//! calculate the intersection plane of two spheres. false if there is no plane or infinite planes.
bool intersect_sphere_sphere(Plane *result, const Sphere &a, const Sphere &b);
//! calculate the intersection line of two planes. returns false if planes are exactly parallel.
//! calculate the intersection plane of two spheres. false if there is no plane or infinite planes.
bool intersect_sphere_sphere(Plane *result, const Sphere &a, const Sphere &b);
//! calculate the intersection line of two planes. returns false if planes are exactly parallel.