[vtkusers] Removing internal cells !

[Berk Geveci]

> Let say i have a square formed with two triangles.
> I extrude this square to get a cube.

Which filter are you using to extrude ? vtkLinearExtrusionFilter
should not create internal faces. 
 
> Because ALL edges are extruded to produce facets, the resulting cube will
> have an unacessary internal diagonal facet.

Is the result of the extrusion
process an unstructured data with 3D cells (in this example, 
wedges) or a polygonal data (triangles and quads) ? 

-Berk