phaser/src/actions/SmoothStep.js
2023-10-26 21:07:39 +01:00

61 lines
2.2 KiB
JavaScript

/**
* @author Richard Davey <rich@photonstorm.com>
* @copyright 2013-2023 Photon Storm Ltd.
* @license {@link https://opensource.org/licenses/MIT|MIT License}
*/
var MathSmoothStep = require('../math/SmoothStep');
/**
* Smoothstep is a sigmoid-like interpolation and clamping function.
*
* 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.
*
* @function Phaser.Actions.SmoothStep
* @since 3.0.0
*
* @generic {Phaser.GameObjects.GameObject[]} G - [items,$return]
*
* @param {(array|Phaser.GameObjects.GameObject[])} items - An array of Game Objects. The contents of this array are updated by this Action.
* @param {string} property - The property of the Game Object to interpolate.
* @param {number} min - The minimum interpolation value.
* @param {number} max - The maximum interpolation value.
* @param {boolean} [inc=false] - Should the property value be incremented (`true`) or set (`false`)?
*
* @return {(array|Phaser.GameObjects.GameObject[])} The array of Game Objects that was passed to this Action.
*/
var SmoothStep = function (items, property, min, max, inc)
{
if (inc === undefined) { inc = false; }
var step = Math.abs(max - min) / items.length;
var i;
if (inc)
{
for (i = 0; i < items.length; i++)
{
items[i][property] += MathSmoothStep(i * step, min, max);
}
}
else
{
for (i = 0; i < items.length; i++)
{
items[i][property] = MathSmoothStep(i * step, min, max);
}
}
return items;
};
module.exports = SmoothStep;