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1028 lines (865 loc) · 28.6 KB
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/**
* @author Richard Davey <rich@photonstorm.com>
* @copyright 2015 Photon Storm Ltd.
* @license {@link https://github.com/photonstorm/phaser/blob/master/license.txt|MIT License}
*/
/**
* A collection of useful mathematical functions.
*
* These are normally accessed through `game.math`.
*
* @class Phaser.Math
* @static
* @see {@link Phaser.Utils}
* @see {@link Phaser.ArrayUtils}
*/
Phaser.Math = {
/**
* Twice PI.
* @property {number} Phaser.Math#PI2
* @default ~6.283
*/
PI2: Math.PI * 2,
/**
* Two number are fuzzyEqual if their difference is less than epsilon.
*
* @method Phaser.Math#fuzzyEqual
* @param {number} a
* @param {number} b
* @param {number} [epsilon=(small value)]
* @return {boolean} True if |a-b|<epsilon
*/
fuzzyEqual: function (a, b, epsilon) {
if (typeof epsilon === 'undefined') { epsilon = 0.0001; }
return Math.abs(a - b) < epsilon;
},
/**
* `a` is fuzzyLessThan `b` if it is less than b + epsilon.
*
* @method Phaser.Math#fuzzyLessThan
* @param {number} a
* @param {number} b
* @param {number} [epsilon=(small value)]
* @return {boolean} True if a<b+epsilon
*/
fuzzyLessThan: function (a, b, epsilon) {
if (typeof epsilon === 'undefined') { epsilon = 0.0001; }
return a < b + epsilon;
},
/**
* `a` is fuzzyGreaterThan `b` if it is more than b - epsilon.
*
* @method Phaser.Math#fuzzyGreaterThan
* @param {number} a
* @param {number} b
* @param {number} [epsilon=(small value)]
* @return {boolean} True if a>b+epsilon
*/
fuzzyGreaterThan: function (a, b, epsilon) {
if (typeof epsilon === 'undefined') { epsilon = 0.0001; }
return a > b - epsilon;
},
/**
* @method Phaser.Math#fuzzyCeil
*
* @param {number} val
* @param {number} [epsilon=(small value)]
* @return {boolean} ceiling(val-epsilon)
*/
fuzzyCeil: function (val, epsilon) {
if (typeof epsilon === 'undefined') { epsilon = 0.0001; }
return Math.ceil(val - epsilon);
},
/**
* @method Phaser.Math#fuzzyFloor
*
* @param {number} val
* @param {number} [epsilon=(small value)]
* @return {boolean} floor(val-epsilon)
*/
fuzzyFloor: function (val, epsilon) {
if (typeof epsilon === 'undefined') { epsilon = 0.0001; }
return Math.floor(val + epsilon);
},
/**
* Averages all values passed to the function and returns the result.
*
* @method Phaser.Math#average
* @params {...number} The numbers to average
* @return {number} The average of all given values.
*/
average: function () {
var sum = 0;
for (var i = 0; i < arguments.length; i++) {
sum += (+arguments[i]);
}
return sum / arguments.length;
},
/**
* @method Phaser.Math#shear
* @param {number} n
* @return {number} n mod 1
*/
shear: function (n) {
return n % 1;
},
/**
* Snap a value to nearest grid slice, using rounding.
*
* Example: if you have an interval gap of 5 and a position of 12... you will snap to 10 whereas 14 will snap to 15.
*
* @method Phaser.Math#snapTo
* @param {number} input - The value to snap.
* @param {number} gap - The interval gap of the grid.
* @param {number} [start] - Optional starting offset for gap.
* @return {number}
*/
snapTo: function (input, gap, start) {
if (typeof start === 'undefined') { start = 0; }
if (gap === 0) {
return input;
}
input -= start;
input = gap * Math.round(input / gap);
return start + input;
},
/**
* Snap a value to nearest grid slice, using floor.
*
* Example: if you have an interval gap of 5 and a position of 12... you will snap to 10.
* As will 14 snap to 10... but 16 will snap to 15.
*
* @method Phaser.Math#snapToFloor
* @param {number} input - The value to snap.
* @param {number} gap - The interval gap of the grid.
* @param {number} [start] - Optional starting offset for gap.
