my_model(x[3], a[1])
{
array center[3];
center = [5,6,0];
el1=hfEllipsoid(x,center,2,4,6);

center[2]=-6;
el2=hfEllipsoid(x,center,5,2,4); 

center[1]=-6;
el3=hfEllipsoid(x,center,4,2,7);

center[1]=-6; center[2]=6;
el4=hfEllipsoid(x,center,3,3,3);

my_model = el1 | el2 | el3 | el4;
}