code: function(x, y, fieldRange, direction, maxViewDistance, entity){
  
              if(fieldRange === void 0){
                  fieldRange = this.fieldRange;
              }
  
              if(direction === void 0){
                  direction = this.direction;
              }
  
              if(fieldRange !== 360 && typeof direction === 'string'){
                  direction = this.directionStringToArray(direction);
              }
              this.direction = direction;
              if(maxViewDistance === void 0){
                  maxViewDistance = this.maxViewDistance;
              }
  
              this.validateFieldRange(fieldRange);
  
              this.visibleTiles = [];
              this.visibleTileKeys = [];
              this.fovMap.reset();
              var entityCanSeeThrough = this.getEntityCanSeeThroughCallback(entity);
              var fov = new ROT.FOV.RecursiveShadowcasting(entityCanSeeThrough);
  
              var setMapTileVisible = this.setMapTileVisible.bind(this);
  
              if(fieldRange === 360){
                  fov.compute(x, y, maxViewDistance, setMapTileVisible);
              }
              else {
                  if(fieldRange === 180){
                      fov.compute180(x, y, maxViewDistance, direction, setMapTileVisible);
                  }
                  else if(fieldRange === 90){
                      fov.compute90(x, y, maxViewDistance, direction, setMapTileVisible);
                  }
              }
          }
docs: Calculates the fovROT data relative to given coords.
  @method update
  @param {Number} x - The map coordinate position to calculate FovROT from on the x axis.
  @param {Number} y - The map coordinate position to calculate FovROT from on the y axis.
  @param {Number} [fieldRange = this.fieldRange || 360] - Field Range of view 90, 180, or 360.
  @param {String|ROT.DIRS[8].x} [direction = this.direction || 'up'] - Direction of fov (not used for fieldRange 360) valid directions: ['up', 'down', 'left', 'right', 'up_left', 'up_right', 'down_left', 'down_right'];.
  @param {Number} [maxViewDistance = this.maxViewDistance] - Max visible distance in tiles.
  @param {Entity} [entity] - The entity to check tile visibility with.