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https://issues.apache.org/jira/browse/MATH-846?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13435962#comment-13435962
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Frank Hess commented on MATH-846:
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I think you are right. I downloaded svn HEAD (r1373782) and the problem seems
to be gone. Thanks for your help.
> Rotation constructor does wrong calculation
> -------------------------------------------
>
> Key: MATH-846
> URL: https://issues.apache.org/jira/browse/MATH-846
> Project: Commons Math
> Issue Type: Bug
> Affects Versions: 3.0
> Environment: Windows java 1.7r5
> Reporter: Frank Hess
>
> The following code produces the wrong result. The resulting Rotation is does
> not even hold a normalized quaternion:
> final Vector3D u1 = new Vector3D(1.0, 0.0, 0.0);
> final Vector3D u2 = new Vector3D(1.0, -1.0, 0.0);
> final Vector3D v1 = new Vector3D(0.9999999, 0., 0.0);
> final Vector3D v2 = new Vector3D(0., 1., 0.0);
> final Rotation rot = new Rotation(u1, u2, v1, v2);
> System.err.println("rot quaternion: " + rot.getQ0() + " " + rot.getQ1() + " "
> + rot.getQ2() + " " + rot.getQ3());
> For me it outputs:
> rot quaternion: 0.0 0.0 0.0 -7.450580596923828E-9
> The correct output should have been:
> rot quaternion: 0.0 1.0 0.0 0.0
> The constructor seems to be hitting some kind of numerical instability.
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