mmode and patch

[David Naegle]

In article <37519 at bu-cs.BU.EDU>, tjh at bu-cs.BU.EDU (Timothy Hall) writes:
> While on the subject of 3-D viewing.  Has anybody out there tried the LCD
> glasses?  (I'm just using colored lenses)  A figuere of $2k seems to stick
> in my mind for them - is that right?  If so, has anybody tried going to 
> Toys R' Us and getting Sega or Nintendo glasses and hooking them up to the SGI?
> (These run about $100)
> 
> -Tim Hall
> Boston Univ. Computer Graphics Lab
> tjh at bu-pub.bu.edu

I haven't seen these glasses in operation, so I can't comment on the contrast 
ratio or the switching speed they provide.  I think they are designed to work 
with 60Hz display monitors, which results in a refresh rate of 30Hz per eye.  
While it works, I doubt you'd be comfortable watching it for very long.  
We decided that 30Hz was an unacceptable refresh rate for an SGI product.
(note: low refresh rates tend to make you crazy; scene update rates have
much lower acceptable limits in most applications)

To fix this flicker problem, we offer a multi-sync monitor as a neccessary part
of the StereoView option.  This monitor displays at 60Hz for all non-stereo
applications, and automatically switches to a 120Hz display when a stereo
application is run, so in either case you see 60Hz per eye.  

The stereo field signal (left eye/right eye) is only available in stereo mode
(120Hz video) so you need the multi-sync monitor, even if you try to interface
cheap game-type LCD glasses to the system.  The current cost of the monitor is
something like $3K (see a sales type for accurate pricing).  

In article <8909051554.AA00507 at aero4.larc.nasa.gov>, blbates at AERO4.LARC.NASA.GOV ("Brent L. Bates AAD/TAB MS294 x42854") writes:
> 
>    Personally, I think the passive glasses systems sound more economical.

Depends on your needs.  A schoolbus is cheaper than a sports car on a per-seat
basis, but it costs more than a sports car.  (not to mention being a lot less
fun to drive :-)  I expect active stereo glasses to complement passive eyewear
systems.  Passive eyewear stereo systems should be used for group presentations
because that's what's most economical.  For individual users (a much bigger
market in my opinion) you need a stereo technology which costs less than 10% 
of the workstation price.

Also note that customer costs are tied to materials costs; it's going to be
hard to make z-screens too much cheaper because of the high costs and low
yeilds of the large-area LCDs involved.  Active LCD glasses, on the other hand,
are easy to make cheaper as the volumes increase, and multi-sync monitors are
not much more expensive than other high-resolution monitors.  So there are
technical reasons to believe that active eyewear stereo will be an inexpensive, 
ubiquitous technology in the 3-D workstation market.

David Naegle
Graphics Hardware Manager
naegle at sgi.com