aoktian/easing

Easing functions implemented in lua (Functions from http://www.robertpenner.com/easing/ )

Easing Library

This is a lua port of the Robert Penner's equations for easing. You can find much more information about it on [http://www.robertpenner.com/easing/](his web site).

This library was based off:

• [http://code.google.com/p/tweener/](Tweener, ActionScript tweening library)
• [http://coderepos.org/share/wiki/JSTweener](JavaScript port of tweener, by Yuichi Tateno)

However, only the easing functions are included, and not any kind of tweening helpers.

Usage

Requiring the easing library returns a table which contains all the different functions.

local easingFunctions = require("easing")

outInBounce = easingFunctions.outInBounce

-- All easing functions take these parameters:
--
-- t = time     should go from 0 to duration
-- b = begin    value of the property being ease.
-- c = change   ending value of the property - beginning value of the property
-- d = duration

-- Some functions allow additional modifiers, like the elastic functions
-- which also can receive an amplitud and a period parameters (defaults
-- are included)

beginVal = 0
endVal = 1
change = endVal - beginVal
duration = 1

print(outInBounce(0             , beginVal, change, duration)) --> 0
print(outInBounce(duration / 4  , beginVal, change, duration)) --> 0.3828125
print(outInBounce(duration / 2  , beginVal, change, duration)) --> 0.5
print(outInBounce(duration / 3/4, beginVal, change, duration)) --> 0.10503472222222
print(outInBounce(duration      , beginVal, change, duration)) --> 1

Examples

There is a plain lua example and an interactive one based on the LÖVE game library. To run the examples you'll need to get the engine from http://love2d.org. Once you have the love executable, move into the examples/love directory and run "love ."

Running Tests

To run the tests you'll need telescope. From the library's root directory, run:

▸ tsc tests/easing_tests.lua
80 tests 80 passed 80 assertions 0 failed 0 errors 0 unassertive 0 pending

TODO

Copy the documentation from the tweener source and convert it to luadoc.

License

Like the tweener library, easing is licensed under the MIT license.

Authors

• Tweener authors
• Yuichi Tateno
• Emmanuel Oga

Contributors

• kikito (Enrique García) (EmmanuelOga#2)