var r = 5, o = r - .5;
var a = CSG.sphere({ radius: r, center: [0, +o, 0], stacks: 40 });
var b = CSG.sphere({ radius: r, center: [0, -o, 0], stacks: 40 });
var c = CSG.sphere({ radius: 1 });
a.setColor(1, 0, 0);
b.setColor(0, 0, 1);
c.setColor(0, 1, 0);
return a.intersect(b).union(c);