* @return {number}
*/
snapToFloor: function (input, gap, start) {
if (typeof start === 'undefined') { start = 0; }
if (gap === 0) {
return input;
}
input -= start;
input = gap * Math.floor(input / gap);
return start + input;
},
/**
* Snap a value to nearest grid slice, using ceil.
*
* Example: if you have an interval gap of 5 and a position of 12... you will snap to 15.
* As will 14 will snap to 15... but 16 will snap to 20.
*
* @method Phaser.Math#snapToCeil
* @param {number} input - The value to snap.
* @param {number} gap - The interval gap of the grid.
* @param {number} [start] - Optional starting offset for gap.
* @return {number}
*/
snapToCeil: function (input, gap, start) {
if (typeof start === 'undefined') { start = 0; }
if (gap === 0) {
return input;
}
input -= start;
input = gap * Math.ceil(input / gap);
return start + input;
},
/**
* Round to some place comparative to a `base`, default is 10 for decimal place.
* The `place` is represented by the power applied to `base` to get that place.
*
* e.g. 2000/7 ~= 285.714285714285714285714 ~= (bin)100011101.1011011011011011
*
* roundTo(2000/7,3) === 0
* roundTo(2000/7,2) == 300
* roundTo(2000/7,1) == 290
* roundTo(2000/7,0) == 286
* roundTo(2000/7,-1) == 285.7
* roundTo(2000/7,-2) == 285.71
* roundTo(2000/7,-3) == 285.714
* roundTo(2000/7,-4) == 285.7143
* roundTo(2000/7,-5) == 285.71429
*
* roundTo(2000/7,3,2) == 288 -- 100100000
* roundTo(2000/7,2,2) == 284 -- 100011100
* roundTo(2000/7,1,2) == 286 -- 100011110
* roundTo(2000/7,0,2) == 286 -- 100011110
* roundTo(2000/7,-1,2) == 285.5 -- 100011101.1
* roundTo(2000/7,-2,2) == 285.75 -- 100011101.11
* roundTo(2000/7,-3,2) == 285.75 -- 100011101.11
* roundTo(2000/7,-4,2) == 285.6875 -- 100011101.1011
* roundTo(2000/7,-5,2) == 285.71875 -- 100011101.10111
*
* Note what occurs when we round to the 3rd space (8ths place), 100100000, this is to be assumed
* because we are rounding 100011.1011011011011011 which rounds up.
*
* @method Phaser.Math#roundTo
* @param {number} value - The value to round.
* @param {number} place - The place to round to.
* @param {number} base - The base to round in... default is 10 for decimal.
* @return {number}
*/
roundTo: function (value, place, base) {
if (typeof place === 'undefined') { place = 0; }
if (typeof base === 'undefined') { base = 10; }
var p = Math.pow(base, -place);
return Math.round(value * p) / p;
},
/**
* @method Phaser.Math#floorTo
* @param {number} value - The value to round.
* @param {number} place - The place to round to.
* @param {number} base - The base to round in... default is 10 for decimal.
* @return {number}
*/
floorTo: function (value, place, base) {
if (typeof place === 'undefined') { place = 0; }
if (typeof base === 'undefined') { base = 10; }
var p = Math.pow(base, -place);
return Math.floor(value * p) / p;
},
/**
* @method Phaser.Math#ceilTo
* @param {number} value - The value to round.
* @param {number} place - The place to round to.
* @param {number} base - The base to round in... default is 10 for decimal.
* @return {number}
*/
ceilTo: function (value, place, base) {
if (typeof place === 'undefined') { place = 0; }
if (typeof base === 'undefined') { base = 10; }
var p = Math.pow(base, -place);
return Math.ceil(value * p) / p;
},
/**
* Find the angle of a segment from (x1, y1) -> (x2, y2).
* @method Phaser.Math#angleBetween
* @param {number} x1
* @param {number} y1
* @param {number} x2
* @param {number} y2
* @return {number} The angle, in radians.
*/
angleBetween: function (x1, y1, x2, y2) {
return Math.atan2(y2 - y1, x2 - x1);
},
/**
* Find the angle of a segment from (x1, y1) -> (x2, y2).
* Note that the difference between this method and Math.angleBetween is that this assumes the y coordinate travels
* down the screen.
*
* @method Phaser.Math#angleBetweenY
* @param {number} x1
* @param {number} y1
* @param {number} x2
* @param {number} y2
* @return {number} The angle, in radians.
