In this tutorial I will show you how to use Blender’s texture painting option to paint your own roughness maps.
Introduction
I have already made a simple barrel prop and I’m using the auto-UV unwrap
If you want to know how to UV unwrap an object, please see my “UV Mapping for beginners” tutorial
Texture Paint Setup
Under the texture paint workspace, I will split the viewport and open the shader editor
I will make sure to switch to material preview so I can see the material
Painting the Roughness Map
I add a new material to the barrel and make it fully metallic
I will also add a bit of blue to the base color
I add an image texture to the shader editor
I make a new 2K image texture for the barrel
For the color, I will change it to 0.5 for the RGB so I can have a 50% gray color as my base
I then connect the image texture node to the roughness of the principled shader
I also need to change the color space to “non-color” so the image texture won’t add any color on the barrel
In the image editor space, I open the image texture I just made
I can either paint directly onto the object or onto the image texture
I will make sure that the brush is set to a fully white color
When I use white and paint on the barrel object, notice that the painted part is now more rough
I can also change the strength of the brush to make the barrel a bit less rough
As I stated, I can also paint on the actual image texture
If I want to make a part of the barrel shiny, I can simply change the brush to a fully black color
Using Alphas for Painting
In addition to the brush, I can also use alphas for painting roughness with some noise
There are two ways of doing this with a texture
Under the brush settings panel, I add a texture
I then open the texture tab and change the type to one of the noise options – in my case, I will choose “marble”
When I go back to the brush settings, I now have a marble texture
I will change the mapping to “random”
I can use this to paint on the barrel just like I did with the brush
I change the strength to 1 and change my color to white and then paint on the barrel
Just like when I use the brush, I can also paint directly onto the image texture
A second way of using a texture is to upload my own alpha
Under the texture tab, I change the type to “image or movie” and open up my alpha
Back under the brush setting, I see the texture to my uploaded alpha
I can now use a higher strength and the color black to bring more metallic noise into the roughness map