> restart;

> c:=plot3d(4-sqrt(abs(x*y)),x=-2..2,y=-2..2,scaling=constrained):

> c;

> with(plottools):

> vrml(c,"c:/040/12/12-10-1.wrl",background_color=white):

> x:=r*cos(t):y:=r*sin(t):z:=4-sqrt(abs(x*y)):

> d:=plot3d([x,y,z],r=0..2,t=0..2*Pi,scaling=constrained,grid=[20,101]):

> d;

> with(plottools):

> vrml(d,"c:/040/12/12-10-2.wrl",background_color=white):

>