add support for exporting mesh to user file format (at least some of the formats available internally)

libsrc/interface/CMakeLists.txt

@@ -3,7 +3,7 @@ add_library(interface ${NG_LIB_TYPE}
         nginterface.cpp nginterface_v2.cpp 
         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
+        writepermas.cpp writetecplot.cpp writetet.cpp writetochnog.cpp writeuser.cpp writevtk.cpp
         wuchemnitz.cpp writegmsh2.cpp writeOpenFOAM15x.cpp 
         )
 

libsrc/interface/writeuser.cpp

@@ -39,8 +39,9 @@ namespace netgen
       "VRML Format", ".*",
       "Gmsh Format", ".gmsh",
       "Gmsh2 Format", ".gmsh2",
+      "VTK Format", ".vtk",
       "OpenFOAM 1.5+ Format", "*",
-	  "OpenFOAM 1.5+ Compressed", "*",
+	    "OpenFOAM 1.5+ Compressed", "*",
       "JCMwave Format", ".jcm",
       "TET Format", ".tet",
       //      { "Chemnitz Format" },
@@ -128,6 +129,9 @@ bool WriteUserFormat (const string & format,
   else if (format == "Gmsh2 Format")
     WriteGmsh2Format (mesh, geom, filename);
 
+  else if (format == "VTK Format")
+    WriteVtkFormat (mesh, filename);
+
   // Philippose - 25/10/2009
   // Added OpenFOAM 1.5+ Mesh export capability
   else if (format == "OpenFOAM 1.5+ Format")

libsrc/interface/writeuser.hpp

@@ -73,6 +73,9 @@ void WriteGmsh2Format (const Mesh & mesh,
                        const NetgenGeometry & geom,
                        const string & filename);
 
+extern
+void WriteVtkFormat (const Mesh & mesh,
+                      const string & filename);
 
 // Philippose - 25/10/2009
 // Added OpenFOAM 1.5+ Mesh Export support

libsrc/interface/writevtk.cpp

@@ -0,0 +1,124 @@
+/*************************************
+ * Write Gmsh file
+ * First issue the 04/26/2004 by Paul CARRICO (paul.carrico@free.fr)
+ * At the moment, the GMSH format is available for
+ * linear tetrahedron elements i.e. in 3D
+ * (based on Neutral Format)
+ *
+ * Second issue the 05/05/2004 by Paul CARRICO
+ * Thanks to Joachim Schoeberl for the correction of a minor bug
+ * the 2 initial Gmsh Format (i.e. volume format and surface format) are group together)
+ * in only one file
+ **************************************/
+
+#include <mystdlib.h>
+
+#include <myadt.hpp>
+#include <linalg.hpp>
+#include <csg.hpp>
+#include <meshing.hpp>
+
+namespace netgen
+{
+#include "writeuser.hpp"
+
+  extern MeshingParameters mparam;
+
+
+/*
+ *  VTK mesh format
+ *  points, elements, surface elements
+ */
+
+void WriteVtkFormat (const Mesh & mesh,
+                      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 point
+  int ne = mesh.GetNE();  /// number of element
+  int nse = mesh.GetNSE();  /// number of surface element (BC)
+
+  outfile << "# vtk DataFile Version 2.0\n";
+  outfile << "Created with netgen\n";
+  outfile << "ASCII\n";
+  outfile << "DATASET UNSTRUCTURED_GRID\n";
+  
+  outfile << "POINTS " << np << " double\n";
+  for (int i=0; i<np; i++)
+  {
+	auto & p = mesh.Point(i+1);
+    outfile << p[0] << " " << p[1] << " " << p[2] << "\n";
+  }
+
+  std::vector<int> types;
+  if (ne > 0)
+  {
+    unsigned int size = 0;
+    for (int i=0; i<ne; i++)
+	  size += mesh.VolumeElement(i+1).GetNV() + 1; // only save "linear" corners
+
+    outfile << "CELLS " << ne << " " << size << "\n";
+    for (int i=0; i<ne; i++)
+    {
+	  auto& el = mesh.VolumeElement(i+1);
+	  switch (el.GetType())
+	  {
+	  case TET:
+	  case TET10: // reorder to follow VTK convention & zero based indices
+        outfile << 4 << " " << el[0]-1 << " " << el[1]-1 << " " << el[3]-1 << " " << el[2]-1 << "\n";
+		types.push_back(10);
+		break;
+	  case PRISM: // reorder to follow VTK convention & zero based indices
+        outfile << 6 << " "
+				<< el[0]-1 << " " << el[2]-1 << " " << el[1]-1 << " " 
+				<< el[3]-1 << " " << el[5]-1 << " " << el[4]-1 << "\n";
+		types.push_back(13);
+		break;
+	  default:
+	    throw ngcore::Exception("Unexpected element type");
+		break;
+	  }
+    }
+  }
+  else
+  {
+    unsigned int size = 0;
+    for (int i=0; i<ne; i++)
+	  size += mesh.SurfaceElement(i+1).GetNV() + 1;
+
+    outfile << "CELLS " << nse << " " << size << "\n";
+    for (int i=0; i<nse; i++)
+    {
+	  auto& el = mesh.SurfaceElement(i+1);
+	  switch (el.GetType())
+	  {
+	  case TRIG:
+	  case TRIG6:
+        outfile << el[0]-1 << " " << el[1]-1 << " " << el[2]-1 << "\n";
+		types.push_back(5);
+		break;
+	  case QUAD:
+        outfile << el[0]-1 << " " << el[1]-1 << " " << el[2]-1 << " " << el[3]-1 << "\n";
+		types.push_back(9);
+	  default:
+	    throw ngcore::Exception("Unexpected element type");
+		break;
+	  }
+    }
+  }
+
+  outfile << "CELL_TYPES " << types.size() << "\n";
+  for (auto type_id: types)
+  {
+    outfile << type_id << "\n";
+  }
+
+  outfile.close();
+}
+}
+
+

