There are actually a bunch of "depth cues" that humans use to perceive 3-dimensionality. Existing computer displays only reproduce a few. Because of redundancy, people can function with only a subset, but it can be a serious handicap. Individuals who are stereoblind can learn to judge distances (such as how far away a stop sign is) from the sizes of familiar objects and other cues ... but it doesn't work that well. Conflicting depth cues are one thing that causes motion sickness.
Rocking or rotating an image is a type of depth cue. Perspective is a depth cue. Lighting effects, such as fading the brightness of an object with distance or placing an object in fog are also depth cues. Focus is a depth due, and so is convergence of the eyes ... neither of those are reproduced by current computer graphics displays (except perhaps experimental ones). There is more to that list. A fair number of people have poor stereo vision ... some don't even realize it. It does not help that stereo systems are sometimes poorly adjusted and sometimes not even done mathematically correctly. Proper stereo transformations require that you know where the person's eyes are located with respect to the screen. A number of years ago, when I ran Cornell's virtual reality CAVE, one visitor told me he was stereo blind and so would not get much out of the experience. But something very unusual happened: when he put on the glasses and motion tracking system, he was apparently able to see stereo for the first time. Perhaps it was something to do with some misalignment in our system that compensated for his vision problem. Anyhow, it was a remarkable experience for him. I've fit density with and without stereo, and personally, I find that stereo adds a great deal. It's not everything, but why throw out a perfectly good depth cue and work stereoblind? It will be interesting to see if the current trend in stereo movies and 3D TV continues or fizzles (as it did in the 50's). Richard Gillilan MacCHESS On Mar 22, 2011, at 11:01 PM, Mayer, Mark (NIH/NICHD) [E] wrote: > what about the fashion statement made by cool glasses? > ________________________________________ > From: Phoebe Rice [[email protected]] > Sent: Tuesday, March 22, 2011 10:16 PM > To: [email protected] > Subject: Re: [ccp4bb] while on the subject of stereo > > My 2 cents worth on the stereo-dependent: > > 1) They have carpal tunnel syndrome that makes it painful to keep the > molecule in motion while rebuilding it (NOTE: enough constant mouse-wiggling > and you will get carpal tunnel problems if you don't have them yet!) > > 2) They work on big, low-resolution structures where you need to see a > bigger-picture view. I've had people tell me that can fit 3-3.5A maps just > fine without stereo, but having viewed their work, I beg to differ. > > Phoebe > > ---- Original message ---- >> Date: Tue, 1 Mar 2011 22:30:54 +0000 >> From: CCP4 bulletin board <[email protected]> (on behalf of Jan Löwe >> <[email protected]>) >> Subject: Re: [ccp4bb] while on the subject of stereo >> To: [email protected] >> >> Ah! The question of to stereo or not to stereo! There has to be a >> scientific reason why this question is more popular than asking for what >> Linux distro is more fashionable this spring or why an Rmerge of 0.90 in >> the outermost shell is good for you and your structure. >> >> I am offering my two (conflicting) theories (and apologies that both >> seem to imply some problem): >> >> A) people who do use stereo have a problem with their brain because they >> cannot produce three dimensional vision from depth cues alone. >> >> B) people who do not use stereo have a problem with their brain because >> they cannot see properly in three dimensions and rely on depth cues alone. >> >> I personally prefer people with A) when I am their passenger in a car >> since they do not need to rotate by 90° to see how far the braking >> lights of the car in front are away :-) >> >> jan >> >> >> >> On 01/03/2011 21:35, Jim Pflugrath wrote: >>> I will offer my view. >>> >>> I hate stereo glasses and hate stereo in general. >>> >>> One should be able to see 3D from the depth-cueing and by keeping the view >>> in motion. For fitting, I like to flip the view by 90 degrees. I know I am >>> going to move in displayX and displayY, but never in displayZ. I then >>> rotate the view around the vertical axis so thatn the old displayZ becomes >>> displayX. >>> >>> Furthermore, I don't waste too much time fitting. I know the software can >>> fit the map better than me, so I let it do its job. I only need to get the >>> coordinates within the radius of convergence of the refinement program. I >>> also know that 9 times out of 10, the displayed electron density is probably >>> suspect, so I believe in stereochemistry more than I believe in the map. >>> >>> The main trick is to realize that as a human being, you really are not that >>> good at fitting the map or that it is unnecessary to waste your time since >>> the software is really so much better than you. Refinement is quick enough >>> that you can try various hypotheses as in: "If I move this here, then >>> refinement will do the trick" and "Well, that didn't work, so I will move >>> that over there and see if refinement will do the trick." >>> >>> As for stereo figures, you should be able to convey what you want to say >>> from a good figure with depth-cueing, shadows, etc. Don't ever use stereo >>> glasses in a public seminar. Maybe my opinion will change with better >>> stereo technology. >>> >>> OK, I know quite a lot of people will disagree with me. :) >>> >>> Jim >>> >>> -----Original Message----- >>> From: CCP4 bulletin board [mailto:[email protected]] On Behalf Of David >>> Roberts >>> Sent: Tuesday, March 01, 2011 10:29 AM >>> To: [email protected] >>> Subject: [ccp4bb] while on the subject of stereo >>> >>> Hi again, >>> >>> I'd like to ask a question about the pedagogy of stereo. That is, using >>> stereo with students in the classroom. >>> >>> Do you all find that, after setting up these elaborate stereo devices, >>> students really use the stereo or do they tend not to? >>> >>> I am a huge fan of stereo - and frankly here we have quite a few options for >>> doing stereo - from the active Nvidia systems that people have recently been >>> discussing to passive zalmans. ... >>> >>> As I mentioned, I like stereo a lot, but really projecting on a nice bright >>> lcd monitor also has it's advantages, and with the ease of moving things >>> using the mouse (or whatever device you use), the overall need for stereo >>> seems to be decreasing. I don't know - I just wonder what peoples views are >>> out there for the actual "need" for stereo. It's incredibly cool - and I >>> think is a very powerful way to show things - but I'm wondering if we focus >>> too much on it because it's cool and not because it's pedagogically >>> necessary. >>> >>> Just wondering, no worries. Thanks >>> >>> Dave
