mirror of
https://github.com/photonstorm/phaser
synced 2024-12-01 08:59:31 +00:00
366 lines
9.7 KiB
JavaScript
366 lines
9.7 KiB
JavaScript
var Point = require('../../geom/Point');
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var Class = require('../../utils/Class');
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/**
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* A data representation of a Hermite Curve (see http://en.wikipedia.org/wiki/Cubic_Hermite_spline)
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*
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* A Hermite curve has a start and end point and tangent vectors for both of them.
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* The curve will always pass through the two control points and the shape of it is controlled
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* by the length and direction of the tangent vectors. At the control points the curve will
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* be facing exactly in the vector direction.
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*
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* As these curves change speed (speed = distance between points separated by an equal change in
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* 't' value - see Hermite.getPoint) this class attempts to reduce the variation by pre-calculating
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* the `accuracy` number of points on the curve. The straight-line distances to these points are stored
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* in the private 'points' array, and this information is used by Hermite.findT() to convert a pixel
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* distance along the curve into a 'time' value.
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*
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* Higher `accuracy` values will result in more even movement, but require more memory for the points
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* list. 5 works, but 10 seems to be an ideal value for the length of curves found in most games on
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* a desktop screen. If you use very long curves (more than 400 pixels) you may need to increase
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* this value further.
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*
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* @param {number} p1x - The x coordinate of the start of the curve.
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* @param {number} p1y - The y coordinate of the start of the curve.
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* @param {number} p2x - The x coordinate of the end of the curve.
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* @param {number} p2y - The y coordinate of the end of the curve.
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* @param {number} v1x - The x component of the tangent vector for the start of the curve.
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* @param {number} v1y - The y component of the tangent vector for the start of the curve.
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* @param {number} v2x - The x component of the tangent vector for the end of the curve.
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* @param {number} v2y - The y component of the tangent vector for the end of the curve.
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* @param {number} [accuracy=10] The amount of points to pre-calculate on the curve.
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*/
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var Hermite = new Class({
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initialize:
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function Hermite (p1x, p1y, p2x, p2y, v1x, v1y, v2x, v2y, accuracy)
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{
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if (accuracy === undefined) { accuracy = 10; }
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/**
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* @property {number} _accuracy - The amount of points to pre-calculate on the curve.
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* @private
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*/
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this._accuracy = accuracy;
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/**
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* @property {number} _p1x - The x coordinate of the start of the curve.
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* @private
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*/
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this._p1x = p1x;
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/**
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* @property {number} _p1y - The y coordinate of the start of the curve.
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* @private
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*/
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this._p1y = p1y;
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/**
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* @property {number} _p2x - The x coordinate of the end of the curve.
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* @private
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*/
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this._p2x = p2x;
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/**
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* @property {number} _p2y - The y coordinate of the end of the curve.
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* @private
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*/
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this._p2y = p2y;
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/**
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* @property {number} _v1x - The x component of the tangent vector for the start of the curve.
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* @private
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*/
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this._v1x = v1x;
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/**
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* @property {number} _v1y - The y component of the tangent vector for the start of the curve.
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* @private
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*/
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this._v1y = v1y;
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/**
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* @property {number} _v2x - The x component of the tangent vector for the end of the curve.
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* @private
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*/
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this._v2x = v2x;
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/**
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* @property {number} _v2y - The y component of the tangent vector for the end of the curve.
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* @private
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*/
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this._v2y = v2y;
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/**
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* @property {array} _points - A local array of cached points.
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* @private
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*/
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this._points = [];
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/**
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* @property {Phaser.Point} _temp1 - A local cached Point object.
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* @private
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*/
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this._temp1 = new Point();
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/**
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* @property {Phaser.Point} _temp2 - A local cached Point object.
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* @private
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*/
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this._temp2 = new Point();
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this.recalculate();
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},
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/**
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* Performs the curve calculations.
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*
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* This is called automatically if you change any of the curves public properties, such as `Hermite.p1x` or `Hermite.v2y`.
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*
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* If you adjust any of the internal private values, then call this to update the points.
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*
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* @method Phaser.Hermite#recalculate
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* @return {Phaser.Hermite} This object.
