ROM Hack [Question] how do you change a character model?

[OffSetEyeBrow]

I've extracted a model from animal crossing wild world (punchy), and I've being trying to change his position from T pose (without success), is there any way that I can do that without adding or deleting polligons?

 

[FAST6191]

The main 3d format for the DS (though by no means is it ubiquitous) is NSBMD. It contains the data for the locations of the vertices in the main model
It is flanked by two other formats
NSBTX (texture files)
NSBCA (animation files)

NSBCA allows movement of these vertices, textures for texture animation will have to be handled. Said textures are not mandatory and plenty of games just use the material colours.

The t pose is a fairly standard model design for 3d models of humanoids as it gives a basic position for all other animations to stem from as well as see how the textures work.

I don't know what you are attempting to do here. You can change the relevant coordinates of the texture file such that the arms are in a different location if you want. This will make standard NSBMD viewers display it accordingly. This would mainly be useful for some kind of machinima or something, in this case not so useful for a ROM hack. I have not played with the 3d viewer of no$gba debug for a while but it might have something you can use here similar to sprite rippers using the OAM/tile viewers of emulators.
Alternatively if your viewer supports NSBCA files (unlikely as standalone viewers of 3d models on the DS are not that advanced) then you could tweak said animations to represent a pose you want and go from there.

I have some limited stuff on how 3d works on the DS in https://gbatemp.net/threads/gbatemp-rom-hacking-documentation-project-new-2016-edition-out.73394/
If you want the tech side of things
http://problemkaputt.de/gbatek.htm#ds3dvideo
I don't have a good document for describing the format (older choices like http://kiwi.ds.googlepages.com/nsbmd.html are rather limited) and you would probably be better off looking at source code for things like tinke and mkds course modifier.

 

[OffSetEyeBrow]

The main 3d format for the DS (though by no means is it ubiquitous) is NSBMD. It contains the data for the locations of the vertices in the main model
It is flanked by two other formats
NSBTX (texture files)
NSBCA (animation files)

NSBCA allows movement of these vertices, textures for texture animation will have to be handled. Said textures are not mandatory and plenty of games just use the material colours.

The t pose is a fairly standard model design for 3d models of humanoids as it gives a basic position for all other animations to stem from as well as see how the textures work.

I don't know what you are attempting to do here. You can change the relevant coordinates of the texture file such that the arms are in a different location if you want. This will make standard NSBMD viewers display it accordingly. This would mainly be useful for some kind of machinima or something, in this case not so useful for a ROM hack. I have not played with the 3d viewer of no$gba debug for a while but it might have something you can use here similar to sprite rippers using the OAM/tile viewers of emulators.
Alternatively if your viewer supports NSBCA files (unlikely as standalone viewers of 3d models on the DS are not that advanced) then you could tweak said animations to represent a pose you want and go from there.

I have some limited stuff on how 3d works on the DS in https://gbatemp.net/threads/gbatemp-rom-hacking-documentation-project-new-2016-edition-out.73394/
If you want the tech side of things
http://problemkaputt.de/gbatek.htm#ds3dvideo
I don't have a good document for describing the format (older choices like http://kiwi.ds.googlepages.com/nsbmd.html are rather limited) and you would probably be better off looking at source code for things like tinke and mkds course modifier.

to view the model and textures im using mkds course modifier, is there a way to change the animation with it?

 

[FAST6191]

I don't know that I have ever seen a step by step animation playback tool, much less an animation editor. Similarly I don't think there is going to be an easy way to export things to a more general 3d modeller either.

Tools for 3d format hacking on the DS are really quite primitive.