A quick follow-up on my own posting: I've just enabled multi-threaded
GL for all of my app except for when I want to synchronise user input
with screen output e.g. when dragging on my globe. I'd be interested
to learn whether synchronising user input with screen output is
something others have had to contend with when going multi-threaded.
Cheers,
-C
On 28/05/2007, at 8:29 PM, Christopher Hunt wrote:
Having finally built my application for Intel (what took you, I hear
you say), I find that enabling Mac OS X's gl multi-threading
capability causes an interesting side effect.
Firstly I don't think my application is particularly CPU bound when
it comes to GL anyhow so I'm not sure that there's a performance gain
to be had with GL multi-threading. Regardless, I enabled it and my
application's CPU based functions are definitely sped up given the
multi-threading mode - however I now see a lag between my app's
processing and what gets rendered. For example, I have a globe with
the earth textured on to it. The earth can be dragged around using
the mouse as you'd expect. What I find is that the earth continues to
spin a bit after I've stopped dragging. If I disable the
multi-threading mode of GL then my rendering is synchronised with my
mouse dragging and there is continued spinning.
Interesting?
I'm double-buffering and flushing via my context's flushBuffer method
to sync with vertical retrace.
Perhaps the GL multi-threaded mode is not for my app given its
present efficiency but I thought I'd share this observation in case
there's something I'm missing i.e. perhaps I should using
multi-threading GL but somehow synchronise with the GL thread when
I'm flushing my context...
Ideas? Comments?
BTW: I'm using a 2.66Ghz Quad Xeon so there's some real parallelism
happening. :-)
Cheers,
-C
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