Skyrim Female Head UV: The Definitive Post
We begin as like a cooking blog's recipe, with a sort of vaguely related yet unnecessary anecdote. I've been thinking about putting modding stuff up on this blog, lately. I used to run into the problem on Discord where I'd be like: man, I'm spamming this channel, who even cares about this stuff anyway? So I made my own dev thread in which to spam these posts. As more and more people started joining, though, and still not replying to anything I wrote, I ran into the same issue where I've now become hesitant to post whatever I want in my own dev thread for fear that people will find it annoying. Silly, I know, but I figure that this here, tumblr, is the option with which I cannot go wrong, right? So long story short: this might turn into a mostly modding blog now.
I'm about to do an explanation of UV mapping as an introduction to this post, for those who know very, very, little about it. Many of you reading this may already be modellers or texturers who don't need this dumbed down, so you are welcome to skip to the big red UV map if you wish.
Without further ado: this is Nur.
Nur is what I would call a 'chatterbox', but she was made in the same way as any paper fortune teller. One thing that you should note about her: she is three-dimensional. I have power over Nur's state of being, and I can unfold her.
Unfolded Nur looks very different. We can see that her mouth, usually a triangular bipyramid minus a couple of faces, is now four separate triangles. We could also conceivably understand this as a '2D' version of Nur. It's flat, but it has all of the colour information that ends up on the surface of her 3D self; the area painted red is the 'mouth' part, the top squares on the left and right are the upper part of the 'face'.
Now, if we were to make a 3D mesh of Nur, we could use something like the second image for her texture and tell the computer which area of it should be shown on the surface of a given polygon. We'd do this by giving every point two dimensional coordinates, instead of inventing some kind of new format where every voxel in 3D space is assigned a colour—after all, it's only the surface that matters, right? This process of giving 3D vertices 2D-coordinates on a texture is called UV mapping. What you should really take away from this is the UV map holds the information of how to wrap a texture on to a mesh.
And, since all vertices already have X, Y, and Z coordinates, (and W is used for something else,) their two-dimensional texture coordinates are U and V.
Now, UV maps can be different from a piece of paper you fold in a few ways. What you mainly need to remember is that in UV Maps, we aren't bound by angles, length, or area – the lines making up a UV map are 'stretchy'. This mapping allows, then, for you to 'stretch' the texture over the surface of the mesh.
Now that everyone is (hopefully) on the same page, let's move on to the subject of the post!
This is the UV map of the female head mesh in Skyrim. Right away, a few weird quirks are going to stand out about it.
It is not truly vertically symmetrical along any X-coordinate.
It is kinda symmetrical along a line a short ways to the left of the centre.
Even along that line, the eye sockets are not symmetrical.
The symmetry along that central line starts falling apart towards the boundaries of the image, where there is not really very much symmetry whatsoever and what there is seems to fold more along the actual central vertical axis.
Now, if none of that stuff stood out immediately to you, or you are having trouble seeing it, that's absolutely fine! This image here should help to clarify the things I just mentioned.
The white line in the middle highlights the true centre of the image, from which (as you can see) the UV of the mesh's 'central line' is offset. The sort of lens-shapes either side of it trace the UV map's eye sockets, which are quite different.
Now, is all of this stuff fine? I mean, kind of. No, it's not really a good UV map (there are serious issues, for example, at the back of the scalp) and the symmetry problems all suck for working with it as a texture, but it's still useable and, for a high-poly to low-poly workflow, won't really impact things all that much for the creator. Painting on to the mesh, baking from a sculpt – all these will suffer for a worse UV map, but are still essentially the same process as with a different UV. The game's textures were made for this UV map, and Bethesda seem to have been able to manage fine with it.
Credit to Bethesda Game Studios. A section of the 'FemaleHead_MSN.dds'.
The issues come in more for people working on a 2D level. Making textures in photoshop? Painting some tintmasks? Then these things are going to annoy you, especially those darned eye sockets. So, is there a better way?
Sorry, that section header is kind of misleading. There's an extent to which this is subjective but, honestly, I don't think there really is a better way. I firmly believe that you can't fix Bethesda's UV because it's not broken. A little annoying to work with? Sure. But it wasn't meant to be another way, and it works with the textures provided by the game. There is nothing to fix.
On the 15th of March of 2012, Enhanced Character Edit (ECE) was published on Nexus Mods, in its description claiming thus:
Fixed asymmetry head mesh for Female.
Enhanced Character Edit had not 'fixed' issue of the off-centre axis of symmetry. What it had done was make the eye socket on the right symmetrical to the one on the left in the UV map. Behold, the ECE head mesh with the vanilla game's texture.
On the left: the ECE head mesh with the vanilla textures. On the right: the vanilla head mesh with the vanilla textures, as Todd intended.
ECE needed its own textures, made for the 'symmetrical' eye socket UV. There were already existing texture sets made this way (even reflecting the same eye; I suppose people preferred the left side), so it wasn't too great a problem—ECE was providing a fix for existing mods, really!
Except, well, it's a little more complicated than that. You can change the mesh, and the textures along with it, which works. This only affects the player character, however—generated face data for NPCs must be regenerated or, in the case of NPC overhauls, manually changed by the user, a thing few users actually know how to do. Pretty soon, though, people were using ECE in their character creation, and then for the NPC overhauls that they put on Nexus. Skin mods were being made specifically with use of this head mesh in mind, like SG Female Textures Renewal, which actually includes ECE as a requirement for this reason.
So everything is great and we can just use ECE, right? Sure, we have to regenerate all of our NPCs' faces which requires the creation kit and a lot of time, but that's workable. Well, not quite. Some mods have mismatched diffuse maps and normal maps when it comes to eye sockets, like Tempered Skins, which has ECE's eye sockets in its diffuse, but bases its normal maps mostly off of vanilla, including keeping its asymmetry. Mods like Mature Skin don't even use the ECE sockets, which means that those textures will look wrong on NPC overhauls based on the ECE head meshes. This issue ends up happening both ways, too—users of ECE-based textures have an even worse issue when using a mismatched mesh, to the extent that Enhanced Female Head Mesh was created, a mod that solves an issue that isn't in the base game. The ECE sockets are that ubiquitous.
Credit to DomainWolf. A comparison image from the mod Enhanced Female Head Mesh, showing the issue that ECE-based textures have when using the vanilla mesh.
Incidentally, this user has also created tintmask mods. Many of the textures included in those would have to be manually edited in order for them to look right on the vanilla head mesh.
We can see that the effects of ECE's change ripple outward without ever really becoming understood by the common modder. When installing High Poly Head, users are presented with the option of Symmetrical Eyes (Female). The average user probably doesn't know what this means, let alone whether the texture that they're using is based on ECE. If they choose the wrong option, many won't think to go back to the FOMOD. ECE itself has been far surpassed in popularity by RaceMenu on SSE—how many people would think to install it for its head mesh alone? Even Enhanced Female Head Mesh, which is specifically mesh-only and for SSE has only ~25 k downloads as of writing. Popular skin mods with symmetrical eye sockets have millions.
This whole thing impacts almost all modders. Most of them know barely anything about it. So, this stubborn ass who refuses to use the 'fixed' eyes and manually converts all of their NPC mods by painstakingly fixing things in NIFSkope wanted to write a post aggregating everything they knew about the subject, endeavouring to maybe improve people's awareness of it.
If you read all of this, thanks! I'm honestly surprised at how long it got. I hope you enjoyed my writing.
Hello, future me here. If you read this before this message was added, please note what I had earlier said about ECE not working on SSE was wrong. I have updated the previous sentence to reflect this information.
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