CODEWITHSUNDEEP
iosanimationopengl-escocos2d-iphone
nonopolarity
nonopolarity

Reputation: 150956

On iOS, how can smooth animation be achieved?

Is it true that for Angry Birds or Cut the Rope, they draw the whole frame of the whole screen first (the whole view), and then paint the whole frame onto the screen, making the animation smooth?

That's because if we animate a metal ball, of size 20 x 20 pixel, and if we erase the ball first, and then draw the ball at a new location, then there might be some flickering very subtle but noticeable.

The same might be if it is animated by drawRect, which will erase the whole screen, and then draw everything in their new locations, which might have even more flicker than above?

Going back to the drawing whole frame method: if a ball was at coordinate (100,100), and now the ball is painted on top of the whole screenshot (with the new background exposed), at coordinate (103, 100), then it is very unnoticeable for the changes. (no disappearing and then reappearing happening at all).

How can smooth animation be achieved that looks like Angry Birds or Cut the Rope game?

Upvotes: 4

Views: 1530

Answers (3)

Scamp Dog
Scamp Dog

Reputation: 88

If an app uses OpenGL, the answer is yes, it does its rendering before the frame buffer is presented to the screen. I think the other ways to draw to the screen use the same technique of drawing to an off-screen buffer before transferring the completed image to the screen, but I'm not so sure about that.

Upvotes: 1

leftspin
leftspin

Reputation: 2488

Use CALayers. They are more lightweight than views.

Upvotes: 1

Hampus Nilsson
Hampus Nilsson

Reputation: 6822

They make use of OpenGL, which is a lot faster than any of the Quartz methods (ie. drawRect) since it makes use of the GPU instead of the CPU for rendering. Using Quartz can be hundreds or thousands of times slower depending on what you are doing exactly.

If you do not want to resort to OpenGL. You can put the object inside a UIView and then animate it. As long as the contents of the view is static, this is plenty fast for most applications. For example, making the background a view, and the metal ball a view, you can move that view around and achieve very smooth animations without problems.

Upvotes: 4

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