[vtkusers] Delete Cells from vtkPolyData

[Mike Jackson]

So, just how do I actually delete a cell from a vtkPolyData? I have  
tried a few things but nothing seems to be working. Here is some  
example code of what I am doing:

void removeDuplicateTriangles(vtkPolyData *data)
{
   vtkSmartPointer<vtkIdList> ptList = vtkSmartPointer<vtkIdList>::New 
();
   vtkIdType v0, v1, v2, vv0, vv1, vv2; //vertex Ids
   int count = data->GetNumberOfPolys();
   vtkSmartPointer<vtkIdList> neighbors =  
vtkSmartPointer<vtkIdList>::New();
   neighbors->Allocate(VTK_CELL_SIZE);
   vtkSmartPointer<vtkIdList> cellList =  
vtkSmartPointer<vtkIdList>::New();
   int duplicateCount = 0;
   vtkSmartPointer<vtkIdList> deadCells =  
vtkSmartPointer<vtkIdList>::New();
   std::cout << "Cell Count: " << count << std::endl;
   for (vtkIdType cellId = 0; cellId < count; ++cellId ) //Main loop  
on all polys
   {
     cellList->Reset();
     data->GetCellPoints(cellId, ptList);
     v0 = ptList->GetId(0);
     v1 = ptList->GetId(1);
     v2 = ptList->GetId(2);
     data->GetCellEdgeNeighbors(cellId, v0, v1, neighbors);
     for (int i = 0; i < neighbors->GetNumberOfIds(); ++i)  
{  cellList->InsertUniqueId(neighbors->GetId(i)); }

     data->GetCellEdgeNeighbors(cellId, v1, v2, neighbors);
     for (int i = 0; i < neighbors->GetNumberOfIds(); ++i)  
{  cellList->InsertUniqueId(neighbors->GetId(i)); }

     data->GetCellEdgeNeighbors(cellId, v2, v0, neighbors);
     for (int i = 0; i < neighbors->GetNumberOfIds(); ++i)  
{  cellList->InsertUniqueId(neighbors->GetId(i)); }

     // Now we have a list of Unique Cells, where each cell is a  
triangle
     for (vtkIdType i = 0; i < cellList->GetNumberOfIds(); ++i)
     {
       data->GetCellPoints( cellList->GetId(i), ptList);
       vv0 = ptList->GetId(0);
       vv1 = ptList->GetId(1);
       vv2 = ptList->GetId(2);
       if (  (v0==vv0 || v0==vv1 || v0==vv2) &&
             (v1==vv0 || v1==vv1 || v1==vv2) &&
             (v2==vv0 || v2==vv1 || v2==vv2) )
       {
         std::cout << "Removing Duplicate Triangle {" << cellId << ",  
" << cellList->GetId(i) << "}" << std::endl;
         if (cellId < cellList->GetId(i)) {
           deadCells->InsertUniqueId(cellId);
         } else {
           deadCells->InsertUniqueId(cellList->GetId(i));
         }
       }
     }
   }

   for (vtkIdType i = 0; i < deadCells->GetNumberOfIds(); ++i)
   {
     data->RemoveCellReference(deadCells->GetId(i));
     data->DeleteCell(deadCells->GetId(i));
   }
   std::cout << "Dead Cells: " << deadCells->GetNumberOfIds() <<  
std::endl;

   vtkSmartPointer<vtkCleanPolyData> cleaner =  
vtkSmartPointer<vtkCleanPolyData>::New();
   cleaner->SetInput(data);
   cleaner->Update();
   std::cout << "Cell Count: " << cleaner->GetOutput()- 
 >GetNumberOfPolys() << std::endl;
}

The triangle counts at the start and end are the same. So anyone tell  
me where I am screwing up?

I did read some archive threads where it was suggested to just build  
a new vtkPolyData object instead of trying to change the first  
vtkPolyData Object. Is there truth to that?

Thanks for any help.

--
Mike Jackson
imikejackson & gmail * com