Add SubsamplingVTKWriter to OutputWriter.

Subsampling level is read from the config file and defaults to 0.

dune/dorie/interface/output.hh

@@ -9,6 +9,7 @@
 #include <dune/common/parametertree.hh>
 
 #include <dune/grid/io/file/vtk/vtksequencewriter.hh>
+#include <dune/grid/io/file/vtk/subsamplingvtkwriter.hh>
 
 #include <dune/pdelab/gridfunctionspace/gridfunctionspaceutilities.hh>
 
@@ -46,6 +47,7 @@ private:
 	using GV = typename Traits::GV;
 	
 	using VTKWriter = Dune::VTKSequenceWriter<GV>;
+	using SubVTK = Dune::SubsamplingVTKWriter<GV>;
 	using UDGF = Dune::PDELab::DiscreteGridFunction<GFS,U>;
 	using FluxDGF = Dune::Dorie::GradientFluxAdapter<GFS,U,Param>;
 	using ConDGF = Dune::Dorie::ConductivityAdapter<Traits,Param>;
@@ -72,11 +74,12 @@ public:
 	 */
 	OutputWriter (Dune::ParameterTree& _inifile, GV& gv, GFS& gfs, Param& param, U& unew)
 	: OutputWriterBase<Traits>(),
-		vtkwriter(gv,
+		vtkwriter(std::make_shared<SubVTK>(gv,
+			Dune::refinementLevels(_inifile.get<int>(
+				"output.subsamplingLevel", 0))),
 			_inifile.get<std::string>("output.fileName"),
 			_inifile.get<std::string>("output.outputPath"),
-			"./",
-			Dune::VTK::nonconforming),
+			"./"),
 		udgf(gfs,unew),
 		fluxdgf(gfs,unew,param,udgf),
 		condgf(gv,param),