So I have created a simple mirror and downloaded a fingerprint texture that I am adding to control the roughness. I am also using a Colorramp to lower the amount of fingerprints visible.

Now my Texture is all over my mirror but I want it just in some parts to make it more realistic and not make the repetition of the texture so obvious.

I thought I can use a Noise texture to mix the fingerprints with just a plain black shader and put that in my roughness but I guess u can not connect output of the mix shader into the roughness node. If I preview the mix shader though it looks like what I want to achieve.

Node Setup:
Node Setup

enter image description here

  • 1
    $\begingroup$ That needs a Mix RGB node, not a Mix Shader node. They're easy to mix up (no pun intended). $\endgroup$
    – KickAir8p
    Commented Apr 2, 2022 at 12:14

1 Answer 1


An image demonstrating the node tree and material preview

Swap the mix shader with a Mix RGB node. You can then set the second colour to black. You won't need to use the black Principled shader.

The input plug for roughness requires an image, colour, or value to be plugged in. The green BSDF cable represents shader output and not an image output.


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