Visually speaking, this is the most important texture as it involves the actual colours of your map. In addition, the alpha channel (transparency) of the texture determines what parts are shiny and what parts are less so: the more transparent the texture is at a certain area (alpha channel black), the more matte the surface will appear in the game.
Note that if you are creating a Restockalike or Nerteaverse-like part, the license for art assets for those mods are protected as All Rights Reserved, meaning you can’t simply copy and paste or otherwise redistribute the textures. You can, however, still have them open as reference and try to make your own textures look similar.
Nertea has documented the standards for Restock’s art assets on the relevant Github wiki, including colour palette and technical modelling standards. Again, feel free to open up textures from your GameData folder if you’d like to see how they are applied.
While each part can be quite different in terms of texturing, I find that structuring my layers in the diffuse colour map like so makes things easier down the line. Below are the layers and effects I use, organised from the bottom of the stack first, and usually in the order I work on/add them in:
I start with a midtone grey underneath everything. For Stockalike/Nertealike, use Porkjet Grey.
Black carbon nozzles with a striated texture. The silhouette can be copied for the heat emission texture. For Stockalike/Nertealike, use NozzleAblative.
Slightly off-white panelling; some variants include a black-and-orange colour scheme. Usually with a subtle striated texture. The silhouette can be copied for the specularity map. For Stockalike/Nertealike, use Porkjet White.
The seams themselves are 1 or 2-pixel-wide lines drawn in 20% grey. I like the following layer effects:
The silhouette can be copied for the normal map, and the outer glow effect can be copied for the specularity map.
Add some wear around the edges, and use the appropriate colours to mark fuel type if making assets for CryoEngines/Nerteaverse. Can be copied for the specularity map.
Things like rivets and reinforcing braces, though you can be creative. Applying a very slight outer shadow adds to the effect of depth. Can be copied for the normal map.
I like these layer effects:
Dimples, depressions, and straight up-holes. Giving them a slight white “glow” with layer effects adds some extra texture. Can be copied for the normal map.
I like these layer effects:
Any additional (usually light) wear markings, often following the edges of objects. Can be copied for the specularity map. I typically use my baked edge wear map with some manual additions. 100% opacity on overlay works well.
On top of all of that, the ambient occlusion map(s) baked earlier are overlaid, set to multiply.
For specific colour palettes and values, refer to the ReStock artistic guidelines.
Once your colour map is done, it’s time to make your specularity map and apply it to the alpha channel.
Create a new layer group, and fill the bottommost layer with a 60% grey (#999999). I like to add a bit of texture here by generating noise, box blurring by about 15px, and then gaussian blurring again by 5px.
If you set up your layers properly in the colour map step, you can simply copy relevant parts to the specular map stack, recolouring them with the correct shade of grey to match the desired specularity. For Restockalike/Nertealike parts, the following is recommended: