Core Animation (Troubles?) -> Box2D (Solution!)
So, we thought that using the CoreAnimation framework (CABasicAnimation functionality) would make it easy to change the sizes of destination rectangles for video playback. But, after trying to access the dimensions of animating objects we realized that you can’t actually access an object’s data in mid-animation. Without looking into it in tons of detail, we figure that CA sets up a thread that handles the animation allowing access only to the final state of the object (i.e. what it’s supposed to look like at the end of the animation). So… This isn’t good…
In order, then, to have access to the resizing of objects we looked into Box2D and found that you cannot change the size of an body once it’s been created.
What you can do, however, is update and delete the shapes inside a given body. If you do this quick enough, the object acts as if it’s changing size while maintaining its mass, acceleration, etc. properties. We found some nice code examples provided by Emanuele Feronato that describe how to scale objects in Box2D. She works mainly in Flash, but the concepts are easily integrated using the appropriate accessors in Cocoa.
