> with(plots):with(plottools):

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

> a:=plot3d([x,y,x^2-y^2],r=0..1,t=0..2*Pi,scaling=constrained,grid=[10,100]):

> a;

> vrml(a,"C:/My Documents/trfa/wrl/11-7.wrl",background_color=white);