[vtkusers] vtkTubeFilter: Cubic interpolation - Howto?

[Divya Rathore]

Hello,

I have to plot a tube of given points in 3D and I am using following 
pipeline:

(vtkCellArray + vtkFloatArray) --->   vtkPolyData ---->
--->  vtkTubeFilter   ---->   vtkPolyDataMapper   -----> vtkActor

The tube comes up nicely but it seems the interpolation to join the 3D 
coordinates is 'linear'. How can I change this interpolation to cubic so as 
to have smoother curves?
It's kind of urgent!

Thank you in advance,
- D Rathore