How to time openGL animations on iPhone?

Question

I wonder if there is a time function in apples SDK that is guaranteed to be monotonically increasing? I heard about [NSDate timeIntervalSinceReferenceDate] (which isn't accurate) and the c function mach_absolute_time.

How do all these people timing their animations in openGL ES (is there a frame independent solution)?

score 2 · Answer 1 · edited May 23 '17 at 12:26

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See this question: How can I get a precise time, for example in milliseconds in objective-c?

edited May 23 '17 at 12:26

Community

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answered Jan 18 '11 at 04:07

nornagon

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AechoLiu · Accepted Answer · 2011-01-18T04:37:18.333

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I use CADisplayLink to timing my animation. When you create a new opengl-es project on xCode, it will give you an sample opengl-es codes, and it control animation by CADisplayLink. alt text

EDIT:

I found I misunderstand this problem. I check the CFAbsoluteTimeGetCurrent() method on this apple on-line doc, and it said the method may be not monotonically increasing. And the method CACurrentMediaTime() which I prefered derived value by mach_absolute_time(). The document about CACurrentMediaTime() is on this link.

edited Jan 18 '11 at 04:37

answered Jan 18 '11 at 03:51

AechoLiu

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CADisplayLink won't give you accurate timings if you skip frames. – nornagon Jan 18 '11 at 04:02

score 1 · Answer 3 · answered Jan 18 '11 at 04:00

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For frame-rate-independent time, I generally use the CFAbsoluteTimeGetCurrent() function. It returns a CFAbsoluteTime (which I believe is typedef'd to double) since some date arbitrarily far in the past.

answered Jan 18 '11 at 04:00

Noah Witherspoon

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How to time openGL animations on iPhone?

3 Answers3