[GEM-dev] Problem with glitching on OS X at high frame rates

[chris clepper]

On Tue, Jul 17, 2012 at 5:35 PM, Cyrille Henry <ch at chnry.net> wrote:

>
>
> if you ask Gem to render at 100Fps, you'll have a new image 10ms after
> last render.
> if your screen is rendering at 60fps, it ask for 16.6 ms between 2 images.
> so, after having render a frame, gem will wait for the scren 6.6ms on
> average. everything will be hang during this 6ms.
> pd time will desincronize from real time.
> that's why the clock from this pd can not be used to compute audio.
> but since pd timing is more than 6ms acurate, you can be certain that
> every computed frame will be rendered for 16.6ms
> So this result on using a timing based on the screen.
> you can use this pd the send bang to an other pd that compute the sound.
>
>
There could be locks on the back buffer when using VBL sync that would
prevent anything more frequent than 1/VBLrate to actually render into it.
 So you might have a situation like this:

render 10ms wait 6.6ms render 3.4ms render 10ms wait 3.3ms to get two
frames.  As I wrote previously, I used to know who to ask to get the actual
answer to this, which was great because the GPU people are really secretive
about their black boxes.
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