
 
returns the relative position of point test
to the oriented sphere defined by $$p, $$q, $$r and $$s.
The order of the points $$p, $$q, $$r, and $$s is important,
since it determines the orientation of the implicitly
constructed sphere. If the points $$p, $$q, $$r and $$s
are positive oriented, positive side is the bounded interior
of the sphere.
