SimModSuite

SimModSuite is a C++ and Python meshing library developed by Simmetrix.

SimModSuite Documentation and Tutorials can be found on the SimModSuite Documentation Site. This method may not be the most efficient way to walk the boundary nodes, but it is intuitive.

Walk Along the Boundary of a Mesh

This tutorial shows how to open a mesh and a model using the SimModSuite API and extract the coordinates of the boundary nodes. This is an extract from the DG2MeshwBoundary Repository.

std::vector<std::array<double, 2>> readWallFromSimMesh(const std::string &model_filename, const std::string &mesh_filename, pProgress progress) {
  const auto model = GM_load(model_filename.c_str(), NULL, progress);
  const auto mesh = M_load(mesh_filename.c_str(), model, progress);

  // find the leftmost mesh vertex to start searching for wall vertices
  VIter v_iter = M_vertexIter(mesh);
  pVertex leftmost_vertex = nullptr;
  pVertex current_vertex = nullptr;

  while (current_vertex = VIter_next(v_iter)) {
    if (!leftmost_vertex) {
      leftmost_vertex = current_vertex;
    } else {
      double current_coords[3];
      double leftmost_coords[3];
      V_coord(current_vertex, current_coords);
      V_coord(leftmost_vertex, leftmost_coords);
      if (current_coords[0] < leftmost_coords[0]) {
        leftmost_vertex = current_vertex;
      }
    }
  }
  VIter_delete(v_iter);

  // traverse the boundary edges to collect wall vertices
  std::vector<std::array<double, 2>> wall_points;
  current_vertex = leftmost_vertex;
  pEdge last_boundary_edge = nullptr;
  while (true) {
    pEdge current_boundary_edge = nullptr;
    const int n_adj_edges = V_numEdges(current_vertex);
    for ( int i = 0; i < n_adj_edges; ++i) {
      current_boundary_edge = V_edge(current_vertex, i);
      if (E_numFaces(current_boundary_edge) == 1 && current_boundary_edge != last_boundary_edge) {
        last_boundary_edge = current_boundary_edge;
        break;
      }
    }
    if (current_boundary_edge == nullptr) {
      double current_coords[3];
      V_coord(current_vertex, current_coords);
      printf("Error: For vertex at (%.6f, %.6f, %.6f), no boundary edge found but it has %d adjacent edges.\n",
             current_coords[0], current_coords[1], current_coords[2], n_adj_edges);
      std::abort();
    }

    // find the next vertex on the boundary edge
    current_vertex = E_otherVertex(current_boundary_edge, current_vertex);

    // store the vertex coordinates
    double coords[3];
    V_coord(current_vertex, coords);
    wall_points.push_back({coords[0], coords[1]});

    // complete the loop
    if (current_vertex == leftmost_vertex) {
      break; // completed the loop
    }
  }

  return wall_points;
}