Hiya. I first started posting this in the meshing forum but the more I thought about it, the more it seemed like a texture issue. If it does actually belong there though then I apologize haha.

I was following a tutorial for converting a hair from 4 to 2, specifically this one, and it turned out pretty well except for some reason, you can see the sim's bald head through the hair :/

I have a theory of what might've caused it, though: in the texture coordinate editor in MilkShape, it doesn't look like the mesh is using some of the texture (a couple strands of hair + what looks like the hairline). I tried all of the original hair's geometries from S4S in MilkShape and none of them had coordinates for those parts of the texture. Also, the coordinates (sorry, not sure if thats what they're actually called) that are there don't line up exactly right with the part of the texture they're supposed to use, which might be causing it to look more transparent than it should in game? I'm bad at explaining things so I just added a screenshot, lol.

Anyway, that's only a guess. I'm pretty new to this and so I was wondering if anyone else might know what's actually going on and how to fix it. Thanks in advance!

You may have to re-map the hair into a 1024x1024 (or 512x512) map. Bodyshop isn't too fond of anything sized above 1024x1024, you could end up with a hair that's invisible ingame (due to shader issues), and you also have to make sure you didn't use a hair mesh made for hats (there tend to be a few hair meshes included). Besides, there's no need for a 1024x2048 map if you can use a smaller one.

Also make sure parts of the mesh aren't mapped beyond the texture, because Bodyshop textures don't tile. You can move the UVmap viewport around bit by holding in Ctrl and click/hold/drag the middle mouse button.