// ----------------------------------------------------------------------------- // // Gmsh C++ tutorial 3 // // Extruded meshes, options // // ----------------------------------------------------------------------------- #include <set> #include <cmath> #include <gmsh.h> int main(int argc, char **argv) { gmsh::initialize(argc, argv); gmsh::model::add("t3"); // Copied from t1.cpp... double lc = 1e-2; gmsh::model::geo::addPoint(0, 0, 0, lc, 1); gmsh::model::geo::addPoint(.1, 0, 0, lc, 2); gmsh::model::geo::addPoint(.1, .3, 0, lc, 3); gmsh::model::geo::addPoint(0, .3, 0, lc, 4); gmsh::model::geo::addLine(1, 2, 1); gmsh::model::geo::addLine(3, 2, 2); gmsh::model::geo::addLine(3, 4, 3); gmsh::model::geo::addLine(4, 1, 4); gmsh::model::geo::addCurveLoop({4, 1, -2, 3}, 1); gmsh::model::geo::addPlaneSurface({1}, 1); gmsh::model::geo::synchronize(); gmsh::model::addPhysicalGroup(1, {1, 2, 4}, 5); int ps = gmsh::model::addPhysicalGroup(2, {1}); gmsh::model::setPhysicalName(2, ps, "My surface"); // As in `t2.cpp', we plan to perform an extrusion along the z axis. But // here, instead of only extruding the geometry, we also want to extrude the // 2D mesh. This is done with the same `extrude()' function, but by specifying // element 'Layers' (2 layers in this case, the first one with 8 subdivisions // and the second one with 2 subdivisions, both with a height of h/2). The // number of elements for each layer and the (end) height of each layer are // specified in two vectors: double h = 0.1, angle = 90.; std::vector<std::pair<int, int> > ov; gmsh::model::geo::extrude({{2, 1}}, 0, 0, h, ov, {8, 2}, {0.5, 1}); // The extrusion can also be performed with a rotation instead of a // translation, and the resulting mesh can be recombined into prisms (we use // only one layer here, with 7 subdivisions). All rotations are specified by // an an axis point (-0.1, 0, 0.1), an axis direction (0, 1, 0), and a // rotation angle (-Pi/2): gmsh::model::geo::revolve({{2, 28}}, -0.1, 0, 0.1, 0, 1, 0, -M_PI / 2, ov, {7}); // Using the built-in geometry kernel, only rotations with angles < Pi are // supported. To do a full turn, you will thus need to apply at least 3 // rotations. The OpenCASCADE geometry kernel does not have this limitation. // A translation (-2*h, 0, 0) and a rotation ((0,0.15,0.25), (1,0,0), Pi/2) // can also be combined to form a "twist". The last (optional) argument for // the extrude() and twist() functions specifies whether the extruded mesh // should be recombined or not. gmsh::model::geo::twist({{2, 50}}, 0, 0.15, 0.25, -2 * h, 0, 0, 1, 0, 0, angle * M_PI / 180., ov, {10}, {}, true); gmsh::model::geo::synchronize(); // All the extrusion functions return a vector of extruded entities: the "top" // of the extruded surface (in `ov[0]'), the newly created volume (in `ov[1]') // and the tags of the lateral surfaces (in `ov[2]', `ov[3]', ...). // We can then define a new physical volume (with tag 101) to group all the // elementary volumes: gmsh::model::addPhysicalGroup(3, {1, 2, ov[1].second}, 101); gmsh::model::mesh::generate(3); gmsh::write("t3.msh"); // Let us now change some options... Since all interactive options are // accessible through the API, we can for example make point tags visible or // redefine some colors: gmsh::option::setNumber("Geometry.PointNumbers", 1); gmsh::option::setColor("Geometry.Points", 255, 165, 0); gmsh::option::setColor("General.Text", 255, 255, 255); gmsh::option::setColor("Mesh.Points", 255, 0, 0); // Note that color options are special: setting a color option of "X.Y" // actually sets the option "X.Color.Y". int r, g, b, a; gmsh::option::getColor("Geometry.Points", r, g, b, a); gmsh::option::setColor("Geometry.Surfaces", r, g, b, a); // Launch the GUI to see the effects of the color changes: std::set<std::string> args(argv, argv + argc); if(!args.count("-nopopup")) gmsh::fltk::run(); // When the GUI is launched, you can use the `Help->Current Options and // Workspace' menu to see the current values of all options. To save the // options in a file, use `File->Export->Gmsh Options', or through the api: // gmsh::write("t3.opt"); gmsh::finalize(); return 0; }