From: Angus Dorbie (dorbie++at++sgi.com)
Date: 04/27/2001 21:25:45
Sujay Kumar wrote:
>
> Hi PfGurus,
>
> As I see the mails, there have been still very less response on "Stereo on Linux", I am very keen to know what kind of cards are available for stereo support on linux(I am very keen on setup with passive glasses and quad buffered stereo). Sorren Vorre had posted the mail, I saw no reponse to that also.
Passive glasses implies polarized filters on the glasses only and no
shuttering on the glasses. It either requires polarised dual video, with
beam splitter, or a very large expensive polarized shutter over the
display.
Quad buffer stereo could work with the shuttered polarized display but
really implies a shuttered glasses approach.
>
> Do the SGI people have an insight into this? Can I get help on it. If I look for a cost effective solutions, how much will it cost, even for experiments?
Tom has done a lot of work on stereo on Linux, but he's not
replying.....
There are some basic elements required for decent stereo, you need to be
able to draw and display left and right eyes, and this implies four
buffers, but not necessarily quad buffers. You can use a conventional
double buffer and position your viewports such that left and right eyes
are in different portions of the framebuffer (top and bottom) and the
video fetches from them sequentially. This then lets you swapbuffers to
change both eyes simultaneously. The next thing is to filter the display
such that the eyes see their respective video fields.
In terms of what a system needs to be able to do, you need some kind of
video output format which supports a stereo field, and a means of
synching glasses to the current video field being output. You also need
to be able to draw the left and right eyes to the correct framebuffer
locations and swap appropriately but this is more tractible because you
can do all sorts things here like draw using stencil masks interlaced to
the framebuffer and use interlaced video formats for alternate field
output.
If this gives you the impression that there are lot's of ways to
approach this problem then you are correct. The trouble is (and this is
my opinion) is that the drivers for the video formats and the
synchronization mechanisms for the glasses (for example driven directly
by the cards or by special blue markers in the first line of video) are
not broadly avbailable or functional. So you are left to experiment and
try and eek out a solution from the options available.
This is all purely a drivers and conventions issue (with some
integration issues related to glasses). The problems that generally
exist right now are availability of video formats to fetch from separate
left & right eyes (quad buffer approach). Using a field sequential video
with an inappropriate video output can mean that if you don't render at
the full frame rate NEVER missing a frame then your video goes out of
sync sending the left video to the right eye etc.
So, you need a vfo, some means of quad buffering (either explicit of
with interlacing) and some means of telling glasses to sync to the whole
shebang.
The problem is the glue and polish is missing at this stage. Either the
vfo's aren't there or the sync mechanism relies on meeting field rate
frame rates. It's almost there but not quite. It could be done today if
the major IHV's saw enough of a market.
Perhaps Tom has some ideas on the best practical solution out there
right now on NVIDIA cards on Linux.
>
> ALSO, when I try to play the sample stereo code, it asks for missing libGLw.so file? Why?
>
> I will be glad if someone can bail me out of these doubts.
>
> Warm Regards.
>
> Sujay
>
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This archive was generated by hypermail 2b29 : Fri Apr 27 2001 - 21:26:21 PDT