def test_normal_reflection(self):
node = Node(name="node")
ctx = Context(n1=1.0, n2=1.5, normal_node=node, normal=(0.0, 0.0, 1.0), kind=Kind.SURFACE, end_path=(10, 10, 10), container=None)
ray = Ray(position=(0.0, 0.0, 0.0), direction=(0.0, 0.0, 1.0), wavelength=None)
interaction = FresnelReflection(ctx)
p = interaction.probability(ray)
assert np.isclose(p, 0.04)
def test_antinormal_reflection(self):
""" FresnelReflection takes the smallest angle between the ray direction and
the normal. Thus the flipped normal will also work.
"""
node = Node(name="node")
ctx = Context(n1=1.0, n2=1.5, normal_node=node, normal=(0.0, 0.0, -1.0), kind=Kind.SURFACE, end_path=(10, 10, 10), container=None)
ray = Ray(position=(0.0, 0.0, 0.0), direction=(0.0, 0.0, 1.0), wavelength=None)
interaction = FresnelReflection(ctx)
p = interaction.probability(ray)
assert np.isclose(p, 0.04)
def generate_interaction_sequence(self, ray, context):
""" Decision tree for crossing a dielectric interface:
- Test for reflection.
- If reflected
- reflect and exit
- If not reflected
- refract and exit.
"""
# Test for reflection.
mech = FresnelReflection(context)
p = mech.probability(ray)
gamma = np.random.uniform()
if gamma < p:
yield mech
else:
yield FresnelRefraction(context)