# Source code for pyfar.classes.orientations

```
from scipy.spatial.transform import Rotation
import numpy as np
import warnings
import pyfar as pf
# this warning needs to be caught and appears if numpy array are generated
# from nested lists containing lists of unequal lengths, e.g.,
# [[1, 0, 0], [1, 0]]
warnings.filterwarnings("error", category=np.VisibleDeprecationWarning)
[docs]
class Orientations(Rotation):
"""
This class for Orientations in the three-dimensional space,
is a subclass of scipy.spatial.transform.Rotation and equally based on
quaternions of shape (N, 4). It inherits all methods of the Rotation class
and adds the creation from perpendicular view and up vectors and a
convenient plot function.
An orientation can be visualized with the triple of view, up and right
vectors and it is tied to the object's local coordinate system.
Alternatively the object's orientation can be illustrated with help of the
right hand: Thumb (view), forefinger (up) and middle finger (right).
Examples
--------
>>> from pyfar import Orientations
>>> views = [[1, 0, 0], [2, 0, 0]]
>>> ups = [[0, 1, 0], [0, -2, 0]]
>>> orientations = Orientations.from_view_up(views, ups)
Visualize orientations at certain positions:
>>> positions = [[0, 0.5, 0], [0, -0.5, 0]]
>>> orientations.show(positions)
Rotate first element of orientations:
>>> from scipy.spatial.transform import Rotation
>>> rot_x45 = Rotation.from_euler('x', 45, degrees=True)
>>> orientations[1] = orientations[1] * rot_x45
>>> orientations.show(positions)
To create `Orientations` objects use ``from_...`` methods.
``Orientations(...)`` is not supposed to be instantiated directly.
Attributes
----------
quat : array_like, shape (N, 4) or (4,)
Each row is a (possibly non-unit norm) quaternion in scalar-last
(x, y, z, w) format. Each quaternion will be normalized to unit
norm.
"""
[docs]
def __init__(self, quat=None, normalize=True, copy=True):
if quat is None:
quat = np.array([0., 0., 0., 1.])
super().__init__(quat, copy=copy)
[docs]
@classmethod
def from_view_up(cls, views, ups):
"""Initialize Orientations from a view an up vector.
Orientations are internally stored as quaternions for better spherical
linear interpolation (SLERP) and spherical harmonics operations.
More intuitionally, they can be expressed as view and up vectors
which cannot be collinear. In this case, they are restricted to be
perpendicular to minimize rounding errors.
Parameters
----------
views : array_like, shape (N, 3) or (3,), Coordinates
A single vector or a stack of vectors, giving the look-direction of
an object in three-dimensional space, e.g. from a listener, or the
acoustic axis of a loudspeaker, or the direction of a main lobe.
Views can also be passed as a Coordinates object.
ups : array_like, shape (N, 3) or (3,), Coordinates
A single vector or a stack of vectors, giving the up-direction of
an object, which is usually the up-direction in world-space. Views
can also be passed as a Coordinates object.
Returns
-------
orientations : `Orientations` instance
Object containing the orientations represented by quaternions.
"""
# init views and up
try:
views = np.atleast_2d(views).astype(np.float64)
ups = np.atleast_2d(ups).astype(np.float64)
except np.VisibleDeprecationWarning:
raise ValueError("Expected `views` and `ups` to have shape (N, 3)")
# check views and ups
if (views.ndim > 2 or views.shape[-1] != 3 or
ups.ndim > 2 or ups.shape[-1] != 3):
raise ValueError(f"Expected `views` and `ups` to have shape (N, 3)"
f" or (3,), got {views.shape}")
if views.shape == ups.shape:
pass
elif views.shape[0] > 1 and ups.shape[0] == 1:
ups = np.repeat(ups, views.shape[0], axis=0)
elif ups.shape[0] > 1 and views.shape[0] == 1:
views = np.repeat(views, ups.shape[0], axis=0)
else:
raise ValueError("Expected 1:1, 1:N or N:1 `views` and `ups` "
f"not M:N, got {views.shape} and {ups.shape}")
if not (np.all(np.linalg.norm(views, axis=1)) and
np.all(np.linalg.norm(ups, axis=1))):
raise ValueError("View and Up Vectors must have a length.")
if not np.allclose(0, np.einsum('ij,kj->k', views, ups)):
raise ValueError("View and Up vectors must be perpendicular.")
