel of scientists think of what research is important. Depending on where you are in your career, however this may not be so key. 4 Start drafting your essay. I want to see complete, supported ideas, not stream-of-consciousness!