[Gmsh] an issue when using api to create second order 2D mesh

Xin Liu liu1512 at purdue.edu
Wed Sep 6 17:44:47 CEST 2017

Dear all,

I am using gmsh API to create a simple second order 2D mesh. The simplified codes are

#include <stdio.h>
#include "Gmsh.h"
#include "GModel.h"

int main(int argc, char **argv)
  GmshInitialize(0, 0);
  GModel *m = new GModel();


  GVertex *v1 = m->addVertex(0, 1, 0, 0.1);
  GVertex *v2 = m->addVertex(0, 2, 0, 0.1);
  GVertex *v3 = m->addVertex(0, 3, 0, 0.1);
  GVertex *v4 = m->addVertex(1, 3, 0, 0.1);
  GVertex *v5 = m->addVertex(1, 2, 0, 0.1);
  GVertex *v6 = m->addVertex(1, 1, 0, 0.1);

  std::vector<GEdge*> edges1;
  edges1.push_back(m->addLine(v1, v2));
  edges1.push_back(m->addLine(v2, v5));
  edges1.push_back(m->addLine(v5, v6));
  edges1.push_back(m->addLine(v6, v1));

  std::vector<GEdge*> edges2;
  edges2.push_back(m->addLine(v2, v3));
  edges2.push_back(m->addLine(v3, v4));
  edges2.push_back(m->addLine(v4, v5));
  edges2.push_back(m->addLine(v5, v2));

  std::vector<std::vector<GEdge*> > loop1;

  std::vector<std::vector<GEdge*> > loop2;

  GFace *f1 = m->addPlanarFace(loop1);
  GFace *f2 = m->addPlanarFace(loop2);

  m->setOrderN(2, 0, 0);
  delete m;

After running the codes, I opened the .msh file with Gmsh. Then, I found there are some repeated nodes at the interface of two surfaces (attachment1). However, if I use gmsh gui to create this model and mesh it, then this issue doesn't exist. Any suggestions or comments are great appreciate.


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