[vtk-developers] Bug correction in vtkCutter deactivates a use case

[TINGAUD Frederic]

Hi,

 

I just spent some time trying to understand why my vtkCutter on a
surface in a structured grid was no longer working while I remembered
seeing it work. The problem was in fact not in my incorrect use of the
cutter, but in a bug correction that was done in vtkCutter, in patch
8fb71b7fc469d4d24b7ca8b67db4087e88aea1c4:

Before the patch, we had the following, were everything except
UNSTRUCTURED_GRID eventually ended up in DataSetCutter:

 

  if (input->GetDataObjectType() == VTK_STRUCTURED_POINTS ||

      input->GetDataObjectType() == VTK_IMAGE_DATA)

   ...

  if (input->GetDataObjectType() == VTK_STRUCTURED_GRID)

    if (input->GetCell(0))

      {

      int dim = input->GetCell(0)->GetCellDimension();

      // only do 3D structured grids (to be extended in the future)

      if (dim >= 3)

        {

        ...

        }

      }

  if (input->GetDataObjectType() == VTK_RECTILINEAR_GRID)

    ...

  if (input->GetDataObjectType() == VTK_UNSTRUCTURED_GRID)

    ...

  else

    {

    vtkDebugMacro(<< "Executing DataSet Cutter");

    this->DataSetCutter(input, output);

    }

 

The patch consisted in changing all the leftmost "if" in "else if".
However, my use case, with a structured grid of dim < 3 is no longer
treated at all, while it previously was treated in the last else.

 

I am by no mean a specialist in 3D visualization and I don't know if
this DataSetCutter is in fact appropriate for the structured grid
surfaces (the resulting lines are not always visible, so perhaps it used
to work by pure luck). So I don't know if the previous behavior should
be reintroduced, by adding the dim>=3 in the main "else if" or if the
new behavior is intended, in which case a warning should at least be
displayed, to avoid having to debug to find the problem.

I can create the patch in any case, but I need a specialist opinion on
what is intended first.

 

Regards,

 

Frederic

 

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