[vtkusers] Delaunay surface triangulation in 3D

[Bill Lorensen]

Just run GeometryFilter without "SomeOtherMethod". I thing the default
behaviour is wnat you want.

On Fri, Oct 17, 2008 at 4:42 PM, Doug Hackworth
<doug.hackworth at vanderbilt.edu> wrote:
>
> Thanks to everyone who's replied so far.  I'm getting on the right track, I
> think, but still have a couple of questions:
>
>
> 1.  Bill said:
>> vtkGeometryFilter will extract surface cells from a volumetric mesh.
>
> The documentation for vtkGeometryFilter certainly makes this sound promising
> ("All 2D faces that are used by only one 3D cell (i.e., boundary faces) are
> extracted") , but it's not clear to me how to actually accomplish this.  The
> methods presented in the class documentation don't make a lot of sense to
> me, and the examples from Kitware (ExtractUGrid.py and pointToCellData.py)
> don't make it obvious to me, either.
>
> I'm imagining something of this sort:
>
> vtkGeometryFilter* geom = vtkGeometryFilter::New();
> geom->SetInput(somePolyData);
> geom->SomeOtherMethods();
> geom->Update();
>
> I'm just not seeing at the moment what SomeOtherMethods() might be... Can
> someone explain this, and/or offer some sample code?
>
>
> 2.  Bjorn said:
>> I never tried it, but vtkSurfaceReconstructionFilter might be one way,
>> but be a little bit of overkill if it is a convex shape like a normal
>> sphere ......
>
> This also sounds promising, since although I'm just working with spheres now
> I will ultimately want to triangulate more complex surfaces which may or may
> not be describable by a mathematical function.  Here again, though, I have
> much the same issue as with vtkGeometryFilter above.  Can anyone enlighten
> me?
>
> Many thanks for your help.
>
> Kindest regards,
> Doug
>
>
>
>
>
>> Doug Hackworth schrieb:
>>>
>>> Greetings.  I have a set of N points that reside on the surface of a
>>> sphere, and I'd like to create a triangular (not tetrahedral) mesh between
>>> these points via Delaunay triangulation.  Using vtkDelaunay2D is out because
>>> it does a different thing (ignoring the Z-coordinate during its
>>> triangulation).  And using vtkDelaunay3D only does part of the right thing
>>> -- it appears to triangulate the surface points nicely, but also creates (as
>>> its primary function) a tetrahedral mesh among all the points in 3
>>> dimensions.
>>>
>>> How can I get a triangulated surface?  Just to be clear on what I want,
>>> the end result should be a hollow volume of triangles, rather like a
>>> geodesic dome.  That make sense?
>>>
>>> It seems as if using vtkDelaunay3D and then extracting the surface
>>> triangles only could be a promising course of action, but I have no idea how
>>> to do this (I'm also not sure that it's guaranteed to produce the right
>>> result).  Can someone offer some guidance on this?  Is there an alternative
>>> method that would be better?  Please, offer me your wisdom.  :-)
>>>
>>> Thanks,
>>> Doug
>>>
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