Animated Page Twist Transition (not the book flip)... how did they do this?

I’ve seen this on several sites and while I imagine its done using several imported images from Photoshop I’m left wondering if there isn’t an app like Swift 3D that has a plug-in that allows for quick generation of this effect.

http://www.learnflash.com/flashtutorials2.htm

Notice how the loader transitions into an animated page that twists and flips into place as the main stage. This is what I’d like to do, but after a long Google search and looking through more Flash tutorials on ‘animation’ than I’d like to admit I’m left wondering ‘how’d they do that’?

Anyone have a link to a tutorial or know a quick answer to help me sleep at night?

Thanks.

TX