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From "Frank Hess (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MATH-846) Rotation constructor does wrong calculation
Date Thu, 16 Aug 2012 13:43:38 GMT

    [ https://issues.apache.org/jira/browse/MATH-846?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13435962#comment-13435962
] 

Frank Hess commented on MATH-846:
---------------------------------

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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