/
barycentricCoordinates.js
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/
barycentricCoordinates.js
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/*global define*/
define([
'./Cartesian2',
'./Cartesian3',
'./defined',
'./DeveloperError'
], function(
Cartesian2,
Cartesian3,
defined,
DeveloperError) {
"use strict";
var scratchCartesian1 = new Cartesian3();
var scratchCartesian2 = new Cartesian3();
var scratchCartesian3 = new Cartesian3();
/**
* Computes the barycentric coordinates for a point with respect to a triangle.
*
* @exports barycentricCoordinates
*
* @param {Cartesian2|Cartesian3} point The point to test.
* @param {Cartesian2|Cartesian3} p0 The first point of the triangle, corresponding to the barycentric x-axis.
* @param {Cartesian2|Cartesian3} p1 The second point of the triangle, corresponding to the barycentric y-axis.
* @param {Cartesian2|Cartesian3} p2 The third point of the triangle, corresponding to the barycentric z-axis.
* @param {Cartesian3} [result] The object onto which to store the result.
* @returns {Cartesian3} The modified result parameter or a new Cartesian3 instance if one was not provided.
*
* @example
* // Returns Cartesian3.UNIT_X
* var p = new Cesium.Cartesian3(-1.0, 0.0, 0.0);
* var b = Cesium.barycentricCoordinates(p,
* new Cesium.Cartesian3(-1.0, 0.0, 0.0),
* new Cesium.Cartesian3( 1.0, 0.0, 0.0),
* new Cesium.Cartesian3( 0.0, 1.0, 1.0));
*/
var barycentricCoordinates = function(point, p0, p1, p2, result) {
//>>includeStart('debug', pragmas.debug);
if (!defined(point) || !defined(p0) || !defined(p1) || !defined(p2)) {
throw new DeveloperError('point, p0, p1, and p2 are required.');
}
//>>includeEnd('debug');
if (!defined(result)) {
result = new Cartesian3();
}
// Implementation based on http://www.blackpawn.com/texts/pointinpoly/default.html.
var v0, v1, v2;
var dot00, dot01, dot02, dot11, dot12;
if(!defined(p0.z)) {
v0 = Cartesian2.subtract(p1, p0, scratchCartesian1);
v1 = Cartesian2.subtract(p2, p0, scratchCartesian2);
v2 = Cartesian2.subtract(point, p0, scratchCartesian3);
dot00 = Cartesian2.dot(v0, v0);
dot01 = Cartesian2.dot(v0, v1);
dot02 = Cartesian2.dot(v0, v2);
dot11 = Cartesian2.dot(v1, v1);
dot12 = Cartesian2.dot(v1, v2);
} else {
v0 = Cartesian3.subtract(p1, p0, scratchCartesian1);
v1 = Cartesian3.subtract(p2, p0, scratchCartesian2);
v2 = Cartesian3.subtract(point, p0, scratchCartesian3);
dot00 = Cartesian3.dot(v0, v0);
dot01 = Cartesian3.dot(v0, v1);
dot02 = Cartesian3.dot(v0, v2);
dot11 = Cartesian3.dot(v1, v1);
dot12 = Cartesian3.dot(v1, v2);
}
var q = 1.0 / (dot00 * dot11 - dot01 * dot01);
result.y = (dot11 * dot02 - dot01 * dot12) * q;
result.z = (dot00 * dot12 - dot01 * dot02) * q;
result.x = 1.0 - result.y - result.z;
return result;
};
return barycentricCoordinates;
});