Stellar is an open source Swift based animation library that makes it easy to create physics based animations from August.
Stellar utilizes the UIDynamic API and features a clean chainable syntax with gravity, snap, attachment, and push animations.
You can animate both layers and views to create unique animations.
Here’s an animation from the readme showing an interesting animation created with Stellar:
You can find Stellar on Github here.
A nice library for creating physical animations.