'use strict';
/**
* Easing and interpolation functions for variable lerping.
*
* @module engine/anime/easing
*/
/**
* Easing functions.
*/
const Easing = {
Linear: {
None: function(k) {
return k;
},
},
Quadratic: {
In: function(k) {
return k * k;
},
Out: function(k) {
return k * (2 - k);
},
InOut: function(k) {
if ((k *= 2) < 1) {return 0.5 * k * k;}
return -0.5 * (--k * (k - 2) - 1);
},
},
Cubic: {
In: function(k) {
return k * k * k;
},
Out: function(k) {
return --k * k * k + 1;
},
InOut: function(k) {
if ((k *= 2) < 1) {return 0.5 * k * k * k;}
return 0.5 * ((k -= 2) * k * k + 2);
},
},
Quartic: {
In: function(k) {
return k * k * k * k;
},
Out: function(k) {
return 1 - (--k * k * k * k);
},
InOut: function(k) {
if ((k *= 2) < 1) {return 0.5 * k * k * k * k;}
return -0.5 * ((k -= 2) * k * k * k - 2);
},
},
Quintic: {
In: function(k) {
return k * k * k * k * k;
},
Out: function(k) {
return --k * k * k * k * k + 1;
},
InOut: function(k) {
if ((k *= 2) < 1) {return 0.5 * k * k * k * k * k;}
return 0.5 * ((k -= 2) * k * k * k * k + 2);
},
},
Sinusoidal: {
In: function(k) {
return 1 - Math.cos(k * Math.PI / 2);
},
Out: function(k) {
return Math.sin(k * Math.PI / 2);
},
InOut: function(k) {
return 0.5 * (1 - Math.cos(Math.PI * k));
},
},
Exponential: {
In: function(k) {
return k === 0 ? 0 : Math.pow(1024, k - 1);
},
Out: function(k) {
return k === 1 ? 1 : 1 - Math.pow(2, -10 * k);
},
InOut: function(k) {
if (k === 0) {return 0;}
if (k === 1) {return 1;}
if ((k *= 2) < 1) {return 0.5 * Math.pow(1024, k - 1);}
return 0.5 * (-Math.pow(2, -10 * (k - 1)) + 2);
},
},
Circular: {
In: function(k) {
return 1 - Math.sqrt(1 - k * k);
},
Out: function(k) {
return Math.sqrt(1 - (--k * k));
},
InOut: function(k) {
if ((k *= 2) < 1) {return -0.5 * (Math.sqrt(1 - k * k) - 1);}
return 0.5 * (Math.sqrt(1 - (k -= 2) * k) + 1);
},
},
Elastic: {
In: function(k) {
var s, a = 0.1,
p = 0.4;
if (k === 0) {return 0;}
if (k === 1) {return 1;}
if (!a || a < 1) {
a = 1;
s = p / 4;
}
else {s = p * Math.asin(1 / a) / (2 * Math.PI);}
return -(a * Math.pow(2, 10 * (k -= 1)) * Math.sin((k - s) * (2 * Math.PI) / p));
},
Out: function(k) {
var s, a = 0.1,
p = 0.4;
if (k === 0) {return 0;}
if (k === 1) {return 1;}
if (!a || a < 1) {
a = 1;
s = p / 4;
}
else {s = p * Math.asin(1 / a) / (2 * Math.PI);}
return (a * Math.pow(2, -10 * k) * Math.sin((k - s) * (2 * Math.PI) / p) + 1);
},
InOut: function(k) {
var s, a = 0.1,
p = 0.4;
if (k === 0) {return 0;}
if (k === 1) {return 1;}
if (!a || a < 1) {
a = 1;
s = p / 4;
}
else {s = p * Math.asin(1 / a) / (2 * Math.PI);}
