[vtkusers] vtkUnstructuredGrid - how to detect if a cell as neighbors?

[Wes Turner]

Look at:

http://www.vtk.org/doc/nightly/html/classvtkMergePoints.html<http://www.vtk.org/doc/nightly/html/classvtkMergePoints.html#3cd8b8f48693148a6b5546c237aab78f>

You can insert your points into a merge points class which will determine if
the point is a duplicate and return the correct point id.  At the end, you
can do:

aVoxelGrid->SetPoints(vMergePts->GetPoints());

- Wes

On Tue, Oct 27, 2009 at 11:16 AM, Teresa Azevedo <dce06003 at fe.up.pt> wrote:

> Hi, Wes. Thank you so much for your quick answer!
>
> If I try your changes, I runs ok: I get two messages.
> But my problem is: I have a set of voxels (with different sizes), from
> which I build my grid. That is, I do not know which voxels share the same
> face points.
> Is there a way to check, on the point list, if a certain point is already
> there?
>
> Teresa
>
>
> Quoting Wes Turner <wes.turner at kitware.com>:
>
>  Teresa,
>>
>> I didn't try to run this, so there may be more issues than just this one,
>> but you are duplicating points not sharing them.  Try the changes I marked
>> below.
>>
>> - Wes
>>
>> On Tue, Oct 27, 2009 at 10:46 AM, Teresa Azevedo <dce06003 at fe.up.pt>
>> wrote:
>>
>>  Hi all.
>>>
>>> I would like to extract the boundary cells of an unstructured grid, that
>>> is, those who have at least one face with no neighbors.
>>> Here is a test code, that builds an unstructured grid, with two voxels
>>> that
>>> share one face. When I check if a cell of the grid has neighbors, the
>>> code
>>> prompts a message box. Unfortunately, when I run it, I never get the
>>> message.
>>> Can someone tell me what I am doing wrong?
>>>
>>>       vtkUnstructuredGrid* aVoxelGrid = vtkUnstructuredGrid::New();
>>>       aVoxelGrid->Allocate(2, 2);
>>>
>>>       vtkPoints* vPts = vtkPoints::New();
>>>       vPts->SetNumberOfPoints(16);
>>>       vPts->InsertPoint( 0, 0, 0, 0);
>>>       vPts->InsertPoint( 1, 1, 0, 0);
>>>       vPts->InsertPoint( 2, 0, 1, 0);
>>>       vPts->InsertPoint( 3, 1, 1, 0);
>>>       vPts->InsertPoint( 4, 0, 0, 1);
>>>       vPts->InsertPoint( 5, 1, 0, 1);
>>>       vPts->InsertPoint( 6, 0, 1, 1);
>>>       vPts->InsertPoint( 7, 1, 1, 1);
>>>
>>>       vtkVoxel* vl = vtkVoxel::New();
>>>       vl->GetPointIds()->SetId(0, 0);
>>>       vl->GetPointIds()->SetId(1, 1);
>>>       vl->GetPointIds()->SetId(2, 2);
>>>       vl->GetPointIds()->SetId(3, 3);
>>>       vl->GetPointIds()->SetId(4, 4);
>>>       vl->GetPointIds()->SetId(5, 5);
>>>       vl->GetPointIds()->SetId(6, 6);
>>>       vl->GetPointIds()->SetId(7, 7);
>>>
>>>       aVoxelGrid->InsertNextCell(VTK_VOXEL, vl->GetPointIds());
>>>
>>>       vPts->InsertPoint( 8, 0, 0, 1);
>>>       vPts->InsertPoint( 9, 1, 0, 1);
>>>       vPts->InsertPoint( 10, 0, 1, 1);
>>>       vPts->InsertPoint( 11, 1, 1, 1);
>>>       vPts->InsertPoint( 12, 0, 0, 2);
>>>       vPts->InsertPoint( 13, 1, 0, 2);
>>>       vPts->InsertPoint( 14, 0, 1, 2);
>>>       vPts->InsertPoint( 15, 1, 1, 2);
>>>
>>>       vtkVoxel* v2 = vtkVoxel::New();
>>>
>>
>>       v2->GetPointIds()->SetId(0, 8);
>>
>>>       v2->GetPointIds()->SetId(1, 9);
>>>       v2->GetPointIds()->SetId(2, 10);
>>>       v2->GetPointIds()->SetId(3, 11);
>>>
>>>
>>       v2->GetPointIds()->SetId(0, 4);
>>       v2->GetPointIds()->SetId(1, 5);
>>       v2->GetPointIds()->SetId(2, 6);
>>       v2->GetPointIds()->SetId(3, 7);
>>
>>
>>        v2->GetPointIds()->SetId(4, 12);
>>>       v2->GetPointIds()->SetId(5, 13);
>>>       v2->GetPointIds()->SetId(6, 14);
>>>       v2->GetPointIds()->SetId(7, 15);
>>>
>>>       aVoxelGrid->InsertNextCell(VTK_VOXEL, v2->GetPointIds());
>>>       aVoxelGrid->SetPoints(vPts);
>>>       aVoxelGrid->Update();
>>>
>>>       vtkGenericCell* cell = vtkGenericCell::New();
>>>       for( int i = 0; i < aVoxelGrid->GetNumberOfCells(); i++ )
>>>       {
>>>               aVoxelGrid->GetCell( i, cell );
>>>               vtkIdList* cellNeighbors = vtkIdList::New();
>>>               int numFaces = cell->GetNumberOfFaces();
>>>               for ( int j = 0; j < numFaces; j++ )
>>>               {
>>>                       vtkCell* face = cell->GetFace( j );
>>>                       aVoxelGrid->GetCellNeighbors( i, face->PointIds,
>>> cellNeighbors);
>>>                       if ( cellNeighbors->GetNumberOfIds() > 0 )
>>>                       {
>>>                               MessageBox(NULL, "Cell has neighbors!",
>>> NULL, MB_OK);
>>>                       }
>>>               }
>>>        }
>>>
>>>
>>> Thank you all.
>>> Teresa
>>>
>>> _______________________________________________
>>> Powered by www.kitware.com
>>>
>>> Visit other Kitware open-source projects at
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>>>
>>> Please keep messages on-topic and check the VTK FAQ at:
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>>>
>>
>>
>> --
>> Wesley D. Turner, Ph.D.
>> Kitware, Inc.
>> Technical Leader
>> 28 Corporate Drive
>> Clifton Park, NY 12065-8662
>> Phone: 518-881-4920
>>
>>
>
> _______________________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
>
> Please keep messages on-topic and check the VTK FAQ at:
> http://www.vtk.org/Wiki/VTK_FAQ
>
> Follow this link to subscribe/unsubscribe:
> http://www.vtk.org/mailman/listinfo/vtkusers
>



-- 
Wesley D. Turner, Ph.D.
Kitware, Inc.
Technical Leader
28 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-881-4920
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