def addGaussNoise(self, sigma):
        """
        Add gaussian noise.

        :param float sigma: sigma is expressed in percent of the diagonal size of actor.
        
        :Example:
            .. code-block:: python
            
                from vtkplotter import Sphere
                
                Sphere().addGaussNoise(1.0).show()
        """
        sz = self.diagonalSize()
        pts = self.coordinates()
        n = len(pts)
        ns = np.random.randn(n, 3) * sigma * sz / 100
        vpts = vtk.vtkPoints()
        vpts.SetNumberOfPoints(n)
        vpts.SetData(numpy_to_vtk(pts + ns, deep=True))
        self.poly.SetPoints(vpts)
        self.poly.GetPoints().Modified()
        return self
Add gaussian noise.

        :param float sigma: sigma is expressed in percent of the diagonal size of actor.
        
        :Example:
            .. code-block:: python
            
                from vtkplotter import Sphere
                
                Sphere().addGaussNoise(1.0).show()