if ((k *= 2) < 1) {return -0.5 * (a * Math.pow(2, 10 * (k -= 1)) * Math.sin((k - s) * (2 * Math.PI) / p));}
return a * Math.pow(2, -10 * (k -= 1)) * Math.sin((k - s) * (2 * Math.PI) / p) * 0.5 + 1;
},
},
Back: {
In: function(k) {
var s = 1.70158;
return k * k * ((s + 1) * k - s);
},
Out: function(k) {
var s = 1.70158;
return --k * k * ((s + 1) * k + s) + 1;
},
InOut: function(k) {
var s = 1.70158 * 1.525;
if ((k *= 2) < 1) {return 0.5 * (k * k * ((s + 1) * k - s));}
return 0.5 * ((k -= 2) * k * ((s + 1) * k + s) + 2);
},
},
Bounce: {
In: function(k) {
return 1 - Easing.Bounce.Out(1 - k);
},
Out: function(k) {
if (k < (1 / 2.75)) {
return 7.5625 * k * k;
}
else if (k < (2 / 2.75)) {
return 7.5625 * (k -= (1.5 / 2.75)) * k + 0.75;
}
else if (k < (2.5 / 2.75)) {
return 7.5625 * (k -= (2.25 / 2.75)) * k + 0.9375;
}
else {
return 7.5625 * (k -= (2.625 / 2.75)) * k + 0.984375;
}
},
InOut: function(k) {
if (k < 0.5) {return Easing.Bounce.In(k * 2) * 0.5;}
return Easing.Bounce.Out(k * 2 - 1) * 0.5 + 0.5;
},
},
};
/**
* Interpolation functions.
*/
const Interpolation = {
Linear: function(v, k) {
var m = v.length - 1,
f = m * k,
i = Math.floor(f),
fn = Interpolation.Utils.Linear;
if (k < 0) {return fn(v[0], v[1], f);}
if (k > 1) {return fn(v[m], v[m - 1], m - f);}
return fn(v[i], v[i + 1 > m ? m : i + 1], f - i);
},
Bezier: function(v, k) {
var b = 0,
n = v.length - 1,
pw = Math.pow,
bn = Interpolation.Utils.Bernstein,
i;
for (i = 0; i <= n; i++) {
b += pw(1 - k, n - i) * pw(k, i) * v[i] * bn(n, i);
}
return b;
},
CatmullRom: function(v, k) {
var m = v.length - 1,
f = m * k,
i = Math.floor(f),
fn = Interpolation.Utils.CatmullRom;
if (v[0] === v[m]) {
if (k < 0) {i = Math.floor(f = m * (1 + k));}
return fn(v[(i - 1 + m) % m], v[i], v[(i + 1) % m], v[(i + 2) % m], f - i);
}
else {
if (k < 0) {return v[0] - (fn(v[0], v[0], v[1], v[1], -f) - v[0]);}
if (k > 1) {return v[m] - (fn(v[m], v[m], v[m - 1], v[m - 1], f - m) - v[m]);}
return fn(v[i ? i - 1 : 0], v[i], v[m < i + 1 ? m : i + 1], v[m < i + 2 ? m : i + 2], f - i);
}
},
Utils: {
Linear: function(p0, p1, t) {
return (p1 - p0) * t + p0;
},
Bernstein: function(n, i) {
var fc = Interpolation.Utils.Factorial;
return fc(n) / fc(i) / fc(n - i);
},
Factorial: (function() {
var a = [1];
return function(n) {
var s = 1, i;
if (a[n]) {return a[n];}
for (i = n; i > 1; i--) {s *= i;}
return a[n] = s;
};
})(),
CatmullRom: function(p0, p1, p2, p3, t) {
var v0 = (p2 - p0) * 0.5,
v1 = (p3 - p1) * 0.5,
t2 = t * t,
t3 = t * t2;
return (2 * p1 - 2 * p2 + v0 + v1) * t3 + (-3 * p1 + 3 * p2 - 2 * v0 - v1) * t2 + v0 * t + p1;
},
},
};
module.exports.Easing = Easing;
module.exports.Interpolation = Interpolation;