canvas-sketch-util/random.js

Utilities for sketching in Canvas, WebGL and generative art

var seedRandom = require('seed-random');
var SimplexNoise = require('simplex-noise');
var defined = require('defined');

function createRandom (defaultSeed) {
  defaultSeed = defined(defaultSeed, null);
  var defaultRandom = Math.random;
  var currentSeed;
  var currentRandom;
  var noiseGenerator;
  var _nextGaussian = null;
  var _hasNextGaussian = false;

  setSeed(defaultSeed);

  return {
    value: value,
    createRandom: function (defaultSeed) {
      return createRandom(defaultSeed);
    },
    setSeed: setSeed,
    getSeed: getSeed,
    getRandomSeed: getRandomSeed,
    valueNonZero: valueNonZero,
    permuteNoise: permuteNoise,
    noise1D: noise1D,
    noise2D: noise2D,
    noise3D: noise3D,
    noise4D: noise4D,
    sign: sign,
    boolean: boolean,
    chance: chance,
    range: range,
    rangeFloor: rangeFloor,
    pick: pick,
    shuffle: shuffle,
    onCircle: onCircle,
    insideCircle: insideCircle,
    onSphere: onSphere,
    insideSphere: insideSphere,
    quaternion: quaternion,
    weighted: weighted,
    weightedSet: weightedSet,
    weightedSetIndex: weightedSetIndex,
    gaussian: gaussian
  };

  function setSeed (seed, opt) {
    if (typeof seed === 'number' || typeof seed === 'string') {
      currentSeed = seed;
      currentRandom = seedRandom(currentSeed, opt);
    } else {
      currentSeed = undefined;
      currentRandom = defaultRandom;
    }
    noiseGenerator = createNoise();
    _nextGaussian = null;
    _hasNextGaussian = false;
  }

  function value () {
    return currentRandom();
  }

  function valueNonZero () {
    var u = 0;
    while (u === 0) u = value();
    return u;
  }

  function getSeed () {
    return currentSeed;
  }

  function getRandomSeed () {
    var seed = String(Math.floor(Math.random() * 1000000));
    return seed;
  }

  function createNoise () {
    return new SimplexNoise(currentRandom);
  }

  function permuteNoise () {
    noiseGenerator = createNoise();
  }

  function noise1D (x, frequency, amplitude) {
    if (!isFinite(x)) throw new TypeError('x component for noise() must be finite');
    frequency = defined(frequency, 1);
    amplitude = defined(amplitude, 1);
    return amplitude * noiseGenerator.noise2D(x * frequency, 0);
  }

  function noise2D (x, y, frequency, amplitude) {
    if (!isFinite(x)) throw new TypeError('x component for noise() must be finite');
    if (!isFinite(y)) throw new TypeError('y component for noise() must be finite');
    frequency = defined(frequency, 1);
    amplitude = defined(amplitude, 1);
    return amplitude * noiseGenerator.noise2D(x * frequency, y * frequency);
  }

  function noise3D (x, y, z, frequency, amplitude) {
    if (!isFinite(x)) throw new TypeError('x component for noise() must be finite');
    if (!isFinite(y)) throw new TypeError('y component for noise() must be finite');
    if (!isFinite(z)) throw new TypeError('z component for noise() must be finite');
    frequency = defined(frequency, 1);
    amplitude = defined(amplitude, 1);
    return amplitude * noiseGenerator.noise3D(
      x * frequency,
      y * frequency,
      z * frequency
    );
  }

  function noise4D (x, y, z, w, frequency, amplitude) {
    if (!isFinite(x)) throw new TypeError('x component for noise() must be finite');
    if (!isFinite(y)) throw new TypeError('y component for noise() must be finite');
    if (!isFinite(z)) throw new TypeError('z component for noise() must be finite');
    if (!isFinite(w)) throw new TypeError('w component for noise() must be finite');
    frequency = defined(frequency, 1);
    amplitude = defined(amplitude, 1);
    return amplitude * noiseGenerator.noise4D(
      x * frequency,
      y * frequency,
      z * frequency,
      w * frequency
    );
  }

  function sign () {
    return boolean() ? 1 : -1;
  }

  function boolean () {
    return value() > 0.5;
  }

  function chance (n) {
    n = defined(n, 0.5);
    if (typeof n !== 'number') throw new TypeError('expected n to be a number');
    return value() < n;
  }

  function range (min, max) {
    if (max === undefined) {
      max = min;
      min = 0;
    }

    if (typeof min !== 'number' || typeof max !== 'number') {
      throw new TypeError('Expected all arguments to be numbers');
    }

    return value() * (max - min) + min;
  }

  function rangeFloor (min, max) {
    if (max === undefined) {
      max = min;
      min = 0;
    }

