[vtkusers] slice structured grid with polydata

[Justin Weber]

I didn't realize this earlier but the vtkClipDataSet tetrahedralizes the
mesh before slicing? It seems that this is required for the algorithm. Do
you know of any ways to prevent this?

BTW, here is the link to the example:
http://www.vtk.org/Wiki/VTK/Examples/Python/Meshes/vtkClipDataSetWithPolydata

Justin

On Mon, Mar 7, 2016 at 5:30 PM, Cory Quammen <cory.quammen at kitware.com>
wrote:

> That's great, Justin. Thanks for reporting back.
>
> Cory
>
> On Mon, Mar 7, 2016 at 4:04 PM, Justin Weber <onlyjus at gmail.com> wrote:
>
>> Cory,
>>
>> Thanks for your help. I got it working! I might put the code up as an
>> example.
>>
>>
>> Justin
>>
>> On Thu, Feb 18, 2016 at 10:58 PM, Cory Quammen <cory.quammen at kitware.com>
>> wrote:
>>
>>> Justin,
>>>
>>> There is nothing canned in VTK to do this, but with some work you should
>>> be able to get there using an implicit function created from your STL file.
>>> At a high level, what you would do is create an instance of
>>> vtkImplicitPolyDataDistance. Set its input to the poly data from the STL
>>> file. Then, create a new point data array in your structured grid that
>>> stores the value from the implicit poly data distance filter. Negative
>>> values will be inside the poly data, positive values outside, and 0 at the
>>> surface. Finally, use vtkClipDataSet to clip the structured grid a function
>>> value 0. This should give you back an unstructured grid in approximately
>>> the shape of your input STL. It won't be exact because of the interpolation
>>> used by vtkClipDataSet, but it should be close.
>>>
>>> Hope that helps.
>>>
>>> Cory
>>>
>>> On Thu, Feb 18, 2016 at 10:08 PM, Justin Weber <onlyjus at gmail.com>
>>> wrote:
>>>
>>>> I would like to generate a "cutcell" mesh using vtk by slicing a
>>>> structured grid with polydata loaded from a STL file. The resulting mesh
>>>> would be an unstructured grid.
>>>>
>>>> Are there any tools in vtk to accomplish this?
>>>>
>>>> I can create the structured grid and polydata successfully. Now I just
>>>> need an algorithm to slice the structured mesh with the polydata surface.
>>>>
>>>> In my searching I could not find anything. However, I could accomplish
>>>> this by ray casting to find the intersections between the structured grid
>>>> and the polydata. Then using those points to create the unstructured grid.
>>>>
>>>> See attached 2d sketch.
>>>>
>>>> Thanks!
>>>> Justin
>>>>
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>>>
>>>
>>> --
>>> Cory Quammen
>>> R&D Engineer
>>> Kitware, Inc.
>>>
>>
>>
>
>
> --
> Cory Quammen
> R&D Engineer
> Kitware, Inc.
>
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