[vtkusers] Convex hull of spherical point cloud has holes

Bill Lorensen bill.lorensen at gmail.com
Wed Aug 9 16:56:26 EDT 2017

I assume Alpha=0.0 for the Delaunay filter?

Can you post a small, standalone compilable program that produces this output?


On Wed, Aug 9, 2017 at 2:18 PM, Amit via vtkusers <vtkusers at vtk.org> wrote:
> Dear all.
> I have a point cloud made up of points lying on surface of a unit sphere
> stored in a vtkPolyData. I want to get the convex hull of this point cloud
> using the vtkDelaunay3D filter. Then using vtkDataSetSurfaceFilter I want to
> extract the surface of the convex hull. This way, I can get a triangulation
> of the point cloud as a hollow spherical shell. Kindly open the attached
> UnstructuredGrid file in Paraview. It represents the output of vtkDelaunay3D
> filter made up of tetrahedrons. But the surface of the convex-hull has some
> missing triangles. Using the SpreadSheet View, I can see that cells with Ids
> 60, 61, 64 have triangular faces in the missing region. Hence, I would not
> have expected these "hole" in the surface. Can somebody explain why the
> triangles are not being rendered? When I extract surface from this
> unstructured grid I get a spherical shell with missing triangles as holes.
> Regards,
> Amit
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