I want to add a decal to my model, which has a procedurally generated metallic car paint shader. To help myself with easy changing of the decals, i don't want to add decals as image textures and with UVs. Hovewer the result looks like the image is not entirely transparent. I am using cycles.

enter image description here

I have prepared decals, that are saved in PNG file.

My steps:

  1. Made sure that the alpha in the background is completely equal to 0 (select whole background in GIMP, delete).
  2. Import "Image as planes" - alpha set to 'straight'. Scaled and rotated, etc.
  3. Added Subdivision (Lev 6) and Shrinkwrap
  4. Added small offset to the Shrinkwrap
  5. Node setup as follows
  6. Tried changing offset value (even to 1mm) of shrinkwrap, settings of the shader (including setting IOR to 1) and light paths. Then reseted everything to default values and posted here.

It seams like the transparent layer of my decal is interacting somehow with the metallic shader underneath... Does anybody have any idea what is happening?

Thank you guys!


PS. In viewport shading it looks perfect.

Viewport shading

PS2. Updated Link

  • 1
    $\begingroup$ Can you share a file? This is potentially interesting. Would need textures packed. $\endgroup$
    – Nathan
    Commented Jan 7, 2022 at 0:20
  • $\begingroup$ Yeah, I prepared a small file with everything that is important. Same problem occurs. It is at the bottom of my first post. @Nathan $\endgroup$ Commented Jan 7, 2022 at 0:34
  • $\begingroup$ Getting a "file format not supported" on your linked file. What version? $\endgroup$
    – Nathan
    Commented Jan 7, 2022 at 0:47
  • $\begingroup$ Blender 3.0, installed a week ago or so $\endgroup$ Commented Jan 7, 2022 at 0:49
  • $\begingroup$ The uploaded file is 0 bytes. @Daniel14223 $\endgroup$
    – Benus
    Commented Jan 7, 2022 at 1:42

1 Answer 1


It looks like the Car Paint nodegroup has issues with noise. I suppose giving more samples would help, but I'm not gonna spend time trying.

What you can do instead of using a mesh plane to add your logo, is to simply mix your logo texture into the carpaint shader:

enter image description here

  • $\begingroup$ Wow, thanks! It's a nice and clean solution $\endgroup$ Commented Jan 7, 2022 at 16:29

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