mirror of
https://github.com/photonstorm/phaser
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52 lines
2.1 KiB
JavaScript
52 lines
2.1 KiB
JavaScript
/**
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* @author Richard Davey <rich@photonstorm.com>
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* @copyright 2019 Photon Storm Ltd.
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* @license {@link https://opensource.org/licenses/MIT|MIT License}
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*/
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var MathSmootherStep = require('../math/SmootherStep');
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/**
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* Smootherstep is a sigmoid-like interpolation and clamping function.
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*
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* The function depends on three parameters, the input x, the "left edge" and the "right edge", with the left edge being assumed smaller than the right edge. The function receives a real number x as an argument and returns 0 if x is less than or equal to the left edge, 1 if x is greater than or equal to the right edge, and smoothly interpolates, using a Hermite polynomial, between 0 and 1 otherwise. The slope of the smoothstep function is zero at both edges. This is convenient for creating a sequence of transitions using smoothstep to interpolate each segment as an alternative to using more sophisticated or expensive interpolation techniques.
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*
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* @function Phaser.Actions.SmootherStep
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* @since 3.0.0
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*
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* @generic {Phaser.GameObjects.GameObject[]} G - [items,$return]
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*
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* @param {(array|Phaser.GameObjects.GameObject[])} items - An array of Game Objects. The contents of this array are updated by this Action.
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* @param {string} property - The property of the Game Object to interpolate.
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* @param {number} min - The minimum interpolation value.
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* @param {number} max - The maximum interpolation value.
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* @param {boolean} [inc=false] - Should the values be incremented? `true` or set (`false`)
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*
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* @return {(array|Phaser.GameObjects.GameObject[])} The array of Game Objects that was passed to this Action.
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*/
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var SmootherStep = function (items, property, min, max, inc)
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{
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if (inc === undefined) { inc = false; }
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var step = Math.abs(max - min) / items.length;
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var i;
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if (inc)
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{
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for (i = 0; i < items.length; i++)
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{
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items[i][property] += MathSmootherStep(i * step, min, max);
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}
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}
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else
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{
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for (i = 0; i < items.length; i++)
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{
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items[i][property] = MathSmootherStep(i * step, min, max);
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}
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}
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return items;
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};
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module.exports = SmootherStep;
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