[osg-users] Fwd: Unstable passive stereo on Quadro using Quadbuffer

[Jan Ciger]

Hello,

On Tue, Nov 15, 2016 at 10:40 AM, ZJ Tian <tianzjyh at gmail.com> wrote:

> Hi, guys,
>
> I encountered a trouble with passive stereo using quadbuffer.
>

That sounds like your display and glasses are not being correctly
synchronized to the graphic card. For stereo to work in a stable manner the
glasses must know which frame is being rendered by the GPU at any given
moment. That is usually achieved either by the old school 3 pin mini-DIN
cable from the Quadro, synchronization signal being sent using a USB dongle
(like Nvidia 3DVision) or the signal being digitally "tagged" with the
left/right frame tags (recent HDMI/Display Port interfaces versions).

Some systems are "dumb" and don't use this sync signal - typically cheap
DLPLink projectors - and rely only on the stability of the input signal to
not swap the left/right frames while in use. The glasses are only told to
switch between left/right but don't really know which image is being
actually displayed by the GPU, so you have to manually "invert" the stereo
at the start, typically by pushing a button somewhere. That is good enough
for something like Bluray video but not for interactive application where
the framerate is never 100% stable.

I am not familiar with the display and glasses you are using so you will
need to check the manual for your hardware how to set it up correctly.
However, in general, simply enabling quad buffer stereo *is not* sufficient
in itself to obtain a reliable stereo without these glitches. The
synchronization between the GPU and the display/glasses must be in place as
well. Be careful that synchronizing the glasses to the display alone (using
radio, infrared signal, display flashes ...) may not be sufficient if the
display is not actually synchronized with the GPU - that's the case of the
common DLPLink systems, but may exist elsewhere too. If the glasses are not
connected to the GPU directly and are driven from the display (common with
3D TVs and projectors), I would expect that this could well be the case.

Regards,

Jan
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openscenegraph.org/pipermail/osg-users-openscenegraph.org/attachments/20161115/9720b4ff/attachment-0003.htm>