def testfun(translation):
translated_convex_cube = ConvexPolyhedron(convex_cube.vertices +
translation)
translated_inertia = translate_inertia_tensor(
translation, convex_cube_inertia_tensor, convex_cube_volume)
mc_tensor = compute_inertia_mc(translated_convex_cube.vertices,
convex_cube_volume, 1e4)
uncentered_inertia_tensor = translated_convex_cube._compute_inertia_tensor(
False)
assert np.allclose(
translated_inertia,
uncentered_inertia_tensor,
atol=2e-1,
rtol=2e-1,
)
assert np.allclose(mc_tensor,
uncentered_inertia_tensor,
atol=2e-1,
rtol=2e-1)
assert np.allclose(mc_tensor, translated_inertia, atol=1e-2, rtol=1e-2)
assert np.allclose(mc_tensor,
translated_convex_cube.inertia_tensor,
atol=1e-2,
rtol=1e-2)
def test_translate_inertia(translation):
shape = PlatonicFamily.get_shape("Cube")
# Choose a volume > 1 to test the volume scaling, but don't choose one
# that's too large because the uncentered polyhedral calculation has
# massive error without fixing that.
shape.volume = 2
shape.center = (0, 0, 0)
translated_shape = ConvexPolyhedron(shape.vertices + translation)
translated_inertia = translate_inertia_tensor(translation,
shape.inertia_tensor,
shape.volume)
mc_tensor = compute_inertia_mc(translated_shape.vertices, 1e4)
assert np.allclose(
translated_inertia,
translated_shape._compute_inertia_tensor(False),
atol=2e-1,
rtol=2e-1,
)
assert np.allclose(mc_tensor,
translated_shape._compute_inertia_tensor(False),
atol=2e-1,
rtol=2e-1)
assert np.allclose(mc_tensor, translated_inertia, atol=1e-2, rtol=1e-2)
assert np.allclose(mc_tensor,
translated_shape.inertia_tensor,
atol=1e-2,
rtol=1e-2)
def test_inertia_tensor(r, center):
sphere = Sphere(r)
assert np.all(sphere.inertia_tensor >= 0)
volume = 4 / 3 * np.pi * r**3
expected = [2 / 5 * volume * r**2] * 3
np.testing.assert_allclose(np.diag(sphere.inertia_tensor), expected)
sphere.center = center
expected = translate_inertia_tensor(center, np.diag(expected), volume)
np.testing.assert_allclose(sphere.inertia_tensor, expected)
def test_inertia_tensor(a, b, c, center):
# First just test a sphere.
ellipsoid = Ellipsoid(a, a, a)
assert np.all(ellipsoid.inertia_tensor >= 0)
volume = ellipsoid.volume
expected = [2 / 5 * volume * a ** 2] * 3
np.testing.assert_allclose(np.diag(ellipsoid.inertia_tensor), expected)
ellipsoid.center = center
expected = translate_inertia_tensor(center, np.diag(expected), volume)
np.testing.assert_allclose(ellipsoid.inertia_tensor, expected)