[vtkusers] decrease triangle size / tesselate?

[Alle Meije Wink]

Hello,

I am trying to show a map on a clipped plane. The scalars for colouring
the plane are the values inside a 3D data set, the plane is a
cross-section through the volume.

I tried two approaches:

1. Use vtkCutter on the volume data to create a cutplane and clip that
   with another vtkCutter that uses the outer normals of the volume.

   This is quite tricky to get to work, because the points of the second
   vtkCutter (after stripping them) are all triangles running through
   the whole volume to one point (in a sort of fan-shape).

   If the points had formed a proper loop, it would have been possible
   to use them with vtkImplictSelectionLoop and that clip the cutplane.

2. Use vtkCutter on the outer normals, and sample the volume on the
   triangles of the cut surface. For resolution, subdivide the triangles
   a number of times.

   The problem with this one is that close to the outer surface the
   triangles are very small already, while the triangles in the centre
   are very large.

   Subdivision needs to be applied 5 or 6 times to get a decent
   resolution in the big triangles, but due to the unnecessary
   computations in the small triangles, this takes hours to visualise
   (interaction is practically impossible).

I have tried to get the first one to work but I'm quite stuck there at
the moment. The documentation has some things abouth re-meshing and
tesselation, could that be a way (instaid of using subdividision) to
make the 2nd approach work? There are no example programs on
tesselations so it's hard to find out...

Thanks,
Alle Meije



-- 

  Brain Mapping Unit
  Dept. of Psychiatry
  University of Cambridge
  Downing Site
  Cambridge CB2 3EB

  tel: (+44) (0)1223 764676
  fax: (+44) (0)1223 336581

  alle_meije at yahoo.co.uk


		
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