[vtkusers] mesh quality using vtkDelaunay3D

Andrew Maclean a.maclean at cas.edu.au
Fri Jun 10 20:31:49 EDT 2005

Which do you think looks better?

To me the smoothed marching cubes surface looks far better than the other

Delaunay3D triangulations do not always provide the optimum triangulation it
is also sensitive to the tolerance parameter.


-----Original Message-----
From: Prashanth Dumpuri [mailto:prashanth.dumpuri at vanderbilt.edu] 
Sent: Saturday, 11 June 2005 06:08
To: vtkusers at vtk.org
Subject: [vtkusers] mesh quality using vtkDelaunay3D

  I'm working on creating a tetrahedral mesh from a MR image volume.
Here's a pseudo-code of what i'm doing:
vtkMarchingCubes mcubes
   mcubes SetInput [image_reader GetOutput]
   # this ensures that i encompass the entire volume in marchin cubes
   mcubes SetValue 0 1  
   mcubes Update

vtkDecimate and vtkSmoothPolyDataFilter the marching cubes surface till
i get a smooth surface.

vtkDelaunay3D del
  del SetInput <smoothed_marching_cubes_surface.vtk>
  del SetTolerance 0.005
  del BoundingTriangulationOff
  del Update
When i look at the tetrahedral mesh created by the Delaunay3D filter,
the mesh does not conform to the surface description provided by
<smoothed_marching_cubes_surface.vtk>. I have attached two pictures :
one of the smoothed marching cubes surface and the other of the
tetrahedral mesh created from the smoothed marching cubes surface. I
used vtkMeshQuality to look at the aspect ratio of the tets and a
majority of them have an aspect ratio less than 0.25. 
I would appreciate it if someone can give me pointers on how to improve
the mesh quality.

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