An object p of type Sphere_point<R> is a point on the surface of a unit sphere. Such points correspond to the nontrivial directions in space and similarly to the equivalence classes of all nontrivial vectors under normalization.
 
ring number type.

 
creates some sphere point.
 
 
creates a sphere
point corresponding to the point of intersection of the ray starting
at the origin in direction $$(x,y,z) and the surface of $$S_{2}.

Access to the coordinates is provided by the following operations. Note that the vector $$(x,y,z) is not normalized.