[AG-TECH] AG and 3D projectors

Brian Corrie bcorrie at sfu.ca
Tue Apr 20 14:32:07 CDT 2010

Hi Jeremy,

Jeremy Mann wrote:
> On Tue, Apr 20, 2010 at 1:34 PM, Tim Scheitlin <scheitln at ucar.edu> wrote:
>> With the active stereo, we didn't need the silver screen - so we just have a white screen now.
> One more question if you don't mind Tim, if its ceiling mounted, what
> is the optimal distance to "see" the 3D affect? The plans for this
> room are to be 9ft wide and 20 feet long.

Most application software that supports stereo will do a decent job for 
your room. Most of them will use a "reasonable" viewing frustum 
(basically the viewing pyramid with the apex at the viewer and the base 
of the pyramid the screen) for the stereo effect that will work with 
most physical environments. As long as your viewers are not too far off 
axis they should perceive reasonable stereopsis. With that said, there 
will be only one point where the stereo is "correct". The farther people 
are away from that sweet spot the more "distortion" they will perceive

To do this correctly is actually relatively complex. You need to tell 
the rendering software the viewing frustum of the room and ensure that 
the models that you are viewing are of the right scale (that is, they 
fit within the view frustum). IF you do this correctly when someone is 
standing in the stereo "sweet spot" it is possible to make the physical 
and display environment "align". This is how CAVE style display systems 
work. The have different viewing frustums for the different walls, all 
calculated in real time based on where the head is located... If you 
have ever been in a well calibrated CAVE system, you will know what I 

Most stereo software uses a default view frustum and in fact most 
packages do not support the creation of complex view frustums. Some 
advanced visualization packages do, and when you get the stereo right it 
is very compelling. Without that capability you are stuck with what the 
software does, possibly with the ability to change the eye separation or 
other simple parameters. This is also why the stereo effect across 
different software packages will result in different amounts of "depth". 
They are using different view frustums and some are going to be better 
for your physical space than others...

BTW, not sure if anyone watched the Master's golf tourney in 3D or not. 
A perfect application for your new 3D display system 8-) It was pretty 
impressive. HD stereo streamed live from Augusta golf course, at what 
seemed to be about 720p resolution. I hear that they are going to be 
filming some of the World Cup in 3D as well, but it doesn't sound like 
they will be broadcasting or streaming it. Too bad, that would have been 
very cool.

Two images from the Master's being viewed in the IRMACS theatre 
attached. The second image, with what I think is the eight hole at 
Augusta, with Jack Nichlaus about to tee-off, was particularly 
impressive, as the depth from the tee to green was quite striking! And 
yes, the images are blurry, as they are showing both the left and right 
eye views. 8-)


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