[vtkusers] Export mesh of cutting plane

Thu Oct 19 02:04:14 EDT 2017

Hello,

Firstly the cutting algorithms are different between
vtkTableBasedClipDataSet and vtkCutter, thus in general the generated
cross sections are quite different.

I have no idea how to extract a section surface directly from output
of vtkTableBasedClipDataSet, however here are two insufficient ways:
1) vtkTableBasedClipDataSet -> vtkCutter (Cutter.tar.gz)
2) vtkTableBasedClipDataSet -> vtkGeometryFilter -> vtkPolyDataNormals
-> vtkConnectivityFilter (Cutter2.tar.gz)

---
1) This method conducts double cutting using the same plane in turn.
But in order to avoid the broken polygons as output of vtkCutter, the
position of a cutting plain need to be slightly shifted from the used
in vtkTableBasedClipDataSet. This means good accuracy of results are
not be retained.
2) This method divides the surface by feature edges (vtkPolyDataNormals)
and then selects the desired surface among them based on polygonal
connectivity (vtkConnectivityFilter). Here, the origin of a cutting
plane need to be known and be only on the cross section of objects so
as to extract the cross section according to the criteria "extract the
region closest to the origin". In addition, in vtkPolyDataNormals the
feature angle to determine feature edges need to be adjusted in
accordance with each dataset.

I'm sorry for my poor English.

