def random_in_unit_disk():
p = Vec()
while True:
p.x = 2 * random()
p.y = 2 * random()
if Vec.dot(p, p) >= 1:
break
return p
def random_in_unit_sphere():
p = Vec()
while True:
p.x = 2 * random() - 1
p.y = 2 * random() - 1
p.z = 2 * random() - 1
if p.squared_length() < 1:
break
return p