Processing 1.0 - Processing Discourse - OpenGL on 2GPU / 4display

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Index › Programming Questions & Help › OpenGL and 3D Libraries › OpenGL on 2GPU / 4display

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OpenGL on 2GPU / 4display (Read 3140 times)

mog

OpenGL on 2GPU / 4display
Jun 4^th, 2010, 3:06am

Hello
I wanted to ask about rendering an application spanning across 4 to 6 displays using multiple GPUs. From what I've found here: http://www.equalizergraphics.com/index.html but though it's described as middleware i don't see a way to hook it up wit Procesing/JOGL application.

I'm thinking of using Gestalt_p5 and rendering the secondary display of each GPU to FBO an then display it in the undecorated window. Is that a good way Are there any limitations with this approach. I'm planning to write some GLSL scripts as well so i don't want to hit the wall in the end of writing the app.

The problem is that i don't have the hardware yet. Otherwise i'd test it myself and write a tutourial covering this topic :)

Cheers!

tex

Re: OpenGL on 2GPU / 4display
Reply #1 - Jun 4^th, 2010, 1:31pm

You can span one opengl context over multiple gpus. I had a setup with 4 screens on 2 graphics card having 1360 * 768 * 4 pixels. The 2 gpus work like one without taking a lot of performance. I had multiple shaders including a gpu particle system running and it all was split nicely over the two devices. From my experience you get the best performance when you connect the two screens on one card to one big horizontal or vertical desktop this gave 20 extra frames per second. For the setup I had two nividia quadro fx 3800. The application developed in plain java using jogl but I guess processing should work as well. Here you can see the applications in action:
http://riekoff.com/doku.php?id=levelgreen

mog

Re: OpenGL on 2GPU / 4display
Reply #2 - Jun 5^th, 2010, 1:32am

Thanks a lot tex! I couldn't imagine a more accurate anwser.
I've got some followup questions though.

- What problems did You encounter while making multi screen applications? Something i should consider before i start buying the equipment and writing the code? I'm thinking of Quadro FX 380 since it's the only low-profile card with 2xDVI out. Quadro FX 3800+ is a bit out of my reach for now. Should i stick with the professional or the consumer line of GPUs?

- Do You know how is the GPU acceleration done in case of using Matrox TripleHead2Go? All the calculations are done on the GPU and then the resulting image is sent to USB for output? It makes some sense but how would i select which card does the numbers crunching? What will happen if i want to use 2xTripleHead? Won't the FSB get clocked?

tex

Re: OpenGL on 2GPU / 4display
Reply #3 - Jun 6^th, 2010, 4:10am

mog wrote on Jun 5^th, 2010, 1:32am:

Thanks a lot tex! I couldn't imagine a more accurate anwser.
I've got some followup questions though.

- What problems did You encounter while making multi screen applications Something i should consider before i start buying the equipment and writing the code I'm thinking of Quadro FX 380 since it's the only low-profile card with 2xDVI out. Quadro FX 3800+ is a bit out of my reach for now. Should i stick with the professional or the consumer line of GPUs

Actually there were no real problems. You have to look into the settings of the graphics driver, different settings might lead to better performance. If you activate vsync for example and your application goes slightly under 60 frames your app will lock to 30 frames although it could runfaster. Another optimization is to connect two screens on one gpu to one desktop, for nvidia you find this settings in the multiscreen setup. Alsotry to avoid rotation of the screen content with the driver this will slow down you application as well instead rotate your content inside your application.

mog wrote on Jun 5^th, 2010, 1:32am:

- Do You know how is the GPU acceleration done in case of using Matrox TripleHead2Go All the calculations are done on the GPU and then the resulting image is sent to USB for output It makes some sense but how would i select which card does the numbers crunching What will happen if i want to use 2xTripleHead Won't the FSB get clocked

If you use a triplehead it will only bundle your connected 3 screens to one big device this has nothing to do with the actual graphic rendering so this is still totally related to your GPU. As your gpu has to fill more pixels this will take performance, but this depends on the number of pixels you fill and not if you have a tripplehead in between.

You not necessarily need a quadro fx. They have the advantage to have certified driver that a conform with cad or simular applications. They also use less power and run more stable. Performancewise you can compare a fx 3800 with a geforce 9800 or a fx 4800 with a gt 260 and a fx 5800 with a geforce 285 so you can get the same performance for far less money if you by a consumer modell. You might also consider to buy an ati card as they allow to connect up to six screens on one device using their eyefintiy technique:
http://hothardware.com/articles/ATI-Radeon-HD-5870-Eyefinity-6-Edition/

mog YaBB Newbies Offline Posts: 11	Re: OpenGL on 2GPU / 4display Reply #4 - Jun 6^th, 2010, 12:04pm You helped me a lot! Thank You very much for sharing Your knowledge.

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