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The bottom-most flat face of my object looks significantly brighter than others, even though it looks correct in edit mode and the normals appear to be facing outward correctly. I also selected the nearby two loops and merged by distance to make sure there weren't any duplicates. Does anyone have any suggestions please?

  1. Here is what it looks like in object mode (and material preview, but all views have this defect). Object mode shading

  2. Here is what it looks like in edit mode. The normal appears to be facing outward correctly. The shading in this view also appears okay. Shading in edit mode

  3. I read in another post that there might be duplicates vertices in the area, so I selected the nearest edge loops and tried to run "merge by distance", but 0 vertices were removed. Attempting to merge duplicates

  4. As per a question in the comments, note that there is something behind the face in question. Here is what the mesh looks like with that face hidden: enter image description here

Does anyone have a clue regarding what may be causing this? Shading is set to smooth.

Blend file:

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  • $\begingroup$ Please share your file by using blend-exchange.com and following the instructions there. Paste the generated link into your post. If you H hide the big face, is there anything left? $\endgroup$ Commented Dec 11, 2023 at 5:34
  • $\begingroup$ @RobinBetts There are parts of the mesh behind the face, which I've added under point (4), however, there is nothing left exactly in its place. I will upload the file, but do I need to disable any extra addons I used/create some sort of "barebones" version of the file, or can I upload it as is? $\endgroup$ Commented Dec 11, 2023 at 6:05
  • $\begingroup$ Are the add-ons involved in this scene, live? If they were just used to generate it, and they're now finished and done with, no problem with a straight-up share. $\endgroup$ Commented Dec 11, 2023 at 6:10
  • $\begingroup$ @RobinBetts I have added the blend file, let me know if that works for you. $\endgroup$ Commented Dec 11, 2023 at 6:17
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    $\begingroup$ There are duplicate vertices around the center circle, see how thick the contour appears: thick contour. Select all with A then M > Merge > By Distance. $\endgroup$ Commented Dec 11, 2023 at 7:41

2 Answers 2

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Jiggling the face in question reveals it's not immediately connected to the surrounding face-loop:

enter image description here

If you draw out the edge loops one by one, you can see the actual connected topology:

enter image description here

As you can see, under smoothing interpolation, that results in the vertex-normals pointing somewhat radially, rather than straight down.

TL;DR All selected, M > Merge > By Distance will weld away your excess loops.

The middle face's vertex-normals will now be interpolated from the surrounding downward-facing faces, and you're fixed.

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  • $\begingroup$ Thank you very much, this worked. In step (3) in my original post I suspected this might be the issue so I selected the nearby loops (as pictured) and tried doing exactly this. Why did that not work? $\endgroup$ Commented Dec 13, 2023 at 2:33
  • $\begingroup$ Hi, @confusionillusion! Edit Mode [A, M > By Distance], in mug12.blend, untouched, as linked, works straight away, with your illustrated threshold, removing 288 verts. So at the moment, I can think of only 2 possibilities. 1: Incomplete selection, maybe using a method that doesn't catch obscured geometry? 2. An investigation which didn't replace geometry exactly where it was beforehand, leaving it outside the merge threshold? (For me, a 'jiggle' is G in the tweak tool.. I'm never in anything else.. followed by a right-click to cancel everything back to where it came from) $\endgroup$ Commented Dec 13, 2023 at 4:51
  • $\begingroup$ I have an idea. I think it may be due to my understanding of how that features works. My assumption for merge by distance was: given the selected vertices, consider all neighboring vertices with distance < x (effectively x is around 0) and remove them. How it might really work: only consider the selected vertices for removal. In that case, me selecting the two loops would not include the "duplicate" loops hiding behind the ones I selected. $\endgroup$ Commented Dec 13, 2023 at 7:35
  • $\begingroup$ @confusionillusion : Bingo! :) $\endgroup$ Commented Dec 13, 2023 at 7:36
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enter image description hereYour inner edge loop sourrounding the big face consist of 6 overlapping edge loops.

To solve, select the big face, press Ctrl Numpad plus seven times to expand the selection until the outer face loop is selected too, then press M > merge by distance and check if 288 vertices have been removed.

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