[vtk-developers] Polyhedral challenge
david.gobbi at gmail.com
Wed Mar 24 14:39:05 EDT 2010
I've finally completed my code for clipping closed polydata shapes and
creating new "cap" polygons so that the result is also a closed
polydata. The solution was more complicated than I originally
thought. After the branch I'll commit it to VTK.
On Thu, Feb 18, 2010 at 2:57 PM, Will Schroeder
<will.schroeder at kitware.com> wrote:
> 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.
>> 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
> (518) 881-4902
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