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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 ( 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 ) {
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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