I had always wondered how games like Grand Theft Auto 5 create tiling textures like roads for miles (in game terms) yet add elements like cracks, potholes and general texture to break up the repetition. I researched and found a portfolio explaining he had used ‘Decals’ in Unreal Engine to create some tracks on a dirt road, so I investigated and it turns out Decals were the answers to my question.
I looked into how to create them, and it turns out I already almost had. They are simply textures with (optional) transparency which can be placed on any asset. I experimented with a bullet hole to see how they worked, by getting a bullet texture from http://nobacks.com/photos/miscellaneous/bullet-holes/ for free, and in fair use I could use. I created a basic sculpt of the hole in Zbrush and baked out a nromal map and ambient occlusion from xNormal, and arranged them on photoshop to create a good decal.
I then imported them into Unreal and created a basic material by connecting these up to the correct nodes. I then changed the material to these settings:
As you may notice, there is no ambient occlusion because there is no decal blend mode which allows that channel to work, but it didn’t really make all that much difference. The final decal looked great on the walls, and it will certainly help show players some shotgun shells have been fired here.