How do you do a page curl animation without using the iPhone's built-in curlUp and curlDown animations?

I would like to animate a page flipping, like is show开发者_运维知识库n here, but without using the built-in UIViewAnimationTransitionCurlUp and UIViewAnimationTransitionCurlDown animations. Is that possible?

Try this. I think it uses private methods, but it works. Its a great starting point to figuring out how do do it yourself.