code: function( skipParents ){
      skipParents = !!skipParents;
  
  
      this.updateMatrix();
      var invalidWorldMatrix = this._hasInvalidWorldMatrix( skipParents );
      if( invalidWorldMatrix ) {
        this._computeWorldMatrix( skipParents );
      }
  
      for (var i = 0; i < this._children.length; i++) {
        var c = this._children[i];
        c._invalidW = c._invalidW || invalidWorldMatrix;
        c.updateWorldMatrix( true );
      }
  
    }
docs: update world matrix and descendants.