x(u,v) = (r + g(v)) cos(u) (1 - v) + v (R + g(v)) cos(u)[br]y(u,v) = (r + g(v)) sin(u) (1 - v) + v (R + g(v)) sin(u)[br]z(u,v) = v (a sin(n u) + h) + f(v)[br][math]0\le u\le2\pi[/math], [math]0\le v\le1[/math]