[vtkusers] Extract PolyData from Unstructured Grid

[Will Schroeder]

Hi Steve-

>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!

You can extract the surface of an unstructured grid with 
vtkGeometryFilter  or vtkExtractUnstructuredGrid.

I can't think of an easy way to extract different depths of the mesh. The 
connectivity filter could be modified to mark points with depth, and then a 
threshold could be applied to pull out appropriate portions of the mesh.

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

I have modified references to vtkUnstructuredGridGeometryFilter (and 
replaced them with vtkExtractUnstructuredGrid). Thanks for the feedback.

Will


William J. Schroeder, Ph.D
Kitware, Inc.
469 Clifton Corporate Parkway
Clifton Park, NY 12065
will.schroeder at kitware.com
1-518-371-3971 x102
1-518-371-3971 (fax)