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

sp1 = 1-(xt[1]/2)^2- (xt[2]/8)^2- (xt[3]/2)^2; 

tmp = hfRotate3DZ(xt,1.57);
sp2 = 1-(xt[1]/2)^2- (xt[2]/8)^2- (xt[3]/2)^2; 

xt[1]=x[1];
xt[2]=x[2];
xt[3]=x[3];
tmp = hfRotate3DY(xt,0.52);
tmp = hfRotate3DX(xt,-1.57);
sp3 = 1-(xt[1]/2)^2- (xt[2]/8)^2- (xt[3]/2)^2;

my_model = sp1 | sp2 | sp3;
}