Hello Modelers! I’m new here, this is my very first post. So i modeled a somewhat realistic looking 3D ball (not by myself, i followed a tutorial on youtube - not trying to take credit or anything 
) and now i need to figure out a way to make it even more realistic by adding dirt on its white spots, i don’t know how to achieve this though for i am still a beginner artist who just started learning modeling no longer than 2 weeks time, here’s a picture of my model: 
Can you tell me how would you go about adding dirt onto this ball? Thanks!
Blender - How can i add dirt on my football?
ferrettank
#2
Ah you are on the right track! 
I love it when people want to add grunge to objects, it makes them so much more believable.
So you have two options here:
One is UV unwrapping it then make a texture for the ball with the dirt on it.
Another is procedural (A bit more complicated):
So what you can do is take the ambient occlusion, then tell the computer if the Ambient Occlusion is black, then show dirt, if it is white, then don’t show dirt. (Kinda like a layer mask in Photoshop
If option #2 is over your head, I suggest researching how to use the material nodes in blender, they are amazing.
Hey ferrettank, thanks for your reply:) think it will try to make a new texture with dirt on it, see how this goes…