The good thing about modeling a train is that there is a lot of repeating geometry. So in reality, I only really needed to model just over a quarter of the train, as a lot could be duplicated and mirrored.
Instead of going for the high to low poly workflow I decided with this asset being quite large it would be better to texture the asset using tiling textures within UE4. So the edges on the asset didn’t look too harsh without having a high poly bake for it I used a script in Maya to face weight the normals.
The inside and outside of the train were given multiple material id’s for texturing in UE4.
I textured the train using the same method as the escalator, making a library of material functions and blending them with masks. The top dirt mask that I used was able to apply the dirt to only parts of the asset that were facing upwards, to look like dust had settled on the asset. The good thing about this setup is that I can use this mask on any asset to get the same effect, and I have quite a lot of control over it.
For the more detailed dirt and graffiti, I will be using deferred decals so that I can get higher resolution. at this point, I only have the outside of the train with the finished material on. all the others just have a base material on at the moment, but with this first material made it should be fairly quick to get the rest done as I can reuse a lot of the elements like top dirt and other masks.
Depending on the weather I hope to get some photogrammetry done this week, getting some surface scans for the floor and tunnel walls, as well as some, scatter assets such as piles of rubbish. but if the weather is bad I will carry on getting the rest of the materials done for the train.