Adding Gmsh v2.xx Mesh Export Capability - Currently upto 2nd Order Triangles, Quadrangles and Tetrahedra

libsrc/interface/Makefile.am

@@ -6,6 +6,6 @@ noinst_LTLIBRARIES = libinterface.la
 libinterface_la_SOURCES = read_fnf_mesh.cpp readtetmesh.cpp readuser.cpp writeabaqus.cpp writediffpack.cpp \
 	writedolfin.cpp writeelmer.cpp writefeap.cpp writefluent.cpp writegmsh.cpp writejcm.cpp \
 	writepermas.cpp writetecplot.cpp writetet.cpp writetochnog.cpp writeuser.cpp \
-	wuchemnitz.cpp
+	wuchemnitz.cpp writegmsh2.cpp
 
 

libsrc/interface/writegmsh2.cpp

@@ -0,0 +1,261 @@
+/*! \file writegmsh2.cpp
+ *  \brief Export Netgen Mesh in the GMSH v2.xx File format
+ *  \author Philippose Rajan
+ *  \date 02 November 2008
+ *
+ *  This function extends the export capabilities of
+ *  Netgen to include the GMSH v2.xx File Format.
+ *
+ *  Current features of this function include:
+ *
+ *  1. Exports Triangles, Quadrangles and Tetrahedra \n
+ *  2. Supports upto second order elements of each type
+ *
+ */
+
+
+#include <mystdlib.h>
+
+#include <myadt.hpp>
+#include <linalg.hpp>
+#include <csg.hpp>
+#include <meshing.hpp>
+
+namespace netgen
+{
+#include "writeuser.hpp"
+
+// Mapping of entities from Netgen definitions to GMSH definitions
+enum GMSH_ELEMENTS {GMSH_TRIG = 2, GMSH_TRIG6 = 9,
+                    GMSH_QUAD = 3, GMSH_QUAD8 = 16,
+					GMSH_TET = 4, GMSH_TET10 = 11};
+const int triGmsh[7] = {0,1,2,3,6,4,5};
+const int quadGmsh[9] = {0,1,2,3,4,5,8,6,7};
+const int tetGmsh[11] = {0,1,2,3,4,5,8,6,7,10,9};
+
+
+/*! GMSH v2.xx mesh format export function
+ *
+ *  This function extends the export capabilities of
+ *  Netgen to include the GMSH v2.xx File Format.
+ *
+ *  Current features of this function include:
+ *
+ *  1. Exports Triangles, Quadrangles and Tetrahedra \n
+ *  2. Supports upto second order elements of each type
+ *
+ */
+void WriteGmsh2Format (const Mesh & mesh,
+			           const CSGeometry & geom,
+			           const string & filename)
+{
+  ofstream outfile (filename.c_str());
+  outfile.precision(6);
+  outfile.setf (ios::fixed, ios::floatfield);
+  outfile.setf (ios::showpoint);
+
+  int np = mesh.GetNP();  /// number of points in mesh
+  int ne = mesh.GetNE();  /// number of 3D elements in mesh
+  int nse = mesh.GetNSE();  /// number of surface elements (BC)
+  int i, j, k, l;
+
+
+  /*
+   * 3D section : Volume elements (currently only tetrahedra)
+   */
+
+  if ((ne > 0)
+	  && (mesh.VolumeElement(1).GetNP() <= 10)
+	  && (mesh.SurfaceElement(1).GetNP() <= 6))
+  {
+    cout << "Write GMSH v2.xx Format \n";
+    cout << "The GMSH v2.xx export is currently available for elements upto 2nd Order\n" << endl;
+
+    int inverttets = mparam.inverttets;
+    int invertsurf = mparam.inverttrigs;
+
+	/// Prepare GMSH 2.0 file (See GMSH 2.0 Documentation)
+	outfile << "$MeshFormat\n";
+	outfile << (float)2.0 << " "
+	        << (int)0 << " "
+	        << (int)sizeof(double) << "\n";
+    outfile << "$EndMeshFormat\n";
+
+    /// Write nodes
+    outfile << "$Nodes\n";
+    outfile << np << "\n";
+
+    for (i = 1; i <= np; i++)
+    {
+      const Point3d & p = mesh.Point(i);
+      outfile << i << " "; /// node number
+      outfile << p.X() << " ";
+      outfile << p.Y() << " ";
+      outfile << p.Z() << "\n";
+    }
+
+	outfile << "$EndNodes\n";
+
+	/// write elements (both, surface elements and volume elements)
+    outfile << "$Elements\n";
+    outfile << ne + nse << "\n";  ////  number of elements + number of surfaces BC
+
+    for (i = 1; i <= nse; i++)
+    {
+	  int elType = 0;
+
+	  Element2d el = mesh.SurfaceElement(i);
+      if(invertsurf) el.Invert();
+
+	  if(el.GetNP() == 3) elType = GMSH_TRIG;	//// GMSH Type for a 3 node triangle
+	  if(el.GetNP() == 6) elType = GMSH_TRIG6;  //// GMSH Type for a 6 node triangle
+	  if(elType == 0)
+	  {
+	    cout << " Invalid surface element type for Gmsh 2.0 3D-Mesh Export Format !\n";
+		return;
+	  }
+
+	  outfile << i;
+      outfile << " ";
+      outfile << elType;
+      outfile << " ";
+	  outfile << "2";                  //// Number of tags (2 => Physical and elementary entities)
