My guess is that they 3D scanning the outfits and are using models with similar proportions to EVE for beter reference on how the outfit looks, then they just adjust it to fit EVE proportions in game.
If the rest of y'all don't mind us taking this topic just a little bit serious among all the jackoff memes...
Sure, I don't know what's the most efficient method for how to clothe a digital figure (especially when there's such a lax concept of "clothe" as here,) but it is possible to use scanned clothing, and/or you could get functional reference info from a full-body capture to inform your computer work.
Thing is, this method of having a real model would (in my inexpert assessment) be more trouble than it's worth for the technical results with what it seems like they're doing here. (It's a different story for the modeler's spank bank, but I'm going to assume they didn't pay for this whole session just for the giggles.) You're limited to what you can actually capture, for one thing, so with the cross-stitched top for example, you only have the outside of the strings (unless they have a mocam in her cleavage) and don't get the reverse of the stretched material, even though you need to recreate some of that in the game (because of course somebody will try to get a down-the-gown camera view.) Then the buckles and chain stuff, all of that is going to shift with body flex and motion, so why capture it attached to the skin when it'll be in different places once the body starts moving? And you ain't going to get any useful bumpmap data from fishnet stockings, so why bother slipping those on her? If these were complex garments with precise tailoring and specific fabrics (that first gown might qualify,) then you'd get something out of a full body scan, but here? It's belts and nylon strips and a wire bunny-ear headdress, all things easier to just build by measurements and deform around the avatar than it would be to convert into polygons from photogrammetry.
NT for comparison went all the way to full costume / full makeup for Hellblade 2 scans (or at least some of them; others were just face or eye scans, and I would bet there were basic undergarment scans of her for the real body.) Obviously, it's a thing. But it makes sense there, with all the complex layers of cloths on top of each other and the thickness of the fabrics and the hang from the body and the way hair drapes on it. It similarly would have made sense to capture the original catsuit and other details when beginning the Eve construction. But eventually, all that detail gets replaced with digital equivalents (the hair for example gets completely replaced so that it can actually move or be lit as needed), and even if they ended up keeping some of the fabric detail as texture, the capture is only a building block, not a model. (Also, I bet every individual clothing piece and even hair braid would have been scanned again on their own, which ShiftUp probably also did.) NT is also doing a 4D scan, meaning they're capturing video with 3D perspectives, and they're getting the info about how this clothing works in real life which will then be used through ML to train the clothing output, something ShiftUp is unlikely to be doing.
And as far as just having a reference, okay, but then why stand in an a-pose? If you want detail of how clothing (or netting or whatever some of these outfits would be called) conforms to the body and stretches or shifts when in action, I'd think you'd take an action pose and work backwards; have the character wearing the CG clothes strike that pose, and adjust the elastics or constraints until it sims the same as reality. And if you just want to trace over your CG clothes to make sure you match the real-life reference, you could do that just as easy with a mannequin. A big-titted mannequin.
Unless it was the 90s and these Stellar Blade character 'skins' had been purely texture map swap, this process of photoscanning tiny, complicated, detailed, skimpy clothes would probably not create much useful for the final game AFAIK. If it was a dude (or dudette) at a computer, it'd almost have to be easier to just make your own digital lingerie. Alhough maybe, maybe ShiftUp has AI specifically trained on cutting out model elements "mapped" to a female human body (ie worn) and converting straps, buckles, and triangular strips of clothing into 3D outfits? Maybe...
...The one reason they
may still be doing this even though it'd be unnecessary from a workflow perspective is if these are signature, famous outfits Yoon Seolhwa has worn in modeling shots? If that were the case, yes, it could be counter-productive and a pain in the ass to have to go back to the initial body modeling process, but the gravure nerds wouldn't have it any other way.
They also sculpted all the bosses of the game in clay and then 3D scanned them.
Well sure, that makes sense though. You're building the entire outside of the model, so having a physical object to start your work with gives you a lot to play with right away. You can tell where the bones would be, you have worked out all the proportions and dimensions, you have a rough approximation maybe of the skin or color or shading (depending on what details you put into the model), and you have a ground sample to revert back to for checking your progress as you replace everything of the scan with a working game figure and its components or accessories.
The sculpting work is generally done for this finished game. They do still need to model out these outfits to add them to the game, but they know what they're going onto and have mechanism from other outfits and the character rig for how these clothes are expected to work on the body. My guess is that it's actually more work to go back to "clay" (or in this case a body scan) with a finished character model to add new accessories like this because they've already done the work to go from concept model to playable/modifiable character?