Face appearing in render preview

Hi everyone,

I’m creating a lamp and running into a face appearing in render preview mode, and I have no idea how to fix it, any idea?

Can you share what your wireframe looks like as well as your UV map, if you are using that?

Sure :

Also what I have noticed is that the face is more opaque than the others as you can see on the UV.

So, I think there are a couple of things here. Let’s take a look. First, in looking at the wireframe, it feels like there is extra geometry. It may just be a subsurf modifier that I’m seeing, but in the following screenshot, there is a faint black edge occupying the same space as the selected face with the white edge:

You have to look really close, but I believe you have a rogue face in your geometry. What I see then is that the rest of your 32ish-face lamp base top is UV mapped to a smaller area on your UV map making the details of the applied texture appear larger. The rogue face is larger on your UV map making the details of the applied texture appear smaller/finer. The quick fix is to delete the rogue face. I would also look into marking some seams on your model so you can better control you UV islands. I’m guessing you unwrapped using something like Smart UV Project, but you have a bit of a mess on your hands.

Manual page for seams:
https://docs.blender.org/manual/en/latest/modeling/meshes/uv/unwrapping/seams.html#seams

Let me know if you have any questions or need clarification! If this doesn’t fix your problem, let us know, too!

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Thank you so much for explaining it very informative, sadly I tried to delete it and actually did not work, I’m pretty new to UV mapping this is why I used Smart UV Project, thinking it would make things easier and better!

Is there another possible way to fix it? I could share the blend file too if it can help.

The bottom looks like it has duplicates or triangles. For the given topology it shouldn’t have more than 4 edges. Mark the top and bottom edge as seam (horizontally) and one of the 3 edges between vertically. Close to everything in your mesh should unwrap pretty accurate since it’s just cylinders. Lengths will become rectangles while caps should become circles.

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Can you explain what you mean when you say that it “did not work” when you tried to delete it? What happened? You weren’t able to delete it? It didn’t fix your problem?

Sharing the .blend file would most definitely help.

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Depending on what you do to the model, you can end up with duplicate faces that oppose each other. If you delete a face - the wrong one of the two - you can have that face with a normal pointing in the opposite direction. Check by using normal lines or normal orientation overlay. The normal lines can be more helpful as it can indicate faces that have been collapsed to a line or point but is still technically a face. But yeah, sharing makes this less of a guessing game.

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Alright so I made the unwrap manually this time I understood that leaving it to Blender with Smart UV Project wasn’t the best way, this is how it looks so far and for the problem I had previously it seems to be fixed, but now I have two other problems, first is that I have this seam visible, is there a way to hide it somehow? Or I should unwrap it differently?

Here is the UV map :

My second problem is that on this part the texture is stretched all the way down, but I don’t understand why it’s case there :

Lamp problem.blend (3.1 MB)

Here is the .blend by the way!

The UV map proportions are not very accurate to the area they actually should represent.

Add seams to edge loops to areas like these to break the UV map into more parts so they can fit better in the UV space.

If you’re using a tiling texture for details you could use box mapping and bake that to textures to avoid seams (or if your deriving properties from one source image you can paint the seams away easily). Didn’t take a look at that in the blend file currently so there could be a better option.

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Thank you for the tip I breaked it in more parts as you stated and it works great!

I’m interested on how to paint to make the seams disappear, but I don’t know how this works, is there a tutorial talking about it? Sorry if I am asking much all of this process is new to me!

As @0451 mentioned, you can use box mapping for your tileable texture. In the shader editor, change the texture coordinate from UV to Object. In each image texture node, select the Flat dropdown and change it to Box. Set the blend value field that has appeared to .150. Profit!

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Indeed my bad I missed it! It’s finally looking the way I wanted :

A huge thank you to all of you guys! :grinning: I feel like I have learned a lot I really thank you for it, you rock!

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