Origins of Virtual Environments

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 • 1. Learn what VR is and how it works as a form of communication. • 2. Understand the concept of virtualization including the differences between virtual space, a virtual image and a virtual environment. • 3. Learn about the history of virtual environments and the important pioneers and forces that shaped its creation. • 4. Understand the variety and types of hardware used in VR. • 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 • VE’s are media, like books, movies or radio • Task of scientists is to make interaction with the media efficient and effortless -- reduce the adaptation period • VE extends the desktop metaphor to 3D. • Historically this uses physical constraints from simulator and telerobotics fields

4. Components of VE • Content • Geometry • Dynamics

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

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

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

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

9. Virtualization • 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. • Three levels: • Virtual space • Virtual image • Virtual Environment

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

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

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

13. Virtual Environments (cont) • “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.” • Device calibration and timing are critical. The sensory systems can often adjust to systematic distortion, but not to time lags.

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

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

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

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

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

23. Applications • 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 • Predated many VR technology • Spurred position tracking technology • Polhemus system • accelerometers • optical tracking • acoustic systems • mechanical systems

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

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

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

28. VE: Performance and Trade-Offs • Performance Advances • Stereoscopic visual strain • Resolution/field-of-view tradeoff • 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 • 1. Learn what VR is and how it works as a form of communication. • 2. Understand the concept of virtualization including the differences between virtual space, a virtual image and a virtual environment. • 3. Learn about the history of virtual environments and the important pioneers and forces that shaped its creation. • 4. Understand the variety and types of hardware used in VR. • 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 • Read the NRC Report, especially 13-24 and 35-66. Skim the rest • 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. • Start drafting your essay. I want to see complete, supported ideas, not stream-of-consciousness!