CGAL 5.0.2  2D and 3D Linear Geometry Kernel

#include <CGAL/Direction_3.h>
An object of the class Direction_3
is a vector in the threedimensional vector space \( \mathbb{R}^3\) where we forget about their length.
They can be viewed as unit vectors, although there is no normalization internally, since this is error prone. Directions are used whenever the length of a vector does not matter. They also characterize a set of parallel lines that have the same orientation or the direction normal to parallel planes that have the same orientation. For example, you can ask for the direction orthogonal to an oriented plane, or the direction of an oriented line.
Creation  
Direction_3 (const Vector_3< Kernel > &v)  
introduces a direction d initialized with the direction of vector v .  
Direction_3 (const Line_3< Kernel > &l)  
introduces the direction d of line l .  
Direction_3 (const Ray_3< Kernel > &r)  
introduces the direction d of ray r .  
Direction_3 (const Segment_3< Kernel > &s)  
introduces the direction d of segment s .  
Direction_3 (const Kernel::RT &x, const Kernel::RT &y, const Kernel::RT &z)  
introduces a direction d initialized with the direction from the origin to the point with Cartesian coordinates \( (x, y, z)\).  
Operations  
Kernel::RT  delta (int i) const 
returns values, such that d == Direction_3<Kernel>(delta(0),delta(1),delta(2)) . More...  
Kernel::RT  dx () const 
returns delta(0) .  
Kernel::RT  dy () const 
returns delta(1) .  
Kernel::RT  dz () const 
returns delta(2) .  
bool  operator== (const Direction_3< Kernel > &e) const 
Test for equality.  
bool  operator!= (const Direction_3< Kernel > &e) const 
Test for inequality.  
Direction_3< Kernel >  operator () const 
The direction opposite to d .  
Vector_3< Kernel >  vector () const 
returns a vector that has the same direction as d .  
Direction_3< Kernel >  transform (const Aff_transformation_3< Kernel > &t) const 
returns the direction obtained by applying t on d .  
Kernel::RT CGAL::Direction_3< Kernel >::delta  (  int  i  )  const 
returns values, such that d
== Direction_3<Kernel>(delta(0),delta(1),delta(2))
.