Parametric Animations! You can use this to create animations with arbitrary parametric time functions, and free yourself from the restrictions of bezier curve based time functions.
Several common time functions are provided but you can easily create your own from scratch, or by composing existing time functions.
Both CALayer (iOS 4 and later) and UIView (iOS 7 and later) animations are supported.
The inspiration for this came from Matt Gallagher's post here: http://www.cocoawithlove.com/2008/09/parametric-acceleration-curves-in-core.html
To run the example project, clone the repo, and run pod install from the Example directory first.
JMJParametricAnimation is available through CocoaPods. To install it, simply add the following line to your Podfile:
pod "JMJParametricAnimation"