File: src/Point.js
module.exports = Point;
/**
* Point related functions
* @class Point
*/
function Point(){};
/**
* Get the area of a triangle spanned by the three given points. Note that the area will be negative if the points are not given in counter-clockwise order.
* @static
* @method area
* @param {Array} a
* @param {Array} b
* @param {Array} c
* @return {Number}
*/
Point.area = function(a,b,c){
return (((b[0] - a[0])*(c[1] - a[1]))-((c[0] - a[0])*(b[1] - a[1])));
};
Point.left = function(a,b,c){
return Point.area(a,b,c) > 0;
};
Point.leftOn = function(a,b,c) {
return Point.area(a, b, c) >= 0;
};
Point.right = function(a,b,c) {
return Point.area(a, b, c) < 0;
};
Point.rightOn = function(a,b,c) {
return Point.area(a, b, c) <= 0;
};
var tmpPoint1 = [],
tmpPoint2 = [];
/**
* Check if three points are collinear
* @method collinear
* @param {Array} a
* @param {Array} b
* @param {Array} c
* @param {Number} [thresholdAngle=0] Threshold angle to use when comparing the vectors. The function will return true if the angle between the resulting vectors is less than this value. Use zero for max precision.
* @return {Boolean}
*/
Point.collinear = function(a,b,c,thresholdAngle) {
if(!thresholdAngle)
return Point.area(a, b, c) == 0;
else {
var ab = tmpPoint1,
bc = tmpPoint2;
ab[0] = b[0]-a[0];
ab[1] = b[1]-a[1];
bc[0] = c[0]-b[0];
bc[1] = c[1]-b[1];
var dot = ab[0]*bc[0] + ab[1]*bc[1],
magA = Math.sqrt(ab[0]*ab[0] + ab[1]*ab[1]),
magB = Math.sqrt(bc[0]*bc[0] + bc[1]*bc[1]),
angle = Math.acos(dot/(magA*magB));
return angle < thresholdAngle;
}
};
Point.sqdist = function(a,b){
var dx = b[0] - a[0];
var dy = b[1] - a[1];
return dx * dx + dy * dy;
};