diff --git a/FDTD/processcurrent.cpp b/FDTD/processcurrent.cpp
index eef3367..eec845c 100644
--- a/FDTD/processcurrent.cpp
+++ b/FDTD/processcurrent.cpp
@@ -26,18 +26,6 @@ ProcessCurrent::~ProcessCurrent()
 {
 }
 
-void ProcessCurrent::OpenFile(string outfile)
-{
-	if (file.is_open()) file.close();
-
-	file.open(outfile.c_str());
-	if (file.is_open()==false)
-	{
-		cerr << "Can't open file: " << outfile << endl;
-		return;
-	}
-}
-
 void ProcessCurrent::DefineStartStopCoord(double* dstart, double* dstop)
 {
 	if (Op->SnapToMesh(dstart,start,true,m_start_inside)==false) cerr << "ProcessCurrent::DefineStartStopCoord: Warning: Snapped line outside field domain!!" << endl;
@@ -96,3 +84,8 @@ int ProcessCurrent::Process()
 	file  << setprecision(m_precision) << (0.5 + (double)Eng->GetNumberOfTimesteps())*Op->GetTimestep() << "\t" << current << endl;
 	return GetNextInterval();
 }
+
+void ProcessCurrent::DumpBox2File( string vtkfilenameprefix, bool /*dualMesh*/ ) const
+{
+	Processing::DumpBox2File( vtkfilenameprefix, true );
+}
diff --git a/FDTD/processcurrent.h b/FDTD/processcurrent.h
index 9650378..247ec7d 100644
--- a/FDTD/processcurrent.h
+++ b/FDTD/processcurrent.h
@@ -26,15 +26,12 @@ public:
 	ProcessCurrent(Operator* op, Engine* eng);
 	virtual ~ProcessCurrent();
 
-	virtual void OpenFile(string outfile);
-
 	virtual void DefineStartStopCoord(double* dstart, double* dstop);
 
 	virtual int Process();
 
+	virtual void DumpBox2File( string vtkfilenameprefix, bool dualMesh = false ) const; //!< dump geometry to file
 protected:
-	ofstream file;
-
 	vector<FDTD_FLOAT> v_current;
 };
 
diff --git a/FDTD/processfields.cpp b/FDTD/processfields.cpp
index 5bb3382..75a8257 100644
--- a/FDTD/processfields.cpp
+++ b/FDTD/processfields.cpp
@@ -349,5 +349,3 @@ bool ProcessFields::DumpVectorArray2HDF5(string filename, string name, FDTD_FLOA
 	dataset.write( hdf5array, H5::PredType::NATIVE_FLOAT );
 	return true;
 }
-
-
diff --git a/FDTD/processfields.h b/FDTD/processfields.h
index 6f71635..71611f4 100644
--- a/FDTD/processfields.h
+++ b/FDTD/processfields.h
@@ -39,10 +39,10 @@ public:
 	virtual void SetSubSampling(unsigned int subSampleRate, int dir=-1);
 
 	//! Used file pattern e.g. pattern="tmp/efield_" --> "tmp/efield_000045.vtk" for timestep 45 or "tmp/efield_2.40000e9.vtk" for 2.4GHz E-field dump. (VTK FileType only) \sa SetFileType
-	void SetFilePattern(string fp) {filePattern=fp;}
+	void SetFilePattern(string fp) {m_filename=filePattern=fp;}
 
 	//! Set the filename for a hdf5 data group file (HDF5 FileType only) \sa SetFileType
-	void SetFileName(string fn) {m_fileName=fn;}
+	void SetFileName(string fn) {m_filename=m_fileName=fn;}
 
 	//! Define the Dump-Mode
 	void SetDumpMode(DumpMode mode) {m_DumpMode=mode;}
diff --git a/FDTD/processing.cpp b/FDTD/processing.cpp
index c729859..8467da9 100644
--- a/FDTD/processing.cpp
+++ b/FDTD/processing.cpp
@@ -29,6 +29,7 @@ Processing::Processing(Operator* op, Engine* eng)
 
