# [PD] Gem gemlist_info and gemlist_matrix

Cyrille Henry ch at chnry.net
Thu Sep 6 10:30:18 CEST 2012

```hello,
i don't really understand what you want to do.
rotating a point in space can be done with rotateXYZ, but this is certainly not the answer you wanted.
if you want to move with no rotation around a sphere, then you can use sph2cart object.
algebra is quite simple :
https://en.wikipedia.org/wiki/Spherical_coordinate

but i don't understand what gemlist_info and gemlist_matrix could have been od any help.

cheers
c

Le 06/09/2012 04:53, Max a écrit :
> bonjour cyrille,
>
> I see, so it's because i'm messing with the view message to change the angle towards the object in my gem scene. So gemlist_info is always referring to the camera in gem, that's important to understand and it means i can't use it what I thought I'd use it for. Actually I just wanted to rotate a point in the space and I was too lazy for the algebra. There must be some abstractions for that and I think I saw some in the PdMtl… tomorrow.
>
> bonne nuit,
> m.
>
> Am 06.09.2012 um 00:06 schrieb Cyrille Henry:
>
>> hello Max,
>>
>> on gemlist_info help patch, the default position is 0 0 -4, rotation, and shear are 0 0 0, size is 1 1 1.
>> changing the translate to 0 0 4 result having the gemlist_info position to 0 0 0.
>> adding the rotation before the translation will result in a different translation (because it was rotated). So the position will not be 0 0 0 any more.
>>
>> since the 1st transformation comes from the camera position and rotation, playing with camera position can result in the value you describe.
>>
>>
>>
>>
>> this object output a 4x4 matrix. but since pd did not have a native matrix type, the 16 float are output as a list.
>>
>> cheers
>> c
>>
>>
>> Le 05/09/2012 23:46, Max a écrit :
>>> dear list,
>>>
>>> i'm wondering how the gemlist_info and gemlist_matrix objects work. gemlist_info for instance has a default position of x, y, z: 0, -2.38419e-07, -13.0551
>>> which i found strange, so i thought i'd add a translateXYZ 0 2.38419e-07 13.0551 before the gemlist_info to get reset the position to zero. but then i get 7.30032, -10.4295, -10.1628
>>> that seems very strange to me can someone enlighten me?
>>> the gemlist_matrix-help seems very incomplete, it doesn't explain what difference of the matrix and the list is and what the output values \$1…\$15 are.
>>>
>>> thanks,
>>> m.
>>>
>>>
>>>
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```