 ## CGAL::Triangle_3<Kernel>

### Definition

An object t of the class Triangle_3<Kernel> is a triangle in the three-dimensional Euclidean space 3. As the triangle is not a full-dimensional object there is only a test whether a point lies on the triangle or not.

### Creation

 Triangle_3 t ( Point_3 p, Point_3 q, Point_3 r); introduces a triangle t with vertices p, q and r.

### Operations

 bool t.operator== ( t2) Test for equality: two triangles t and t2 are equal, iff there exists a cyclic permutation of the vertices of t2, such that they are equal to the vertices of t. bool t.operator!= ( t2) Test for inequality. Point_3 t.vertex ( int i) returns the i'th vertex modulo 3 of t. Point_3 t.operator[] ( int i) returns vertex(int i). Plane_3 t.supporting_plane () returns the supporting plane of t, with same orientation.

### Predicates

 bool t.is_degenerate () t is degenerate if its vertices are collinear. bool t.has_on ( Point_3 p) A point is on t, if it is on a vertex, an edge or the face of t.

### Miscellaneous

 Kernel::FT t.squared_area () returns a square of the area of t. Bbox_3 t.bbox () returns a bounding box containing t. Triangle_3 t.transform ( Aff_transformation_3 at) returns the triangle obtained by applying at on the three vertices of t.

### See Also

Kernel::Triangle_3