+	  outfile << " ";
+      outfile << mesh.GetFaceDescriptor (el.GetIndex()).BCProperty() << " ";
+      /// that means that physical entity = elementary entity (arbitrary approach)
+      outfile << mesh.GetFaceDescriptor (el.GetIndex()).BCProperty() << " ";
+      for (j = 1; j <= el.GetNP(); j++)
+      {
+        outfile << " ";
+        outfile << el.PNum(triGmsh[j]);
+      }
+      outfile << "\n";
+    }
+
+
+    for (i = 1; i <= ne; i++)
+    {
+      int elType = 0;
+
+	  Element el = mesh.VolumeElement(i);
+      if (inverttets) el.Invert();
+
+	  if(el.GetNP() == 4) elType = GMSH_TET;    //// GMSH Element type for 4 node tetrahedron
+	  if(el.GetNP() == 10) elType = GMSH_TET10; //// GMSH Element type for 10 node tetrahedron
+	  if(elType == 0)
+	  {
+	    cout << " Invalid volume element type for Gmsh 2.0 3D-Mesh Export Format !\n";
+		return;
+	  }
+
+      outfile << nse + i;                       //// element number (Remember to add on surface elements)
+      outfile << " ";
+      outfile << elType;
+      outfile << " ";
+	  outfile << "2";                   //// Number of tags (2 => Physical and elementary entities)
+	  outfile << " ";
+      outfile << 100000 + el.GetIndex();
+      /// that means that physical entity = elementary entity (arbitrary approach)
+      outfile << " ";
+      outfile << 100000 + el.GetIndex();   /// volume number
+      outfile << " ";
+      for (j = 1; j <= el.GetNP(); j++)
+      {
+        outfile << " ";
+        outfile << el.PNum(tetGmsh[j]);
+      }
+      outfile << "\n";
+    }
+    outfile << "$EndElements\n";
+  }
+  /*
+   * End of 3D section
+   */
+
+
+  /*
+   * 2D section : available for triangles and quadrangles
+   *              upto 2nd Order
+   */
+  else if(ne == 0)   /// means that there's no 3D element
+  {
+    cout << "\n Write Gmsh v2.xx Surface Mesh (triangle and/or quadrangles upto 2nd Order)" << endl;
+
+	/// Prepare GMSH 2.0 file (See GMSH 2.0 Documentation)
+	outfile << "$MeshFormat\n";
+	outfile << (float)2.0 << " "
+	        << (int)0 << " "
+	        << (int)sizeof(double) << "\n";
+    outfile << "$EndMeshFormat\n";
+
+	/// Write nodes
+    outfile << "$Nodes\n";
+    outfile << np << "\n";
+
+    for (i = 1; i <= np; i++)
+    {
+      const Point3d & p = mesh.Point(i);
+      outfile << i << " "; /// node number
+      outfile << p.X() << " ";
+      outfile << p.Y() << " ";
+      outfile << p.Z() << "\n";
+    }
+    outfile << "$EndNodes\n";
+
+    /// write triangles & quadrangles
+    outfile << "$Elements\n";
+    outfile << nse << "\n";
+
+    for (k = 1; k <= nse; k++)
+    {
+      int elType = 0;
+
+      const Element2d & el = mesh.SurfaceElement(k);
+
+	  if(el.GetNP() == 3) elType = GMSH_TRIG;   //// GMSH Type for a 3 node triangle
+	  if(el.GetNP() == 6) elType = GMSH_TRIG6;  //// GMSH Type for a 6 node triangle
+      if(el.GetNP() == 4) elType = GMSH_QUAD;   //// GMSH Type for a 4 node quadrangle
+      if(el.GetNP() == 8) elType = GMSH_QUAD8;  //// GMSH Type for an 8 node quadrangle
+	  if(elType == 0)
+	  {
+	    cout << " Invalid surface element type for Gmsh 2.0 2D-Mesh Export Format !\n";
+		return;
+	  }
+
+	  outfile << k;
+      outfile << " ";
+      outfile << elType;
+      outfile << " ";
+	  outfile << "2";
+	  outfile << " ";
+      outfile << mesh.GetFaceDescriptor (el.GetIndex()).BCProperty() << " ";
+      /// that means that physical entity = elementary entity (arbitrary approach)
+      outfile << mesh.GetFaceDescriptor (el.GetIndex()).BCProperty() << " ";
+      for (l = 1; l <= el.GetNP(); l++)
+      {
+        outfile << " ";
+		if((elType == GMSH_TRIG) || (elType == GMSH_TRIG6))
+		{
+		  outfile << el.PNum(triGmsh[l]);
+		}
+		else if((elType == GMSH_QUAD) || (elType == GMSH_QUAD8))
+		{
+	      outfile << el.PNum(quadGmsh[l]);
+		}
+      }
+      outfile << "\n";
+    }
+    outfile << "$EndElements\n";
+  }
+  /*
+   * End of 2D section
+   */
+
+  else
+  {
+    cout << " Invalid element type for Gmsh v2.xx Export Format !\n";
+  }
+} // End: WriteGmsh2Format
+} // End: namespace netgen
+
+

