lf::io::GmshReader Class Reference

Reads a Gmsh *.msh file into a mesh::MeshFactory and provides a link between mesh::Entity objects and the gmsh's physical entities. More...

#include <lf/io/gmsh_reader.h>

Public Types
using	size_type = mesh::Mesh::size_type
using	dim_t = base::RefEl::dim_t
using	GmshFileVariant = std::variant<GMshFileV2, GMshFileV4>

Public Member Functions
std::shared_ptr< mesh::Mesh >	mesh ()
	Get the mesh that was read by this reader.
std::shared_ptr< const mesh::Mesh >	mesh () const
	Get the mesh that was read by this reader.
size_type	PhysicalEntityName2Nr (const std::string &name, dim_t codim=-1) const
	maps the name of a physical entity to the physical entity number of gmsh.
std::string	PhysicalEntityNr2Name (size_type number, dim_t codim=-1) const
	Gives the name of a physical entity (inverse of PhysicalEntityName2Nr())
std::vector< std::pair< size_type, std::string > >	PhysicalEntities (dim_t codim) const
	Retrieve a list of all (Gmsh) physical entities of the given codim.
std::vector< size_type >	PhysicalEntityNr (const mesh::Entity &e) const
	Return the Physical Entity Numbers associated with this mesh entity, sorted ascending.
bool	IsPhysicalEntity (const mesh::Entity &e, size_type physical_entity_nr) const
	Test whether the given entity belongs to a Gmsh physical entity.
	GmshReader (std::unique_ptr< mesh::MeshFactory > factory, const GmshFileVariant &msh_file)
	Create a new GmshReader from the given MshFile (advanced usage)
	GmshReader (std::unique_ptr< mesh::MeshFactory > factory, const std::string &filename)
	Create a new GmshReader by reading from the specified file.

Private Member Functions
void	InitGmshFile (const GMshFileV2 &msh_file)
void	InitGmshFile (const GMshFileV4 &msh_file)

Private Attributes
std::shared_ptr< mesh::Mesh >	mesh_
	The underlying grid created by the grid factory.
std::unique_ptr< mesh::MeshFactory >	mesh_factory_
std::shared_ptr< mesh::utils::AllCodimMeshDataSet< std::vector< size_type > > >	physical_nrs_
	The PhysicalEntityNr of every entity (0 if not set):
std::multimap< std::string, std::pair< size_type, dim_t > >	name_2_nr_
	Map from physicalEntity name -> nr, codim.
std::multimap< size_type, std::pair< std::string, dim_t > >	nr_2_name_
	Map from physicalEntity nr -> name, codim.

Detailed Description

Reads a Gmsh *.msh file into a mesh::MeshFactory and provides a link between mesh::Entity objects and the gmsh's physical entities.

In order to import the *.msh file successfully make sure that:

• Save the mesh in Gmsh's proprietary *.msh file format (Version 2 ASCII, Version 2 Binary, Version 4 ASCII or Version 4 Binary)
• If you have specified physical entities in Gmsh and you want to export them, make sure you don't tick Save all (ignore physical groups) and make sure that every surface (2d) / volume (3d) belongs to at least one physical entity. (Otherwise the corresponding mesh elements are not exported by Gmsh)
• If you didn't specify any physical entities in Gmsh, you should tick Save all (ignore physical groups).
• The GmshReader doesn't support the options "Save parametric coordinates" and "Save one file per partition".

The import of meshes from Gmsh-generated mesh files is also discussed in Lecture Document Example 2.7.1.11.

Sample usage:

  // Read *.msh_file
  auto mesh_factory = std::make_unique<mesh::hybrid2d::MeshFactory>(2);
  GmshReader reader(std::move(mesh_factory), "my_mesh.msh");
  // print all physical entities:
  std::cout << "Physical Entities in Gmsh File " << std::endl;
  std::cout
      << "---------------------------------------------------------------\n";
  for (lf::base::dim_t codim = 0; codim <= 2; ++codim) {
    for (auto& pair : reader.PhysicalEntities(codim)) {
      std::cout << "codim = " << static_cast<int>(codim) << ": " << pair.first
                << " <=> " << pair.second << std::endl;
    }
  }
  std::cout << std::endl << std::endl;
 
  // Get Physical Entity Number from it's name (as specified in Gmsh):
  auto air_nr = reader.PhysicalEntityName2Nr("air");
 
  // Get all codim=0 entities that belong to the "air" physical entity:
  for (auto& e : reader.mesh()->Entities(0)) {
    if (reader.IsPhysicalEntity(*e, air_nr)) {
      // This entity belongs to the "air" physical entity.
    }
  }

Note about mesh completeness:

In principle, Gmsh can export meshes that are not "complete", i.e. meshes containing entities with codim>0 that are not sub-entities of cell-entities. Also, if Gmsh exports a higher-order mesh, it has to introduce "auxilliary nodes" in order to define the higher-order mesh elements (these auxilliary nodes are normally placed on edges, faces or in the interior of cells).

