[vtk-developers] Polyhedral challenge

David Gobbi david.gobbi at gmail.com
Wed Apr 7 15:00:28 EDT 2010

Hi Casey,

The reason for tolerance on the point insertion is that sometimes when
I contoured the data prior to creating the "cap" polygons, the
contours weren't connected and the creation of the polygons failed.
However, I have written new contouring code and will check to see if
it allows me to set the tolerance back to zero.  If it does, then I'll
commit the code to VTK tomorrow morning.

Right now I'm finding the biggest problem with the class is that it
does triangulation at every step, and does it poorly.  Eventually I
hope to change the algorithm so that it only does triangulation at the
very end.

  - David

On Wed, Apr 7, 2010 at 12:38 PM, Casey Goodlett
<casey.goodlett at kitware.com> wrote:
> Hi David,
> I tested this filter, and it seems very nice.  Thanks for adding this.
> In my test, I also ran into the problem with not getting watertight outputs
> despite having watertight inputs.  I was able to fix this, at least for my
> cases, by setting the tolerance to zero in the point locator on line 309.  I
> think because I have very narrow triangles near the clipping surface some
> points are getting merged by the point locator and the resulting cap polygon
> ends up with a small hole.
> Any reason I should not be doing that?  Should the locator have a zero
> tolerance, or could we set a user controllable tolerance to the class?
> Thanks
> Casey Goodlett
> On Tue, Mar 30, 2010 at 9:16 AM, David Gobbi <david.gobbi at gmail.com> wrote:
>> Hi Will,
>> The vtkClipClosedSurface filter is in VTK cvs now. I've put together a
>> wiki page here:
>> http://www.vtk.org/Wiki/VTK/Closed_Surface_Clipping
>> The test is Graphics/Testing/Tcl/TestClipClosedSurface.tcl
>>  David
>> On Wed, Mar 24, 2010 at 1:20 PM, Will Schroeder
>> <will.schroeder at kitware.com> wrote:
>> > David-
>> > This is good timing. Hua has been looking into the problem too. We came
>> > up
>> > with an initial, very limited solution and it will be good to have a
>> > more
>> > thorough approach. We are looking forward to seeing what you did.
>> > I'm curious, did you create a filter to do this? How did you implement
>> > it in
>> > VTK....
>> > Will
>> >
>> > On Wed, Mar 24, 2010 at 2:39 PM, David Gobbi <david.gobbi at gmail.com>
>> > wrote:
>> >>
>> >> Hi Will,
>> >>
>> >> 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.
>> >>
>> >>   David
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