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#include <cstdio>
#include <gmsh.h>
#include <set>
int main(int argc, char **argv)
{
// initialize Gmsh
gmsh::initialize(argc, argv);
// create a new Gmsh model
gmsh::model::add("my test model");
// create three solids using the OpenCASCADE CAD kernel
int v1 = gmsh::model::occ::addBox(0, 0, 0, 1, 1, 1);
int v2 = gmsh::model::occ::addBox(1, 0, 0, 1, 1, 1);
int v3 = gmsh::model::occ::addSphere(1.5, 0.5, 0.5, 0.25);
// fragment all volumes to have a conformal, non-overlapping geometry
std::vector<std::pair<int, int> > ov;
std::vector<std::vector<std::pair<int, int> > > ovv;
gmsh::model::occ::fragment({{3, v1}, {3, v2}, {3, v3}}, {}, ov, ovv);
// synchronize the CAD model with the Gmsh model
gmsh::model::occ::synchronize();
// generate 3D mesh
gmsh::model::mesh::generate(3);
// explore the mesh: what type of 3D elements do we have?
std::vector<int> eleTypes;
gmsh::model::mesh::getElementTypes(eleTypes, 3);
if(eleTypes.size() != 1) {
gmsh::logger::write("Hybrid meshes not handled in this example!", "error");
return 1;
}
int eleType3D = eleTypes[0];
std::string name;
int dim, order, numNodes, numPrimaryNodes;
std::vector<double> paramCoord;
gmsh::model::mesh::getElementProperties(eleType3D, name, dim, order, numNodes,
paramCoord, numPrimaryNodes);
gmsh::logger::write("3D elements are of type '" + name +
"' (type = " + std::to_string(eleType3D) + ") ");
// iterate over all volumes, get the 3D elements and create new 2D elements
// for all faces
std::vector<std::pair<int, int> > entities;
gmsh::model::getEntities(entities, 3);
for(std::size_t i = 0; i < entities.size(); i++) {
int v = entities[i].second;
std::vector<std::size_t> elementTags, nodeTags;
gmsh::model::mesh::getElementsByType(eleType3D, elementTags, nodeTags, v);
gmsh::logger::write("- " + std::to_string(elementTags.size()) +
" elements in volume " + std::to_string(v));
// get the nodes on the triangular faces of the 3D elements
std::vector<std::size_t> nodes;
gmsh::model::mesh::getElementFaceNodes(eleType3D, 3, nodes, v);
// create a new discrete entity of dimension 2
int s = gmsh::model::addDiscreteEntity(2);
// and add new 2D elements to it, for all faces
int eleType2D = gmsh::model::mesh::getElementType("triangle", order);
gmsh::model::mesh::addElementsByType(s, eleType2D, {}, nodes);
// this will create two 2D elements for each face; to create unique elements
// it would be useful to call getElementFaceNodes() with the extra `primary'
// argument set to 'true' (to only get corner nodes even in the high-order
// case, i.e. consider topological faces), then sort them and make them
// unique.
// this could be enriched with additional info: each topological face could
// be associated with the tag of its parent element; in the sorting process
// (eliminating duplicates) a second tag can be associated for internal
// faces, allowing to keep track of neighbors
}
// gmsh::write("faces.msh");
// iterate over all 2D elements and get integration information
gmsh::model::mesh::getElementTypes(eleTypes, 2);
int eleType2D = eleTypes[0];
std::vector<double> uvw, q;
gmsh::model::mesh::getIntegrationPoints(eleType2D, "Gauss3", uvw, q);
std::vector<double> bf;
int numComp, numOrientations;
gmsh::model::mesh::getBasisFunctions(eleType2D, uvw, "Lagrange", numComp,
bf, numOrientations);
gmsh::model::getEntities(entities, 2);
for(std::size_t i = 0; i < entities.size(); i++) {
int s = entities[i].second;
std::vector<std::size_t> elementTags, nodeTags;
gmsh::model::mesh::getElementsByType(eleType2D, elementTags, nodeTags, s);
gmsh::logger::write("- " + std::to_string(elementTags.size()) +
" elements on surface " + std::to_string(s));
std::vector<double> jac, det, pts;
gmsh::model::mesh::getJacobians(eleType2D, uvw, jac, det, pts, s);
}
std::set<std::string> args(argv, argv + argc);
if(!args.count("-nopopup")) gmsh::fltk::run();
gmsh::finalize();
return 0;
}
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