{ RCSid: $Id: rev.cal,v 2.3 2003/02/22 02:07:24 greg Exp $ }
{
Phong normal interpolation for surfaces of revolution about z.
11/7/88
(A1,A2) = (Mz,Bz)
(A3,A4) = (Mr,Br)
}
rev_dr = rev_rad*A3 + A4;
rev_rad = sqrt(Px*Px + Py*Py);
rev_dx = rev_dr * Px/rev_rad;
rev_dy = rev_dr * Py/rev_rad;
rev_dz = Pz*A1 + A2;