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//
// Copyright (C) 2001 - 2016 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__mapping_q_h
#define dealii__mapping_q_h
#include <deal.II/base/config.h>
#include <deal.II/fe/mapping_q_generic.h>
DEAL_II_NAMESPACE_OPEN
template <int dim, typename PolynomialType> class TensorProductPolynomials;
/*!@addtogroup mapping */
/*@{*/
/**
* A class that implements a polynomial mapping $Q_p$ of degree $p$ on cells
* at the boundary of the domain (or, if requested in the constructor, for all
* cells) and linear mappings for interior cells.
*
* The class is in fact poorly named since (unless explicitly specified during
* the construction of the object, see below), it does not actually use
* mappings of degree $p$ <i>everywhere</i>, but only on cells at the
* boundary. This is in contrast to the MappingQGeneric class which indeed
* does use a polynomial mapping $Q_p$ of degree $p$ everywhere. The point of
* the current class is that in many situations, curved domains are only
* provided with information about how exactly edges at the boundary are
* shaped, but we do not know anything about internal edges. Thus, in the
* absence of other information, we can only assume that internal edges are
* straight lines, and in that case internal cells may as well be treated is
* bilinear quadrilaterals or trilinear hexahedra. (An example of how such
* meshes look is shown in step-1 already, but it is also discussed in the
* "Results" section of step-6.) Because bi-/trilinear mappings are
* significantly cheaper to compute than higher order mappings, it is
* advantageous in such situations to use the higher order mapping only on
* cells at the boundary of the domain. This class implements exactly this
* behavior.
*
* There are a number of special cases worth considering:
* - If you want to use a higher order mapping for all cells, you can
* achieve this by setting the second argument to the constructor to true.
* This only makes sense if you can actually provide information about how
* interior edges and faces of the mesh should be curved. This is typically
* done by associating a Manifold with interior cells and edges. A simple
* example of this is discussed in the "Results" section of step-6; a full
* discussion of manifolds is provided in step-53.
* - If you pass true as the second argument to this class, then it
* is in fact completely equivalent to generating a MappingQGeneric object
* right away.
* - This class is also entirely equivalent to MappingQGeneric if the
* polynomial degree provided is one. This is because in that case, no
* distinction between the mapping used on cells in the interior and on the
* boundary of the domain can be made.
* - If you are working on meshes embedded in higher space dimensions,
* i.e., if dim!=spacedim, then every cell is considered to be at the boundary
* of the domain and consequently a higher order mapping is used for all
* cells; again this class is then equivalent to using MappingQGeneric right
* away.
*
* @author Ralf Hartmann, 2000, 2001, 2005; Guido Kanschat 2000, 2001,
* Wolfgang Bangerth, 2015
*/
template <int dim, int spacedim=dim>
class MappingQ : public Mapping<dim,spacedim>
{
public:
/**
* Constructor. @p polynomial_degree denotes the polynomial degree of the
* polynomials that are used to map cells boundary.
*
* The second argument determines whether the higher order mapping should
* also be used on interior cells. If its value is <code>false</code> (the
* default), then a lower order mapping is used in the interior. This is
* sufficient for most cases where higher order mappings are only used to
* better approximate the boundary. In that case, cells bounded by straight
* lines are acceptable in the interior. However, there are cases where one
* would also like to use a higher order mapping in the interior. The
* MappingQEulerian class is one such case.
*
* The value of @p use_mapping_q_on_all_cells is ignored if @p dim is not
* equal to @p spacedim, i.e., if we are considering meshes on surfaces
* embedded into higher dimensional spaces.
*/
MappingQ (const unsigned int polynomial_degree,
const bool use_mapping_q_on_all_cells = false);
/**
* Copy constructor.
*/
MappingQ (const MappingQ<dim,spacedim> &mapping);
/**
* Return the degree of the mapping, i.e. the value which was passed to the
* constructor.
*/
unsigned int get_degree () const;
/**
* Always returns @p true because the default implementation of functions in
* this class preserves vertex locations.
*/
virtual
bool preserves_vertex_locations () const;
/**
* Transforms the point @p p on the unit cell to the point @p p_real on the
* real cell @p cell and returns @p p_real.
*/
virtual
Point<spacedim>
transform_unit_to_real_cell (
const typename Triangulation<dim,spacedim>::cell_iterator &cell,
const Point<dim> &p) const;
/**
* Transforms the point @p p on the real cell to the point @p p_unit on the
* unit cell @p cell and returns @p p_unit.