 Processing::~Processing()
 {
+	file.close();
 }
 
 void Processing::Reset()
@@ -122,6 +123,71 @@ double Processing::CalcLineIntegral(unsigned int* start, unsigned int* stop, int
 	return result;
 }
 
+void Processing::OpenFile( string outfile )
+{
+	if (file.is_open())
+		file.close();
+
+	file.open( outfile.c_str() );
+	if (!file.is_open())
+		cerr << "Can't open file: " << outfile << endl;
+
+	m_filename = outfile;
+}
+
+void Processing::DumpBox2File( string vtkfilenameprefix, bool dualMesh ) const
+{
+	string vtkfilename = vtkfilenameprefix + m_filename + ".vtk";
+
+	ofstream file( vtkfilename.c_str() );
+	if (!file.is_open())
+	{
+		cerr << "Processing::DumpBoxes2File(): Can't open file: " << vtkfilename << endl;
+		return;
+	}
+
+	// normalize coordinates
+	double s1[3], s2[3];
+	for (int i=0; i<3; i++) {
+		s1[i] = min(Op->GetDiscLine(i,start[i],dualMesh),Op->GetDiscLine(i,stop[i],dualMesh));
+		s2[i] = max(Op->GetDiscLine(i,start[i],dualMesh),Op->GetDiscLine(i,stop[i],dualMesh));
+	}
+
+	// fix degenerate box/plane -> line (paraview display problem)
+	if (((s1[0] == s2[0]) && (s1[1] == s2[1])) || ((s1[0] == s2[0]) && (s1[2] == s2[2])) || ((s1[2] == s2[2]) && (s1[1] == s2[1]))) {
+		// line are not displayed correctly -> enlarge
+		for (int i=0; i<3; i++) {
+			double delta = min( Op->GetMeshDelta( i, start,dualMesh ), Op->GetMeshDelta( i, stop,dualMesh ) ) / Op->GetGridDelta() / 4.0;
+			s1[i] -= delta;
+			s2[i] += delta;
+		}
+	}
+
+	file << "# vtk DataFile Version 2.0" << endl;
+	file << "" << endl;
+	file << "ASCII" << endl;
+	file << "DATASET POLYDATA" << endl;
+
+	file << "POINTS 8 float" << endl;
+	file << s1[0] << " " << s1[1] << " " << s1[2] << endl;
+	file << s2[0] << " " << s1[1] << " " << s1[2] << endl;
+	file << s2[0] << " " << s2[1] << " " << s1[2] << endl;
+	file << s1[0] << " " << s2[1] << " " << s1[2] << endl;
+	file << s1[0] << " " << s1[1] << " " << s2[2] << endl;
+	file << s2[0] << " " << s1[1] << " " << s2[2] << endl;
+	file << s2[0] << " " << s2[1] << " " << s2[2] << endl;
+	file << s1[0] << " " << s2[1] << " " << s2[2] << endl;
+
+	file << "POLYGONS 6 30" << endl;
+	file << "4 0 1 2 3" << endl;
+	file << "4 4 5 6 7" << endl;
+	file << "4 7 6 2 3" << endl;
+	file << "4 4 5 1 0" << endl;
+	file << "4 0 4 7 3" << endl;
+	file << "4 5 6 2 1" << endl;
+
+	file.close();
+}
 
 void ProcessingArray::AddProcessing(Processing* proc)
 {
@@ -157,3 +223,9 @@ int ProcessingArray::Process()
 	}
 	return nextProcess;
 }
+
+void ProcessingArray::DumpBoxes2File( string vtkfilenameprefix ) const
+{
+	for (size_t i=0;i<ProcessArray.size();++i)
+		ProcessArray.at(i)->DumpBox2File( vtkfilenameprefix );
+}
diff --git a/FDTD/processing.h b/FDTD/processing.h
index d42d912..5224b51 100644
--- a/FDTD/processing.h
+++ b/FDTD/processing.h
@@ -49,6 +49,9 @@ public:
 	//! Set the dump precision
 	void SetPrecision(unsigned int val) {m_precision = val;}
 
