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Re: issues for VJ apps with Quartz Composer

I'm also working on a VJ app using QC and Core Image. 

The issue of interchanging QC compositions, QT Movies and CI Images is someone complex. I sketched out a class hierarchy to allowing media sources to be interchanged about 4 weeks ago. Then, to my surprise, I checked the QC example folder again and found that someone at Apple had implemented a very similar hierarchy in the Quartz Performer application :) 

Tom Birch wrote:

If you want to do it programmatically, I think you'd have to create
multiple instances of QCRenderer, one for each composition, and you'd
extract the rendered image for each and pass it around to another
composition, but that might get a little processor intensive, as I
haven't tried multiple QCRenderer instances yet. You'd most likely
have to disable the renderers you aren't using (or just set it to not
call renderAtTime:)


If you run the Quartz Performer app and drag a composition on both sources you're actually creating two QCRender instances at runtime. Both seem to render correctly, so I would imagine you could add additional QCRender instances without causing problems. However, as with OpenGL, QC patches are not thread safe. You'll need to protect the OpenGL context and each QC patch from being accessed by your rendering thread, UI thread or any MIDI event processing threads concurrently.



can one Quartz Composer patch feed it's result into a second patch
as a
texture stream?


yes, you just need to enclose a composition in a "Render In Image"
macro for it to output its result as an image, which can then be used
in any image input

I haven't verified this in the GM of Tiger, but the last time I checked images output from published QC compositions were of type NSImage, not CIImage, which causes a performance hit when chaining compositions.  

Pierre, has this changed in the GM?

Thanks, 

- Scott


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