// vector functions
/*
#declare X=vaxis_rotate(A,B,F); // rotate A about B by F
#declare X=vcross(A,B);         // cross product of A and B
#declare X=vdot(A,B);           // dot product of A and B
#declare X=vrotate(A,B);        // rotate A about origin by B
#declare X=vnormalize(A);       // normalize vector A
#declare X=vturbulence(Lambda,Omega,Octaves, A);
                                // X+A gives a turbulated version of A
*/