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POHow many times a second should CADisplayLink's displayLink be called?
 

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  1. POHow many times a second should CADisplayLink's displayLink be called?
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    <p>I have a <code>CADisplayLink</code> running in line with Chipmunk Physics, and I'm getting very slow performance. I put an <code>NSLog</code> in the method that's called on the <code>CADisplayLink</code> update, and it's being called an average of 22 times per second. I was under the impression that that should be nearer 60. I have the <code>frameInterval</code> set to 1, so should it be 60fps, in a perfect world? The delta times are averaging around 0.0167 seconds (and 1 / 60 IS 0.0167, which is confusing me even further).</p> <p>I just have four walls around the bounds of my screen and just eight circle-shaped bodies on-screen, updating to <code>UIButton</code> instances on each call, so I don't think I'm doing anything that should tax it to this extent on both my 4S and iPad3. I'm applying a random force to each button once every 2.5 seconds in a separate method. Running in the simulator is butter-smooth, so it's a device-only issue. Can anyone help me spot what's causing the slowdown here, and what I can do about it?</p> <p>Here's the relevant code, first that which sets up the link:</p> <pre><code>[NSTimer scheduledTimerWithTimeInterval: 2.5f target: self selector: @selector(updateForces) userInfo: nil repeats: YES]; _displayLink = [CADisplayLink displayLinkWithTarget: self selector: @selector(update)]; _displayLink.frameInterval = 1; [_displayLink addToRunLoop: [NSRunLoop mainRunLoop] forMode: NSRunLoopCommonModes]; </code></pre> <p>Here's the method that should be called (I think!) 60 times per second, but is called only 22 or so:</p> <pre><code>if (!gameIsPaused) { cpFloat dt = _displayLink.duration * _displayLink.frameInterval; cpSpaceStep([[AGChipmunkSpace sharedInstance] space], dt); for (LCBall *i in balls) { cpVect pos1 = cpBodyGetPos(i.body); CGAffineTransform trans1 = CGAffineTransformMakeTranslation(pos1.x, pos1.y); CGAffineTransform rot1 = CGAffineTransformMakeRotation(cpBodyGetAngle(i.body)); i.button.transform = CGAffineTransformConcat(rot1, trans1); } } </code></pre> <p>And finally, here's the method that's called every 2.5 seconds, to apply the random forces (updateForces):</p> <pre><code>if (!gameIsPaused) { for (LCBall *i in balls) { int randomAngle = arc4random() % 360; CGPoint point1 = [self getVectorFromAngle: randomAngle AndMagnitude: (arc4random() % 40) + ((arc4random() % 20) + 15)]; i.body -&gt; f = cpv(point1.x, point1.y); } } </code></pre> <p>(Also, here's my method to get a vector from an angle, which I doubt is causing the issue):</p> <pre><code>angle = (angle / 180.0) * M_PI; float x = magnitude * cos(angle); float y = magnitude * sin(angle); CGPoint point = CGPointMake(x, y); return point; </code></pre>
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    1. USLuke
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    1. COYou could run this under the timer profiler and see what's sponging the time.
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      1. POHow many times a second should CADisplayLink's displayLink be called?
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    2. COHmm. Yeah, unless there are a lot more balls than you think, you shouldn't be running into performance issues. Only the profiler will tell you anything interesting.
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      1. POHow many times a second should CADisplayLink's displayLink be called?
      1. USslembcke
 

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