Skeletons and Bodies: Explanation Requested

[Lestroisrois]

Okay, please allow me to start by saying that I am very new at 3D modeling, animation, and mod-making. I'm lucky enough that my curriculum in college involves the former two, but I'm still far from understanding the details of all of this, especially with regards to mods. As such, I thought it in my best interest to come here and ask a question.

 

Something I encounter every now and again here on the Nexus is mods stating they only work with a specific "body" or "skeleton." As far as I understand, these are two different things, yet at the same time I don't really understand their relation. To take two examples, the body type UNP and the skeleton XP32. I take it the former modifies the model's polygons while the latter modifies the rigging, but as far as I understand, rigging is for the most part model-specific; you can't just slap any rig onto any model without getting stretching and awkward movement of various limbs, etc. Yet as far as I've seen, most body and skeleton mods don't state any correlation.

 

So here is my question, or rather three questions: am I misunderstanding? Are people referring to something different when they say "body" and "skeleton?" Do the two not list a correlation because any "skeleton" can be used with any "body?"

 

Thanks in advance for any assistance or explanation, as well as for taking the time to read all of this.

[Vic88]

Well, as you said, they are different and separate things, while at the same time they are related.

 

So, animation 101: The skeleton contains the bones used in the animations (as in, moved to "animate" the bodies or whatever) . So, you have things like "left forearm", "right foot", and so on. The meshes then are weighted to the bones where it makes sense, so the left forearm in the body or armor is weighted to the left forearm so it moves when the corresponding bone moves (and that's how you animate any character). That's pretty straightforward.

 

The "body" refers to the actual body 3d model, and the difference between them is usually the shape and/or the UV map. So you have different bodies with different shapes and UV's (so their textures are not cross-compatible) like UNP and CBBE, and you have bodies with different shapes but the same UV (so the textures are compatible). For example, any UNP derivative body such as SevenBase can use UNP-compatible textures.

 

Now, on to the relation between them. The thing is, whenever a body or armor is weighted to a bone that is not present in the skeleton, issues happen. Back in Oblivion the part of the model with the missing weight would stretch into infinity whenever said model was loaded. In Skyrim, it simply causes the game to crash. So, whenever a body replacer "requires" a certain skeleton, is because the body is weighted to a bone absent from the vanilla skeleton (such as breast bones, belly bones, wing bones...), and thus would make the game crash without said custom skeleton.

 

So, meshes rigged to the vanilla skeleton will work with any skeleton, but meshes rigged to custom skeleton requires that skeleton or another one with the same bones.

 

Now, for example, the XPMSE skeleton (as the XP32 one is currently outdated) unifies the different skeletons by combining their bones into one single skeleton, so by installing that one you are guaranteed compatibility with any model or animation that requires custom non-vanilla bones.

 

Hope this is clear enough.

[wolfsangeleyes]

Wow, complicated stuff but the more I read your explanation, the more it begins to make sense. (I am currently following Nightasy's tutorials so most of this stuff is double Dutch)

 

And thank you for explaining the difference between XPMSE and XP32. I never quite understood it untill now.

Am I therefore right in assuming that if a mod requires XP32, you can safely install XPMSE instead?

[Vic88]

 

And thank you for explaining the difference between XPMSE and XP32. I never quite understood it untill now.

Am I therefore right in assuming that if a mod requires XP32, you can safely install XPMSE instead?

Yes, you are. XPMSE is the updated version of XP32. I think there were some important changes from XP32 version 1.93 (the last one) to XPMSE 2.0 (it is at 3.8 by now), and that's why it was released with a different "brand", but don't quote me on that.

 

Anyway, there shouldn't be any problem. Any XP32 compatible mod will work with XPMSE just fine.

[wolfsangeleyes]

 

 

 

 

And thank you for explaining the difference between XPMSE and XP32. I never quite understood it untill now.

Am I therefore right in assuming that if a mod requires XP32, you can safely install XPMSE instead?

Yes, you are. XPMSE is the updated version of XP32. I think there were some important changes from XP32 version 1.93 (the last one) to XPMSE 2.0 (it is at 3.8 by now), and that's why it was released with a different "brand", but don't quote me on that.

 

Anyway, there shouldn't be any problem. Any XP32 compatible mod will work with XPMSE just fine.

 

 

 

 

Thank you for the reply and info. Kudos to you.

[Lestroisrois]

I think I understand what you are saying (I very-much appreciate the full explanation, by the way). So in this case the bodies such as UNP and CBBE are designed to work with the vanilla skeleton and do not actually bring in their own specialty skeleton. This means that XPMSE, a skeleton that expands the original vanilla skeleton to include more bones for the model to interact with while maintaining the original vanilla skeleton's bones and structure is compatible with these models. At the same time, however, the extra bones added by XPMSE enable other mods which require bones that were not present in the vanilla skeleton to also function properly since it adds in the extra bones most mods require into the skeleton. Is this correct?

[Vic88]

 

Yep, you got it right.

 

The only thing I would add to your coment is the fact that, while body replacers such as CBBE, UNP and their derivatives most of the times have a "vanilla" version (as in, for the vanilla skeleton), the "standard" for body replacers is for them to have non-vanilla bone weights (namely breast bones and the like), and thus require any skeleton with those bones (XPMSE being the most convenient because is actively supported and includes compatibility for nearly EVERYTHING).

Edited June 16, 2016 by Vic88

[Lestroisrois]

I see. Thanks for the help, folks. I appreciate you increasing the sum of my programming and modding knowledge. (^_^)