• Triangle2D.js

  • ¶ 
    function sign(a, b, c) {
  return (a.x - c.x) * (b.y - c.y) - (b.x - c.x) * (a.y - c.y);
}

function Triangle2D(a, b, c) {
  this.a = a;
  this.b = b;
  this.c = c;
}
  • ¶

    http://stackoverflow.com/a/2049593 doesn’t properly handle points on the edge of the triangle

    Triangle2D.prototype.contains = function (p) {
  var signAB = sign(this.a, this.b, p) < 0;
  var signBC = sign(this.b, this.c, p) < 0;
  var signCA = sign(this.c, this.a, p) < 0;
  return signAB == signBC && signBC == signCA;
};
  • ¶

    Calculates triangle area using Heron’s formula http://en.wikipedia.org/wiki/Triangle#Using_Heron.27s_formula

    Triangle2D.prototype.getArea = function() {
  var ab = this.a.distance(this.b);
  var ac = this.a.distance(this.c);
  var bc = this.b.distance(this.c);

  var s = (ab + ac + bc) / 2; //perimeter
  return Math.sqrt(s * (s - ab) * (s - ac) * (s - bc));
}


module.exports = Triangle2D;