*
* Uses Newton iteration and the @p transform_unit_to_real_cell function.
*
* In the codimension one case, this function returns the normal projection
* of the real point @p p on the curve or surface identified by the @p cell.
*
* @note Polynomial mappings from the reference (unit) cell coordinates to
* the coordinate system of a real cell are not always invertible if the
* point for which the inverse mapping is to be computed lies outside the
* cell's boundaries. In such cases, the current function may fail to
* compute a point on the reference cell whose image under the mapping
* equals the given point @p p. If this is the case then this function
* throws an exception of type Mapping::ExcTransformationFailed . Whether
* the given point @p p lies outside the cell can therefore be determined by
* checking whether the return reference coordinates lie inside of outside
* the reference cell (e.g., using GeometryInfo::is_inside_unit_cell) or
* whether the exception mentioned above has been thrown.
*/
virtual
Point<dim>
transform_real_to_unit_cell (const typename Triangulation<dim,spacedim>::cell_iterator &cell,
const Point<spacedim> &p) const;
// for documentation, see the Mapping base class
virtual
void
transform (const ArrayView<const Tensor<1,dim> > &input,
const MappingType type,
const typename Mapping<dim,spacedim>::InternalDataBase &internal,
const ArrayView<Tensor<1,spacedim> > &output) const;
// for documentation, see the Mapping base class
virtual
void
transform (const ArrayView<const DerivativeForm<1, dim, spacedim> > &input,
const MappingType type,
const typename Mapping<dim,spacedim>::InternalDataBase &internal,
const ArrayView<Tensor<2,spacedim> > &output) const;
// for documentation, see the Mapping base class
virtual
void
transform (const ArrayView<const Tensor<2, dim> > &input,
const MappingType type,
const typename Mapping<dim,spacedim>::InternalDataBase &internal,
const ArrayView<Tensor<2,spacedim> > &output) const;
// for documentation, see the Mapping base class
virtual
void
transform (const ArrayView<const DerivativeForm<2, dim, spacedim> > &input,
const MappingType type,
const typename Mapping<dim,spacedim>::InternalDataBase &internal,
const ArrayView<Tensor<3,spacedim> > &output) const;
// for documentation, see the Mapping base class
virtual
void
transform (const ArrayView<const Tensor<3, dim> > &input,
const MappingType type,
const typename Mapping<dim,spacedim>::InternalDataBase &internal,
const ArrayView<Tensor<3,spacedim> > &output) const;
/**
* Return a pointer to a copy of the present object. The caller of this copy
* then assumes ownership of it.
*/
virtual
Mapping<dim,spacedim> *clone () const;
/**
* @name Interface with FEValues
* @{
*/
protected:
/**
* Storage for internal data of this mapping. See Mapping::InternalDataBase
* for an extensive description.
*
* This includes data that is computed once when the object is created (in
* get_data()) as well as data the class wants to store from between the
* call to fill_fe_values(), fill_fe_face_values(), or
* fill_fe_subface_values() until possible later calls from the finite
* element to functions such as transform(). The latter class of member
* variables are marked as 'mutable'.
*
* The current class uses essentially the same fields for storage as the
* MappingQGeneric class. Consequently, it inherits from
* MappingQGeneric::InternalData, rather than from
* Mapping::InternalDataBase. The principal difference to
* MappingQGeneric::InternalData is that MappingQ switches between $Q_1$ and
* $Q_p$ mappings depending on the cell we are on, so the internal data
* object needs to also store a pointer to an InternalData object that
* pertains to a $Q_1$ mapping.
*/
class InternalData : public Mapping<dim,spacedim>::InternalDataBase
{
public:
/**
* Constructor.
*/
InternalData ();
/**
* Return an estimate (in bytes) or the memory consumption of this object.
*/
virtual std::size_t memory_consumption () const;
/**
* Flag that is set by the <tt>fill_fe_[[sub]face]_values</tt> function.
*
* If this flag is @p true we are on an interior cell and the @p
* mapping_q1_data is used.
*/
mutable bool use_mapping_q1_on_current_cell;
/**
* A pointer to a structure to store the information for the pure $Q_1$
* mapping that is, by default, used on all interior cells.