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*/
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recalculate: function ()
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{
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this._ax = (2 * this._p1x - 2 * this._p2x + this._v1x + this._v2x);
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this._ay = (2 * this._p1y - 2 * this._p2y + this._v1y + this._v2y);
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this._bx = (-3 * this._p1x + 3 * this._p2x - 2 * this._v1x - this._v2x);
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this._by = (-3 * this._p1y + 3 * this._p2y - 2 * this._v1y - this._v2y);
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this.length = this.calculateEvenPoints();
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return this;
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},
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/**
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* Calculate a number of points along the curve, based on `Hermite.accuracy`, and stores them in the private `_points` array.
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*
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* @method Phaser.Hermite#calculateEvenPoints
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* @return {number} The total length of the curve approximated as straight line distances between the points.
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*/
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calculateEvenPoints: function ()
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{
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var totalLength = 0;
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this._temp1.setTo(0, 0); // pnt
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this._temp2.setTo(this._p1x, this._p1y); // lastPnt
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this._points[0] = 0;
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for (var i = 1; i <= this._accuracy; i++)
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{
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this.getPoint(i / this._accuracy, this._temp1);
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totalLength += this._temp1.distance(this._temp2);
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this._points[i] = totalLength;
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this._temp2.copyFrom(this._temp1);
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}
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return totalLength;
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},
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/**
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* @name Phaser.Hermite#accuracy
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* @property {number} accuracy - The amount of points to pre-calculate on the curve.
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*/
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accuracy: {
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get: function ()
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{
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return this._accuracy;
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},
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set: function (value)
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{
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if (value !== this._accuracy)
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{
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this._accuracy = value;
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this.recalculate();
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}
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}
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},
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/**
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* @name Phaser.Hermite#p1x
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* @property {number} p1x - The x coordinate of the start of the curve. Setting this value will recalculate the curve.
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*/
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p1x: {
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get: function ()
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{
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return this._p1x;
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},
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set: function (value)
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{
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if (value !== this._p1x)
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{
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this._p1x = value;
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this.recalculate();
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}
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}
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},
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/**
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* @name Phaser.Hermite#p1y
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* @property {number} p1y - The y coordinate of the start of the curve. Setting this value will recalculate the curve.
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*/
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p1y: {
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get: function ()
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{
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return this._p1y;
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},
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set: function (value)
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{
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if (value !== this._p1y)
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{
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this._p1y = value;
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this.recalculate();
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}
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}
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},
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/**
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* @name Phaser.Hermite#p2x
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* @property {number} p2x - The x coordinate of the end of the curve. Setting this value will recalculate the curve.
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*/
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p2x: {
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get: function ()
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{
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return this._p2x;
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},
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set: function (value)
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{
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if (value !== this._p2x)
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{
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this._p2x = value;
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this.recalculate();
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}
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}
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},
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/**
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* @name Phaser.Hermite#p2y
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* @property {number} p2y - The y coordinate of the end of the curve. Setting this value will recalculate the curve.
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*/
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p2y: {
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get: function ()
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{
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return this._p2y;
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},
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set: function (value)
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{
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if (value !== this._p2y)
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{
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this._p2y = value;
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this.recalculate();
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}
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}
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},
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/**
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* @name Phaser.Hermite#v1x
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* @property {number} v1x - The x component of the tangent vector for the start of the curve. Setting this value will recalculate the curve.
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*/
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v1x: {
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get: function ()
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{
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return this._v1x;
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},
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set: function (value)
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{
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if (value !== this._v1x)
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{
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this._v1x = value;
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this.recalculate();
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}
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}
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},
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/**
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* @name Phaser.Hermite#v1y
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* @property {number} v1y - The y component of the tangent vector for the start of the curve. Setting this value will recalculate the curve.
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*/
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v1y: {
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get: function ()
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{
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return this._v1y;
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},
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set: function (value)
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{
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if (value !== this._v1y)
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{
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this._v1y = value;
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this.recalculate();
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}
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}
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},
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/**
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* @name Phaser.Hermite#v2x
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* @property {number} v2x - The x component of the tangent vector for the end of the curve. Setting this value will recalculate the curve.
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*/
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v2x: {
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get: function ()
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{
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return this._v2x;
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},
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set: function (value)
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{
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if (value !== this._v2x)
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{
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this._v2x = value;
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this.recalculate();
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}
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}
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},
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/**
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* @name Phaser.Hermite#v2y
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* @property {number} v2y - The y component of the tangent vector for the end of the curve. Setting this value will recalculate the curve.
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*/
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v2y: {
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get: function ()
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{
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return this._v2y;
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},
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set: function (value)
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{
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if (value !== this._v2y)
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{
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this._v2y = value;
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this.recalculate();
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}
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}
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}
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});
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module.exports = Hermite;
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