code: function _DepthCullingState() {
                  this._isDepthTestDirty = false;
                  this._isDepthMaskDirty = false;
                  this._isDepthFuncDirty = false;
                  this._isCullFaceDirty = false;
                  this._isCullDirty = false;
                  this._isZOffsetDirty = false;
                  this.reset();
              }
docs: Initializes the state.