def test_child_normal():
g1 = Group()
g1.set_transform(RotationY(math.pi / 2))
g2 = Group()
g2.set_transform(Scaling(1, 2, 3))
g1.add_child(g2)
s = Sphere()
s.set_transform(Translation(5, 0, 0))
g2.add_child(s)
n = s.normal_at(Point(1.7321, 1.1547, -5.5774))
assert n == Vector(0.2857, 0.4286, -0.8571)
def test_normal_is_normal():
s = Sphere()
num = math.sqrt(3) / 3
n = s.normal_at(Point(num, num, num))
assert n == n.normalize()
def test_sphere_z_normal():
s = Sphere()
n = s.normal_at(Point(0, 0, 1))
assert n == Vector(0, 0, 1)
def test_sphere_nonaxial_normal():
s = Sphere()
num = math.sqrt(3) / 3
n = s.normal_at(Point(num, num, num))
assert n == Vector(num, num, num)
def test_sphere_y_normal():
s = Sphere()
n = s.normal_at(Point(1, 0, 0))
assert n == Vector(1, 0, 0)