[vtkusers] Convex hull of spherical point cloud has holes

Bill Lorensen bill.lorensen at gmail.com
Wed Aug 9 19:03:34 EDT 2017

If you save your polydata in a .vtp file you can try this example:

It reports the # of verts, lines, triangles and tets.

On Wed, Aug 9, 2017 at 4:56 PM, Bill Lorensen <bill.lorensen at gmail.com> wrote:
> I assume Alpha=0.0 for the Delaunay filter?
> Can you post a small, standalone compilable program that produces this output?
> Bill
> 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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