> restart:

> x:=r*cos(t):

> y:=r*sin(t):

> z:=x^2-y^2:

> a:=plot3d([x,y,z],r=0..1,t=0..2*Pi,scaling=constrained,grid=[5,50]):

> with(plots):

> with(plottools):

> vrml(a,"c:/My documents/87124/11/11-07.wrl",background_color=white):

> display(a);

>