AHEasing
A supplemental library of easing functions for C, C++, and Objective-C
The useful portion of this project consists of two parts:
- A stand-alone easing function library, implemented in C (easing.h/easing.c)
- CAAnimation category methods to more easily use easing in your Core Animation projects
Supported functions
The following types of easing functions are supported:
- Linear
- Quadratic
- Cubic
- Quartic
- Quintic
- Sine
- Circular
- Elastic
- Bounce
- Back
Each of these has corresponding ease-in, ease-out, and ease-in-out variants. Here's a handy cheat sheet that includes visualizations and animation demos for these functions.
The core easing functions are implemented as C functions that take a time parameter and return a progress parameter, which can subsequently be used to interpolate any quantity.
Goals
The design goals of AHEasing are:
- To be as fast as conceivably possible while maintaining human readability
- To be portable to any system with a C runtime
- To elucidate the mathematical underpinnings of common easing functions
Inspiration
This work is a spiritual descendent (not to say derivative work) of works done by the following individuals:
- Robert Penner (http://www.robertpenner.com/easing/)
- George McGinley Smith (http://gsgd.co.uk/sandbox/jquery/easing/)
- James Padolsey (http://james.padolsey.com/demos/jquery/easing/)
- Authors of jQuery (http://plugins.jquery.com/project/Easing)
- Matt Gallagher (http://cocoawithlove.com/2008/09/parametric-acceleration-curves-in-core.html)
- Jesse Crossen (http://stackoverflow.com/questions/5161465/how-to-create-custom-easing-function-with-core-animation)