"Boundary" of unstructured point data

[Tim Hutton]

At 09:45 10/09/99 -0500, you wrote:
>Hello All,
>
>I would like some advice on how to compute the "boundary mesh" of a set
>of points in an UnstructuredGrid dataset. In other words, construct a
>mesh from only the boundary of the set of points.
>
>The dataset is quite large: ~50,000 points, so Delaunay3D for example is
>prohibitively expensive.
>
>I thought perhaps some combination of parameters to vtkDelaunay3D might
>do the trick? Apparently vtkExtractEdges and vtkFeatureEdges require
>polygons and dont work on point data alone.  ContourFilter wont do the
>trick either.

If your points are spread throughout the volume, the only way to do this
that I know of is to use Delaunay but I appreciate this would take a long
time for 50,000 points. 

If on the other hand your points are scattered only on the surface of the
object you can use vtkSurfaceReconstructionFilter followed by Marching
Cubes to generate a mesh that approximates the surface.

Hope this is of some help,

Tim.

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Tim Hutton, Research Assistant            Email: T.Hutton at eastman.ucl.ac.uk
MINORI Project                     http://www.eastman.ucl.ac.uk/~dmi/MINORI
Dental and Medical Informatics                   Tel: [+44] (0171) 915 2344
Eastman Dental Institute                         Fax: [+44] (0171) 915 2303
256 Gray's Inn Road, London WC1X 8LD, UK
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