def test_a_ray_misses_s_sphere():
# Given
r = Ray(Point(0, 2, -5), Vector(0, 0, 1))
s = Sphere()
# When
xs = s.intersect(r)
# Then
assert len(xs) == 0
def test_intersecting_a_translated_sphere_with_a_ray():
# Given
r = Ray(Point(0, 0, -5), Vector(0, 0, 1))
s = Sphere()
# When
s.transform = translation(5, 0, 0)
xs = s.intersect(r)
# Then
assert len(xs) == 0
def test_a_ray_intersects_a_sphere_at_two_points():
# Given
r = Ray(Point(0, 0, -5), Vector(0, 0, 1))
s = Sphere()
# When
xs = s.intersect(r)
# Then
assert len(xs) == 2
assert xs[0].t == 4.0
assert xs[1].t == 6.0
def test_intersect_sets_the_object_on_the_intersection():
# Given
r = Ray(Point(0, 0, -5), Vector(0, 0, 1))
s = Sphere()
# When
xs = s.intersect(r)
# Then
assert len(xs) == 2
assert xs[0].object == s
assert xs[1].object == s
def test_a_sphere_is_behind_a_ray():
# Given
r = Ray(Point(0, 0, 5), Vector(0, 0, 1))
s = Sphere()
# When
xs = s.intersect(r)
# Then
assert len(xs) == 2
assert xs[0].t == -6.0
assert xs[1].t == -4.0
def test_a_ray_originates_inside_a_sphere():
# Given
r = Ray(Point(0, 0, 0), Vector(0, 0, 1))
s = Sphere()
# When
xs = s.intersect(r)
# Then
assert len(xs) == 2
assert xs[0].t == -1.0
assert xs[1].t == 1.0
def test_a_ray_intersects_a_sphere_at_a_tangent():
# Then
r = Ray(Point(0, 1, -5), Vector(0, 0, 1))
s = Sphere()
# When
xs = s.intersect(r)
# Then
assert len(xs) == 2
assert xs[0].t == 5.0
assert xs[1].t == 5.0
def test_intersecting_a_scaled_sphere_with_a_ray():
# Given
r = Ray(Point(0, 0, -5), Vector(0, 0, 1))
s = Sphere()
# When
s.transform = scaling(2, 2, 2)
xs = s.intersect(r)
# Then
assert len(xs) == 2
assert xs[0].t == 3
assert xs[1].t == 7
light_position = Point(-10, 10, -10)
light_color = Color(1, 1, 1)
light = PointLight(light_position, light_color)
# for each row of pixels in the canvas
for y in range(canvas_pixcels):
# compute the world y coordinate (top = +half, bottom = -half)
world_y = half - pixel_size * y
for x in range(canvas_pixcels):
# compute the world x coordinate (left = -half, right = half)
world_x = -half + pixel_size * x
# describe the point on the wall that the ray will target
position = Point(world_x, world_y, wall_z)
r = Ray(ray_origin, (position - ray_origin).normalize())
xs = shape.intersect(r)
if isinstance(xs, Intersections):
hit = xs[0]
point = r.position(hit.t)
normal = hit.object.normal_at(point)
eye = -r.direction
color = hit.object.material.lighting(light, point, eye, normal)
canvas.write_pixel(x, y, color)
print(canvas.to_ppm())