*/
std_cxx11::unique_ptr<typename MappingQGeneric<dim,spacedim>::InternalData> mapping_q1_data;
/**
* A pointer to a structure to store the information for the full $Q_p$
* mapping that is, by default, used on all boundary cells.
*/
std_cxx11::unique_ptr<typename MappingQGeneric<dim,spacedim>::InternalData> mapping_qp_data;
};
protected:
// documentation can be found in Mapping::requires_update_flags()
virtual
UpdateFlags
requires_update_flags (const UpdateFlags update_flags) const;
// documentation can be found in Mapping::get_data()
virtual
InternalData *
get_data (const UpdateFlags,
const Quadrature<dim> &quadrature) const;
// documentation can be found in Mapping::get_face_data()
virtual
InternalData *
get_face_data (const UpdateFlags flags,
const Quadrature<dim-1>& quadrature) const;
// documentation can be found in Mapping::get_subface_data()
virtual
InternalData *
get_subface_data (const UpdateFlags flags,
const Quadrature<dim-1>& quadrature) const;
// documentation can be found in Mapping::fill_fe_values()
virtual
CellSimilarity::Similarity
fill_fe_values (const typename Triangulation<dim,spacedim>::cell_iterator &cell,
const CellSimilarity::Similarity cell_similarity,
const Quadrature<dim> &quadrature,
const typename Mapping<dim,spacedim>::InternalDataBase &internal_data,
internal::FEValues::MappingRelatedData<dim,spacedim> &output_data) const;
// documentation can be found in Mapping::fill_fe_face_values()
virtual void
fill_fe_face_values (const typename Triangulation<dim,spacedim>::cell_iterator &cell,
const unsigned int face_no,
const Quadrature<dim-1> &quadrature,
const typename Mapping<dim,spacedim>::InternalDataBase &internal_data,
internal::FEValues::MappingRelatedData<dim,spacedim> &output_data) const;
// documentation can be found in Mapping::fill_fe_subface_values()
virtual void
fill_fe_subface_values (const typename Triangulation<dim,spacedim>::cell_iterator &cell,
const unsigned int face_no,
const unsigned int subface_no,
const Quadrature<dim-1> &quadrature,
const typename Mapping<dim,spacedim>::InternalDataBase &internal_data,
internal::FEValues::MappingRelatedData<dim,spacedim> &output_data) const;
/**
* @}
*/
protected:
/**
* The polynomial degree of the cells to be used on all cells at the
* boundary of the domain, or everywhere if so specified.
*/
const unsigned int polynomial_degree;
/**
* If this flag is set @p true then @p MappingQ is used on all cells, not
* only on boundary cells.
*/
const bool use_mapping_q_on_all_cells;
/**
* Pointer to a Q1 mapping. This mapping is used on interior cells unless
* use_mapping_q_on_all_cells was set in the call to the constructor. The
* mapping is also used on any cell in the transform_real_to_unit_cell() to
* compute a cheap initial guess for the position of the point before we
* employ the more expensive Newton iteration using the full mapping.
*
* @note MappingQEulerian resets this pointer to an object of type
* MappingQ1Eulerian to ensure that the Q1 mapping also knows about the
* proper shifts and transformations of the Eulerian displacements. This
* also means that we really need to store our own Q1 mapping here, rather
* than simply resorting to StaticMappingQ1::mapping.
*
* @note If the polynomial degree used for the current object is one, then
* the qp_mapping and q1_mapping variables point to the same underlying
* object.
*/
std_cxx11::shared_ptr<const MappingQGeneric<dim,spacedim> > q1_mapping;
/**
* Pointer to a Q_p mapping. This mapping is used on boundary cells unless
* use_mapping_q_on_all_cells was set in the call to the constructor (in
* which case it is used for all cells).
*
* @note MappingQEulerian and MappingC1 reset this pointer to an object of
* their own implementation to ensure that the Q_p mapping also knows about
* the proper shifts and transformations of the Eulerian displacements
* (Eulerian case) and proper choice of support points (C1 case).
*
* @note If the polynomial degree used for the current object is one, then
* the qp_mapping and q1_mapping variables point to the same underlying
* object.
*/
std_cxx11::shared_ptr<const MappingQGeneric<dim,spacedim> > qp_mapping;
};
/*@}*/
DEAL_II_NAMESPACE_CLOSE
#endif
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