and I would like to add some dirt and graffiti, however I wanted to know if I could add these separately, without adding them to the original wall texture, as I obviously don’t want the graffiti to repeat itself several times along the same wall. I’m sure it’s possible to do this, I just don’t know how ;).
So any help will be appreciated.
Here’s the scene I’m working on to give you some idea, obviously it’s far from finished, but as you can see, it’s a very clean alleyway.
I would only use a separate mesh if the object was a separate object, like a sign or poster something. Not for paint and grafitti. Unless there was some really good reasons for it. Your node setup is missing glossy, unless you’ve tried this already and have too much noise. In my example I just used the clipping border of the decal as a mask, you might want to use a separate image, some alpha channel, or hand painted. For things like painted bumpy surfaces, I would let some of the original bumps be inherited on the decal mixed in with its own bumps. So the setup would be something like this:
