[squeak-dev] Re: Still pounding head against wall
over glReadPixels => external buffer
lenglish5 at cox.net
Fri Feb 12 06:33:11 UTC 2010
Lawson English wrote:
> Josh Gargus wrote:
>> Very cool, nice work!
>> If it turns out that you need more CPU cycles, you might try using
>> PBOs to asynchronously read the pixels... when you call
>> glReadPixels(), the function does not return until the pixels have
>> been completely read, and while you're waiting for the pixels to
>> cross the PCI-E bus, Squeak isn't doing any processing. If you're
>> reading back 30fps at 5ms per frame (according to your measurements
>> below), you're sitting idle about 15% of the time.
>> Search for "Asynchronous glReadPixels:" in the PBO extension spec
>> Google will turn up many more tutorials.
>> It probably won't be your top priority right now, but I wanted to
>> ensure that you're aware of the option.
> Thanks. I was aware of PBOs and the like but didn't want to get into
> them until I got something simple working. Am I misunderstanding
> I get more like 160fps x 1megapixel raw blitting speed which sounds
> fast until one realizes that not much else is going on period.
doh 160 MB/sec ~ 30fps, like you said. LOL
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