code: function DirectionalLight(name, direction, scene) {
              var _this = _super.call(this, name, scene) || this;
              _this._shadowFrustumSize = 0;
              _this._shadowOrthoScale = 0.5;
              _this.autoUpdateExtends = true;
              // Cache
              _this._orthoLeft = Number.MAX_VALUE;
              _this._orthoRight = Number.MIN_VALUE;
              _this._orthoTop = Number.MIN_VALUE;
              _this._orthoBottom = Number.MAX_VALUE;
              _this.position = direction.scale(-1.0);
              _this.direction = direction;
              return _this;
          }
docs: Creates a DirectionalLight object in the scene, oriented towards the passed direction (Vector3).
  The directional light is emitted from everywhere in the given direction.
  It can cast shawdows.
  Documentation : http://doc.babylonjs.com/tutorials/lights