Weird seam visible on some female bottoms with skin costume parts

[GeneralIdiot]

So I was playing around with some costumes and noticed this jarringly visible seam between the chest and hips that appears when using some bottoms with skin costume parts on female characters.

[attachment id=0 msg=687]

Notice on the left the skin is unbroken, there might be a seam there if you look closely but it's pretty minor. On the right, there's a distinct line where the shading is different between top and bottom. In my own experimentation with it this seems to be affecting only certain costume parts, those being the ones that use the different geometry with the thighs sunk slightly back. Never understood why those are different but they are. Bikini 3, Angelic, Disco, and a few others.

Notably this bug does not happen with the legacy version of the same costume parts currently accessible in the costume creator if you use the presets, thus I assume it's likely something introduced with the redone versions for asymmetrical costumes - my guess would be the texturing for those is generic across all costume parts and not taking into account that some have different geometry that results in the same texture rendering slightly differently but that's only a guess.

[SilverAgeFan]

We already corresponded on the Discord, but leaving a note here for anyone browsing.

This is being looked into. It's likely related to the asym work I did honoring the places where Cryptic and Paragon decided to use the skirt/shorts hips in the "with skin" category for female hips.

Currently exploring best means to address this for better in game display without perceivable distortion of pattern masks from their original creators intended layout on the character model.

[GeneralIdiot]

As requested in the aforementioned conversation on Discord I took a look through all the bottoms with skin patterns and your theory of it being related to using the tights under skirts model instead of the normal tights one would appear to be correct as it's every pattern that uses that model that appears with the visible seam.

These are, for reference:
Bikini 2
Bikini 3
Angelic
Angelic Plus
Assassin
Athletic Shorts
Baroque
Blast
Disco
Hacker
Heart
Hearts Plus
Holes
Shorts 1
Shorts 1 + Tights
Shorts 2
Shorts 2 + Tights
Shorts 3
Shorts 3 + Tights
Straps 2

Note that these same patterns don't display the same seam when applied over tights (where they all use the normal tights model rather than being different) but only when used as bottoms with skin. The actual texture used for the pattern is the same file either way (I tested this myself by dropping a modified file over one of them and seeing if it showed up in both places which it did.) Thus I can only assume there's some workaround applied on the original legacy versions to make them appear correct on the tights under skirt model, though whether locating and redoing that would be less work than actually fixing it properly is as debatable as anything involving this game's code.

Interestingly, you speculated at first on Discord that it could be the white levels in the relevent textures being off. That doesn't appear to be the actual problem but I extracted a couple of them from the Rebirth piggs myself to see and they actually are slightly off, they have a faint greenish tint to the white parts that doesn't seem to actually cause any problems but it's there. Note that's not unique to the ones experiencing the bug with the visible seam, it appears to be all of them including the few chest textures I looked at.
[attachment id=0 msg=692]
New texture on the right, legacy on the left. Not sure if that's a problem worth the effort to fix but still.

[GeneralIdiot]

An update because I noticed a similar issue affecting the seam between bottoms and boots, though this one is slightly different and I'm guessing it's due to the boots still using legacy textures while the bottoms are using the updated ones.

[attachment id=0 msg=701]

On the left, the legacy bottoms with skin as they appear on Homecoming or when using the legacy pieces here. In the middle, the current bottoms with skin on Rebirth. On the right, current tights on Rebirth. I didn't exhaustively test every costume piece but I can confirm it definitely applies to skin, tights, tights sleek and the several bodysuit styles. Thus I assume it likely affects every costume set where the bottoms have been updated with new asymmetrical textures but the matching boots are still using legacy textures.

[GeneralIdiot]

So this particular bug happened to come up in conversation between me and a friend and I realised it's approaching two years since I reported it. And I'm just wondering, did it prove to be harder to fix than anticipated or has it slipped between the cracks somewhere and been forgotten about? Because it's still there ingame, I just checked to be sure.