[Gmsh] Implementing loop direction in C++

[Mikhail Artemiev]

Hi Tolga,
this is a code that solves your problem (based on code 
written by Takuya OSHIMA 
http://www.geuz.org/pipermail/gmsh/2011/006803.html):

#include "Gmsh.h"
#include "GModel.h"
#include "MElement.h"
#include "MVertex.h"
#include <iostream>

int main(int argc, char **argv)
{
   GmshInitialize(argc, argv);

   GModel *m = new GModel;

   GmshSetOption("General", "Terminal", 1.);
   GmshSetOption("General", "Verbosity", 99.);

   const double cl1 = 0.1;
   GVertex *gv1 = m->addVertex(0.0, 0.0, 0.0, cl1);
   GVertex *gv2 = m->addVertex(1.0, 0.0, 0.0, cl1);
   GVertex *gv3 = m->addVertex(0.0, -1.0, 0.0, cl1);
   GVertex *gv4 = m->addVertex(0.0, 0.0, 1.0, cl1);

   GEdge *ge1 = m->addLine(gv1, gv2);
   GEdge *ge2 = m->addLine(gv1, gv3);
   GEdge *ge3 = m->addLine(gv1, gv4);
   GEdge *ge4 = m->addLine(gv2, gv3);
   GEdge *ge5 = m->addLine(gv2, gv4);
   GEdge *ge6 = m->addLine(gv3, gv4);

   std::vector<std::vector<GEdge *> > lineLoop1(1);
   lineLoop1[0].push_back(ge1);
   lineLoop1[0].push_back(ge2);
   lineLoop1[0].push_back(ge4);

   std::vector<std::vector<GEdge *> > lineLoop2(1);
   lineLoop2[0].push_back(ge1);
   lineLoop2[0].push_back(ge3);
   lineLoop2[0].push_back(ge5);
   
   std::vector<std::vector<GEdge *> > lineLoop3(1);
   lineLoop3[0].push_back(ge2);
   lineLoop3[0].push_back(ge3);
   lineLoop3[0].push_back(ge6);
   
   std::vector<std::vector<GEdge *> > lineLoop4(1);
   lineLoop4[0].push_back(ge4);
   lineLoop4[0].push_back(ge5);
   lineLoop4[0].push_back(ge6);

   GFace *gf1 = m->addPlanarFace(lineLoop1);
   GFace *gf2 = m->addPlanarFace(lineLoop2);
   GFace *gf3 = m->addPlanarFace(lineLoop3);
   GFace *gf4 = m->addPlanarFace(lineLoop4);

   std::vector<std::vector<GFace *> > faceLoop1(1);
   faceLoop1[0].push_back(gf1);
   faceLoop1[0].push_back(gf2);
   faceLoop1[0].push_back(gf3);
   faceLoop1[0].push_back(gf4);

   GRegion *gr1 = m->addVolume(faceLoop1);

   m->writeGEO("test.geo");

   m->mesh(3);
   m->writeMSH("test.msh");

   GmshFinalize();
   return 0;
}

Look at "test.geo" to see how Gmsh defines line loops 
(some lines have "-" direction automatically).
Hope this helps.

The code was tested with Gmsh 2.6.0 library.

Mikhail Artemiev