On 12 Jan 2008, at 19:24, David Stolarsky wrote:
I can't tell what exactly the deal here is...I'm considering purchasing a Mac Pro with 4 dual out graphics cards for a 2 X 4 monitor display wall. Can I drive all the screens with a single composition running inside quartz composer? QC Visualizer? Would I need to use QCViews or QCRenderers? I read in the archives about Render in Image and Image with Movie problems with multiple graphics cards, but maybe that was just Tiger.
You could use Quartz Composer Visualizer which does a nice job of rendering each screen in a different thread and synchronising the different screens. This however causes problems if you use a Movie Loader since you can't handle a QuickTime movie in a different thread than it was initialised in. I had filed this as a bug (rdar://5673045) but got a response back recently which explained the solution clearly.
QCV supports running a separate .qtz as a processing composition, the published outputs of which are automatically sent on to the published inputs for each screens. So you just need to put your Movie Loader into a dedicated processing .qtz and publish an image output with a certain name, then for the rendering .qtz, publish an image input with the same name, and it should work. I've not tried it yet but that's the official word from Apple Engineering.
Having this explained has really helped me understand things a bit more clearly. Of course, even if you had 8 processors in your Mac running 8 separate screens, you really don't want to duplicate any CPU load for each one. So having 8 Movie Loaders all reading the same .mov file would be silly, even if it did work. The moral here is to extend this practice to anything that would cause unnecessary duplication of work across your threads, and separating processing from rendering helps achieve this - it's the old MVC paradigm again.
Lastly, I've been experimenting along similar lines myself recently and found that running more than one display off one graphics card can slow down fps when using QCV since you've got multiple threads accessing the same GPU (that's my guess only, I'm probably wrong). I'm not sure this holds true in all scenarios, some more testing and discussion here would be very useful.
Please let us know how you get on, I'm extremely keen on using QC to do some large scale multi-display systems in the near future and would love to know what best practices are.
Cheers, Ade. _______________________________________________ Do not post admin requests to the list. They will be ignored. Quartzcomposer-dev mailing list ([email protected]) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/quartzcomposer-dev/archive%40mail-archive.com This email sent to [EMAIL PROTECTED]
