How to ReplaceCell to a vtkEmptyCell in vtkUnstructuredGrid ?

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1

I use vtkUnstructuredGrid to store cell dates , and I want replace a cell to a vtkEmptyCell . But fail.

2

I’m pretty confident that just replacing the Types array at id cellId to VTK_EMPTY_CELL should work, if the cell is already allocated. This way you can just shallow-copy the unstructured grid and save memory. Let me write an example:

vtkSmartPointer<vtkUnstructuredGrid> EditUnstructuredGrid(
    vtkUnstructuredGrid* input, vtkIdList* cellIds)
{
  vtkSmartPointer<vtkUnstructuredGrid> output = vtkSmartPointer<vtkUnstructuredGrid>::New();
  output->ShallowCopy(input);

  // We need a new types array with a deep copy so we don't edit the input.
  vtkNew<vtkUnsignedCharArray> types;
  types->DeepCopy(input->GetCellTypesArray());

  // We reset the cells in the output with the new types array
  output->SetCells(types, output->GetCells(), output->GetFaceLocations(), output->GetFaces());

  // We can now edit the types
  for (vtkIdType i = 0; i < cellIds->GetNumberOfIds(); ++i)
  {
    types->SetValue(cellIds->GetId(i), VTK_EMPTY_CELL);
  }

  // WARNING This only works because an empty cell always has less points than
  // any other cell. If you replace a VTK_LINE with a VTK_TRIANGLE,
  // you'll be messing up the cell array.

  return output;
}
3

thank you sir! your example is work well in my software.