marc_to_vtk.py takes Marc input file, subdivides it and creates a
vtkUnstructuredGrid .vtu file with the resulting geometry. Currently
supports hexahedron elements.
vtk_addGridData.py adds nodal/cell data to some VTK grid. It is
essentially vtk_addRectilinearGridData with support for unstructured
grid (.vtu) format, which is marc_to_vtk.py's output.