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//
// Copyright (C) 2005 - 2015 by the deal.II authors
//
// This file is part of the deal.II library.
//
// The deal.II library 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 2.1 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 deal.II distribution.
//
// ---------------------------------------------------------------------
#ifndef dealii__qprojector_h
#define dealii__qprojector_h
#include <deal.II/base/quadrature.h>
#include <deal.II/base/geometry_info.h>
DEAL_II_NAMESPACE_OPEN
/*!@addtogroup Quadrature */
/*@{*/
/**
* This class is a helper class to facilitate the usage of quadrature formulae
* on faces or subfaces of cells. It computes the locations of quadrature
* points on the unit cell from a quadrature object for a manifold of one
* dimension less than that of the cell and the number of the face. For
* example, giving the Simpson rule in one dimension and using the
* project_to_face() function with face number 1, the returned points will be
* (1,0), (1,0.5) and (1,1). Note that faces have an orientation, so when
* projecting to face 3, you will get (0,0), (0,0.5) and (0,1), which is in
* clockwise sense, while for face 1 the points were in counterclockwise
* sense.
*
* For the projection to subfaces (i.e. to the children of a face of the unit
* cell), the same applies as above. Note the order in which the children of a
* face are numbered, which in two dimensions coincides with the orientation
* of the face.
*
* The second set of functions generates a quadrature formula by projecting a
* given quadrature rule on <b>all</b> faces and subfaces. This is used in the
* FEFaceValues and FESubfaceValues classes. Since we now have the quadrature
* points of all faces and subfaces in one array, we need to have a way to
* find the starting index of the points and weights corresponding to one face
* or subface within this array. This is done through the DataSetDescriptor
* member class.
*
* The different functions are grouped into a common class to avoid putting
* them into global namespace. However, since they have no local data, all
* functions are declared <tt>static</tt> and can be called without creating
* an object of this class.
*
* For the 3d case, you should note that the orientation of faces is even more
* intricate than for two dimensions. Quadrature formulae are projected upon
* the faces in their standard orientation, not to the inside or outside of
* the hexahedron. To make things more complicated, in 3d we allow faces in
* two orientations (which can be identified using
* <tt>cell->face_orientation(face)</tt>), so we have to project quadrature
* formula onto faces and subfaces in two orientations. (Refer to the
* documentation of the Triangulation class for a description of the
* orientation of the different faces, as well as to
* @ref GlossFaceOrientation "the glossary entry on face orientation"
* for more information on this.) The DataSetDescriptor member class is used
* to identify where each dataset starts.
*
* @author Wolfgang Bangerth, Guido Kanschat, 1998, 1999, 2003, 2005
*/
template <int dim>
class QProjector
{
public:
/**
* Define a typedef for a quadrature that acts on an object of one dimension
* less. For cells, this would then be a face quadrature.
*/
typedef Quadrature<dim-1> SubQuadrature;
/**
* Compute the quadrature points on the cell if the given quadrature formula
* is used on face <tt>face_no</tt>. For further details, see the general
* doc for this class.
*/
static void project_to_face (const SubQuadrature &quadrature,
const unsigned int face_no,
std::vector<Point<dim> > &q_points);
/**
* Compute the cell quadrature formula corresponding to using
* <tt>quadrature</tt> on face <tt>face_no</tt>. For further details, see
* the general doc for this class.
*/
static Quadrature<dim>
project_to_face (const SubQuadrature &quadrature,
const unsigned int face_no);
/**
* Compute the quadrature points on the cell if the given quadrature formula
* is used on face <tt>face_no</tt>, subface number <tt>subface_no</tt>
* corresponding to RefineCase::Type <tt>ref_case</tt>. The last argument is
* only used in 3D.
*
* @note Only the points are transformed. The quadrature weights are the
* same as those of the original rule.
*/
static void project_to_subface (const SubQuadrature &quadrature,
const unsigned int face_no,
const unsigned int subface_no,
std::vector<Point<dim> > &q_points,
const RefinementCase<dim-1> &ref_case=RefinementCase<dim-1>::isotropic_refinement);
/**
* Compute the cell quadrature formula corresponding to using
* <tt>quadrature</tt> on subface <tt>subface_no</tt> of face
* <tt>face_no</tt> with RefinementCase<dim-1> <tt>ref_case</tt>. The last
* argument is only used in 3D.
