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

[Wes Turner]

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
>
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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
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