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From "Albert Huang (JIRA)" <>
Subject [jira] Commented: (MATH-363) please clarify quaternion conventions in org.apache.commons.math.geometry.Rotation
Date Thu, 15 Apr 2010 15:42:49 GMT


Albert Huang commented on MATH-363:

Looks good to me, thanks!

> please clarify quaternion conventions in org.apache.commons.math.geometry.Rotation
> ----------------------------------------------------------------------------------
>                 Key: MATH-363
>                 URL:
>             Project: Commons Math
>          Issue Type: Improvement
>    Affects Versions: 2.0
>         Environment: all
>            Reporter: Albert Huang
>            Priority: Minor
> Please clarify which quaternion convention is used in the Rotation documentation, and
provide constructor methods to use alternate quaternion conventions.
> For example, the computer graphics community has standardized on representing a rotation
of angle theta about the unit vector (i, j, k)  with the quaternion
> { cos(theta/2), i * sin(theta/2), j * sin(theta/2), k * sin(theta/2) }
> e.g., any introductory computer graphics textbook referring to quaternions will describe
them in this convention.  This is also the convention appearing on Mathworld, Wikipedia, etc.

> The convention in org.apache.commons.math.geometry.Rotation instead appears to be
> { cos(-theta/2),  i * sin(-theta/2),  j * sin(-theta/2), k * sin(-theta/2) }
> Since I'm not likely to convince you to switch conventions, please at least document
the convention and provide ways to convert from the alternate (this should be trivial?)

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