code: function (deltaTime) {
  
          deltaTime = deltaTime || 16;
  
          if (this._rotating) {
              var radian = (this.autoRotateDirection === 'cw' ? 1 : -1)
                  * this.autoRotateSpeed / 180 * Math.PI;
              this._phi -= radian * deltaTime / 1000;
              this._needsUpdate = true;
          }
          else if (this._rotateVelocity.len() > 0) {
              this._needsUpdate = true;
          }
  
          if (Math.abs(this._zoomSpeed) > 0.01 || this._panVelocity.len() > 0) {
              this._needsUpdate = true;
          }
  
          if (!this._needsUpdate) {
              return;
          }
  
          // Fixed deltaTime
          this._updateDistanceOrSize(Math.min(deltaTime, 50));
          this._updatePan(Math.min(deltaTime, 50));
  
          this._updateRotate(Math.min(deltaTime, 50));
  
          this._updateTransform();
  
          this.target.update();
  
          this.trigger('update');
  
          this._needsUpdate = false;
      }
docs: Call update each frame
  @param  {number} deltaTime Frame time