TriangulationDSFaceBase_2 Concept Reference

Definition

Refines

TriangulationDataStructure_2::Face

The concept TriangulationDSFaceBase_2 describes the requirements for the face base class of a CGAL::Triangulation_data_structure_2<Vb,Fb>.

Note that if the CGAL::Triangulation_data_structure_2 is plugged into a triangulation class, the face base class may have additional geometric requirements depending on the triangulation class.

At the base level, (see Sections Software Design and The Default Triangulation Data Structure ), a face stores handles on its three vertices and on the three neighboring faces. The vertices and neighbors are indexed 0,1 and 2. Neighbor i lies opposite to vertex i.

Since the CGAL::Triangulation_data_structure_2 is the class which defines the handle types, the face base class has to be somehow parameterized by the triangulation data structure. But since the CGAL::Triangulation_data_structure_2 itself is parameterized by the face and vertex base classes, there is a cycle in the definition of these classes. In order to break the cycle, the base classes for faces and vertices which are plugged in to instantiate a CGAL::Triangulation_data_structure_2 use void as triangulation data structure parameter. Then, the CGAL::Triangulation_data_structure_2 uses a rebind mechanism (similar to the one specified in std::allocator) in order to plug itself as parameter in the face and vertex base classes. This mechanism requires that the base class provides a templated nested class Rebind_TDS that itself provides the subtype Rebind_TDS::Other which is the rebound version of the base class. This rebound base class is the class that the CGAL::Triangulation_data_structure_2 actually uses as a base class for the class CGAL::Triangulation_data_structure_2::Face.

Has models

CGAL::Triangulation_ds_face_base_2<TDS>

See also

TriangulationDSVertexBase_2

CGAL::Triangulation_data_structure_2<Vb,Fb>

Types
The concept TriangulationDSFaceBase_2 has to provide the following types.
template<typename TDS2 >
using	Rebind_TDS = unspecified_type
	This template class has to define a type Rebind_TDS<TDS_2>::Other which is the rebound face base, where the CGAL::Triangulation_data_structure_2 is actually plugged in.
typedef TriangulationDataStructure_2	Triangulation_data_structure
typedef TriangulationDataStructure_2::Vertex_handle	Vertex_handle
typedef TriangulationDataStructure_2::Face_handle	Face_handle
typedef TriangulationDataStructure_2::Face_data	TDS_data

Creation
	TriangulationDSFaceBase_2 ()
	default constructor.
	TriangulationDSFaceBase_2 (Vertex_handle v0, Vertex_handle v1, Vertex_handle v2)
	Initializes the vertices with v0, v1, v2 and the neighbors with Face_handle().
	TriangulationDSFaceBase_2 (Vertex_handle v0, Vertex_handle v1, Vertex_handle v2, Face_handle n0, Face_handle n1, Face_handle n2)
	initializes the vertices with v0,v1, v2 and the neighbors with n0, n1, n2.

Access Functions
int	dimension ()
	returns the dimension.

Orientation
void	reorient ()
	Changes the orientation of the face by exchanging vertex(0) with vertex(1) and neighbor(0) with neighbor(1).
void	ccw_permute ()
	performs a counterclockwise permutation of the vertices and neighbors of the face.
void	cw_permute ()
	performs a clockwise permutation of the vertices and neighbors of the face.

Checking
bool	is_valid (bool verbose=false) const
	performs any required test on a face.

Various
These member functions are required by CGAL::Triangulation_data_structure_2 because it uses CGAL::Compact_container to store its faces. See the documentation of CGAL::Compact_container for the exact requirements.
void *	for_compact_container () const
void	for_compact_container (void *p)

Internal
Advanced These functions are used internally by the triangulation data structure. The user is not encouraged to use them directly as they may change in the future.
TDS_data &	tds_data ()
const TDS_data &	tds_data () const

Member Typedef Documentation

Rebind_TDS

template<typename TDS2 >

using TriangulationDSFaceBase_2::Rebind_TDS = unspecified_type

This template class has to define a type Rebind_TDS<TDS_2>::Other which is the rebound face base, where the CGAL::Triangulation_data_structure_2 is actually plugged in.

This type Other will be the actual base of the class CGAL::Triangulation_data_structure_2::Face.

Note

It can be implemented using a nested template class.

See also

Section The Rebind Mechanism

Member Function Documentation

is_valid()

bool TriangulationDSFaceBase_2::is_valid

(

bool

verbose = false

)

const

performs any required test on a face.

If verbose is set to true, messages are printed to give a precise indication of the kind of invalidity encountered.