Core Animation Starfield

Here's a little Core Animation sample with 3d layers.

It looks better when moving ! :)

After learning that core animation doesn't like a root layer with a perspective transform, this sample sets up the perspective transform on a container layer, and stores the CATextLayer layers there. Works pretty well this time !

This uses preferredFrameSize to set the CATextLayer bounds, animates zPosition with CABasicAnimation and opacity with CAKeyframeAnimation to get a smooth transition from invisible, visible, invisible.


As we're going 3d, we don't work with (x,y) beetween ([0…frame width], [0 … frame height]) but with centered coordinates : [-width…width, -height…height]. This means our container layer needs to be centered in the view, or the 3d objects will appear to spring from the bottom left corner.


  • hit testing a layer doesn't work reliably.
  • the main layer is manually centered. Couldn't wrap my head around constraints.
  • how do you use Cocoa controls on a HUD window ? They don't look that good …


Core Animation

Jonathan Wight
2008 04 06

Nice code!

Runs like a dog on Macbook (1st gen) until you turn bloom filter off. Then runs really smoothly.


Patrick Geiller
2008 04 06

Woops ! Maybe I should have Bloom disabled by default. But it's so much prettier ... :)

2009 07 25

Very nice example ! Thanks a lot. Apple should provide that as sample code for CATextLayer.

2012 11 06

awesome,I'm learning your code

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