30 lines
751 B
Python
30 lines
751 B
Python
import numpy as np
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def qrot(q, v):
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"""
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Rotate vector(s) v about the rotation described by quaternion(s) q.
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Expects a tensor of shape (*, 4) for q and a tensor of shape (*, 3) for v,
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where * denotes any number of dimensions.
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Returns a tensor of shape (*, 3).
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"""
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assert q.shape[-1] == 4
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assert v.shape[-1] == 3
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assert q.shape[:-1] == v.shape[:-1]
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qvec = q[..., 1:]
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uv = np.cross(qvec, v)
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uuv = np.cross(qvec, uv)
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return (v + 2 * (q[..., :1] * uv + uuv))
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def qinverse(q, inplace=False):
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# We assume the quaternion to be normalized
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if inplace:
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q[..., 1:] *= -1
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return q
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else:
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w = q[..., :1]
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xyz = q[..., 1:]
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return np.hstack((w, -xyz))
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