[eigen] precision loss after conversion from rotation matrix to quaternion and back |

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Hello all,
So here is my problem:
I have this rotation matrix (Scalar type double):
0.124564 -0.800873 0.584451
-0.971925 0.0176983 0.231399
-0.19596 -0.597765 -0.777352

`Then I convert it to a Quaternion (Scalar type double) using the
``constructor. The quaternion coefficients (x,y,z,w) are:
`0.686334 -0.645749 0.14151 -0.302026

`Finally I convert the Quaternion back to a rotation matrix using the
``function toRotationMatrix(), which yields a slightly different matrix:
`
0.125967 -0.80092 0.584312
-0.971878 0.0178409 0.231823
-0.195821 -0.597341 -0.776092
0.686334 -0.645749 0.14151 -0.302026

`As you can see some numbers differ on the third significant digit, which
``cannot be explained by floating point rounding errors. So where does it
``come from? If I repeat the procedure the rotation matrix will not differ
``again. It changes only on the first forth-and-back conversion.
`I'd appreciate any help.
Best regards,
Tobias