The goal

I want a material that will have two decals painted on the mesh.

The process

I do that by combining two transparent PNGs into one mask that is used to replace the primary paint with black color.

The problem

Notice on the two screenshots attached how the bottom portion of the object (around the "brand" sign) becomes very-very-slightly dimmer when the 2nd transparent PNG is introduced via the Math(Add) shader.

(It does not seem to make any difference when I split the object into two meshes.)

only one transparent PNG

two transparent PNGs combined

The file

What I tried

Turning on Clamp on the Math(Add) shader, sadly no luck:

  • on the left: two PNGs mixed, results in slightly dimmer color
  • on the right: only one PNG involved, color is correct

enter image description here

  • 1
    $\begingroup$ Try enabling Clamp on that Add maths node. That will limit the Fac to range 0.0 to 1.0. $\endgroup$ Dec 29, 2021 at 21:35
  • $\begingroup$ @RichSedman gave it a shot, no luck... thanks tho $\endgroup$ Dec 29, 2021 at 22:40

1 Answer 1


The root cause was in one of the two UV-mappings...

...all the irrelevant faces somehow ended up collapsed into a singular vertex, which was sitting at a not-completely-transparent pixel at [0;0] coords, hence slightly affecting the paint color in the render output.


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