*/
angleBetweenY: function (x1, y1, x2, y2) {
return Math.atan2(x2 - x1, y2 - y1);
},
/**
* Find the angle of a segment from (point1.x, point1.y) -> (point2.x, point2.y).
* @method Phaser.Math#angleBetweenPoints
* @param {Phaser.Point} point1
* @param {Phaser.Point} point2
* @return {number} The angle, in radians.
*/
angleBetweenPoints: function (point1, point2) {
return Math.atan2(point2.y - point1.y, point2.x - point1.x);
},
/**
* Find the angle of a segment from (point1.x, point1.y) -> (point2.x, point2.y).
* @method Phaser.Math#angleBetweenPointsY
* @param {Phaser.Point} point1
* @param {Phaser.Point} point2
* @return {number} The angle, in radians.
*/
angleBetweenPointsY: function (point1, point2) {
return Math.atan2(point2.x - point1.x, point2.y - point1.y);
},
/**
* Reverses an angle.
* @method Phaser.Math#reverseAngle
* @param {number} angleRad - The angle to reverse, in radians.
* @return {number} Returns the reverse angle, in radians.
*/
reverseAngle: function (angleRad) {
return this.normalizeAngle(angleRad + Math.PI, true);
},
/**
* Normalizes an angle to the [0,2pi) range.
* @method Phaser.Math#normalizeAngle
* @param {number} angleRad - The angle to normalize, in radians.
* @return {number} Returns the angle, fit within the [0,2pi] range, in radians.
*/
normalizeAngle: function (angleRad) {
angleRad = angleRad % (2 * Math.PI);
return angleRad >= 0 ? angleRad : angleRad + 2 * Math.PI;
},
/**
* Adds the given amount to the value, but never lets the value go over the specified maximum.
*
* @method Phaser.Math#maxAdd
* @param {number} value - The value to add the amount to.
* @param {number} amount - The amount to add to the value.
* @param {number} max - The maximum the value is allowed to be.
* @return {number}
*/
maxAdd: function (value, amount, max) {
return Math.min(value + amount, max);
},
/**
* Subtracts the given amount from the value, but never lets the value go below the specified minimum.
*
* @method Phaser.Math#minSub
* @param {number} value - The base value.
* @param {number} amount - The amount to subtract from the base value.
* @param {number} min - The minimum the value is allowed to be.
* @return {number} The new value.
*/
minSub: function (value, amount, min) {
return Math.max(value - amount, min);
},
/**
* Ensures that the value always stays between min and max, by wrapping the value around.
*
* If `max` is not larger than `min` the result is 0.
*
* @method Phaser.Math#wrap
* @param {number} value - The value to wrap.
* @param {number} min - The minimum the value is allowed to be.
* @param {number} max - The maximum the value is allowed to be, should be larger than `min`.
* @return {number} The wrapped value.
*/
wrap: function (value, min, max) {
var range = max - min;
if (range <= 0)
{
return 0;
}
var result = (value - min) % range;
if (result < 0)
{
result += range;
}
return result + min;
},
/**
* Adds value to amount and ensures that the result always stays between 0 and max, by wrapping the value around.
*
* Values _must_ be positive integers, and are passed through Math.abs. See {@link Phaser.Math#wrap} for an alternative.
*
* @method Phaser.Math#wrapValue
* @param {number} value - The value to add the amount to.
* @param {number} amount - The amount to add to the value.
* @param {number} max - The maximum the value is allowed to be.
* @return {number} The wrapped value.
*/
wrapValue: function (value, amount, max) {
var diff;
value = Math.abs(value);
amount = Math.abs(amount);
max = Math.abs(max);
diff = (value + amount) % max;
return diff;
},
/**
* Returns true if the number given is odd.
*
* @method Phaser.Math#isOdd
* @param {integer} n - The number to check.
* @return {boolean} True if the given number is odd. False if the given number is even.
*/
isOdd: function (n) {
// Does not work with extremely large values
return !!(n & 1);
},
/**
* Returns true if the number given is even.
*
* @method Phaser.Math#isEven
* @param {integer} n - The number to check.
* @return {boolean} True if the given number is even. False if the given number is odd.
*/
isEven: function (n) {
// Does not work with extremely large values
return !(n & 1);
},
/**
* Variation of Math.min that can be passed either an array of numbers or the numbers as parameters.
*
* Prefer the standard `Math.min` function when appropriate.