    if (typeof min !== 'number' || typeof max !== 'number') {
      throw new TypeError('Expected all arguments to be numbers');
    }

    return Math.floor(range(min, max));
  }

  function pick (array) {
    if (array.length === 0) return undefined;
    return array[rangeFloor(0, array.length)];
  }

  function shuffle (arr) {
    if (!Array.isArray(arr)) {
      throw new TypeError('Expected Array, got ' + typeof arr);
    }

    var rand;
    var tmp;
    var len = arr.length;
    var ret = arr.slice();
    while (len) {
      rand = Math.floor(value() * len--);
      tmp = ret[len];
      ret[len] = ret[rand];
      ret[rand] = tmp;
    }
    return ret;
  }

  function onCircle (radius, out) {
    radius = defined(radius, 1);
    out = out || [];
    var theta = value() * 2.0 * Math.PI;
    out[0] = radius * Math.cos(theta);
    out[1] = radius * Math.sin(theta);
    return out;
  }

  function insideCircle (radius, out) {
    radius = defined(radius, 1);
    out = out || [];
    onCircle(1, out);
    var r = radius * Math.sqrt(value());
    out[0] *= r;
    out[1] *= r;
    return out;
  }

  function onSphere (radius, out) {
    radius = defined(radius, 1);
    out = out || [];
    var u = value() * Math.PI * 2;
    var v = value() * 2 - 1;
    var phi = u;
    var theta = Math.acos(v);
    out[0] = radius * Math.sin(theta) * Math.cos(phi);
    out[1] = radius * Math.sin(theta) * Math.sin(phi);
    out[2] = radius * Math.cos(theta);
    return out;
  }

  function insideSphere (radius, out) {
    radius = defined(radius, 1);
    out = out || [];
    var u = value() * Math.PI * 2;
    var v = value() * 2 - 1;
    var k = value();

    var phi = u;
    var theta = Math.acos(v);
    var r = radius * Math.cbrt(k);
    out[0] = r * Math.sin(theta) * Math.cos(phi);
    out[1] = r * Math.sin(theta) * Math.sin(phi);
    out[2] = r * Math.cos(theta);
    return out;
  }

  function quaternion (out) {
    out = out || [];
    var u1 = value();
    var u2 = value();
    var u3 = value();

    var sq1 = Math.sqrt(1 - u1);
    var sq2 = Math.sqrt(u1);

    var theta1 = Math.PI * 2 * u2;
    var theta2 = Math.PI * 2 * u3;

    var x = Math.sin(theta1) * sq1;
    var y = Math.cos(theta1) * sq1;
    var z = Math.sin(theta2) * sq2;
    var w = Math.cos(theta2) * sq2;
    out[0] = x;
    out[1] = y;
    out[2] = z;
    out[3] = w;
    return out;
  }

  function weightedSet (set) {
    set = set || [];
    if (set.length === 0) return null;
    return set[weightedSetIndex(set)].value;
  }

  function weightedSetIndex (set) {
    set = set || [];
    if (set.length === 0) return -1;
    return weighted(set.map(function (s) {
      return s.weight;
    }));
  }

  function weighted (weights) {
    weights = weights || [];
    if (weights.length === 0) return -1;
    var totalWeight = 0;
    var i;

    for (i = 0; i < weights.length; i++) {
      totalWeight += weights[i];
    }

    if (totalWeight <= 0) throw new Error('Weights must sum to > 0');

    var random = value() * totalWeight;
    for (i = 0; i < weights.length; i++) {
      if (random < weights[i]) {
        return i;
      }
      random -= weights[i];
    }
    return 0;
  }

  function gaussian (mean, standardDerivation) {
    mean = defined(mean, 0);
    standardDerivation = defined(standardDerivation, 1);

    // https://github.com/openjdk-mirror/jdk7u-jdk/blob/f4d80957e89a19a29bb9f9807d2a28351ed7f7df/src/share/classes/java/util/Random.java#L496
    if (_hasNextGaussian) {
      _hasNextGaussian = false;
      var result = _nextGaussian;
      _nextGaussian = null;
      return mean + standardDerivation * result;
    } else {
      var v1 = 0;
      var v2 = 0;
      var s = 0;
      do {
        v1 = value() * 2 - 1; // between -1 and 1
        v2 = value() * 2 - 1; // between -1 and 1
        s = v1 * v1 + v2 * v2;
      } while (s >= 1 || s === 0);
      var multiplier = Math.sqrt(-2 * Math.log(s) / s);
      _nextGaussian = (v2 * multiplier);
      _hasNextGaussian = true;
      return mean + standardDerivation * (v1 * multiplier);
    }
  }
}

module.exports = createRandom();