nglib/nglib.cpp

@@ -18,6 +18,7 @@
 #include <geometry2d.hpp>
 #include <meshing.hpp>
 #include <../visualization/soldata.hpp>
+#include <../interface/writeuser.hpp>
 
 #ifdef OCCGEOMETRY
 #include <occgeom.hpp>
@@ -154,6 +155,25 @@ namespace nglib
 
 
 
+   DLL_HEADER void Ng_ExportMesh(Ng_Mesh * ng_mesh, Ng_Export_Formats format, const char* filename)
+   {
+      Mesh * mesh = (Mesh*)ng_mesh;
+      switch (format)
+      {
+      case NG_GMSH:
+         WriteUserFormat( "Gmsh Format", *mesh, filename ); break;
+      case NG_GMSH2:
+         WriteUserFormat( "Gmsh2 Format", *mesh, filename ); break;
+      case NG_VTK:
+         WriteUserFormat( "VTK Format", *mesh, filename ); break;
+      case NG_FLUENT:
+         WriteUserFormat( "Fluent Format", *mesh, filename ); break;
+      case NG_ABAQUS:
+         WriteUserFormat( "Abaqus Format", *mesh, filename ); break;
+      }
+   }
+
+
 
    // Merge another mesh file into the currently loaded one
    DLL_HEADER Ng_Result Ng_MergeMesh( Ng_Mesh* mesh, const char* filename)
@@ -265,6 +285,8 @@ namespace nglib
          n = 5; break;
       case NG_PRISM:
          n = 6; break;
+      case NG_HEX:
+         n = 8; break;
       case NG_TET10:
          n = 10; break;
       default: break;
@@ -279,8 +301,6 @@ namespace nglib
    }
 
 
-
-
    // Obtain the number of points in the mesh
    DLL_HEADER int Ng_GetNP (Ng_Mesh * mesh)
    {
@@ -366,6 +386,7 @@ namespace nglib
       case 4: et = NG_TET; break;
       case 5: et = NG_PYRAMID; break;
       case 6: et = NG_PRISM; break;
+      case 8: et = NG_HEX; break;
       case 10: et = NG_TET10; break;
       default:
          et = NG_TET; break; // for the compiler
@@ -1202,6 +1223,53 @@ namespace nglib
    }
 