*
* @method Phaser.Math#min
* @return {number} The lowest value from those given.
* @see {@link http://jsperf.com/math-s-min-max-vs-homemade}
*/
min: function () {
if (arguments.length === 1 && typeof arguments[0] === 'object')
{
var data = arguments[0];
}
else
{
var data = arguments;
}
for (var i = 1, min = 0, len = data.length; i < len; i++)
{
if (data[i] < data[min])
{
min = i;
}
}
return data[min];
},
/**
* Variation of Math.max that can be passed either an array of numbers or the numbers as parameters.
*
* Prefer the standard `Math.max` function when appropriate.
*
* @method Phaser.Math#max
* @return {number} The largest value from those given.
* @see {@link http://jsperf.com/math-s-min-max-vs-homemade}
*/
max: function () {
if (arguments.length === 1 && typeof arguments[0] === 'object')
{
var data = arguments[0];
}
else
{
var data = arguments;
}
for (var i = 1, max = 0, len = data.length; i < len; i++)
{
if (data[i] > data[max])
{
max = i;
}
}
return data[max];
},
/**
* Variation of Math.min that can be passed a property and either an array of objects or the objects as parameters.
* It will find the lowest matching property value from the given objects.
*
* @method Phaser.Math#minProperty
* @return {number} The lowest value from those given.
*/
minProperty: function (property) {
if (arguments.length === 2 && typeof arguments[1] === 'object')
{
var data = arguments[1];
}
else
{
var data = arguments.slice(1);
}
for (var i = 1, min = 0, len = data.length; i < len; i++)
{
if (data[i][property] < data[min][property])
{
min = i;
}
}
return data[min][property];
},
/**
* Variation of Math.max that can be passed a property and either an array of objects or the objects as parameters.
* It will find the largest matching property value from the given objects.
*
* @method Phaser.Math#maxProperty
* @return {number} The largest value from those given.
*/
maxProperty: function (property) {
if (arguments.length === 2 && typeof arguments[1] === 'object')
{
var data = arguments[1];
}
else
{
var data = arguments.slice(1);
}
for (var i = 1, max = 0, len = data.length; i < len; i++)
{
if (data[i][property] > data[max][property])
{
max = i;
}
}
return data[max][property];
},
/**
* Keeps an angle value between -180 and +180; or -PI and PI if radians.
*
* @method Phaser.Math#wrapAngle
* @param {number} angle - The angle value to wrap
* @param {boolean} [radians=false] - Set to `true` if the angle is given in radians, otherwise degrees is expected.
* @return {number} The new angle value; will be the same as the input angle if it was within bounds.
*/
wrapAngle: function (angle, radians) {
return radians ? this.wrap(angle, -Math.PI, Math.PI) : this.wrap(angle, -180, 180);
},
/**
* A Linear Interpolation Method, mostly used by Phaser.Tween.
*
* @method Phaser.Math#linearInterpolation
* @param {Array} v - The input array of values to interpolate between.
* @param {number} k - The percentage of interpolation, between 0 and 1.
* @return {number} The interpolated value
*/
linearInterpolation: function (v, k) {
var m = v.length - 1;
var f = m * k;
var i = Math.floor(f);
if (k < 0)
{
return this.linear(v[0], v[1], f);
}
if (k > 1)
{
return this.linear(v[m], v[m - 1], m - f);
}
return this.linear(v[i], v[i + 1 > m ? m : i + 1], f - i);
},
/**
* A Bezier Interpolation Method, mostly used by Phaser.Tween.
*
* @method Phaser.Math#bezierInterpolation
* @param {Array} v - The input array of values to interpolate between.
* @param {number} k - The percentage of interpolation, between 0 and 1.
* @return {number} The interpolated value
*/
bezierInterpolation: function (v, k) {
var b = 0;
var n = v.length - 1;
for (var i = 0; i <= n; i++)
{
b += Math.pow(1 - k, n - i) * Math.pow(k, i) * v[i] * this.bernstein(n, i);
}
return b;
},
/**
* A Catmull Rom Interpolation Method, mostly used by Phaser.Tween.
*
* @method Phaser.Math#catmullRomInterpolation
* @param {Array} v - The input array of values to interpolate between.
* @param {number} k - The percentage of interpolation, between 0 and 1.
