Forums > Jitter

help – multiple displays problem

April 9, 2009 | 1:20 pm

I’m rendering 4 different windows to 4 different displays.

My setup is this:
MacPro 2 x 2.8Ghz quad core
2 x Nvidia 8800 512mb graphics cards
Running 4 LG monitors at 1920x 1080

The computer boots up like this:
Card 1 – Display 1 and Display 4
Card 2 – Display 2 and Display 3

If I render all 4 on Display 1, my framerate is good. 1 jit.window on Display 1 and 1 jit.window on Display 4 is ok. BUT as soon as I render on Display 2 and 3 (card in slot 2), then framerate goes down to 12fps. Even when I’m not sending any video or images to the windows (just rendering blue). So, I guess it’s something to do with how I’m using the second graphics card.

All windows are rendered by separate objects. But I guess I’m just doing this wrong.

Any help? Please? Exhibit opens next week…

screenshot of the abstraction that does the open gl stuff is here in case anyone has time to look at it.


April 12, 2009 | 8:05 pm


each video output needs a
maybe try to first place the windows on the right video outputs and then start the metro .

here i’m working on a macpro with 4 gpu’s and no problem
maybe you can post a patch ….

April 13, 2009 | 12:36 am

Hey – thanks for the response. I figured it out thanks to some help from Anton. Yes, you’re right, the initial position of the windows was the problem. They need to be positioned on the correct windows for each GPU BEFORE rendering is started.

There might have been something going on with sharing video files across 2 GPU’s as well, but I’m really not sure right now. Anyway, I’ve gone from 12fps to 30/40 fps depending on activity. A mixture of slide show and video at 1080p (prores codec).

April 13, 2009 | 8:20 am
There might have been something going on with sharing video files across 2 GPU’s as well

you mean using the "shared_context" on
it’s only possible to share textures between two which are on the same gpu
so in your case display 1 & 4 and display 2 & 3
not display 1 & 3 etc…

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