message: ENH: add sphere-sphere intersect() operator
  Add a corresponding sphere-sphere intersect() operator.
diff: #ifndef INTERSECTION_HPP_
  #define INTERSECTION_HPP_
  -#include "primal/OrientedBoundingBox.hpp"
  #include "primal/BoundingBox.hpp"
  +#include "primal/OrientedBoundingBox.hpp"
  #include "primal/Point.hpp"
  #include "primal/Ray.hpp"
  #include "primal/Segment.hpp"
  +#include "primal/Sphere.hpp"
  #include "primal/Triangle.hpp"
  +
  #include "axom_utils/Utilities.hpp"
  #include "primal/intersect_impl.hpp"
  @@ -128,6 +130,25 @@ bool intersect( const BoundingBox< T, DIM >& bb1,
  return bb1.intersectsWith(bb2);
  }
  +/*!
  + * \brief Determines if two spheres intersect.
  + *
  + * \param [in] s1 user-supplied sphere object to check for intersection.
  + * \param [in] s2 user-supplied sphere object to check for intersection.
  + * \param [in] TOL tolerance used for intersection check (optional)
  + *
  + * \note If TOL is not supplied, the default is 1.e-9.
  + *
  + * \return status true iff s1 intersects with s2, otherwise, false.
  + */
  +template < typename T, int DIM >
  +bool intersect( const Sphere< T,DIM >& s1,
  + const Sphere< T,DIM >& s2,
  + double TOL=1.e-9 )
  +{
  + return s1.intersectsWith( s2, TOL );
  +}
  +
  /*!
  * \brief Determines if a triangle and a bounding box intersect
  * \param [in] tri user-supplied triangle (with three vertices).
  