* @return {number} The interpolated value
*/
catmullRomInterpolation: function (v, k) {
var m = v.length - 1;
var f = m * k;
v
1898
ar i = Math.floor(f);
if (v[0] === v[m])
{
if (k < 0)
{
i = Math.floor(f = m * (1 + k));
}
return this.catmullRom(v[(i - 1 + m) % m], v[i], v[(i + 1) % m], v[(i + 2) % m], f - i);
}
else
{
if (k < 0)
{
return v[0] - (this.catmullRom(v[0], v[0], v[1], v[1], -f) - v[0]);
}
if (k > 1)
{
return v[m] - (this.catmullRom(v[m], v[m], v[m - 1], v[m - 1], f - m) - v[m]);
}
return this.catmullRom(v[i ? i - 1 : 0], v[i], v[m < i + 1 ? m : i + 1], v[m < i + 2 ? m : i + 2], f - i);
}
},
/**
* Calculates a linear (interpolation) value over t.
*
* @method Phaser.Math#linear
* @param {number} p0
* @param {number} p1
* @param {number} t
* @return {number}
*/
linear: function (p0, p1, t) {
return (p1 - p0) * t + p0;
},
/**
* @method Phaser.Math#bernstein
* @protected
* @param {number} n
* @param {number} i
* @return {number}
*/
bernstein: function (n, i) {
return this.factorial(n) / this.factorial(i) / this.factorial(n - i);
},
/**
* @method Phaser.Math#factorial
* @param {number} value - the number you want to evaluate
* @return {number}
*/
factorial : function( value ){
if (value === 0)
{
return 1;
}
var res = value;
while(--value)
{
res *= value;
}
return res;
},
/**
* Calculates a catmum rom value.
*
* @method Phaser.Math#catmullRom
* @protected
* @param {number} p0
* @param {number} p1
* @param {number} p2
* @param {number} p3
* @param {number} t
* @return {number}
*/
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;
},
/**
* The (absolute) difference between two values.
*
* @method Phaser.Math#difference
* @param {number} a
* @param {number} b
* @return {number}
*/
difference: function (a, b) {
return Math.abs(a - b);
},
/**
* Round to the next whole number _away_ from zero.
*
* @method Phaser.Math#roundAwayFromZero
* @param {number} value - Any number.
* @return {integer} The rounded value of that number.
*/
roundAwayFromZero: function (value) {
// "Opposite" of truncate.
return (value > 0) ? Math.ceil(value) : Math.floor(value);
},
/**
* Generate a sine and cosine table simultaneously and extremely quickly.
* The parameters allow you to specify the length, amplitude and frequency of the wave.
* This generator is fast enough to be used in real-time.
* Code based on research by Franky of scene.at
*
* @method Phaser.Math#sinCosGenerator
* @param {number} length - The length of the wave
* @param {number} sinAmplitude - The amplitude to apply to the sine table (default 1.0) if you need values between say -+ 125 then give 125 as the value
* @param {number} cosAmplitude - The amplitude to apply to the cosine table (default 1.0) if you need values between say -+ 125 then give 125 as the value
* @param {number} frequency - The frequency of the sine and cosine table data
* @return {{sin:number[], cos:number[]}} Returns the table data.
*/
sinCosGenerator: function (length, sinAmplitude, cosAmplitude, frequency) {
if (typeof sinAmplitude === 'undefined') { sinAmplitude = 1.0; }
if (typeof cosAmplitude === 'undefined') { cosAmplitude = 1.0; }
if (typeof frequency === 'undefined') { frequency = 1.0; }
var sin = sinAmplitude;
var cos = cosAmplitude;
var frq = frequency * Math.PI / length;
var cosTable = [];
var sinTable = [];
for (var c = 0; c < length; c++) {
cos -= sin * frq;
sin += cos * frq;
cosTable[c] = cos;
sinTable[c] = sin;
}
return { sin: sinTable, cos: cosTable, length: length };
},
/**
* Returns the euclidian distance between the two given set of coordinates.
*
* @method Phaser.Math#distance
* @param {number} x1
* @param {number} y1
* @param {number} x2
* @param {number} y2
* @return {number} The distance between the two sets of coordinates.
*/
distance: function (x1, y1, x2, y2) {
var dx = x1 - x2;
var dy = y1 - y2;
return Math.sqrt(dx * dx + dy * dy);
},
/**
* Returns the euclidean distance squared between the two given set of
* coordinates (cuts out a square root operation before returning).
