Re: genlocking

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Angus Dorbie (dorbie++at++sgi.com)
Wed, 17 Nov 1999 14:32:27 -0800


"Dauth, Eric" wrote:
>
> Greetings,
>
> i am trying to render multiple pipes into my helmet. Currently we are
> using a single pipe per helmet (stereoscopic, i.e. two channels per helmet,
> using 180 Hz field sequential). My system is a 2pipe Onyx running 6.5,
> and currently we give each helmet a dedicated pipe.
> For performance a pipe per eye would nice to have.
> Now there are a couple of ways of doing it, but I'd like some feedback on my
> options.
>
> option 1 (standard):
> Disabling one channel (i.e. eye) per pipe (i.e helmet) in the old
> configuration, then genlocking the two pipes and let our electronics
> downstream mix the two separate video streams together again.
> I know that in Performer pfChannel has the SWAPBUFFER and SWAPBUFFER_HW
> flags
> to enable the gangswapping... If I am on a single machine to I still
> need to physically hardwire the genlock cable on the back of the machine?

You must genlock the swapready is more of an option.

> Or is that only needed when I go across machines with the app...
> So far the procedure seems to be :
>
> To hardwire I go from 'sync H/C' from the master pipe to a 'genlock in'
> of the next pipe right? then i terminate the gelock out of the second pipe
> right?

Yes, and select a composite sync output for the video channel in
question.

> Do I connect the 'swap ready' inputs at all?

You can if you want, you wire swapready straight to swapready and
channel share the swapbuffers_hw.
You should share swapbuffers to swap eyes in lockstep. You should only
ever share swapbuffers_hw AND wire swapready at the same time.

>
> Then I use 'setmon -g -n format' on the second pipe to tell it to
> look for external synch right?

On Reality Engine use this. On infinite Reality use the gui ircombine.
On the master pipe/channel select composite sync out and an internal
sync. On the slave select external sync and specify the masters vfo for
the sync timing.

When you've loaded these type "gfxinfo -v | grep ync" and that should
give you the sync status for all pipes on the system.

>
> When I got all that working do I still need to tell performer to
> LOCK the PHASE shift or is it implied by the genlock hardware?

Yes you need to select an appropriate pfPhase. But that's not what LOCK
phase means, you could use LIMIT for example. See the pfPhase manual.

> Questions that probably have been asked many many times before.. Sorry...
> The SGI online documentation on rigging the back of the IG is not
> un-ambiguous...
>
> option 2.
> Seeing the pfHyperpipe stuff in perfly I think that's a cleaner
> way of doing it since it alternates the pipes into a single channel (?).
> I'm a little unsure what exactly is going on and how to set it up:
> the HYPERPIPE mode in perfly doesn't seem to work as it's supposed to ?

This is definitely NOT what you need. That's about turning two pipes
into one video stream what used to be called 'cyclops' mode on a
skywriter. As the name implies this is definitely not what you need for
stereo rendering.

>
> can anyone tell me where I am going wrong implementing option 1? The second
> pipe keeps
> crashing....
> Has anyone tested the Hyperpipe stuff in perfly?

Hyper pipe works great if you have the DPLEX options. It is not what you
need in this instance.

Good Luck.

Cheers,ANgus.

-- 
"Success is the ability to go from one failure to another with
 no loss of enthusiasm."    -    Winston Churchill.

Performer + OpenGL examples and tutors: http://www.dorbie.com/


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