From: edlantz@aol.com (Edlantz) Subject: Re: HUMAN-FACTORS: SIDs & HMDs Date: 10 Oct 1996 22:44:50 -0400 Organization: America Online, Inc. (1-800-827-6364) John Wann wrote: <...> >If you are using a SID for group experience there can only be 1 >"driver", who controls the viewpoint goemetry... This can actually be an advantage. An experienced and rehearsed "navigator" can bring "passengers" for a walk-through or tour without requiring HMD/DataGlove related training. Anyone, including handicapped, elderly, and technophobes can deal with this. It's like watching a movie. I would bet that most of the public at large would prefer a passive viewing experience to a fully interactive one (of course, this is probably changing). >...and for all those who >aren't at the "sweet-spot" the projection geometry is incorrect. >(e.g. someone sat infront of or behind the driver, sees the scale >slightly compressed or extended). SIDS present geometrically incorrect >images for groups... True. But this is also true at the movies when you sit off-axis. The brain quickly compensates. Extreme off-axis viewing, however, could increase the risk of cybersickness for intense terrain/environment flybys, since the optic flow is distorted. We are looking into this. Also, cylinder and dome screens exhibit a "graceful" degradation for off-axis viewing as opposed to rectilinear SIDs such as the CAVE. >SIDS present geometrically incorrect >images for groups and this is a fundamental flaw if it was being used >for a precise working environment. Without a head-tracked view point (possible for only one person in a SID), there are applications for which the results are unacceptable. For instance, a flight simulator using a cab (cockpit mock-up) appears to be landing sideways to the co-pilot if the design eyepoint is directed towards the pilot. Collimated displays are used in this case which place the virtual image at infinity. >>Keep in mind that commercial SID systems are young and have not yet been >>optimized for low cost. "SimCenters" are emerging which lease time on >>these systems making them (potentially) profitable. >Even if the cost of projectors does plummet, then you still can't get >round the requirement of a large dedicated space, and if the only >option is booking time downtown, then this is fine to demo the product >to your CEO, but not for a day-to-day visualisation aid. We are looking at rear-projected desktop systems resembling a "wrap-around monitor" for day-to-day visualization. >>frankly, many of these corporations view HMD's as toys or lab curiosities >>as far as their applications are concerned. >Thats my concern - I really have no issue with what you're saying >about SIDs being useful for corporate sectors, and I'm not proposing >that 5 execs should sit in a conference with HMDs on. But there is a >real role for HMDs in design/visualisation where there are 1 or 2 >participants working together. A number of VR protagonists are eager >to extol the virtues of the CAVE etc.. without also considering its >limitations. I think it would be a pity if the impetus was lost from >the HMD market because the influential parties in "corporate VR" are >pushing SIDs I agree 100%. My beef is that HMDs have received far more attention and research $ from VR interests than SIDs. Both have strengths and weaknesses. I am simply suggesting that SIDs can succeed at presenting a VE experience in applications where HMDs have failed. Consider that the content (the VE) is essentially the same in both cases. The delivery system (including HMI) is a bit different, but you still have to model a VE and provide a means of navigation and interaction, which is most of the work. Setting up view ports and external controllers is not that difficult once you have the model. I propose that SIDs give creators of VE experiences another method of distributing and sharing their work. Thanks, Dr. Wann, for another stimulating discussion. Ed Lantz Edlantz@aol.com