 ## CGAL::Ray_3<Kernel>

### Definition

An object r of the data type Ray_3<Kernel> is a directed straight ray in the three-dimensional Euclidean space 3. It starts in a point called the source of r and it goes to infinity.

### Creation

 Ray_3 r ( Point_3 p, Point_3 q); introduces a ray r with source p and passing through point q. Ray_3 r ( Point_3 p, Direction_3 d); introduces a ray r with source p and with direction d. Ray_3 r ( Point_3 p, Vector_3 v); introduces a ray r with source p and with a direction given by v. Ray_3 r ( Point_3 p, Line_3 l); introduces a ray r starting at source p with the same direction as l.

### Operations

 bool r.operator== ( h) Test for equality: two rays are equal, iff they have the same source and the same direction. bool r.operator!= ( h) Test for inequality. Point_3 r.source () returns the source of r Point_3 r.point ( int i) returns a point on r. point(0) is the source. point(i), with i>0, is different from the source. Precondition: i 0. Direction_3 r.direction () returns the direction of r. Vector_3 r.to_vector () returns a vector giving the direction of r. Line_3 r.supporting_line () returns the line supporting r which has the same direction. Ray_3 r.opposite () returns the ray with the same source and the opposite direction. bool r.is_degenerate () ray r is degenerate, if the source and the second defining point fall together (that is if the direction is degenerate). bool r.has_on ( Point_3 p) A point is on r, iff it is equal to the source of r, or if it is in the interior of r. Ray_3 r.transform ( Aff_transformation_3 t) returns the ray obtained by applying t on the source and on the direction of r.