From: john1@ed.ac.uk Subject: Re: DESIGN: 3D computing vs. virtual reality Date: Fri, 15 Dec 1995 10:33:28 +0000 From: john1@ed.ac.uk John Wann wrote: > >> There is no need to seperate tele-operation from computer-generated >> displays. Both are virtual in the optical sense. A virtual optic array >> is one where the rays appear to come from luminous surfaces that are not >>>> located at their apparant depth (e.g. a planar mirror). [etc] >> > John Costella replied: > > it is natural that you use "virtual" in its optical sense. But I do not > believe that this is generally relevant for "virtual world" or "virtual > reality". > What if you use a VET or CAVE in which there are no intermediary optics I maybe didn't expand enough, the "optical" argument holds for computer generate HMD and tele-operation HMD presentations, but it can also be extended (over both spatial temporal samples) for systems without optics. i) Spatial samples: A stereoscopic CAVE is a virtual array because the stereoscopic half-images presented on its walls specific an object hanging in front of you (e.g. as before the luminous surfaces appear to be where they are not) - no "optics" required. If a CAVE is not stereoscopic then its clearly not VR - its just a room with pictures on its flat walls UNLESS..... ii) Temporal samples: If the CAVE is not stereoscopic then it can still satisfy my VR criteria if the images are head responsive. If you move your head and see relative motion parallax of the objects projected on the walls, then once again this is equivalent to the object surfaces being at different depths (e.g. they are once agian virtual). These are not "OPTICAL" criteria but "PERCEPTUAL" criteria - the essence of what is or is not VR is the perceiver - if you perceive "virtual depth" then the system has to be a VE - BUT if there are natural human responses that negate the illusion of virtual 3D space then it is confusing to label these as VR e.g. If a "desktop" system is niether stereoscopic nor head-responsive then small head movements will dispel the illusion of virtual 3D structure - the display will look like what it really is - a 2D picture on a 2D screen. I am aware of a huge group of people who disagree with this, and argue that users get "immersed" in their interactive desktop systems - but people get "immersed" in films/books and conventional computer games (which are also interactive and allow manipulation) - where do you stop labelling things as VR? The perceptual definition is clear - if the system supports the percept of surfaces at illusory depths then it is a virtual environment and this clearly includes tele-operation as a sub-set. Where there are strong perceptual cues that the surfaces are not actually at the depth that is depicted (e.g. standard desktop) then why evoke the term "VR" when "3D model" is a more suitable label? ********************************************************* Dr John P. Wann or < J.P.Wann@rdg.ac.uk> ********************************************************** Edinburgh VEL Group - Now sited at: (Wann, Mon-Williams) (Rushton, Hawkes) Department of Psychology AND Department of Psychology University of Reading University of Edinburgh PO Box 238 7 George Square Reading RG6 6AL Edinburgh EH8 9JZ +44 1734 318532 +44 131 650 3426 Fx +44 1734 316604 +44 131 650 3461 ***********************************************************