-- Sand
my_model(x[3], a[1])
{
xt = x[1];
yt = x[2];
zt = x[3];
s1=(10-zt)/20;
s2=(10-zt)/20;
r1 = 1+10*s1;
r2 = 1+10*s2;
xt1 = (x[1])*cos(r1)-(x[2])*sin(r1);
yt2 = (x[1])*sin(r1)+(x[2])*cos(r1);
xt3 = (x[1])*cos(r2)-(x[2])*sin(r2);
yt3 = (x[1])*sin(r2)+(x[2])*cos(r2);

obj1 = 1-(xt1/10)^4-(yt2/10)^4-((zt-10)/4)^4;
obj2 = 1-(xt1/10)^4-(yt2/10)^4-((zt+10)/4)^4;

obj3 = 1^2-( xt-5 )^2-( yt -5)^2 & ( zt+8 ) & -( zt-8);
obj4 = 1^2-( xt-5 )^2-( yt +5)^2 & ( zt+8 ) & -( zt-8);
obj5 = 1^2-( xt+5 )^2-( yt -5)^2 & ( zt+8 ) & -( zt-8);
obj6 = 1^2-( xt+5 )^2-( yt +5)^2 & ( zt+8 ) & -( zt-8);

sphere1=16-xt^2-yt^2-(x[3]-5)^2;
sphere2=16-xt^2-yt^2-(x[3]+5)^2;

area = ( xt+10 ) & -( xt-10 ) & ( yt+10 ) & -( yt-10 ) & ( zt+10 ) & -( zt-10 ) ;
a0 = 10;
a1 = 20;

ukeke =sphere1+sphere2+((sphere1^2+sphere2^2)^(1/2))+(a0/(1+(sphere1/a1)^2+(sphere2/a1)^2));

paul = obj3|obj4|obj5|obj6;
main =obj1 | obj2 | paul | ukeke;
last = main & area;
model = last;

my_model = model;

}