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README.md

orx-easing

Easing functions for smooth animation or non-linear interpolation.

Similar to those on https://easings.net

type
linear easeLinear
constant 0 easeZero
constant 1 easeOne
type in in out out
quad easeQuadIn easeQuadInOut easeQuadOut
cubic easeCubicIn easeCubicInOut easeCubicOut
quart easeQuartIn easeQuartInOut easeQuartOut
quint easeQuintIn easeQuintInOut easeQuintOut
circ easeCircIn easeCircInOut easeCircOut
expo easeExpoIn easeExpoInOut easeExpoOut
sine easeSineIn easeSineInOut easeSineOut
back easeBackIn easeBackInOut easeBackOut
bounce easeBounceIn easeBounceInOut easeBounceOut
elastic easeElasticIn easeElasticInOut easeElasticOut

Usage

fun easeX(
  t: Double,       // current time
  b: Double = 0.0, // beginning (output value when t is 0.0)
  c: Double = 1.0, // change (output delta)
  d: Double = 1.0  // duration = end time
)

The most common usage involves repeatedly calling the easing function increasing the t argument while keeping other arguments unchanged. When t increases from 0.0 up to d, the returned value slides from b to b + c.

Example

For accelerating from 40.0 down to 10.0 in 10 steps:

repeat(10) {
    val y = easeQuadIn(it.toDouble(), 40.0, -30.0, 9.0)
    println("$it -> $y")
}

Outputs

0 -> 40.0
1 -> 39.629629629629626
2 -> 38.51851851851852
3 -> 36.666666666666664
4 -> 34.074074074074076
5 -> 30.74074074074074
6 -> 26.666666666666668
7 -> 21.85185185185185
8 -> 16.2962962962963
9 -> 10.0

Note how most result values are closer to 40.0 than to 10.0, due to the usage of an In easing function. easeCubicIn, easeQuartIn and easeQuinticIn functions would make this even more obvious.

Default arguments

When t is in [0, 1] we can omit most arguments

val e0 = easeQuadIn(t, 0.0, 1.0, 1.0)
val e1 = easeQuadIn(t)

Using the Easing enumeration

The Easing enum contains all easing functions.

val et = Easing.QuadIn.function(t, 0.0, 1.0, 1.0)

// list all easing function names
Easing.values().forEach { easing ->
    println(easing.name)
}

// find out how many easing functions are available
println(Easing.values().size)

Demos

DemoEasings01

source code

DemoEasings01Kt