UIView animateWithDuration: slows down animation frame rate

Question

I am using CADisplayLink to draw frames using the EAGLView method in a game at 60 times per second.

When I call UIView animateWithDuration: the framerate drops down to exactly half, from 60 to 30 fps for the duration of the animation. Once the animation is over, the fps rises instantly back up to 60.

I also tried using NSTimer animation method instead of CADisplayLink and still get the same result.

The same behavior happens when I press the volume buttons while the speaker icon is fading out, so it may be using animateWithDuration . As I would like to be able to handle the speaker icon smoothly in my app, this means I can't just rewrite my animation code to use a different method other than animateWithDuration , but need to find a solution that works with it.

I am aware that there is an option to slow down animations for debug on the simulator, however, I am experiencing this on the device and no such option is enabled. I also tried using various options for animateWithDuration such as the linear one and the user interaction, but none had an improvement.

I am also aware I can design an engine that can still work with a frame rate that varies widely. However, this is not an ideal solution to this problem, as high fps is desirable for games.

Has someone seen this problem or solved it before?

Answer 1

The solution to this is to do your own animation and blit during the CADisplayLink callback.

1) for the volume issue, put a small volume icon in the corner, or show it if the user takes some predefined touch action, and give them touch controls. With that input you can use AVAudioPlayer to vary the volume, and just avoid the system control altogether. you might even be able to determine the user has pressed the volume buttons, and pop some note saying do it your way. This gets you away from any animations happening by the system.

2) When you have an animation you want to do, well, create a series of images in code (either then or before hand), and every so many callbacks in the displayLink blit the image to the screen.

Answer 2

Here's an old thread that describes similar drops in frame rate . In that case, the cause of the problem was adding two or more semi-transparent sprites, but I'd guess that any time you try to composite several layers together you may be doing enough work to cut the frame rate, and animateWithDuration very likely does exactly that kind of thing.

Answer 3

Either use OpenGL or CoreAnimation. They are not compatible.

To test this remove any UIView animation, the frame rate will be what you expect. Add back UIView animation, it will drop to 30fps.

You said:

When I call UIView animateWithDuration: the framerate drops down to exactly half, from 60 to 30 fps for the duration of the animation. Once the animation is over, the fps rises instantly back up to 60

I dont know why your not accepting my answer, this is exactly what happens when you combine UIView animation with CA animation not using a UIView.