Since incomplete meshes are usually not useful in a FEM context, GmshReader doesn't insert into the mesh auxilliary nodes or nodes not belonging to at least one cell. Auxilliary nodes are however used in the construction of higher order geometry objects.

Definition at line 70 of file gmsh_reader.h.

Member Typedef Documentation

dim_t

using lf::io::GmshReader::dim_t = base::RefEl::dim_t

Definition at line 73 of file gmsh_reader.h.

GmshFileVariant

using lf::io::GmshReader::GmshFileVariant = std::variant<GMshFileV2, GMshFileV4>

Definition at line 74 of file gmsh_reader.h.

size_type

using lf::io::GmshReader::size_type = mesh::Mesh::size_type

Definition at line 72 of file gmsh_reader.h.

Constructor & Destructor Documentation

GmshReader() [1/2]

lf::io::GmshReader::GmshReader	(	std::unique_ptr< mesh::MeshFactory >	factory,
		const GmshFileVariant &	msh_file )

Create a new GmshReader from the given MshFile (advanced usage)

Parameters

factory	The mesh::MeshFactory that is used to construct the mesh.
msh_file	A LehrFEM++ specific representation of a GmshFile.

See also

MshFile

Definition at line 24 of file gmsh_reader.cc.

References InitGmshFile().

GmshReader() [2/2]

lf::io::GmshReader::GmshReader	(	std::unique_ptr< mesh::MeshFactory >	factory,
		const std::string &	filename )

Create a new GmshReader by reading from the specified file.

Parameters

factory	The mesh::MeshFactory that is used to construct the mesh.
filename	The filename of the .msh file that is read.

Note

If the factory.DimWorld() == 3, there must be at least one 3D mesh element in the *.msh file. Similarly, if factory.DimWorld() == 2 there should be only 2D mesh elements in the *.msh file!

GmshReader supports ASCII and Binary .msh files.

Definition at line 30 of file gmsh_reader.cc.

Member Function Documentation

InitGmshFile() [1/2]

void lf::io::GmshReader::InitGmshFile ( const GMshFileV2 & msh_file )

private

Definition at line 120 of file gmsh_reader.cc.

References lf::io::DimOf(), lf::io::GMshFileV2::EDGE2, lf::io::GMshFileV2::EDGE3, lf::io::GMshFileV2::Elements, lf::base::RefEl::kPoint(), lf::base::RefEl::kQuad(), lf::base::RefEl::kSegment(), lf::base::RefEl::kTria(), mesh_, mesh_factory_, name_2_nr_, lf::io::GMshFileV2::Nodes, nr_2_name_, lf::io::GMshFileV2::Periodic, physical_nrs_, lf::io::GMshFileV2::PhysicalEntities, lf::io::GMshFileV2::POINT, lf::io::GMshFileV2::QUAD4, lf::io::GMshFileV2::QUAD8, lf::io::GMshFileV2::QUAD9, lf::io::RefElOf(), lf::io::GMshFileV2::TRIA3, and lf::io::GMshFileV2::TRIA6.

Referenced by GmshReader().

InitGmshFile() [2/2]

void lf::io::GmshReader::InitGmshFile ( const GMshFileV4 & msh_file )

private

Definition at line 349 of file gmsh_reader.cc.

References lf::io::DimOf(), lf::io::GMshFileV4::EDGE2, lf::io::GMshFileV4::EDGE3, lf::io::GMshFileV4::Elements::element_blocks, lf::io::GMshFileV4::elements, lf::io::GMshFileV4::entities, lf::base::RefEl::kPoint(), lf::base::RefEl::kQuad(), lf::base::RefEl::kSegment(), lf::base::RefEl::kTria(), lf::io::GMshFileV4::Nodes::max_node_tag, mesh_, mesh_factory_, lf::io::GMshFileV4::Nodes::min_node_tag, name_2_nr_, lf::io::GMshFileV4::Nodes::node_blocks, lf::io::GMshFileV4::nodes, nr_2_name_, lf::io::GMshFileV4::PartitionedEntities::num_partitions, lf::io::GMshFileV4::PartitionedEntities::partitioned_entities, lf::io::GMshFileV4::partitioned_entities, lf::io::GMshFileV4::periodic_links, lf::io::GMshFileV4::physical_names, physical_nrs_, lf::io::GMshFileV4::QUAD4, lf::io::GMshFileV4::QUAD8, lf::io::GMshFileV4::QUAD9, lf::io::RefElOf(), lf::io::GMshFileV4::TRIA3, and lf::io::GMshFileV4::TRIA6.

IsPhysicalEntity()

bool lf::io::GmshReader::IsPhysicalEntity	(	const mesh::Entity &	e,
		size_type	physical_entity_nr ) const

Test whether the given entity belongs to a Gmsh physical entity.

Parameters

e	The entity that should be tested.
physical_entity_nr	The number of the gmsh physical entity.

