# Transf WD Euler transformation

Laurent MICHEL laurent.michel at astro.unistra.fr
Fri Apr 3 15:11:18 CEST 2020

```Hello,

I do not practice Euler transformations daily, but according to my
college souvenirs, that is by definition a 3D rotation with a well
defined sequence of rotation axis.
In my understanding, the Euler rotation is even not a particular case of
the Transf rotation since the 3 Euler rotations are not about native
axis as stated in the definition you give.

> Defines a rotation operation in a 3-dimensional cartesian coordinate space, defined as a series of rotations about the native axes (x,y,z)

If I'm right, the class should be renamed (RotationSequence ?). If not,
my comment is no longer relevant.

Laurent

Le 02/04/2020 à 16:40, CresitelloDittmar, Mark a écrit :
> Laurent,
>
> This came directly from the implementation group discussions back in Dec
> 2018.
> gWCS has use cases where more than 3 rotations are useful, for example
> EulerRotation(angles=[12, 1, 2, 3], axes=‘xyzx’).
> So we've taken this approach of having a sequence of EulerAngles which
> specify the 'axis of rotation' (of the 3D space as either 'x', 'y', or
> 'z') and angle.
>
> Mark
>
>
> On Thu, Apr 2, 2020 at 8:31 AM Laurent MICHEL
> <laurent.michel at astro.unistra.fr
> <mailto:laurent.michel at astro.unistra.fr>> wrote:
>
>     Dear,
>
>     My comment #1: Why is the Euler Transformation class so complex?
>
>     - It is always a 3D transformation, this there is no reason to setup a
>     1-* aggregation with angles.
>
>     - Euler angles (nutation, rotation, intrinsic rotation) are well
>     defined, there is no need for a specific datatype (EulerAngle). So we
>     could just have 3 class attributes.
>
>     - Using a specific datatype where angles are identified by a the
>     name of
>     the rotation axis supposes we have a vocabulary for this, which is a
>     bit
>     complicated for this purpose with the risk a implementation errors.
>
>     Take care of yourself.
>
>     LM
>
>     --
>     ---- Laurent MICHEL              Tel  (33 0) 3 68 85 24 37
>            Observatoire de Strasbourg  Fax  (33 0) 3 68 85 24 32
>            11 Rue de l'Universite      Mail
>     laurent.michel at astro.unistra.fr <mailto:laurent.michel at astro.unistra.fr>
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>     ---
>

--
---- Laurent MICHEL              Tel  (33 0) 3 68 85 24 37
Observatoire de Strasbourg  Fax  (33 0) 3 68 85 24 32
11 Rue de l'Universite      Mail laurent.michel at astro.unistra.fr
67000 Strasbourg (France)   Web  http://astro.u-strasbg.fr/~michel
---
```