# Assuming that the direction of the cross product is defined
# by the right-hand rule
rights = np.cross(views, ups)
rotation_matrix = np.asarray([views, ups, rights])
rotation_matrix = np.swapaxes(rotation_matrix, 0, 1)
return super().from_matrix(rotation_matrix)
[docs]
def show(self, positions=None,
show_views=True, show_ups=True, show_rights=True, **kwargs):
"""
Visualize Orientations as triples of view (red), up (green) and
right (blue) vectors in a quiver plot.
Parameters
----------
positions : array_like, shape (O, 3), O is len(self)
These are the positions of each vector triple. If not provided,
all triples are positioned in the origin of the coordinate system.
show_views: bool
select wether to show the view vectors or not.
The default is True.
show_ups: bool
select wether to show the up vectors or not.
The default is True.
show_rights: bool
select wether to show the right vectors or not.
The default is True.
Returns
-------
ax : matplotlib.axes._subplots.Axes3DSubplot
The axis used for the plot.
"""
if positions is None:
positions = np.zeros((self.as_quat().shape[0], 3))
positions = np.atleast_2d(positions).astype(np.float64)
if positions.shape[0] != self.as_quat().shape[0]:
raise ValueError("If provided, there must be the same number"
"of positions as orientations.")
# Create view, up and right vectors from Rotation object
views, ups, rights = self.as_view_up_right()
kwargs.pop('color', None)
ax = None
if show_views:
ax = pf.plot.quiver(
positions, views, color=pf.plot.color('r'), **kwargs)
if show_ups:
ax = pf.plot.quiver(
positions, ups, ax=ax, color=pf.plot.color('g'), **kwargs)
if show_rights:
ax = pf.plot.quiver(
positions, rights, ax=ax, color=pf.plot.color('b'), **kwargs)
[docs]
def as_view_up_right(self):
"""Get Orientations as a view, up, and right vector.
Orientations are internally stored as quaternions for better spherical
linear interpolation (SLERP) and spherical harmonics operations.
More intuitionally, they can be expressed as view and and up of vectors
which cannot be collinear. In this case are restricted to be
perpendicular to minimize rounding errors.
Returns
----------
vector_triple: ndarray, shape (N, 3), normalized vectors
- views, see `Orientations.from_view_up.__doc__`
- ups, see `Orientations.from_view_up.__doc__`
- rights, see `Orientations.from_view_up.__doc__`
A single vector or a stack of vectors, pointing to the right of
the object, constructed as a cross product of ups and rights.
"""
# Apply self as a Rotation (base class) on eye i.e. generate orientions
# as rotations relative to standard basis in 3d
vector_triple = super().as_matrix()
if vector_triple.ndim == 3:
return np.swapaxes(vector_triple, 0, 1)
return vector_triple
[docs]
def copy(self):
"""Return a deep copy of the Orientations object."""
return self.from_quat(self.as_quat())
def _encode(self):
"""Return object in a proper encoding format."""
# Use public interface of the scipy super-class to prevent
# error in case of chaning super-class implementations
return {'quat': self.as_quat()}
@classmethod
def _decode(cls, obj_dict):
"""Decode object based on its respective `_encode` counterpart."""
return cls.from_quat(obj_dict['quat'])
def __setitem__(self, idx, val):
"""
Assign orientations(s) at given index(es) from object.
Parameters
----------
idx : see NumPy Indexing
val : array_like quaternion(s), shape (N, 4) or (4,)
"""
if isinstance(val, Orientations):
val = val.as_quat()
quat = np.atleast_2d(val)
if quat.ndim > 2 or quat.shape[-1] != 4:
raise ValueError(f"Expected assigned value to have shape"
f" or (1, 4), got {quat.shape}")
quats = self.as_quat()
quats[idx] = quat
self = super().from_quat(quats)
def __eq__(self, other):
"""Check for equality of two objects."""
return np.array_equal(self.as_quat(), other.as_quat())
```