those functions have to be removed and wVtkExport has to be used instead. However, there are currently two difficulties.
Each save_MPI function save on different meshes, a contact mesh has to be created and given to one of the VtkExport.
wVtkExport do not support MPI for now and some #ifdef VTK_HAS_MPI are currently unwanted in wVtkExport. At the end of the day, instead of using element[i]->no-1 it will be required to use a map to translate the global mesh id to local ones, those map will be trivial for one proc cases, and more complex when MPI is used. This will allow each proc to write only the data that it has computed. Moreover, Vtk MPI initialization and finalization will have to be used. Those can be done using some unwanted #ifdef VTK_HAS_MPI or using more elegant strategies or requiring VTK binaries that support MPI.