100 lines
2.8 KiB
Markdown
100 lines
2.8 KiB
Markdown
# orx-easing
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Easing functions for smooth animation or non-linear interpolation.
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Similar to those on https://easings.net
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| type | |
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|:-----------|:-------------|
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| linear | `easeLinear` |
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| constant 0 | `easeZero` |
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| constant 1 | `easeOne` |
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| type | in | in out | out |
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|---------|----------------:|-------------------:|-----------------:|
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| quad | `easeQuadIn` | `easeQuadInOut` | `easeQuadOut` |
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| cubic | `easeCubicIn` | `easeCubicInOut` | `easeCubicOut` |
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| quart | `easeQuartIn` | `easeQuartInOut` | `easeQuartOut` |
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| quint | `easeQuintIn` | `easeQuintInOut` | `easeQuintOut` |
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| circ | `easeCircIn` | `easeCircInOut` | `easeCircOut` |
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| expo | `easeExpoIn` | `easeExpoInOut` | `easeExpoOut` |
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| sine | `easeSineIn` | `easeSineInOut` | `easeSineOut` |
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| back | `easeBackIn` | `easeBackInOut` | `easeBackOut` |
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| bounce | `easeBounceIn` | `easeBounceInOut` | `easeBounceOut` |
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| elastic | `easeElasticIn` | `easeElasticInOut` | `easeElasticOut` |
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## Usage
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```
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fun easeX(
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t: Double, // current time
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b: Double = 0.0, // beginning (output value when t is 0.0)
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c: Double = 1.0, // change (output delta)
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d: Double = 1.0 // duration = end time
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)
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```
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The most common usage involves repeatedly calling the easing function increasing
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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`.
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### Example
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For accelerating from 40.0 down to 10.0 in 10 steps:
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```kotlin
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repeat(10) {
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val y = easeQuadIn(it.toDouble(), 40.0, -30.0, 9.0)
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println("$it -> $y")
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}
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```
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Outputs
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```
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0 -> 40.0
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1 -> 39.629629629629626
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2 -> 38.51851851851852
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3 -> 36.666666666666664
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4 -> 34.074074074074076
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5 -> 30.74074074074074
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6 -> 26.666666666666668
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7 -> 21.85185185185185
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8 -> 16.2962962962963
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9 -> 10.0
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```
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Note how most result values are closer to 40.0 than to 10.0, due to the usage of
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an `In` easing function. `easeCubicIn`, `easeQuartIn` and `easeQuinticIn` functions would make this even more obvious.
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### Default arguments
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When `t` is in `[0, 1]` we can omit most arguments
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```kotlin
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val e0 = easeQuadIn(t, 0.0, 1.0, 1.0)
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val e1 = easeQuadIn(t)
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```
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### Using the `Easing` enumeration
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The `Easing` enum contains all easing functions.
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```kotlin
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val et = Easing.QuadIn.function(t, 0.0, 1.0, 1.0)
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// list all easing function names
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Easing.values().forEach { easing ->
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println(easing.name)
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}
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// find out how many easing functions are available
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println(Easing.values().size)
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```
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<!-- __demos__ -->
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## Demos
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### DemoEasings01
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[source code](src/jvmDemo/kotlin/DemoEasings01.kt)
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