The face class Tds::Face of a triangulation data structure stores three pointers to its three vertices and three pointers to its three neighbors The vertices are indexed 0,1, and 2 in counterclockwise order. The neighbor indexed $i$ lies opposite to vertex i.

Types

Creation

For user defined triangulation algorithms, faces need to be explicitly constructed and linked to their neighbors.

Tds::Face f;
	Introduces a variable f and initializes all vertices and neighbors with NULL.
Tds::Face f ( Vertex* v0, Vertex* v1, Vertex* v2);
	Introduces a variable f, and initializes the vertices. The neighbors are initialized with NULL.
Tds::Face f ( Vertex* v0, Vertex* v1, Vertex* v2, Face* n0, Face* n1, Face* n2);
	Introduces a variable f, and initializes the vertices and the neighbors.

Setting

void	f.set_vertex ( int i, Vertex* v)
		Set vertex i to be v. Precondition: .
void	f.set_neighbor ( int i, Face* n)
		Set neighbor i to be n. Precondition: .
void	f.set_vertices ()	set the vertices pointers to NULL.
void	f.set_vertices ( Vertex* v0, Vertex* v1, Vertex* v2)
		set the vertices pointers.
void	f.set_neighbors ()	set the neighbors pointers to NULL.
void	f.set_neighbors ( Face* n0, Face* n1, Face* n2)
		set the neighbors pointers.

Vertex Access Functions

Vertex*	f.vertex ( int i)	Returns the vertex i of f. Precondition: .
int	f.index ( Vertex* v)
		Returns the index of vertex v in f. Precondition: v is a vertex of f
bool	f.has_vertex ( Vertex* v)
		Returns true if v is a vertex of f.
bool	f.has_vertex ( Vertex* v, int& i)
		Returns true if v is a vertex of f, and computes the index i of the vertex.

Neighbor Access Functions

The neighbor with index i is the neighbor which is opposite to the vertex with index i.

Face*	f.neighbor ( int i)
		Returns the neighbor i of f. Precondition: .
int	f.index ( Face* n)	Returns the index of face n. Precondition: n is a neighbor of f.
bool	f.has_neighbor ( Face* n)
		Returns true if n is a neighbor of f.
bool	f.has_neighbor ( Face* n, int& i)
		Returns true if n is a neighbor of f, and compute the index i of the neighbor.

Checking

bool

f.is_valid ()

Returns true if the base class is_valid() function returns true and if the triangle shares two vertices with its neighbors, and these neighbors have a correct reciprocal neighboring link.

Miscellaneous

int	f.ccw ( int i)	Returns $i+1$ modulo 3. Precondition: .
int	f.cw ( int i)	Returns $i+2$ modulo 3. Precondition: .