The TS4 skintone system has a lot of potential, and I've been working on a tool to make it easier to work with, similar to Skininator for TS3.
Definition of Terms: (These are the terms I'm using - they're not 'official'.)
TONE : A game file which defines a skintone. It links to the color images, the overlays, and contains various settings.
Skintone : The skin you click on in CAS, which is defined by a TONE file.
Body skin details : A texture with shading, contouring, and details such as muscles and belly buttons. (Yes, I know there's a separate 'skin details' in CAS. Couldn't think of a better term.) There are separate textures for each age/gender/bodytype.
Skin color image : A texture which applies color and some shading composited with the skin details. There is one skin color texture which is applied to all age/genders.
Overlay : A texture which is layered on top of the skin details and skin color. The ages and genders it applies to can be specified.
Tool Overview:
Create/Edit Custom Skin Colors
Cloning Tool : Clones game skintones and creates a package with the TONE files.
Clone Package Editor : Open and modify cloned packages.
TONE Manager : Add/Delete TONEs, modify flags defining the type and usage, modify the swatch color and various other settings, import and export the skin color images.
Overlay Manager : Add/Delete overlays, define which ages/genders each overlay applies to, import and export overlay images.
Previewer : Preview skintones.
Create/Edit Default Replacement Skin Details
Make New Default Replacement Package : Select which skin details you want to replace and clone them to a new package.
Edit/Test Default Replacement Package : Import/Export textures and preview the skin details.
Notes:
If it seems like there's a million body skin details textures, that's because THERE ARE. There's a separate texture for every age and every body type. For many purposes you're better off using an overlay. As far as I know there can be only one set of body skin detail textures, no non-defaults.
Speaking of overlays, only one will be used for each age/gender.
While the preview is reasonably accurate for game skintones, if you modify the overlaid color you probably will not get the same color in-game. EA uses some compositing method I don't understand and can't completely duplicate. CAS and the game are the only true test.
There are two skin color textures; one (a DDS image) is used in CAS and the other (an RLE2 image) in the game. For the CAS image you can import either an uncompressed DDS or a DXT5 DDS. For the game image you must import a DXT5 DDS. You can use the same DDS if you wish. However, you can add a logo or identifier to the CAS image which will show up on the sim in CAS but not in the game. That might be useful since there's no way to customize the swatch except for its color.
Moar notes:
Randomization: Skins are chosen randomly based on the archetypes defined in their flags. The more archetypes a skin has, the more often it gets chosen. If it has no archetypes it will get chosen randomly only if there are no other skins that do have archetypes. The game skins for humans all have archetypes; the game skins for aliens don't have any.
The 'Occult' flag determines if a skin shows up for humans, aliens, or both. Future occult types will probably have their own skins too.
I've also attached a set of templates showing how the body is mapped to the textures.
Face textures: There are about a billion of them and I haven't even tried to identify them and include them in the tool. I've uploaded two packages with all the face textures I could find, so anyone wanting to work with them can use that as a starting point.
Extract the attached zip, open the folder, and run TS4Skininator.exe. Please report any problems/suggestions/comments about the tool here. Please post problems and questions about creating specific content in the TS4 / CAS Creation forum.
Additional Credits:
With thanks to Peter and Inge Jones, Kuree, and everyone else who's contributed to s4pi and s4pe, and to Snaitf for figuring out how to make non-default skintones.