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// -----------------------------------------------------------------------------
//
// 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;
}
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