*
* @note Only the points are transformed. The quadrature weights are the
* same as those of the original rule.
*/
static Quadrature<dim>
project_to_subface (const SubQuadrature &quadrature,
const unsigned int face_no,
const unsigned int subface_no,
const RefinementCase<dim-1> &ref_case=RefinementCase<dim-1>::isotropic_refinement);
/**
* Take a face quadrature formula and generate a cell quadrature formula
* from it where the quadrature points of the given argument are projected
* on all faces.
*
* The weights of the new rule are replications of the original weights.
* Thus, the sum of the weights is not one, but the number of faces, which
* is the surface of the reference cell.
*
* This in particular allows us to extract a subset of points corresponding
* to a single face and use it as a quadrature on this face, as is done in
* FEFaceValues.
*
* @note In 3D, this function produces eight sets of quadrature points for
* each face, in order to cope possibly different orientations of the mesh.
*/
static Quadrature<dim>
project_to_all_faces (const SubQuadrature &quadrature);
/**
* Take a face quadrature formula and generate a cell quadrature formula
* from it where the quadrature points of the given argument are projected
* on all subfaces.
*
* Like in project_to_all_faces(), the weights of the new rule sum up to the
* number of faces (not subfaces), which is the surface of the reference
* cell.
*
* This in particular allows us to extract a subset of points corresponding
* to a single subface and use it as a quadrature on this face, as is done
* in FESubfaceValues.
*/
static Quadrature<dim>
project_to_all_subfaces (const SubQuadrature &quadrature);
/**
* Project a given quadrature formula to a child of a cell. You may want to
* use this function in case you want to extend an integral only over the
* area which a potential child would occupy. The child numbering is the
* same as the children would be numbered upon refinement of the cell.
*
* As integration using this quadrature formula now only extends over a
* fraction of the cell, the weights of the resulting object are divided by
* GeometryInfo<dim>::children_per_cell.
*/
static
Quadrature<dim>
project_to_child (const Quadrature<dim> &quadrature,
const unsigned int child_no);
/**
* Project a quadrature rule to all children of a cell. Similarly to
* project_to_all_subfaces(), this function replicates the formula generated
* by project_to_child() for all children, such that the weights sum up to
* one, the volume of the total cell again.
*
* The child numbering is the same as the children would be numbered upon
* refinement of the cell.
*/
static
Quadrature<dim>
project_to_all_children (const Quadrature<dim> &quadrature);
/**
* Project the one dimensional rule <tt>quadrature</tt> to the straight line
* connecting the points <tt>p1</tt> and <tt>p2</tt>.
*/
static
Quadrature<dim>
project_to_line(const Quadrature<1> &quadrature,
const Point<dim> &p1,
const Point<dim> &p2);
/**
* Since the project_to_all_faces() and project_to_all_subfaces() functions
* chain together the quadrature points and weights of all projections of a
* face quadrature formula to the faces or subfaces of a cell, we need a way
* to identify where the starting index of the points and weights for a
* particular face or subface is. This class provides this: there are static
* member functions that generate objects of this type, given face or
* subface indices, and you can then use the generated object in place of an
* integer that denotes the offset of a given dataset.
*
* @author Wolfgang Bangerth, 2003
*/
class DataSetDescriptor
{
public:
/**
* Default constructor. This doesn't do much except generating an invalid
* index, since you didn't give a valid descriptor of the cell, face, or
* subface you wanted.
*/
DataSetDescriptor ();
/**
* Static function to generate the offset of a cell. Since we only have
* one cell per quadrature object, this offset is of course zero, but we
* carry this function around for consistency with the other static
* functions.
*/
static DataSetDescriptor cell ();
/**
* Static function to generate an offset object for a given face of a cell
* with the given face orientation, flip and rotation. This function of
* course is only allowed if <tt>dim>=2</tt>, and the face orientation,
* flip and rotation are ignored if the space dimension equals 2.
*
* The last argument denotes the number of quadrature points the lower-
* dimensional face quadrature formula (the one that has been projected
* onto the faces) has.
*/
static
DataSetDescriptor
face (const unsigned int face_no,
const bool face_orientation,
const bool face_flip,
const bool face_rotation,
const unsigned int n_quadrature_points);
/**
* Static function to generate an offset object for a given subface of a
* cell with the given face orientation, flip and rotation. This function
* of course is only allowed if <tt>dim>=2</tt>, and the face orientation,
* flip and rotation are ignored if the space dimension equals 2.
