The logarithm of such a rotation matrix can be readily computed from the antisymmetric part of Rodrigues' rotation formula Engø (2001) (see also Axis angle), except when has eigenvalues equal to − 1 where the log is not unique.
The logarithm of such a rotation matrix can be readily computed from the antisymmetric part of Rodrigues' rotation formula Engø (2001) (see also Axis angle). It yields the logarithm of minimal Frobenius norm, but fails when has eigenvalues equal to − 1 where this is not unique.