 
+   void Ng_SetRefinementFlag (Ng_Mesh * ng_mesh, int ei, int flag)
+   {
+      Mesh * mesh = (Mesh*) ng_mesh;
+      
+      if (mesh->GetDimension() == 3)
+      {
+         mesh->VolumeElement(ei).SetRefinementFlag (flag != 0);
+         mesh->VolumeElement(ei).SetStrongRefinementFlag (flag >= 10);
+      }
+      else
+      {
+         mesh->SurfaceElement(ei).SetRefinementFlag (flag != 0);
+         mesh->SurfaceElement(ei).SetStrongRefinementFlag (flag >= 10);
+      }
+   }
+
+
+   void Ng_SetSurfaceRefinementFlag (Ng_Mesh * ng_mesh, int ei, int flag)
+   {
+      Mesh * mesh = (Mesh*) ng_mesh;
+
+      if (mesh->GetDimension() == 3)
+      {
+         mesh->SurfaceElement(ei).SetRefinementFlag (flag != 0);
+         mesh->SurfaceElement(ei).SetStrongRefinementFlag (flag >= 10);
+      }
+   }
+
+
+   void Ng_Refine (Ng_Mesh * ng_mesh)
+   {
+      Mesh * mesh = (Mesh*) ng_mesh;
+      BisectionOptions biopt;
+      biopt.usemarkedelements = 1;
+      biopt.refine_p = 0; // only h-refinement
+      biopt.refine_hp = 0;
+
+      if (auto geom = mesh->GetGeometry())
+         geom->GetRefinement().Bisect (*mesh, biopt);
+      else
+         Refinement().Bisect (*mesh, biopt);
+
+      // not sure if this is needed?
+      //mesh -> UpdateTopology();
+      //mesh -> GetCurvedElements().SetIsHighOrder (false);
+   }
+
 
 
    DLL_HEADER void Ng_2D_Uniform_Refinement (Ng_Geometry_2D * geom,
@@ -1212,7 +1280,6 @@ namespace nglib
 
 
 
-
    DLL_HEADER void Ng_STL_Uniform_Refinement (Ng_STL_Geometry * geom,
       Ng_Mesh * mesh)
    {
@@ -1312,7 +1379,6 @@ void Ng_InitSolutionData (Ng_SolutionData * soldata) { ; }
 */
 
 // Force linking libinterface to libnglib
-#include <../interface/writeuser.hpp>
 void MyDummyToForceLinkingLibInterface(Mesh &mesh, NetgenGeometry &geom)
 {
   netgen::WriteUserFormat("", mesh, /* geom, */ "");

nglib/nglib.h

@@ -71,7 +71,7 @@ enum Ng_Surface_Element_Type
 
 /// Currently implemented volume element types
 enum Ng_Volume_Element_Type 
-   { NG_TET = 1, NG_PYRAMID = 2, NG_PRISM = 3, NG_TET10 = 4 };
+   { NG_TET = 1, NG_PYRAMID = 2, NG_PRISM = 3, NG_TET10 = 4, NG_HEX = 5 };
 
 /// Values returned by Netgen functions
 enum Ng_Result 
@@ -258,6 +258,13 @@ DLL_HEADER void Ng_SaveMesh(Ng_Mesh * mesh, const char* filename);
 DLL_HEADER Ng_Mesh * Ng_LoadMesh(const char* filename);
 
 
+/*! \brief Save mesh in various external formats, e.g. fluent, gmsh, gmsh2, vtk, ...
+
+*/
+enum Ng_Export_Formats { NG_GMSH = 1, NG_GMSH2 = 2, NG_VTK = 3, NG_FLUENT = 4, NG_ABAQUS = 5 };
+DLL_HEADER void Ng_ExportMesh(Ng_Mesh * mesh, Ng_Export_Formats format, const char* filename);
+
+
 /*! \brief Merge a Netgen VOL Mesh from disk into an existing mesh in memory
 
     A Netgen mesh saved in the internal VOL format can be merged 
@@ -362,7 +369,7 @@ DLL_HEADER void Ng_AddSurfaceElement (Ng_Mesh * mesh, Ng_Surface_Element_Type et
 
 */
 DLL_HEADER void Ng_AddVolumeElement (Ng_Mesh * mesh, Ng_Volume_Element_Type et, int * pi, int domain=1);
-  
+
 // ------------------------------------------------------------------
 
 
@@ -712,6 +719,14 @@ DLL_HEADER Ng_Result Ng_OCC_GetFMap(Ng_OCC_Geometry * geom,
 DLL_HEADER void Ng_Uniform_Refinement (Ng_Mesh * mesh);
 
 
+// non-uniform mesh refinement
+DLL_HEADER void Ng_SetRefinementFlag (Ng_Mesh * ng_mesh, int ei, int flag);
+
+DLL_HEADER void Ng_SetSurfaceRefinementFlag (Ng_Mesh * ng_mesh, int ei, int flag);
+
+DLL_HEADER void Ng_Refine (Ng_Mesh * ng_mesh);
+
+
 // uniform mesh refinement with geometry adaption:
 
 DLL_HEADER void Ng_2D_Uniform_Refinement (Ng_Geometry_2D * geom,