> restart;

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

> a;

> x:=r*cos(t);

> y:=r*sin(t);

> z:=4-sqrt(abs(x*y));

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

> b;

> with(plottools):

> vrml(a,"c:/042/12/12-10.wrl",background_color=white);

> vrml(b,"c:/042/12/12-10'.wrl",background_color=white);

>