import graph3; size(200,0); currentlight=Viewport; triple f(pair t) { return(10*sin(t.y),cos(t.x)*(cos(t.y)+log(abs(tan(t.y/2)))), sin(t.x)*(cos(t.y)+log(abs(tan(t.y/2))))); } surface s=surface(f,(0,pi/2),(2pi,pi-0.1),7,15,Spline); draw(s,olive);