From @uga.cc.uga.edu:owner-virtu-l@VMD.CSO.UIUC.EDU Tue May 9 20:56:22 1995 Return-Path: <@uga.cc.uga.edu:owner-virtu-l@VMD.CSO.UIUC.EDU> Received: from mx4.u.washington.edu by stein2.u.washington.edu (5.65+UW95.02/UW-NDC Revision: 2.32 ) id AA05489; Tue, 9 May 95 20:56:22 -0700 Received: from uga.cc.uga.edu by mx4.u.washington.edu (5.65+UW95.02/UW-NDC Revision: 2.31 ) id AA00200; Tue, 9 May 95 20:56:21 -0700 Message-Id: <9505100356.AA00200@mx4.u.washington.edu> Received: from UGA.CC.UGA.EDU by uga.cc.uga.edu (IBM VM SMTP V2R2) with BSMTP id 4327; Tue, 09 May 95 23:54:23 EDT Received: from UGA.CC.UGA.EDU (NJE origin LISTSERV@UGA) by UGA.CC.UGA.EDU (LMail V1.2a/1.8a) with BSMTP id 3936; Tue, 9 May 1995 21:11:08 -0400 Date: Tue, 9 May 1995 15:44:45 +0000 Reply-To: john wann Sender: "VR / sci.virtual-worlds" From: john wann Subject: Re: PROD: Comparing HMD's To: Multiple recipients of list VIRTU-L Status: OR Jim Melzer suggested: > If you have small IPD, the imagery will appear divergent. If you have >large IPD, the imagery will appear convergent. The optimum situation is >to have the eyepiece set at infinity. That way, no matter where your eye is >located, binocularly the imagery will appear to be from infinity. By >offsetting the imagery, it can be made to appear closer. ..........and Arthur Zwern asked: >Jim, .............. It is also my understanding that during use, the eye >adapts to >the false vergence cues, which causes errors in your depth >perception that >persist after the HMD comes off. Is this really >eliminated with infinity >optics? Jim is right to stress the problems of displays that may require divergence, but this is only a small part of the picture. The ray diagrams that Jim is talking about tell you nothing about the physiological response of the eye. We have clinically evaluated (and published**) the effects of HMDs with fixed IPD, software/hardware changeable IPD, images at infinity or close to, and the degree of stereo<->focal depth disparity presented. The simple answer is that neither setting the image to focal infinity or having a tunable IPD is a total solution, although a close focal image with a fixed IPD is certainly worse. What is interesting is that if you allow users to set their own IPD they do not do so accurately, but set it with a consistent "vergence bias". Most of these issues are discussed in an article "in press" for Vision Research (which also presents a software tool for accurately setting IPD) or in our Displays paper. The simple answer is that the focal depth of the image is only one of a number of geometrical and physiological parameters that needs consideration in the design process. John Wann Edinburgh VEL _______________________________________________ ** Toni Emerson hasn't included any of our publications in her database so for those who want more background on this issue these are some reference papers: Mon-Williams, M., Rushton, S.K. & Wann, J.P. (in press) Investigating the reciprocal cross-links between accommodation and vergence: Implications for virtual reality displays. Wann, J.P. Rushton, S.K. & Mon-Williams M. (in press) Natural problems for stereoscopic depth perception in Virtual Environments. Vision Research. Rushton S., Mon-Williams, M. and Wann, J. (1994). Binocular vision in a bi-ocular world: new generation head-mounted displays avoid causing visual deficit. Displays 15, 255-260 Mon-Williams, M, Wann, J.P. & Rushton, S.K. (1993). Binocular Vision in a Virtual World: Visual deficits following the wearing of a head-mounted display. Ophthalmic and Physiological Optics. 13 , 387-391 Mon-Williams M.A., Wann J.P., Rushton S.K., Ackerley R. (1993) Real problems with virtual worlds.Ophthalmic and Physiological Optics. 13, 435-436. Wann J.P & Rushton S.K. (1993) Perceptual Issues in Visualisation with Virtual Environment Displays. Proc of the ANZ Conf on Intelligent Information Systems Perth , WA 1-3 Dec. 1993, IEEE WA Division pp 755-759. ISBN: 0-86-42-22-91-2 Rushton, S. & Wann, J. (1993). Problems in Perception and Action in Virtual Worlds. in T. Feldman (ed) Virtual Reality 1993 : Proceedings of the 3rd Annual Conference on Virtual Reality in London. Antony Rowe, Wilts, pp43-55. ISBN: 0-88736-935-9 Wann J.P., Rushton S.K. & Mon-Williams M. (1993) Whats wrong with your head-mounted display? CyberEdge Journal. 17, Sept/Oct 1993, Monograph 3, p1-2 ___________________________________________________