code: function() {
              var polygonArea = 0;
              for (var i = 0; i < this.vertices.length - 2; i++) {
                  polygonArea += this.vertices[i+1].pos.minus(this.vertices[0].pos)
                      .cross(this.vertices[i+2].pos.minus(this.vertices[i+1].pos)).length();
              }
              polygonArea /= 2;
              return polygonArea;
          }
docs: Note: could calculate vectors only once to speed up