[GEM-dev] Problem with glitching on OS X at high frame rates
tb504 at york.ac.uk
Thu Jul 19 15:22:30 CEST 2012
Chris and Cyrille, thank you both for this very useful information and
ideas for testing etc. I will investigate some more and post results
when I get some.
Thanks to all
On 19/07/2012 13:49, chris clepper wrote:
> On Thu, Jul 19, 2012 at 6:14 AM, Theo Burt <tb504 at york.ac.uk
> <mailto:tb504 at york.ac.uk>> wrote:
> Does anyone know how the vsync works on OSX? I mean how does GEM
> wait for the vsync, to flip the buffer? Does it block the process
> at any point? Is the process blocked by any part of GEM at any
> point, on a per frame basis?
> VBL sync is a single line of code that turns it on/off. GEM's render
> engine doesn't do anything different based on that state.
> For example, after the all the opengl has been executed, I'm
> presuming a system call is made to actually render the screen?
> What is this call, and could it simply be that something, perhaps
> operating system related, is causing it to take too long to
> return? That would tie in with moving windows around the desktop
> making the problem worse...
> The last call in any GL chain is glFinish() which flushes all of the
> commands to the card via the driver. The driver can block the
> uploading of commands to the card for various reasons most of which
> are not documented anywhere. Apple has OpenGL profiling tools that
> can show where time is being spent in the driver.
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