This is for UE. I have a set of modular pieces (it will be many more). These pieces will usually be seen together in the scene. There will be many more types of meshes that will use this material too.
Procedure:
1 material, 2 textures, 2 UV maps.
Texture 1: base wall texture.
Texture 2: atlas with opacity mask that will contain all the decals/overlays (in this case I am using an alpha channel because it’s just a test, but I plan on using an opacity mask).
BaseUV: coordinates that will control the base wall texture.
DetailsUV: coordinates that will control the position of the faces on the atlas decal texture.
Material: it mixes both textures, using the two different UV maps to control each one.
Firstly, the whole mesh will be unwrapped on BaseUV. This positions the base wall texture seamlessly.
Secondly, the faces of the mesh that need an overlay will be placed accordingly on the DetailsUV. The faces that do not need it, will be collapsed into a single dot (selected in the image below) and positioned in a masked location.
Result:
Is this efficient? Is there a better way to do this?