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

[Xin Liu]

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();

  m->setFactory("Gmsh");

  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;
  loop1.push_back(edges1);

  std::vector<std::vector<GEdge*> > loop2;
  loop2.push_back(edges2);


  GFace *f1 = m->addPlanarFace(loop1);
  f1->addPhysicalEntity(1);
  GFace *f2 = m->addPlanarFace(loop2);
  f2->addPhysicalEntity(2);


  m->mesh(2);
  m->setOrderN(2, 0, 0);
  m->writeSC("test.msh");
  delete m;
  GmshFinalize();
}

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.




Thanks
Lambert



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