On Nov 19, 2010, at 2:36 PM, Christopher Wright wrote:
>
>> This brings up a larger question: My program is a Foundation tool, so I
>> create my QCView with:
>>
>> myQCView = [[QCView alloc] initWithFrame:NSMakeRect(100.0, 100.0, 160.0,
>> 128.0)];
>>
>> and then load and render my qtz composition.
>>
>> Does QC actually do anything unless I insert the QCView into a window? I
>> notice that when I say:
>>
>> status = [myQCView startRendering];
>>
>> ...there is a system process called IIDCVideoAssistant that runs at 6.5%
>> CPU. (My composition accesses a Firewire camera; my program reads frames
>> through a published output in the composition.) I don't see anything
>> onscreen, but if it's rendering frames, I guess I'll be able to read them?
>
> That's actually a tricky question.
>
> QCViews (and NSViews in general) like to live on NSWindows (or subclasses
> thereof). If you just want to read frames/output, you should use QCRenderer
> instead of QCView.
>
> a QCView may not be fully/completely initialized until it's on a window, so
> while some things may work (e.g., a simple composition that adds 2 numbers,
> and outputs the result via a published port), more complex things (e.g.,
> anything that requires OpenGL) may fail/act strangely/crash (hopefully not
> crash, but I've never tried it :).
>
> Seeing supporting services spin up is expected, because -startRendering will
> actually set up timers and initialize the patches so that they'll either
> start doing work, or at least be able to.
Interesting. I downloaded the Apple sample project "Quartz Composer Offline":
http://developer.apple.com/library/mac/#samplecode/Offline/Introduction/Intro.html
This uses QCRenderer -initOffScreenWithSize:colorSpace:composition: which would
fit the bill perfectly, but it unfortunately doesn't seem to work for
compositions that access a camera, it returns blank white images, maybe because
it doesn't wait for the camera to come on? Is there a way to modify this to
work with a camera?
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