*
* @method Phaser.Math#distanceSq
* @param {number} x1
* @param {number} y1
* @param {number} x2
* @param {number} y2
* @return {number} The distance squared between the two sets of coordinates.
*/
distanceSq: function (x1, y1, x2, y2) {
var dx = x1 - x2;
var dy = y1 - y2;
return dx * dx + dy * dy;
},
/**
* Returns the distance between the two given set of coordinates at the power given.
*
* @method Phaser.Math#distancePow
* @param {number} x1
* @param {number} y1
* @param {number} x2
* @param {number} y2
* @param {number} [pow=2]
* @return {number} The distance between the two sets of coordinates.
*/
distancePow: function (x1, y1, x2, y2, pow) {
if (typeof pow === 'undefined') { pow = 2; }
return Math.sqrt(Math.pow(x2 - x1, pow) + Math.pow(y2 - y1, pow));
},
/**
* Force a value within the boundaries by clamping `x` to the range `[a, b]`.
*
* @method Phaser.Math#clamp
* @param {number} x
* @param {number} a
* @param {number} b
* @return {number}
*/
clamp: function (x, a, b) {
return ( x < a ) ? a : ( ( x > b ) ? b : x );
},
/**
* Clamp `x` to the range `[a, Infinity)`.
* Roughly the same as `Math.max(x, a)`, except for NaN handling.
*
* @method Phaser.Math#clampBottom
* @param {number} x
* @param {number} a
* @return {number}
*/
clampBottom: function (x, a) {
return x < a ? a : x;
},
/**
* Checks if two values are within the given tolerance of each other.
*
* @method Phaser.Math#within
* @param {number} a - The first number to check
* @param {number} b - The second number to check
* @param {number} tolerance - The tolerance. Anything equal to or less than this is considered within the range.
* @return {boolean} True if a is <= tolerance of b.
* @see {@link Phaser.Math.fuzzyEqual}
*/
within: function (a, b, tolerance) {
return (Math.abs(a - b) <= tolerance);
},
/**
* Linear mapping from range <a1, a2> to range <b1, b2>
*
* @method Phaser.Math#mapLinear
* @param {number} x the value to map
* @param {number} a1 first endpoint of the range <a1, a2>
* @param {number} a2 final endpoint of the range <a1, a2>
* @param {number} b1 first endpoint of the range <b1, b2>
* @param {number} b2 final endpoint of the range <b1, b2>
* @return {number}
*/
mapLinear: function (x, a1, a2, b1, b2) {
return b1 + ( x - a1 ) * ( b2 - b1 ) / ( a2 - a1 );
},
/**
* Smoothstep function as detailed at http://en.wikipedia.org/wiki/Smoothstep
*
* @method Phaser.Math#smoothstep
* @param {number} x
* @param {number} min
* @param {number} max
* @return {number}
*/
smoothstep: function (x, min, max) {
x = Math.max(0, Math.min(1, (x - min) / (max - min)));
return x * x * (3 - 2 * x);
},
/**
* Smootherstep function as detailed at http://en.wikipedia.org/wiki/Smoothstep
*
* @method Phaser.Math#smootherstep
* @param {number} x
* @param {number} min
* @param {number} max
* @return {number}
*/
smootherstep: function (x, min, max) {
x = Math.max(0, Math.min(1, (x - min) / (max - min)));
return x * x * x * (x * (x * 6 - 15) + 10);
},
/**
* A value representing the sign of the value: -1 for negative, +1 for positive, 0 if value is 0.
*
* This works differently from `Math.sign` for values of NaN and -0, etc.
*
* @method Phaser.Math#sign
* @param {number} x
* @return {integer} An integer in {-1, 0, 1}
*/
sign: function (x) {
return ( x < 0 ) ? -1 : ( ( x > 0 ) ? 1 : 0 );
},
/**
* Work out what percentage value `a` is of value `b` using the given base.
*
* @method Phaser.Math#percent
* @param {number} a - The value to work out the percentage for.
* @param {number} b - The value you wish to get the percentage of.
* @param {number} [base=0] - The base value.
* @return {number} The percentage a is of b, between 0 and 1.
*/
percent: function (a, b, base) {
if (typeof base === 'undefined') { base = 0; }
if (a > b || base > b)
{
return 1;
}
else if (a < base || base > a)
{
return 0;
}
else
{
return (a - base) / b;
}