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Logo of Eichhof Beer Brand, on the wall of a white Beer stand. the transparent parts of the logo have a grey tintI want to put a logo on a Beer stand. When Adding the image to the scene (using the "images as planes" import) everything looks good. When placing the plane on the stand, the plane that has the image as a texture is visible. The only difference is, that the plane is now in the shadow and not under direct sunlight. This also shows up in the final render and it happens as well when setting the alpha slider of the BSDF to 0 (meaning obviously no picture is visible but the plane still is). Any Idea and help is appreciated!

Settings:
| Render engine: Cycles
| Max Samples: 100
| Total light bounces: 12
| Transparent light bounces: 10

Specs:
Apple M1 Max
Using Metal GPU
Blender 3.5.1

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    $\begingroup$ Can you share the failing section of your blend on blend-exchange.com (including your image, packed )? $\endgroup$
    – Robin Betts
    Jun 26, 2023 at 19:00
  • $\begingroup$ What do you mean by "failing section" of my blend? The Image is strait from Wikipedia (de.wikipedia.org/wiki/Brauerei_Eichhof) $\endgroup$
    – Marius
    Jun 26, 2023 at 20:38
  • $\begingroup$ Cheers! Some people include a lot of stuff in the file which has no bearing on their problem.. just avoiding that possibility. Will check the logo $\endgroup$
    – Robin Betts
    Jun 26, 2023 at 20:45
  • $\begingroup$ I'm getting no problem with the logo, with absolutely default settings on my system, so there must be something else.. will need your blend to check it out. $\endgroup$
    – Robin Betts
    Jun 26, 2023 at 21:08
  • $\begingroup$ I opened a new project, imported the image and made a similar setup to my original file. The Issue didn't show up. Deleted everything and appended the collection of the file with the issue. the issue showed up. no idea what is happening here :) $\endgroup$
    – Marius
    Jun 27, 2023 at 18:31

1 Answer 1

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You're using Ambient Occlusion for dirt-mapping, and a transparent plate for placing a logo on your surface.

It turns out to be a known issue with the Ambient Occlusion shader that, for efficiency in an already relatively slow call, it does not take transparency into account, when it casts probing rays into the hemisphere around the shading-point, looking for hits.

You can eliminate the contribution of the plate to the beer stand's surface by setting the stand's AO node to 'Only Local'.

Personally, I think it would be better to UV map the beer-stand, lose the plate, and use the alpha of the image to mask it into the surface texture of the beer-stand itself, as sketched in here:

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    $\begingroup$ Damn it, i overlooked that. Thank you very much for having a look at it! Thank you also for the detailed description of why the problem with ambient occlusion occurs. I know that UV unwrapping would be the correct way to do this but the project is extremely underpaid and the stand is only a "small" portion of a whole campus so i didn't bother to uv unwrap and texture in a detailed manner. $\endgroup$
    – Marius
    Jun 28, 2023 at 20:37
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    $\begingroup$ I got around the problem by using the knife tool an making an outline of the Logo, therefore getting rid of the transparent geometry. But i'm sure to check for AO the next time running into this problem! Have a great day/night and thanks again for your help. $\endgroup$
    – Marius
    Jun 28, 2023 at 20:37
  • $\begingroup$ np @Marius .. glad to be of help :) $\endgroup$
    – Robin Betts
    Jun 28, 2023 at 20:42

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