In the recent iOS 4.2 update, Apple introduced a nice animation for creating one level directories. I am trying to figure out how to implement a similar animation in my project. I would deeply appreciate it if anyone could give me any pointers to do this efficiently.

From my investigation, I believe this animation or effect could be done very efficiently using Core Image which would allow me to write a custom filter. Unfortunately, Core Image is not available in iPhone. So how can do it?

I read a blog post that explained a core animation scheme to create an iPad flip clock. The problem I have is similar but has important differences. Besides, I not excited about saving the subimage combinations, which I believe can cause a memory issue.

Please enlighten me on the possible ways of doing this animation. I am relatively new to iOS programming, so I might have missed obvious ways of doing this animation or effect.