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WeightedRandomize.js
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WeightedRandomize.js
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/**
* @author Richard Davey <rich@phaser.io>
* @copyright 2013-2024 Phaser Studio Inc.
* @license {@link https://opensource.org/licenses/MIT|MIT License}
*/
var GetTilesWithin = require('./GetTilesWithin');
var MATH = require('../../math');
/**
* Randomizes the indexes of a rectangular region of tiles (in tile coordinates) within the
* specified layer. Each tile will receive a new index. New indexes are drawn from the given
* weightedIndexes array. An example weighted array:
*
* [
* { index: 6, weight: 4 }, // Probability of index 6 is 4 / 8
* { index: 7, weight: 2 }, // Probability of index 7 would be 2 / 8
* { index: 8, weight: 1.5 }, // Probability of index 8 would be 1.5 / 8
* { index: 26, weight: 0.5 } // Probability of index 27 would be 0.5 / 8
* ]
*
* The probability of any index being choose is (the index's weight) / (sum of all weights). This
* method only modifies tile indexes and does not change collision information.
*
* @function Phaser.Tilemaps.Components.WeightedRandomize
* @since 3.0.0
*
* @param {number} tileX - The left most tile index (in tile coordinates) to use as the origin of the area.
* @param {number} tileY - The top most tile index (in tile coordinates) to use as the origin of the area.
* @param {number} width - How many tiles wide from the `tileX` index the area will be.
* @param {number} height - How many tiles tall from the `tileY` index the area will be.
* @param {object[]} weightedIndexes - An array of objects to randomly draw from during
* randomization. They should be in the form: { index: 0, weight: 4 } or
* { index: [0, 1], weight: 4 } if you wish to draw from multiple tile indexes.
* @param {Phaser.Tilemaps.LayerData} layer - The Tilemap Layer to act upon.
*/
var WeightedRandomize = function (tileX, tileY, width, height, weightedIndexes, layer)
{
if (!weightedIndexes) { return; }
var i;
var tiles = GetTilesWithin(tileX, tileY, width, height, null, layer);
var weightTotal = 0;
for (i = 0; i < weightedIndexes.length; i++)
{
weightTotal += weightedIndexes[i].weight;
}
if (weightTotal <= 0) { return; }
for (i = 0; i < tiles.length; i++)
{
var rand = MATH.RND.frac() * weightTotal;
var sum = 0;
var randomIndex = -1;
for (var j = 0; j < weightedIndexes.length; j++)
{
sum += weightedIndexes[j].weight;
if (rand <= sum)
{
var chosen = weightedIndexes[j].index;
randomIndex = Array.isArray(chosen)
? chosen[Math.floor(MATH.RND.frac() * chosen.length)]
: chosen;
break;
}
}
tiles[i].index = randomIndex;
}
};
module.exports = WeightedRandomize;