def get_sample_local(resolution=2, center=None, grid_width=10):
"""
Generates a grid of rotations about a given rotation
Parameters
----------
resolution : float, optional
The characteristic distance between a rotation and its neighbour (degrees)
center : orix.quaternion.rotation.Rotation, optional
The rotation at which the grid is centered. If None (default) uses the identity
grid_width : float, optional
The largest angle of rotation away from center that is acceptable (degrees)
Returns
-------
q : orix.quaternion.rotation.Rotation
Grid of rotations lying within grid_width of center
See Also
--------
orix.sampling_utils.uniform_SO3_sample
"""
q = uniform_SO3_sample(resolution)
half_angle = np.deg2rad(grid_width / 2)
half_angles = np.arccos(q.a.data)
mask = np.logical_or(half_angles < half_angle, half_angles >
(2 * np.pi - half_angle))
q = q[mask]
if center is not None:
q = center * q
return q
def get_sample_fundamental(resolution=2, point_group=None, space_group=None):
"""
Generates an equispaced grid of rotations within a fundamental zone.
Parameters
----------
resolution : float, optional
The characteristic distance between a rotation and its neighbour (degrees)
point_group : orix.quaternion.symmetry.Symmetry, optional
One of the 11 proper point groups, defaults to None
space_group: int, optional
Between 1 and 231, defaults to None
Returns
-------
q : orix.quaternion.rotation.Rotation
Grid of rotations lying within the specified fundamental zone
See Also
--------
orix.sampling.utils.uniform_SO3_sample
Examples
--------
>>> from orix.quaternion.symmetry import C2,C4
>>> grid = get_sample_fundamental(1, point_group=C2)
"""
if point_group is None:
point_group = get_point_group(space_group, proper=True)
q = uniform_SO3_sample(resolution)
fundamental_region = OrientationRegion.from_symmetry(point_group)
return q[q < fundamental_region]
def test_uniform_SO3_sample_resolution(sample):
""" Checks that doubling resolution doubles density (8-fold counts) """
lower = uniform_SO3_sample(4)
x, y = lower.size * 8, sample.size
assert np.isclose(x, y, rtol=0.025)
def sample():
return uniform_SO3_sample(2)