Jerky/juttery (core-)animation in a screensaver?

Question

I've built a screensaver for Leopard which utilises core-animation. It doesn't do anything overly complicated; uses a tree of CALayers and CATextLayers to produce a "table" of data in the following structure:

- root
  › maincontainer
    › subcontainer
      › row [multiple]
        › cell [multiple]
          › text layer

At most there are 50 CALayers rendered on the screen at any one time.

Once I've built the "table", I'm adding animating the "subcontainer" into view using CABasicAnimation. Again, I'm not doing anything fancy - just a simple fade-in.

The problem is that while the animation does happen its painful to watch. It's jerky on my development machine which is a 3.06Ghz iMac with 4GB of RAM, and seems to chop the animation into 10 steps rather than showing a gradual change.

It gets worse on the ppc mac-mini the screensaver is targeted for; it refuses to even play the animation, generally "tweening" from the beginning of the animation (0% opacity) to half-way (50%) then completing.

I'm relatively new to ObjectiveC and my experience is based on using garbage-collected environments, but I can't believe I'm leaking enough memory at the point the screensaver starts to cause such problems.

Also, I'm quite sure its not a problem with the hardware. I've tested the built-in screensavers which use core-animation, and downloaded a few free CA-based for comparison, and they run without issue on both machines.

Information is pretty thin on Google with regards to using CA in screensavers, or using CA in general for that matter, and advice/tutorials on profiling/troubling screensavers seems to be non-existant. So any help the community can provide would be well welcomed!

--- UPDATE ---

Seems as though implicit animations help smooth things out a little. Still kinda jerky, but not as bad as trying to animate everything with explicit animations as in my solution.

Answer 1

There isn't much special about a screen saver. I assume you've started with the Core Animation Programming Guide? Running it through Instruments will give you a lot of information about where you're taking too much time.

The code you're using to do the fade-in would be useful. For what you're describing, you don't even need CABasicAnimation; you can just set the animatable properties of the layers, and they by default animate. Make sure you've read up on Implicit Animations. The rest of that page is probably of use as well.

Most of your job in CoreAnimation is getting out of the way. I generally knows what it's doing, and most problems come from second guessing it to trying to tell it too much.