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41 results

t21.cpp

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  • t3.cpp 5.80 KiB
    // -----------------------------------------------------------------------------
    //
    //  Gmsh C++ tutorial 3
    //
    //  Extruded meshes, ONELAB parameters, options
    //
    // -----------------------------------------------------------------------------
    
    #include <set>
    #include <cmath>
    #include <gmsh.h>
    
    int main(int argc, char **argv)
    {
      gmsh::initialize(argc, argv);
    
      auto createGeometryAndMesh = []()
      {
        // Clear all models and create a new one
        gmsh::clear();
        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);
        gmsh::model::addPhysicalGroup(2, {1}, -1, "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;
        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),
        // angle * Pi / 180) 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. The `angle'
        // parameter is retrieved from the ONELAB database (it can be set
        // interactively in the GUI -- see below):
        std::vector<double> angle;
        gmsh::onelab::getNumber("Parameters/Twisting angle", angle);
        gmsh::model::geo::twist({{2, 50}}, 0, 0.15, 0.25, -2 * h, 0, 0, 1, 0, 0,
                                angle[0] * 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.Color.Points", 255, 165, 0);
      gmsh::option::setColor("General.Color.Text", 255, 255, 255);
      gmsh::option::setColor("Mesh.Color.Points", 255, 0, 0);
    
      // Note that for conciseness "Color." can be ommitted in color options:
      int r, g, b, a;
      gmsh::option::getColor("Geometry.Points", r, g, b, a);
      gmsh::option::setColor("Geometry.Surfaces", r, g, b, a);
    
      // We create a ONELAB parameter to define the angle of the twist. ONELAB
      // parameters can be modified interactively in the GUI, and can be exchanged
      // with other codes connected to the same ONELAB database. The database can be
      // accessed through the Gmsh C++ API using JSON-formatted strings (see
      // https://gitlab.onelab.info/doc/tutorials/-/wikis/ONELAB-JSON-interface for
      // more information):
      gmsh::onelab::set(R"( [
      {
        "type":"number",
        "name":"Parameters/Twisting angle",
        "values":[90],
        "min":0,
        "max":120,
        "step":1
      }
      ] )");
    
      // Create the geometry and mesh it:
      createGeometryAndMesh();
    
      // Launch the GUI and handle the "check" event (recorded in the
      // "ONELAB/Action" parameter) to recreate the geometry with a new twisting
      // angle if necessary:
      auto checkForEvent = [=]() -> bool {
        std::vector<std::string> action;
        gmsh::onelab::getString("ONELAB/Action", action);
        if(action.size() && action[0] == "check") {
          gmsh::onelab::setString("ONELAB/Action", {""});
          createGeometryAndMesh();
          gmsh::graphics::draw();
        }
        return true;
      };
    
      std::set<std::string> args(argv, argv + argc);
      if(!args.count("-nopopup")) {
        gmsh::fltk::initialize();
        while(gmsh::fltk::isAvailable() && checkForEvent())
          gmsh::fltk::wait();
      }
    
      // 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;
    }