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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[v]
this[k] = v
if (f) f.call(this)
return this
}
}
export let 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 (t0, x0, t1, x1) {
return function (t) {
// TODO: FINISH
}
}
}
export class Stepper {
done () { return false }
}
/***
Easing Functions
================
***/
export class Ease extends Stepper {
constructor (fn) {
super()
this.ease = easing[fn || timeline.ease] || 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
}
step (current, target, dt, c) {
return this.stepper(current, target, dt, c)
}
done (c) {
return c.done
}
}
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, overshoot) {
super()
this.duration(duration || 500)
.overshoot(overshoot || 0)
}
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, i, d, windup) {
super()
p = p == null ? 0.1 : p
i = i == null ? 0.01 : i
d = d == null ? 0 : d
windup = windup == null ? 1000 : windup
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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