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Custom easing functions for use with SpriteKit / SKAction
//
// SKTimingFunction.swift
// Studious ToolKit
//
// Created by Allan Weir on 09/01/2017.
// Copyright © 2017 Allan Weir. All rights reserved.
// Adapted from a JavaScript version found at https://gist.github.com/gre/1650294
//
class SpriteKitTimingFunctions {
// no easing, no acceleration
static var easeLinear: SKActionTimingFunction = {
var t: Float = $0
return t
}
// accelerating from zero velocity
static var easeInQuad: SKActionTimingFunction = {
var t: Float = $0
return t*t
}
// decelerating to zero velocity
static var easeOutQuad: SKActionTimingFunction = {
var t: Float = $0
return t*(2-t)
}
// acceleration until halfway, then deceleration
static var easeInOutQuad: SKActionTimingFunction = {
var t: Float = $0
return t<0.5 ? 2*t*t : -1+(4-2*t)*t
}
// accelerating from zero velocity
static var easeInCubic: SKActionTimingFunction = {
var t: Float = $0
return t*t*t
}
// decelerating to zero velocity
static var easeOutCubic: SKActionTimingFunction = {
var t: Float = $0
return (t - 1)*t*t+1
}
// acceleration until halfway, then deceleration
static var easeInOutCubic: SKActionTimingFunction = {
var t: Float = $0
return t<0.5 ? 4*t*t*t : (t-1)*(2*t-2)*(2*t-2)+1
}
// accelerating from zero velocity
static var easeInQuart: SKActionTimingFunction = {
var t: Float = $0
return t*t*t*t
}
// decelerating to zero velocity
static var easeOutQuart: SKActionTimingFunction = {
var t: Float = $0
return 1-(t-1)*t*t*t
}
// acceleration until halfway, then deceleration
static var easeInOutQuart: SKActionTimingFunction = {
var t: Float = $0
return t<0.5 ? 8*t*t*t*t : 1-8*(t-1)*t*t*t
}
// accelerating from zero velocity
static var easeInQuint: SKActionTimingFunction = {
var t: Float = $0
return t*t*t*t*t
}
// decelerating to zero velocity
static var easeOutQuint: SKActionTimingFunction = {
var t: Float = $0
return 1+(t-1)*t*t*t*t
}
// acceleration until halfway, then deceleration
static var easeInOutQuint: SKActionTimingFunction = {
var t: Float = $0
return t<0.5 ? 16*t*t*t*t*t : 1+16*(t-1)*t*t*t*t
}
static var easeInSin: SKActionTimingFunction = {
var t: Float = $0
return 1 + sin(Float.pi / 2 * t - Float.pi / 2)
}
static var easeOutSin : SKActionTimingFunction = {
var t: Float = $0
return sin(Float.pi / 2 * t)
}
static var easeInOutSin: SKActionTimingFunction = {
var t: Float = $0
return (1 + sin(Float.pi * t - Float.pi / 2)) / 2
}
// elastic bounce effect at the beginning
static var easeInElastic: SKActionTimingFunction = {
var t: Float = $0
return (0.04 - 0.04 / t) * sin(25 * t) + 1
}
// elastic bounce effect at the end
static var easeOutElastic: SKActionTimingFunction = {
var t: Float = $0
return 0.04 * t / (t - 1) * sin(25 * t)
}
// elastic bounce effect at the beginning and end
static var easeInOutElastic: SKActionTimingFunction = {
var t: Float = $0
return (t < 0.5) ? (0.01 + 0.01 / t) * sin(50 * t) : (0.02 - 0.01 / t) * sin(50 * t) + 1
}
}
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