yade-users team mailing list archive

[Janek Kozicki <janek_listy@xxxxx>]

Jerome Duriez said:     (by the date of Tue, 12 Feb 2008 16:55:13 +0100)

> Hello everybody. I am focusing about the "RotationEngine" (in 
> pkg/common/Engine/DeusExMachina) and trying to understand well what it 
> does, so I have for instance one simple question :
> 
> - which is the purpose of the line 
> "/rb->se3.orientation.ToAxisAngle(ax,an);/" ? I think I understand what 
> it does : it affects to the 3-real vector "/ax/" and the real "/an"/ 

It does not affect ax and an. The se3.orientation is built from
axis,angle. This command calculates 3D orientation (rotation) from
two arguments - the axis of rotation, and the angle of rotation
around this axis.

> (both declared few lines above) respectively the axis and angle of the 
> rotation corresponding to the quaternion "/orientation/".
> But why ?
> These "/an/" and "/ax/" seem indeed never to be used after that...

So axis, angle are not used after that, because we don't need them
anymore - we are using se3.orientation built from them.

To understand this better have a look at page 145 of

  http://janek.kozicki.pl/phdthesis/kozicki_2007_PhD.pdf

best regards
-- 
Janek Kozicki                                                         |
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