2017-10-18 23:00 GMT+09:00 Fernando Nellmeldin
<f.nellmeldin at open-engineering.com>:
> Hello, sorry for coming back to this topic, but I have found some cases
> where this doesn't work.
>
> I attached a screenshot.
> On top is the 3d mesh cut by a plane parallel to the screen. We can see that
> are some elements (hexahedrons) that got cut and they were split in sets of
> tetrahedrons.
> At the bottom, we see the result of calling vtkCutter ->
> vtkCleanUnstructuredGrid -> vtkXMLUnstructuredGridWriter. The result are all
> quads and all the generated nodes by the cut are gone, and we see no
> triangles.
> I would expect to have the same result that we see on the top, but with 2d
> elements instead of 3d.
>
> Here's my code:
>
> void cutModel(vtkSmartPointer<vtkUnstructuredGrid> model, double normal[3])
> {
> vtkSmartPointer<vtkPlane> plane = vtkSmartPointer<vtkPlane>::New();
> plane->SetOrigin(0.0, 0.0, 0.0);
> plane->SetNormal(normal);
>
> vtkSmartPointer<vtkCutter> cutter = vtkSmartPointer<vtkCutter>::New();
> cutter->SetCutFunction(plane);
> cutter->SetInputData(model);
> cutter->GenerateTrianglesOff();
> cutter->Update();
>
> vtkSmartPointer<vtkCleanUnstructuredGrid> cleaner =
> vtkSmartPointer<vtkCleanUnstructuredGrid>::New();
> cleaner->SetInputConnection(cutter->GetOutputPort());
> cleaner->Update();
> vtkSmartPointer<vtkXMLUnstructuredGridWriter> writer =
> vtkSmartPointer<vtkXMLUnstructuredGridWriter>::New();
> writer->SetFileName("planecut.vtu");
> writer->SetInputConnection(cleaner->GetOutputPort());
> writer->SetDataModeToAscii();
> writer->Write();
> }
>
>
>
> Thank you.
>
>
> On 29 September 2017 at 13:23, Fernando Nellmeldin
> <f.nellmeldin at open-engineering.com> wrote:
>>
>> Hello, that worked as a charm, thank you very much for your time!!
>>
>> On 29 September 2017 at 11:31, kenichiro yoshimi <rccm.kyoshimi at gmail.com>
>> wrote:
>>>
>>> Hi Fernando,
>>>
>>> This will be accomplished by using vtkCleanUnstructuredGrid class
>>> found in ParaView without triangulation. I have attached a simple
>>> code.
>>>
>>> Thanks
>>>
>>> 2017-09-29 16:37 GMT+09:00 Fernando Nellmeldin
>>> <f.nellmeldin at open-engineering.com>:
>>> > Hello. That did the job! (although I get a triangle mesh while the
>>> > initial
>>> > surface was full of sliced hexahedron (quads).
>>> >
>>> > Thank you!
>>> >
>>> > On 29 September 2017 at 04:05, kenichiro yoshimi
>>> > <rccm.kyoshimi at gmail.com>
>>> > wrote:
>>> >>
>>> >> Hello,
>>> >>
>>> >> Using vtkDataSetTriangleFilter is a simple way which allows you to
>>> >> convert polyData to unstructuredGrid. Something like this (VTK-8.0.0):
>>> >> ---
>>> >>   // Create cutter
>>> >>   vtkSmartPointer<vtkCutter> cutter =
>>> >>     vtkSmartPointer<vtkCutter>::New();
>>> >>   cutter->SetCutFunction(plane);
>>> >>   cutter->SetInputConnection(model->GetOutputPort());
>>> >>
>>> >>   // Convert polyData to unstructuredGrid
>>> >>   vtkSmartPointer<vtkDataSetTriangleFilter> triFilter =
>>> >>     vtkSmartPointer<vtkDataSetTriangleFilter>::New();
>>> >>   triFilter->SetInputConnection(cutter->GetOutputPort());
>>> >>   triFilter->Update();
>>> >>
>>> >>   vtkSmartPointer<vtkXMLUnstructuredGridWriter> writer =
>>> >>     vtkSmartPointer<vtkXMLUnstructuredGridWriter>::New();
>>> >>   writer->SetFileName("unstructuredGrid.vtu");
>>> >>   writer->SetInputConnection(triFilter->GetOutputPort());
>>> >>   writer->Write();
>>> >> ---
>>> >>
>>> >> Regards
>>> >>
>>> >> 2017-09-28 23:43 GMT+09:00 Fernando Nellmeldin
>>> >> <f.nellmeldin at open-engineering.com>:
>>> >> > Hello.
>>> >> > I have a method to cut a volume in a vtkUnstructuredGrid given a
>>> >> > vtkPlane.
>>> >> > I'm using vtkTableBasedClipDataSet to extract half of the model,
>>> >> > also as
>>> >> > vtkUnstructuredGrid. This is working.
>>> >> >
>>> >> > Now, I would like to obtain ONLY the surface of the cut, than means:
>>> >> > I
>>> >> > want
>>> >> > a vtkUnstructuredGrid with the nodes and faces being on the surface
>>> >> > of
>>> >> > the
>>> >> > cut.
>>> >> > How can this be achieved?
>>> >> >
