[vtk-developers] Polyhedral challenge

[Will Schroeder]

Awesome David, simply great. You are ahead of us for now, but we will
definitely need something like this soon. Can we ping you when we are ready?


On Thu, Feb 18, 2010 at 3:04 PM, David Gobbi <david.gobbi at gmail.com> wrote:

> Hi Will,
>
> Have you and Hua done the "Clip" part of the cell implementation yet?
> If not, I might have some code that will help.  I've been working on a
> class for clipping of watertight polydata in VTK.  It does the capping
> of the open end after a clip:
>
> - contouring the polydata at the clip plane to get the clip-edges of
> the clipped polygons
> - joining the new edge line segments into a one or more cap polygons
> - identifying complex polygons, i.e. polygons with holes
> - triangulating the polygons (*partly done*)
>
> The "triangulating" part is the only part that I haven't finished
> (that's why I asked about Delaunay earlier).  I'm using ear-cut
> triangulation, which only works for simple polygons, but other than
> that everything is done.
>
>   David
>
>
> On Thu, Feb 18, 2010 at 9:38 AM, Will Schroeder
> <will.schroeder at kitware.com> wrote:
> > Hua and I have made progress on adding a vtkPolyhedron cell to VTK. We
> have
> > a wiki page describing the tasks (which will take some time
> > to implement depending on our funding and
> > schedule http://www.vtk.org/Wiki/VTK/Polyhedron_Support). We are using
> the
> > interpolation method of mean value coordinates which Hua has already
> > implemented, thus far it is a super algorithm. Comments are welcome.
> > We are now starting the integration into vtkUnstructuredGrid. If you are
> > interested let me know and at the appropriate point we can make our git
> > repository available.
> >
> >
> > On Thu, Jan 21, 2010 at 6:53 AM, Will Schroeder <
> will.schroeder at kitware.com>
> > wrote:
> >>
> >> FYI-
> >>
> >> Hua Yang and I are adding a new cell type to VTK: the polyhedral cell.
> >> This is mainly to support our CFD friends who like to compute flow
> solutions
> >> using flux approaches (balance mass and energy in and out of a region).
> >>
> >> One of the key questions is how to interpolate across the interior of
> such
> >> a cell. In the past I have seen two typical approaches 1) tessellate the
> >> polyhedron into tetrahedra, and then use the tetrahedra to interpolate;
> and
> >> 2) use a 1/r**2 (or similar weighting function) to interpolate from the
> cell
> >> nodes to an interior point in the polyhedron. Both approaches have
> problems
> >> with continuity, etc.
> >>
> >> We are also researching other approaches. However in the interest of
> >> completeness, if anybody has suggestions for alternatives we'd love to
> hear
> >> about them.
> >>
> >> Will
> >
> >
> >
> > --
> > William J. Schroeder, PhD
> > Kitware, Inc.
> > 28 Corporate Drive
> > Clifton Park, NY 12065
> > will.schroeder at kitware.com
> > http://www.kitware.com
> > (518) 881-4902
> >
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-- 
William J. Schroeder, PhD
Kitware, Inc.
28 Corporate Drive
Clifton Park, NY 12065
will.schroeder at kitware.com
http://www.kitware.com
(518) 881-4902
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