compute_linear_transformation.h

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// ---------------------------------------------------------------------
//
// Copyright (C) 2022 by Luca Heltai
//
// This file is part of the FSI-suite platform, based on the deal.II library.
//
// The FSI-suite platform is free software; you can use it, redistribute it,
// and/or modify it under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation; either version 3.0 of the License,
// or (at your option) any later version. The full text of the license can be
// found in the file LICENSE at the top level of the FSI-suite platform
// distribution.
//
// ---------------------------------------------------------------------
 
#ifndef compute_linear_transformation_h
#define compute_linear_transformation_h
 
#include <deal.II/base/quadrature_lib.h>
 
#include <deal.II/dofs/dof_tools.h>
 
#include <deal.II/fe/fe_nothing.h>
#include <deal.II/fe/fe_values.h>
 
#include <deal.II/grid/grid_generator.h>
 
 
template <int dim, int spacedim, int N>
dealii::Quadrature<spacedim>
compute_linear_transformation(
  const dealii::Quadrature<dim>                &quadrature,
  const std::array<dealii::Point<spacedim>, N> &vertices);
 
 
 
// Template implementation
#ifndef DOXYGEN
template <int dim, int spacedim, int N>
dealii::Quadrature<spacedim>
compute_linear_transformation(
  const dealii::Quadrature<dim>                &quadrature,
  const std::array<dealii::Point<spacedim>, N> &vertices)
{
  Assert(N > 1, dealii::ExcInternalError());
  const auto CellType = dealii::ReferenceCell::n_vertices_to_type(
    dim, N); // understand the kind of reference cell from vertices
 
  dealii::Triangulation<dim, spacedim> tria;
  dealii::GridGenerator::reference_cell(
    tria, CellType); // store reference cell stored in tria
  dealii::FE_Nothing<dim, spacedim> dummy_fe(CellType);
  dealii::DoFHandler<dim, spacedim> dh(tria);
  dh.distribute_dofs(dummy_fe);
  dealii::FEValues<dim, spacedim> fe_values(dummy_fe,
                                            quadrature,
                                            dealii::update_quadrature_points |
                                              dealii::update_JxW_values);
  const auto                     &cell = dh.begin_active();
  for (unsigned int i = 0; i < N; ++i)
    cell->vertex(i) = vertices[i]; // the vertices of this real cell
  fe_values.reinit(cell);
 
  return dealii::Quadrature<spacedim>(
    fe_values.get_quadrature_points(),
    fe_values.get_JxW_values()); // points and weigths in the real space
}
#endif
 
#endif