> restart;

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

> x:=r*cos(u):y:=r*sin(u):

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

> c:=plot3d([x,y,z],v=0..2*Pi,u=-Pi/4..3*Pi/2,scaling=constrained,grid=[20,50]):

> c;

> with(plottools):

> vrml(c,"c:/040/12/12-3.wrl",background_color=white):

>