rpeasings 0.0.3

Robert Penner's easings functions in python

Robert Penner's Easing Functions

There are a plethora of versions available of these, many of which provide an object oriented interface, while most of the original easing functions could be simple inline expressions.

This library takes the purely functional approach. No class instantiation, just a function call.

See https://easings.net for a good visualisation of these to chose the right one.

Module contents

With the exception of null, in_expx and out_expx, this is a pure python port of "Penner's Easing Functions", based on the js code from https://easings.net where you can also see a catalog of them in action to chose the right one.

The following functions are included:

in_back         out_back        in_out_back
in_bounce       out_bounce      in_out_bounce
in_circ         out_circ        in_out_circ
in_cubic        out_cubic       in_out_cubic
in_elastic      out_elastic     in_out_elastic
in_expo         out_expo        in_out_expo
in_quad         out_quad        in_out_quad
in_quart        out_quart       in_out_quart
in_quint        out_quint       in_out_quint
in_sine         out_sine        in_out_sine

Additionally, I added a 'null' function, so easing can be disabled without changing the interface in the application. It's basically a nop.

null(t) -> t

In case you want to control the easing function by user input, the easings dictionary provides a map from function names to functions, e.g.

eased = rpeasings.easings['out_elastic']

To use any of the included functions, create a t (for 'time') value in the range 0-1 from your required range (e.g. t = current / max).

Putting this t into most(!) easing function, will give you a new 'eased' value in the range 0-1.

Note: the following functions over-/undershoot:

`in_back`     `out_back`     `in_out_back`
`in_elastic`  `out_elastic`  `in_out_elastic`

Additionally, you can then put that eased value as input into a lerp function to add dynamics to an otherwise linear range.

Have fun, once you started using one, you'll probably find usecases for them everywhere in your game...