libsrc/interface/writeuser.cpp

@@ -32,6 +32,7 @@ void RegisterUserFormats (Array<const char*> & names)
       "STL Format",
       "VRML Format",
       "Gmsh Format",
+      "Gmsh2 Format"
       "JCMwave Format",
       "TET Format",
       //      { "Chemnitz Format" },
@@ -101,6 +102,11 @@ bool WriteUserFormat (const string & format,
   else if (format == "Gmsh Format")
     WriteGmshFormat (mesh, geom, filename);
 
+  // Philippose - 29/01/2009
+  // Added Gmsh v2.xx export capability
+  else if (format == "Gmsh2 Format")
+    WriteGmsh2Format (mesh, geom, filename);
+
   else if (format == "JCMwave Format")
     WriteJCMFormat (mesh, geom, filename);
 

libsrc/interface/writeuser.hpp

@@ -55,6 +55,14 @@ void WriteGmshFormat (const Mesh & mesh,
                          const CSGeometry & geom,
                          const string & filename);
 
+
+// Philippose - 29/01/2009
+// Added GMSH v2.xx Mesh Export support
+void WriteGmsh2Format (const Mesh & mesh,
+			           const CSGeometry & geom,
+			           const string & filename);
+
+
 extern
 void WriteUserChemnitz (const Mesh & mesh,
 			const string & filename);