+	virtual void OpenFile( string outfile );
+
+	virtual void DumpBox2File( string vtkfilenameprefix, bool dualMesh = false ) const; //!< dump geometry to file
 protected:
 	Operator* Op;
 	Engine* Eng;
@@ -70,6 +73,9 @@ protected:
 	bool m_start_inside[3];
 	bool m_stop_inside[3];
 
+	ofstream file;
+	string m_filename;
+
 	double CalcLineIntegral(unsigned int* start, unsigned int* stop, int field);
 };
 
@@ -88,6 +94,8 @@ public:
 
 	int Process();
 
+	void DumpBoxes2File( string vtkfilenameprefix ) const;
+
 protected:
 	unsigned int maxInterval;
 	vector<Processing*> ProcessArray;
diff --git a/FDTD/processvoltage.cpp b/FDTD/processvoltage.cpp
index c3eba24..abb8fe8 100644
--- a/FDTD/processvoltage.cpp
+++ b/FDTD/processvoltage.cpp
@@ -24,19 +24,6 @@ ProcessVoltage::ProcessVoltage(Operator* op, Engine* eng) : Processing(op, eng)
 
 ProcessVoltage::~ProcessVoltage()
 {
-	file.close();
-}
-
-void ProcessVoltage::OpenFile(string outfile)
-{
-	if (file.is_open()) file.close();
-
-	file.open(outfile.c_str());
-	if (file.is_open()==false)
-	{
-		cerr << "Can't open file: " << outfile << endl;
-		return;
-	}
 }
 
 int ProcessVoltage::Process()
diff --git a/FDTD/processvoltage.h b/FDTD/processvoltage.h
index 4c3a0df..7272343 100644
--- a/FDTD/processvoltage.h
+++ b/FDTD/processvoltage.h
@@ -27,13 +27,9 @@ public:
 	ProcessVoltage(Operator* op, Engine* eng);
 	virtual ~ProcessVoltage();
 
-	virtual void OpenFile(string outfile);
-
 	virtual int Process();
 
 protected:
-	ofstream file;
-
 	vector<FDTD_FLOAT> voltages;
 };
 
diff --git a/openems.cpp b/openems.cpp
index 016e3c2..a918e6d 100644
--- a/openems.cpp
+++ b/openems.cpp
@@ -47,6 +47,7 @@ openEMS::openEMS()
 	Enable_Dumps = true;
 	DebugMat = false;
 	DebugOp = false;
+	m_debugBox = false;
 	endCrit = 1e-6;
 	m_OverSampling = 4;
 
@@ -93,6 +94,12 @@ bool openEMS::parseCommandLineArgument( const char *argv )
 		DebugOperator();
 		return true;
 	}
+	else if (strcmp(argv,"--debug-boxes")==0)
+	{
+		cout << "openEMS - dumping boxes to 'box_dump*.vtk'" << endl;
+		DebugBox();
+		return true;
+	}
 	else if (strcmp(argv,"--engine=multithreaded")==0)
 	{
 		cout << "openEMS - enabled multithreading" << endl;
@@ -364,6 +371,13 @@ int openEMS::SetupFDTD(const char* file)
 				delete 	ProcTD;
 		}
 	}
+
+	// dump all boxes (voltage, current, fields, ...)
+	if (m_debugBox)
+	{
+		PA->DumpBoxes2File("box_dump_");
+	}
+
 	return 0;
 }
 
diff --git a/openems.h b/openems.h
index 3b144e2..475a5cd 100644
--- a/openems.h
+++ b/openems.h
@@ -42,6 +42,7 @@ public:
 
 	void DebugMaterial() {DebugMat=true;}
 	void DebugOperator() {DebugOp=true;}
+	void DebugBox() {m_debugBox=true;}
 
 protected:
 	void SetupExcitation(TiXmlElement* Excite);
@@ -53,6 +54,7 @@ protected:
 	bool Enable_Dumps;
 	bool DebugMat;
 	bool DebugOp;
+	bool m_debugBox;
 	double endCrit;
 	int m_OverSampling;
 	Operator* FDTD_Op;