[Insight-users] Quaternion Parameters

[Andy Eow]

Hi,

Have a question regarding quaternions. I obtained the following parameters from running MultiResMIRegistration:

[-0.000237939, -0.0875924, 0.171368, 0.981306, 11.589, 2.08898, 1.14517]

I need to apply a transform that is half the rotation and half the translation of the QuaternionRigidTransform as given by the parameters above. The last 3 parameters are translation so halving those is trivial. Question is how do I go about halving the effective rotation of the transform? Which of the first 4 parameters do I change and can I simply half the rotation angle or do I have to maintain a unit quaternion to avoid scaling issues?

Thanks.

Cheers,
Andy
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