Returns

True if the entity e belongs to the physical entity.

This method is related to the method PhysicalEntityNr(): It returns true, if the vector returned by PhysicalEntityNr(e) contains physical_entity_nr

See also

PhysicalEntityNr() and the code snippet in the documentation of GmshReader.

Definition at line 17 of file gmsh_reader.cc.

References PhysicalEntityNr().

mesh() [1/2]

std::shared_ptr< mesh::Mesh > lf::io::GmshReader::mesh ( )

inline

Get the mesh that was read by this reader.

Definition at line 79 of file gmsh_reader.h.

References mesh_.

mesh() [2/2]

std::shared_ptr< const mesh::Mesh > lf::io::GmshReader::mesh ( ) const

inline

Get the mesh that was read by this reader.

Definition at line 84 of file gmsh_reader.h.

References mesh_.

PhysicalEntities()

std::vector< std::pair< size_type, std::string > > lf::io::GmshReader::PhysicalEntities

(

dim_t

codim

)

const

Retrieve a list of all (Gmsh) physical entities of the given codim.

Parameters

codim

The codimension

Returns

A list of physical entities (number, name)

See the code snippet in the documentation of GmshReader.

Definition at line 102 of file gmsh_reader.cc.

References nr_2_name_.

PhysicalEntityName2Nr()

size_type lf::io::GmshReader::PhysicalEntityName2Nr	(	const std::string &	name,
		dim_t	codim = -1 ) const

maps the name of a physical entity to the physical entity number of gmsh.

Parameters

name	Name of the physical entity.
codim	Optionally the codimension of the physical entity (w.r.t dimMesh), only needed if there are physical entities with the same name but different dimensions.

Returns

Number of the physical entity (as shown in Gmsh)

Note

If you have defined a physical entity in GMSH without giving it a name, you cannot use this function.

See also

PhysicalEntityNr2Name() and the code snippet in the documentation of GmshReader.

Definition at line 34 of file gmsh_reader.cc.

References name_2_nr_.

PhysicalEntityNr()

std::vector< size_type > lf::io::GmshReader::PhysicalEntityNr

(

const mesh::Entity &

e

)

const

Return the Physical Entity Numbers associated with this mesh entity, sorted ascending.

Parameters

e	The entity of the grid.

Returns

The Physical Entity Number that was assigned in GMSH.

Definition at line 114 of file gmsh_reader.cc.

References physical_nrs_.

Referenced by IsPhysicalEntity().

PhysicalEntityNr2Name()

std::string lf::io::GmshReader::PhysicalEntityNr2Name	(	size_type	number,
		dim_t	codim = -1 ) const

Gives the name of a physical entity (inverse of PhysicalEntityName2Nr())

Parameters

number	The number of the physical entity (as obtained from PhysicalEntityName2Nr() )
codim	Specify additionally the codimension of the physical entity. If not specified and there is exactly one physical entity with the given number, that entity is returned. If there are multiple entities with the same number and codim=-1, an error is thrown.

Returns

The name of the physical entity with number number

See also

PhysicalEntityNr2Name

Definition at line 68 of file gmsh_reader.cc.

References nr_2_name_.

Member Data Documentation

mesh_

std::shared_ptr<mesh::Mesh> lf::io::GmshReader::mesh_

private

The underlying grid created by the grid factory.

Definition at line 178 of file gmsh_reader.h.

Referenced by InitGmshFile(), InitGmshFile(), mesh(), and mesh().

mesh_factory_

std::unique_ptr<mesh::MeshFactory> lf::io::GmshReader::mesh_factory_

private

Definition at line 180 of file gmsh_reader.h.

Referenced by InitGmshFile(), and InitGmshFile().

name_2_nr_

std::multimap<std::string, std::pair<size_type, dim_t> > lf::io::GmshReader::name_2_nr_

private

Map from physicalEntity name -> nr, codim.

Definition at line 187 of file gmsh_reader.h.

Referenced by InitGmshFile(), InitGmshFile(), and PhysicalEntityName2Nr().

nr_2_name_

std::multimap<size_type, std::pair<std::string, dim_t> > lf::io::GmshReader::nr_2_name_

private

Map from physicalEntity nr -> name, codim.

Definition at line 190 of file gmsh_reader.h.

Referenced by InitGmshFile(), InitGmshFile(), PhysicalEntities(), and PhysicalEntityNr2Name().

physical_nrs_

std::shared_ptr<mesh::utils::AllCodimMeshDataSet<std::vector<size_type> > > lf::io::GmshReader::physical_nrs_

private

The PhysicalEntityNr of every entity (0 if not set):

Definition at line 184 of file gmsh_reader.h.

Referenced by InitGmshFile(), InitGmshFile(), and PhysicalEntityNr().

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The documentation for this class was generated from the following files:

• /__w/lehrfempp/lehrfempp/lib/lf/io/gmsh_reader.h
• /__w/lehrfempp/lehrfempp/lib/lf/io/gmsh_reader.cc