-- generate Mobius curve viewport for ViewportPage
port := draw(surface((v*cos(u/2)+1)*cos(u),(v*cos(u/2)+1)*sin(u), _
                      v*sin(u/2)), u=-%pi..%pi, v=-0.5..0.5)
write(port, "mobius", ["bitmap","pixmap"])
close port
)lisp (quit)
