A quick update on progress so far for the Master Material for the entire scene in keeping with using just tiling textures (Trim sheets will be worked on later).
I'm going to run through my initial workflow but this is all subject to change as I learn more.
In blender each asset to the scene is given two UV sets; the first is texel density correct (I am going for a texel density of 1024/meter using 2048 textures due to how close the camera is going to be to everything being such a small scene), the second set is packed to use up the entirety of the 0-1 UV space and will be the one sent to Substance Painter.
To make sure Painter accepts the correct UV select the camera icon by the UV set you're using (this was the same back in Maya)
In Painter the prop's baked onto itself and then I create the 3 channels like in the previous project, each associated with a channel of R, G or B and add the wear and tear (right hand mesh). I also assigned different parts of the prop a colour once again in R, G, B or left plane white (left hand mesh). I export 2 textures; the ID mask and the wear and tear mask (making sure to set them to Masks inside of the engine).
In engine the Master material is currently set up as so. I plan to break a lot of it down into Material Functions once I had the general layout sorted and a lot of stuff is placeholder.
1 - Tiling texture has its inputs; a UV editing function for scaling and rotation, and then some minor parameters like normal strength and rough. This should all be done before any additional changes in the material.
2 - This is where I use the ID mask and break it into its channels. First the Base Colour is sent through a 'Desaturate' node in case I want to completely wipe the colour and just have a grayscale colour map. Once greyscale the colour is sent through a 'Blend Overlay' function with a colour parameter that is then added back onto the original texture through a LERP, the channel mask acting as the Alpha. This is done for each of the 3 channels.
3 - I have separate mask inputs for both the prop mask and ID. A texture coordinate is plugged into both and it is assigned to the second UV set of the prop.
4 & 5 - These are placeholder right now for the mask changes, one being a general grime material and the other being for edge wear. The Red channel is used as a LERP back in 1 for a slight roughness change.
6 - All these materials are layered over each other.
7 - This is a final detail normal input that should properly be put earlier in the material but it is just empty right now.
8 - Here everything is combined, I use 'Saturate' nodes to help clamp the different inputs before they are fed into the final Material.
The results without the layered wear and tear using one tiling texture and an ID mask.