¦^§@·~12

> a:=2;

a := 2

> r:=a+cos(u/2)*sin(v)-sin(u/2)*sin(2*v);

r := 2+cos(1/2*u)*sin(v)-sin(1/2*u)*sin(2*v)

> x:=r*cos(u);

x := (2+cos(1/2*u)*sin(v)-sin(1/2*u)*sin(2*v))*cos(...

> y:=r*sin(u);

y := (2+cos(1/2*u)*sin(v)-sin(1/2*u)*sin(2*v))*sin(...

> z:=sin(u/2)*sin(v)+cos(u/2)*sin(2*v);

z := sin(1/2*u)*sin(v)+cos(1/2*u)*sin(2*v)

> c:=plot3d([x,y,z],v=0..2*Pi,u=-Pi/4..3*Pi/2,scaling=constrained):

> c;

[Maple Plot]

> with(plottools):

> vrml(c,"c:/042/12/12-3.wrl",background_color=white);

>