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Adding Dirt and patina to my *sterile* models

Dear Unreal Experts,

almost two years ago I started a project in which i rebuild my home city how it once looked before whole disctricts were destroyed in ww II. I plan to release this project for free one day. Now I am at a point in which I want to tweak what I created to far. I always had some nice knowledge regarding photoshop, but I never modeled in my life. I finally decided to use the easy to learn SKETCHUP since the major modeling part is about recreating buildings.

So I created many buildings, gave each part of the buildings textures in sketchup and then exported them into .FBX files. I imported the blank model (without material import) into Unreal Editor, everything worked pretty well and in Unreal Editor I created new materials with textures (such as roofs, walls, wooden parts, windows etc…). I used a “texture sample” as a “base color” in my material and gave it some roughness doesnt end up shiny. Some also use normal maps, which works quite nice. it might be a weird method, but worked pretty fine.

The problem is that these models look pretty sterile and clean. Thats why I want to add dirt, rust, patina and moss. I was going through some tutorials, but many of them look quite complicated and are different to the materials I created.

Now my question: Cant i not just add another texture layer including alpha channels (a.e. moss) on top of my my base texture layer (a.e. wood)? is there an easy method to achieve what I want to do?

Thanks a lot for replying and helping! :slight_smile:

UE4 can technically layer materials, but it decreases performance to do it that way (each additional material that an object uses is another draw call).
The best way to get a good result is to do it properly, make your textures in Photoshop or use a texturing software like Substance. Some things are done with decals or vertex painting as a way to add things in specific locations so that you can use tiled materials underneath.

Thanks a lot for replying :slight_smile:

I tried the vertex coloring technique and had a look at some youtube tutorials. but as far as i understand I can only paint parts with vertices nearby (makes sense!!). But thats going to be a problem with flat walls, because they only have vertices in the corner. Anyway, I will try to add a grid onto my walls, as long as there are no better suggestions?

If you were authoring in Substance Painter, you could have just added a dirt/grime layer and exported. Unless you feel like going back and refactoring all of your assets, I’d probably go the decal route.

In 4.9 a new mask option was added to UE4

https://docs.unrealengine.com/en-us/…Notes/2015/4_9

New: Ambient Occlusion Mask.

The new Ambient Occlusion Material Mask feature lets you access Lightmass calculated AO in your material, which can be useful for procedural texturing, for example to add in aging effects and dirt in areas where it would accumulate.
https://youtube.com/watch?v=hYvnQ5wzFmI
Decals would also be a good option.