I’ve been playing a little with CATransform3D and moving things around with perspectives. Transformation matrices are still a little bit beyond me, but I’ve figured out a few things and got a Flipboard-esque page turn working within about two hours. This guide is particularly well-written: milen.me/technical/core-animation-3d-model/.
The main thing that was tripping me up was the location of the anchor point. To create a perspective effect, you set the m34 property of the transform to something small, like 1/2000. However, as the “page” was swinging open, the perspective was only skewing the layer on the bottom (and not on the top).
Not fully understanding how the transformation matrix worked, I was looking for a property that corresponds to m34 for the other top. A little trial and error showed that the layer’s anchorPoint property, which I had set to the top left, was controlling it. The Apple guide for layer geometry describes how it affects scaling and rotating, but it seems obvious in retrospect that it would control the perspective as well.
