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import { timeline } from '../modules/core/defaults.js'
import { extend } from '../utils/adopter.js'
/***
Base Class
==========
The base stepper class that will be
***/
function makeSetterGetter (k, f) {
return function (v) {
if (v == null) return this[k]
this[k] = v
if (f) f.call(this)
return this
}
}
export const easing = {
'-': function (pos) {
return pos
},
'<>': function (pos) {
return -Math.cos(pos * Math.PI) / 2 + 0.5
},
'>': function (pos) {
return Math.sin(pos * Math.PI / 2)
},
'<': function (pos) {
return -Math.cos(pos * Math.PI / 2) + 1
},
bezier: function (x1, y1, x2, y2) {
// see https://www.w3.org/TR/css-easing-1/#cubic-bezier-algo
return function (t) {
if (t < 0) {
if (x1 > 0) {
return y1 / x1 * t
} else if (x2 > 0) {
return y2 / x2 * t
} else {
return 0
}
} else if (t > 1) {
if (x2 < 1) {
return (1 - y2) / (1 - x2) * t + (y2 - x2) / (1 - x2)
} else if (x1 < 1) {
return (1 - y1) / (1 - x1) * t + (y1 - x1) / (1 - x1)
} else {
return 1
}
} else {
return 3 * t * (1 - t) ** 2 * y1 + 3 * t ** 2 * (1 - t) * y2 + t ** 3
}
}
},
// see https://www.w3.org/TR/css-easing-1/#step-timing-function-algo
steps: function (steps, stepPosition = 'end') {
// deal with "jump-" prefix
stepPosition = stepPosition.split('-').reverse()[0]
let jumps = steps
if (stepPosition === 'none') {
--jumps
} else if (stepPosition === 'both') {
++jumps
}
// The beforeFlag is essentially useless
return (t, beforeFlag = false) => {
// Step is called currentStep in referenced url
let step = Math.floor(t * steps)
const jumping = (t * step) % 1 === 0
if (stepPosition === 'start' || stepPosition === 'both') {
++step
}
if (beforeFlag && jumping) {
--step
}
if (t >= 0 && step < 0) {
step = 0
}
if (t <= 1 && step > jumps) {
step = jumps
}
return step / jumps
}
}
}
export class Stepper {
done () {
return false
}
}
/***
Easing Functions
================
***/
export class Ease extends Stepper {
constructor (fn = timeline.ease) {
super()
this.ease = easing[fn] || fn
}
step (from, to, pos) {
if (typeof from !== 'number') {
return pos < 1 ? from : to
}
return from + (to - from) * this.ease(pos)
}
}
/***
Controller Types
================
***/
export class Controller extends Stepper {
constructor (fn) {
super()
this.stepper = fn
}
done (c) {
return c.done
}
step (current, target, dt, c) {
return this.stepper(current, target, dt, c)
}
}
function recalculate () {
// Apply the default parameters
var duration = (this._duration || 500) / 1000
var overshoot = this._overshoot || 0
// Calculate the PID natural response
var eps = 1e-10
var pi = Math.PI
var os = Math.log(overshoot / 100 + eps)
var zeta = -os / Math.sqrt(pi * pi + os * os)
var wn = 3.9 / (zeta * duration)
// Calculate the Spring values
this.d = 2 * zeta * wn
this.k = wn * wn
}
export class Spring extends Controller {
constructor (duration = 500, overshoot = 0) {
super()
this.duration(duration)
.overshoot(overshoot)
}
step (current, target, dt, c) {
if (typeof current === 'string') return current
c.done = dt === Infinity
if (dt === Infinity) return target
if (dt === 0) return current
if (dt > 100) dt = 16
dt /= 1000
// Get the previous velocity
var velocity = c.velocity || 0
// Apply the control to get the new position and store it
var acceleration = -this.d * velocity - this.k * (current - target)
var newPosition = current
+ velocity * dt
+ acceleration * dt * dt / 2
// Store the velocity
c.velocity = velocity + acceleration * dt
// Figure out if we have converged, and if so, pass the value
c.done = Math.abs(target - newPosition) + Math.abs(velocity) < 0.002
return c.done ? target : newPosition
}
}
extend(Spring, {
duration: makeSetterGetter('_duration', recalculate),
overshoot: makeSetterGetter('_overshoot', recalculate)
})
export class PID extends Controller {
constructor (p = 0.1, i = 0.01, d = 0, windup = 1000) {
super()
this.p(p).i(i).d(d).windup(windup)
}
step (current, target, dt, c) {
if (typeof current === 'string') return current
c.done = dt === Infinity
if (dt === Infinity) return target
if (dt === 0) return current
var p = target - current
var i = (c.integral || 0) + p * dt
var d = (p - (c.error || 0)) / dt
var windup = this._windup
// antiwindup
if (windup !== false) {
i = Math.max(-windup, Math.min(i, windup))
}
c.error = p
c.integral = i
c.done = Math.abs(p) < 0.001
return c.done ? target : current + (this.P * p + this.I * i + this.D * d)
}
}
extend(PID, {
windup: makeSetterGetter('_windup'),
p: makeSetterGetter('P'),
i: makeSetterGetter('I'),
d: makeSetterGetter('D')
})
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