[vtkusers] Convex hull of spherical point cloud has holes

[David Cole]

Are you using vtkCleanPolyData on your input data as shown in this example?

    http://www.vtk.org/gitweb?p=VTK.git;a=blob;f=Examples/Modelling/Cxx/Delaunay3D.cxx

Have you read carefully the docs starting here?

    http://www.vtk.org/doc/nightly/html/classvtkDelaunay3D.html#details

If so, ... then hopefully somebody else chimes in, able to address
your specific question about the cells. Are those cells maybe
specified in an opposite direction to the rest of the cells that do
render properly?


HTH,
David C.



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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