*
* The last but one argument denotes the number of quadrature points the
* lower-dimensional face quadrature formula (the one that has been
* projected onto the faces) has.
*
* Through the last argument anisotropic refinement can be respected.
*/
static
DataSetDescriptor
subface (const unsigned int face_no,
const unsigned int subface_no,
const bool face_orientation,
const bool face_flip,
const bool face_rotation,
const unsigned int n_quadrature_points,
const internal::SubfaceCase<dim> ref_case=internal::SubfaceCase<dim>::case_isotropic);
/**
* Conversion operator to an integer denoting the offset of the first
* element of this dataset in the set of quadrature formulas all projected
* onto faces and subfaces. This conversion operator allows us to use
* offset descriptor objects in place of integer offsets.
*/
operator unsigned int () const;
private:
/**
* Store the integer offset for a given cell, face, or subface.
*/
const unsigned int dataset_offset;
/**
* This is the real constructor, but it is private and thus only available
* to the static member functions above.
*/
DataSetDescriptor (const unsigned int dataset_offset);
};
private:
/**
* Given a quadrature object in 2d, reflect all quadrature points at the
* main diagonal and return them with their original weights.
*
* This function is necessary for projecting a 2d quadrature rule onto the
* faces of a 3d cube, since there we need both orientations.
*/
static Quadrature<2> reflect (const Quadrature<2> &q);
/**
* Given a quadrature object in 2d, rotate all quadrature points by @p
* n_times * 90 degrees counterclockwise and return them with their original
* weights.
*
* This function is necessary for projecting a 2d quadrature rule onto the
* faces of a 3d cube, since there we need all rotations to account for
* face_flip and face_rotation of non-standard faces.
*/
static Quadrature<2> rotate (const Quadrature<2> &q,
const unsigned int n_times);
};
/*@}*/
// ------------------- inline and template functions ----------------
template <int dim>
inline
QProjector<dim>::DataSetDescriptor::
DataSetDescriptor (const unsigned int dataset_offset)
:
dataset_offset (dataset_offset)
{}
template <int dim>
inline
QProjector<dim>::DataSetDescriptor::
DataSetDescriptor ()
:
dataset_offset (numbers::invalid_unsigned_int)
{}
template <int dim>
typename QProjector<dim>::DataSetDescriptor
QProjector<dim>::DataSetDescriptor::cell ()
{
return 0;
}
template <int dim>
inline
QProjector<dim>::DataSetDescriptor::operator unsigned int () const
{
return dataset_offset;
}
/* -------------- declaration of explicit specializations ------------- */
#ifndef DOXYGEN
template <>
void
QProjector<1>::project_to_face (const Quadrature<0> &,
const unsigned int,
std::vector<Point<1> > &);
template <>
void
QProjector<2>::project_to_face (const Quadrature<1> &quadrature,
const unsigned int face_no,
std::vector<Point<2> > &q_points);
template <>
void
QProjector<3>::project_to_face (const Quadrature<2> &quadrature,
const unsigned int face_no,
std::vector<Point<3> > &q_points);
template <>
Quadrature<1>
QProjector<1>::project_to_all_faces (const Quadrature<0> &quadrature);
template <>
void
QProjector<1>::project_to_subface (const Quadrature<0> &,
const unsigned int,
const unsigned int,
std::vector<Point<1> > &,
const RefinementCase<0> &);
template <>
void
QProjector<2>::project_to_subface (const Quadrature<1> &quadrature,
const unsigned int face_no,
const unsigned int subface_no,
std::vector<Point<2> > &q_points,
const RefinementCase<1> &);
template <>
void
QProjector<3>::project_to_subface (const Quadrature<2> &quadrature,
const unsigned int face_no,
const unsigned int subface_no,
std::vector<Point<3> > &q_points,
const RefinementCase<2> &face_ref_case);
template <>
Quadrature<1>
QProjector<1>::project_to_all_subfaces (const Quadrature<0> &quadrature);
template <>
bool
QIterated<1>::uses_both_endpoints (const Quadrature<1> &base_quadrature);
template <>
QIterated<1>::QIterated (const Quadrature<1> &base_quadrature,
const unsigned int n_copies);
#endif // DOXYGEN
DEAL_II_NAMESPACE_CLOSE
#endif
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