[vtkusers] Extract PolyData from Unstructured Grid

[Steve Boyd]

Hello,

I have an unstructured grid data set (hexahedron mesh) from which I'd
like to extract a polygon data set representing the surface of the
mesh.  I would like to be able to extract the polygon data (2D cells)
from the outer surface, as well as surfaces that lie 1, 2, 3, (etc) deep
from the outer surface.  
Is there a way to extract these surfaces from different depths of the
mesh?  Do I need to calculate a distance transformation on the points in
the data set first?  Is there a way to do this with existing VTK
classes?

Any direction, suggestions would be welcome!

Sincerely,

Steve

ps. In the man pages I noticed vtkUnstructuredGridGeometryFilter is
mentioned, but apparently not implemented.