def threefold(n, h, d, points=True):
s = System(hextess(n, points))
ct = []
ct.append(PatternRangeConstraint(min=0, max=1.))
for p in 0, 4*np.pi/3, 2*np.pi/3:
x = np.array([d/3**.5*np.cos(p), d/3**.5*np.sin(p), h])
r = euler_matrix(p, np.pi/2, np.pi/4, "rzyz")[:3, :3]
for i in "x y z xy xz yz".split():
ct.append(PotentialObjective(derivative=i, x=x,
rotation=r, value=0))
for i, v in ("xx", 1), ("yy", 1):
ct.append(PotentialObjective(derivative=i, x=x,
rotation=r, value=v))
s.rfs, c = s.optimize(ct)
return s, c
