Help understanding MappingQ(2) for curved elements

[Matteo Malvestiti]

Good morning,

I've been following the instructions on step-38 to use curved elements.

Problem is: only the elements at the boundary get curved (see attached photo).

Here is a simple test program:

// Mesh

const std::string filename = "../mesh.msh";

std::ifstream input_file(filename);

Triangulation<2,2> triangulation;

GridIn<2> grid_in;

grid_in.attach_triangulation(triangulation);

grid_in.read_msh(input_file);

//Manifold

const Point<2> center(0.0, 0.0);

SphericalManifold<2,2> circular_manifold(center);

triangulation.reset_all_manifolds();

triangulation.set_all_manifold_ids(0);

triangulation.set_manifold (0, circular_manifold);

// DoFHandler, Mapping, and FE

DoFHandler<2,2> dof_handler(triangulation);

MappingQ<2,2> mapping(2);

const FE_Q<2,2> fe(1);

dof_handler.distribute_dofs(fe);

// Output

DataOut<2> data_out;

data_out.attach_dof_handler(dof_handler);

data_out.build_patches(mapping, 5);

std::ofstream out("output_mesh.vtu");

data_out.write(out, DataOutBase::vtu);

I'm surely doing something wrong, any hint?

I leave a zip file attached with all the necessary to compile and run this snippet of code.

[Peter Munch]

Hi Matteo,

it is probably only the output. DataOut::build_patches() has an additional parameter that specifies the curved region (https://www.dealii.org/developer/doxygen/deal.II/classDataOut.html#a1303b5d99f10f3fae984e7d406cfeb37). Select CurvedCellRegion::curved_inner_cells. 

Best,
Peter

[Matteo Malvestiti]

Thanks a lot,

That solved the issue!

I really appreciate your help.

For future readers, here is the correct call to build_patches():

data_out.build_patches(mapping, 5, DataOut<2,2>::CurvedCellRegion::curved_inner_cells);

Best regards,

Matteo Malvestiti