From: rick@tekig1.PEN.TEK.COM (Fredrick Wilson)
Newsgroups: alt.3d
Subject: Re: How do I generate the two views for a 3d image (LCD glasses)
Date: 2 Sep 92 23:56:32 GMT
Organization: Tektronix, Inc., Beaverton,  OR.

In article <BtxoEA.6JH@ie.utoronto.ca> drascic@ie.utoronto.ca (SpIke) writes:

>A few years ago I designed a mount for our stereoscopic video camera
>pair that permits their separation and convergence angle to be
>controlled by a computer.  Using heuristics and input from the operator,
>the computer will eventually be able to adjust the cameras continuously,
>optimising the stereo depth resolution while keeping eye-stress to a
>minimum.  

Good job.  Technology improvements like that might give stereo
a good name in Hollywood someday.  I would still argue that the
very best results would come from removing the convergence and
optimizing the stereo depth resolution via real-time video processing
instead.  But the movie industry uses film instead of video so they would 
need different equipment.  


>What kind of viewing technique do you use?  We've got alternating
>field displays (showing the left and right views alternately, switching
>rapidly at either 60 Hz or 120 Hz depending the equipment we use) and
>active liquid crystal shuttering glasses.  The lenses switch from clear
>to black.  The left lens is clear only when the left image is displayed,
>and the right shutter only when the right image is displayed.  In this
>way we use one display and channel separate images to the two eyes.

When I can seperate the images (as in discrete photos) I free view -
parallel or crossed.

Most of my "shutter" viewing is on Tektronix systems.
They are like yours except:
60 Hz or 120 Hz depending on user selected vertical resolution of
1024 lines or 512 lines; (1280 pixels wide;)
The LC shutter is on the screen, not the glasses.  This allows use
of more-comfortable normal polorized glasses by an unlimited number 
of simaltanious viewers.

I don't have a 1992 Tektronix catalog at my desk, so I don't know if
we have any new stereo offerings in addition to various products
based on the above concept.  I know some are being worked on, especially
in the color shutter group, but they aren't products yet.


>> If I 
>>take a photo of a video, and then digitize the photo, and add 
>>digital graphics to it, it's all the same.
>
>Unless you want to have real-time displays.

True.  Real-time video requires realtime processing.


>>>>Convergence error can be compensated for to some extent by rotating
>>>>the images (and cropping again) but you can only fix part of
>>>>the picture at a time.  You can't fix the whole picture at once without
>>>>fancy image processing.

>>>This will work for computer graphics, but not for video.

>>It works for photography too, but it's better to take the originals
>>so they don't have to be rotated.  I agree that rotating your
>>swiched video views on a monitor would be a royal pain.  We probably
>>make something here at Tek in either the TV group or the stereoscopic
>>monitor group that is capable of it, but I'm sure most people would
>>rather not have to use it.

>You must have some really fancy stuff at Tek.  In Star Trek: The Next
>Generation, I saw them use a two-dimensional photograph and extrapolate
>the solid three-dimensional original, but even their computers were
>straining to do it.

Well, they should have called us. :-)  They do use some of our other 
equipment.  But that's not what I mean.

>
>Oh, you mean filming the left image, rotating the real object, and then
>taking the right image!  Hmm.  Can't do that in real-time video,
>though.

That's the same as converging the cameras.
I mean rotating the displayed *image* for one eye.  o to   o
                                                    |     /
                                                    o    o

But just a few degrees.
Convergence error can be pseudo-corrected for this way.

I don't work in the Tektronix TV group, so I'm not familiar with
all of our offerings, but all the video and graphic effects you
saw on the Olympic broadcasts were done with Tek, or Tek subsidiary
products.  I'm sure we have several products that can rotate and
crop video images.  We're the world leader in TV test equipment, and
our Grass Valley subsidiary is the world leader in video production
switchers and effects boards.


>From one photo, you want to generalise to all converged-camera
>situations?  Despite having said yourself that "some worked and some
>didn't?"  Hmm.  Not very good science, methinks.

I'm an engineer, not a scientist.  I'll bypass the jokes about the differences
between scientists, engineers, and mathamaticians. :-)

From an engineer standpoint I found that convergence can fail,
parallel can not.  I picked the robust one.

Are all you lurkers learning anything from this discussion?
Are there any lurkers left?


      Rick   Wilson             Rick Wilson       Cross-eyed STEREO
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     |       O      |         |      O       |
     |    O         |         |     O        |    rick@sable.pen.tek.com
     |              |         |              |    Tektronix
     \    _     O   |         |\    _  O     |    Beaverton, Orygun
     |\  /      _   |         | \  /   _     |
     | \/   \  /    |         |  \/\  /      | 
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Newsgroups: alt.3d