OpenGL Vertical Syncing effect on run loops
OpenGL Vertical Syncing effect on run loops
- Subject: OpenGL Vertical Syncing effect on run loops
- From: Jerry Krinock <email@hidden>
- Date: Tue, 22 Sep 2015 18:56:39 -0700
In Apple document QA1385, in Listing 2, describing how to drive OpenGL Rendering Loops 10 years ago, an NSTimer, repeating every 1 millisecond, is added to an app’s run loop [1]. Referring to this timer, the text says that:
"When vertical synchronization is enabled in your OpenGL application, during each retrace period, when the timer fires, …”
Hmmmm, a timer with time interval of 1 millisecond is now going to fire during each retrace period, 16.7 milliseconds or so! This implies that when vertical synchronization is enabled in an OpenGL application, the application’s run loop, in all modes, is synchronized to the video frame and can go no faster. Is this correct?
Jerry
[1]
renderTimer = [NSTimer timerWithTimeInterval:0.001 // 1ms
target:self
selector:@selector(timerFired:)
userInfo:nil
repeats:YES] ;
[[NSRunLoop currentRunLoop] addTimer:renderTimer
forMode:NSDefaultRunLoopMode];
[[NSRunLoop currentRunLoop] addTimer:renderTimer
forMode:NSEventTrackingRunLoopMode];
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