No need to always use a vtkUnstructuredGrid as material output mesh
The !58 (merged) highlighted the fact that always requiring the material output mesh to be a vtkUnstructuredGrid may lead to poor performances when passing the input to the output (passToOutput method). For example if the input is a vtkPolyData then we deep copy the cells into the output.
In fact the type of output (when FillMaterial=On) should be the same as the type of the input.