>>> >> > I tried using vtkCutter with vtkStripper but the mesh I get doesn't
>>> >> > have
>>> >> > any
>>> >> > cells, only the points and their associated data.
>>> >> >
>>> >> > Here's how my code looks like.
>>> >> >
>>> >> > Thank You!
>>> >> >
>>> >> > vtkSmartPointer<vtkUnstructuredGrid> model =
>>> >> > vtkSmartPointer<vtkUnstructuredGrid>::New();
>>> >> > // fill the ugrid ...
>>> >> >
>>> >> > // Create The Plane to cut
>>> >> > vtkSmartPointer<vtkPlane> plane = vtkSmartPointer<vtkPlane>::New();
>>> >> > plane->SetOrigin(0.0, 0.0, 0.0);
>>> >> > plane->SetNormal(1.0, 0, 0);
>>> >> >
>>> >> > // Code to cut the model in half
>>> >> > vtkSmartPointer<vtkTableBasedClipDataSet> clipDataSet =
>>> >> > vtkSmartPointer<vtkTableBasedClipDataSet>::New();
>>> >> > clipDataSet->SetClipFunction(plane);
>>> >> > clipDataSet->InsideOutOn();
>>> >> > clipDataSet->GenerateClippedOutputOn();
>>> >> > clipDataSet->SetInputConnection(model->GetProducerPort());
>>> >> > clipDataSet->Update();
>>> >> >
>>> >> > // This has half the model, this is Ok but not what I want
>>> >> > vtkSmartPointer<vtkUnstructuredGrid> halfModel =
>>> >> > clipDataSet->GetOutput();
>>> >> >
>>> >> > ////****////
>>> >> > // BEGINS code not working to extract the surface of the cut
>>> >> > vtkSmartPointer<vtkCutter> cutter =
>>> >> > vtkSmartPointer<vtkCutter>::New();
>>> >> > cutter->SetCutFunction(plane);
>>> >> > cutter->SetInputConnection(model->GetProducerPort());
>>> >> > cutter->Update();
>>> >> >
>>> >> > vtkSmartPointer<vtkStripper> stripper =
>>> >> > vtkSmartPointer<vtkStripper>::New();
>>> >> > stripper->SetInputConnection(cutter->GetOutputPort());
>>> >> > stripper->Update();
>>> >> >
>>> >> > vtkSmartPointer<vtkPolyData> pd =
>>> >> > vtkSmartPointer<vtkPolyData>::New();
>>> >> > pd->SetPoints(stripper->GetOutput()->GetPoints());
>>> >> > pd->SetPolys(stripper->GetOutput()->GetLines());
>>> >> >
>>> >> > vtkSmartPointer<vtkUnstructuredGrid> clipped =
>>> >> > vtkSmartPointer<vtkUnstructuredGrid>::New();
>>> >> > clipped->ShallowCopy(pd);
>>> >> >
>>> >> > // Here I see that there is no Cells
>>> >> > clipped->Print(std::cout);
>>> >> >
>>> >> > // ENDS code to extract the surface of the cut
>>> >> > ////****////
>>> >> >
>>> >> > // Write the unstructured grid
>>> >> > vtkSmartPointer<vtkXMLUnstructuredGridWriter> writer =
>>> >> > vtkSmartPointer<vtkXMLUnstructuredGridWriter>::New();
>>> >> > writer->SetFileName("d:/unstructuredGrid.vtu");
>>> >> > writer->SetInput(clipped);
>>> >> > writer->SetDataModeToAscii();
>>> >> > writer->Write();
>>> >> > // file doesnt have any cell, only points and pointdata
>>> >> >
>>> >> > _______________________________________________
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>>> >
>>> >
>>> >
>>> >
>>> > --
>>> > Fernando NELLMELDIN
>>> > Software Engineer
>>> > _______________________________________________________________
>>> >
>>> > Open Engineering s.a.
>>> >
>>> > Rue Bois Saint-Jean 15/1
>>> > B-4102 Seraing (Belgium)
>>> > Tel: +32.4.353.30.34
>>> >
>>> > http://www.open-engineering.com
>>> > https://www.linkedin.com/company/open-engineering?trk=biz-companies-cym
>>> >
>>> > _________________________________________________________________________
>>
>>
>>
>>
>> --
>> Fernando NELLMELDIN
>> Software Engineer
>> _______________________________________________________________
>>
>> Open Engineering s.a.
>>
>> Rue Bois Saint-Jean 15/1
>> B-4102 Seraing (Belgium)
>> Tel: +32.4.353.30.34
>>
>> http://www.open-engineering.com
>> https://www.linkedin.com/company/open-engineering?trk=biz-companies-cym
>> _________________________________________________________________________
>
>
>
>
> --
> Fernando NELLMELDIN
> Software Engineer
> _______________________________________________________________
>
> Open Engineering s.a.
>
> Rue Bois Saint-Jean 15/1
> B-4102 Seraing (Belgium)
> Tel: +32.4.353.30.34
>
> http://www.open-engineering.com
> https://www.linkedin.com/company/open-engineering?trk=biz-companies-cym
> _________________________________________________________________________
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