compute mean of a set of rotations#160
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myeatman-bdai merged 16 commits intobdaiinstitute:masterfrom Jan 26, 2025
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Need to make log() method handle a multi-value quaternion.
…ued quaternion object.
… a vector, v is an array.
…ase when vector part is zero.
myeatman-bdai
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Jan 22, 2025
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See inline comments.
spatialmath/pose3d.py
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| eta = tol * np.finfo(float).eps | ||
| R_mean = self[0] # initial guess | ||
| while True: | ||
| r = np.dstack((self.inv() * self).log()).mean(axis=2) |
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It's unclear to me what section of the reference paper outlines this algorithm (admittedly, I did not thoroughly read it) . Would you mind pointing it out to me?
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I've clarified that.
…for a quaternion implementation, rather than converting to/from SO(3) matrices.
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Ok, fixed some bugs, tests pass. There is a randomised test but it is reproducible, using a seeded random number generator. I've commented out, for now, the quaternion mean. Naively applying the SO(3) algorithms for quaternions didn't work, and I need to do more reading. |
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New method
mean()for each ofSO3andUnitQuaternion, computes the Karcher (rotational) mean.Relatively straightforward for
SO3butUnitQuaternionrequired a bunch of changes to allow more methods to handle multi-valuedUnitQuaternionobjects. Fixed forRPY(),Eul(),UnitQuaternion()constructor,log()andexp(). Also had to fix edge case forlog()andexp()for the unit quaternions case.Tests and doco updated.
The result is a lot of changes, but generally improved functionality for the
UnitQuaternionclass.