In this tutorial I will show you how to use grunge maps to make surface imperfections on your objects in Blender.
Grunge Map
I will be using a simple barrel that I made and applied just a very basic metal material to it
The grunge map I will be using to make the surface imperfections is from AmibientCG
Surface Imperfections
Under the UV editing workspace, I drag in the image texture – this would be either a color map or an albedo map
When I connect the surface imperfection texture to the roughness map, notice that I can now see the texture on the barrel
If I add a color ramp in between the texture and the principled shader, I can use the color stops to adjust the surface imperfections
Notice how shiny the barrel has become – if I switch the color stops, I can now make a more rough-looking barrel
Since I have the node wrangler add-on installed, I can select the image texture and use CTRL + T to add a mapping and texture coordinate node
I will keep the UV connection from the texture coordinate node since I’ve already unwrapped the barrel
I can now use the scale and rotation options on the mapping node to further control the surface imperfections
To control the color of the surface imperfections, I will duplicate the color ramp
I then connect the new color ramp to the base color
I also connect the image texture node to the second color ramp
For the white color stop, I’m going to change it to the original color of the barrel [#5A3534]
For the black color stop, I change the color to a lighter orange [#CB5026]
To give the surface imperfections some more interest, I add a bump node and connect it to the normal input of the principled shader
I then connect the first color ramp into the height of the bump node
I can then adjust the strength of the bump node