phaser/v3/merge/hermite/HermiteCurve.js
2017-09-29 16:38:04 +01:00

147 lines
5 KiB
JavaScript

// Created for Phaser 3
// Curve class based work done in three.js by [zz85](http://www.lab4games.net/zz85/blog)
var Class = require('../../../utils/Class');
var Curve = require('../Curve');
var Vector2 = require('../../../math/Vector2');
// Phaser.Curves.Hermite
/**
* A data representation of a Hermite Curve (see http://en.wikipedia.org/wiki/Cubic_Hermite_spline)
*
* A Hermite curve has a start and end point and tangent vectors for both of them.
* The curve will always pass through the two control points and the shape of it is controlled
* by the length and direction of the tangent vectors. At the control points the curve will
* be facing exactly in the vector direction.
*
* As these curves change speed (speed = distance between points separated by an equal change in
* 't' value - see Hermite.getPoint) this class attempts to reduce the variation by pre-calculating
* the `accuracy` number of points on the curve. The straight-line distances to these points are stored
* in the private 'points' array, and this information is used by Hermite.findT() to convert a pixel
* distance along the curve into a 'time' value.
*
* Higher `accuracy` values will result in more even movement, but require more memory for the points
* list. 5 works, but 10 seems to be an ideal value for the length of curves found in most games on
* a desktop screen. If you use very long curves (more than 400 pixels) you may need to increase
* this value further.
*
* @param {number} p1x - The x coordinate of the start of the curve.
* @param {number} p1y - The y coordinate of the start of the curve.
* @param {number} p2x - The x coordinate of the end of the curve.
* @param {number} p2y - The y coordinate of the end of the curve.
* @param {number} v1x - The x component of the tangent vector for the start of the curve.
* @param {number} v1y - The y component of the tangent vector for the start of the curve.
* @param {number} v2x - The x component of the tangent vector for the end of the curve.
* @param {number} v2y - The y component of the tangent vector for the end of the curve.
* @param {number} [accuracy=10] The amount of points to pre-calculate on the curve.
*/
var HermiteCurve = new Class({
Extends: Curve,
initialize:
// p0 = start point
// p1 = end point
// v0 = start tangent point
// v1 = end tangent point
function HermiteCurve (p0, p1, v0, v1)
{
Curve.call(this);
if (Array.isArray(p0))
{
v1 = new Vector2(p0[6], p0[7]);
v0 = new Vector2(p0[4], p0[5]);
p1 = new Vector2(p0[2], p0[3]);
p0 = new Vector2(p0[0], p0[1]);
}
this.p0 = p0;
this.p1 = p1;
this.v0 = v0;
this.v1 = v1;
},
getStartPoint: function (out)
{
if (out === undefined) { out = new Vector2(); }
return out.copy(this.p0);
},
getResolution: function (divisions)
{
return divisions;
},
/**
* Performs the curve calculations.
*
* This is called automatically if you change any of the curves public properties, such as `Hermite.p1x` or `Hermite.v2y`.
*
* If you adjust any of the internal private values, then call this to update the points.
*
* @method Phaser.Hermite#recalculate
* @return {Phaser.Hermite} This object.
*/
recalculate: function ()
{
this._ax = (2 * this._p1x - 2 * this._p2x + this._v1x + this._v2x);
this._ay = (2 * this._p1y - 2 * this._p2y + this._v1y + this._v2y);
this._bx = (-3 * this._p1x + 3 * this._p2x - 2 * this._v1x - this._v2x);
this._by = (-3 * this._p1y + 3 * this._p2y - 2 * this._v1y - this._v2y);
this.length = this.calculateEvenPoints();
return this;
},
getPoint: function (t, out)
{
if (out === undefined) { out = new Vector2(); }
var t2 = t * t;
var t3 = t * t2;
var ax = (2 * this.p0.x - 2 * this.p1.x + this.v0.x + this.v1.x);
var ay = (2 * this.p0.y - 2 * this.p1.y + this.v0.y + this.v1.y);
var bx = (-3 * this.p0.x + 3 * this.p1.x - 2 * this.v0.x - this.v1.x);
var by = (-3 * this.p0.y + 3 * this.p1.y - 2 * this.v0.y - this.v1.y);
out.x = t3 * ax + t2 * bx + t * this.v0.x + this.p0.x;
out.y = t3 * ay + t2 * by + t * this.v0.y + this.p0.y;
return out;
},
// Given u ( 0 .. 1 ), get a t to find p. This gives you points which are equidistant
getUtoTmapping: function (u, distance, divisions)
{
// Find the _points which bracket the distance value
var ti = Math.floor(distance / this.length * divisions);
while (ti > 0 && this._points[ti] > distance)
{
ti--;
}
while (ti < divisions && this._points[ti] < distance)
{
ti++;
}
// Linear interpolation to get a more accurate fix
var dt = this._points[ti] - this._points[ti - 1];
var d = distance - this._points[ti - 1];
return ((ti - 1) / divisions) + d / (dt * divisions);
},
});
module.exports = HermiteCurve;