CGAL 5.6.1  2D and 3D Linear Geometry Kernel

AdaptableBinaryFunction
CGAL::Plane_3<Kernel>
Operations  
Kernel::Vector_3  operator() (const Kernel::Plane_3 &h, int index) 
when index == 1, returns a vector b1 that is orthogonal to the normal n to plane h ; when index == 2, returns a vector b2 that is orthogonal to n and b1 and such that for an arbitrary point p on the plane h , the orientation of p , p + b1 , p + b2 , and p + n is positive.  