my_model(x[3], a[1])
{
array xt[3];
xt[1]=x[1];
xt[2]=x[2];
xt[3]=x[3];

tmp = hfScale3D(xt,1.5,0.5,0.4);
sp1 = 25-(xt[1])^2- (xt[2])^2- (xt[3])^2; 

my_model = sp1;
}