Model has weird artifacts in blender

[stuck sky]

Hello! I am fairly new to 3D modelling. I made this low-poly model of the robot from the cover of Chronologic by Caravan Palace and I imported it as .obj into Blender so I could play around and experiment with lighting and materials but as you can see on the picture, for some reason there are some very ugly artifacts. I have no idea why they are there, as the topology and stuff looks fine to me. Also, the right eye is completely weird, but I literally just copy / pasted it from the left one so I have no idea why it's behaving differently. I've noticed that in face orientation view mode back in Blockbench, there's some faces marked red, but I am not quite sure if there's a correlation, as the eye and rest of the mouth looks normal. Some help would be really appreciated.

[raven dagger]

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[stuck sky]

So I figured out how to get rid of the red faces (although I am still not sure what the color actually means) by inverting the red faces (which I also don't quite understand what that does exactly) but the imported model still has the same artifacts in Blender. Also, I've noticed that the inside of the head is all red in face orientation view mode, but I guess that's how it's supposed to be? For some reason, I can't really find any information on that.

[spring mango]

not sure about blender myself, but to answer about the red faces:
the red faces mean the inner faces, while the greens would be the outward faces. this is important cus for some settings, sometimes inner faces wont be render, usually to cut render cost

[ruby matrix]

^ Some settings is Backface Culling which is important when you’re using the model in other environments

I’d recon mend recalculating normals in Blender through the Normals menu, you can find it through the find action search bar. I’d alsomake sure there aren’t any custom split normals set

[stuck sky]

Thanks so much for answering! Okay I get it now, but blender itself doesn’t really have this problem, right? I don’t see a “invert faces” option there. Also, I’m wondering about how the faces actually get to be the wrong way out in the first place, I just extruded and did nothing unusual from other stuff I was doing, so idkk. How can I avoid this?

[stuck sky]

Sounds like the problem I’m having, but after fixing the red faces the problem still occurs.

[ruby matrix]

blender has the same problem but you can invert(flip) the wrong facing ones using the normals menu I mention earlier

[stuck sky]

I’m trying this in a sec hold on

What exactly is a custom split normals set? Also, I don’t know exactly how to use recalculate normals, when I do it with the affected faces selected, nothing happens. Same when I got the whole model selected.

[stuck sky]

Okay so I just had an epiphany and removed the textures I applied in Blockbench and this almost solved my problem. Now, only the 2 faces on the "mouth" have artifacts, but the eye and head appear normal. using Shift+N on those faces still doesn't do anything though.

[ruby matrix]

Does removing the material work?

[stuck sky]

It worked for all the faces except the ones you see in the picture above. I had to remove the textures inside of Blockbench though, removing the material in blender after importing the model with the texture screwed it up on a whole other level.

[stuck sky]

I figured it out and it’s very stupid. These artifacts were there because there were 2 faces on top of each other. I have no idea how this could have happened and there was also no z-fighting occurring. I am very stumped, but thanks for your help!

What’s also very weird is that when I undo (undelete the duplicate faces), the artifacts aren’t there as if they haven’t been there the whole time. I am beyond confused.

[ruby matrix]

Also, if you need to fix faces that are in the same space try merging by distance, that will merge all the faces and verts inside of another

[stuck sky]

Aight thanks for the tip! Why would this happen in the first place though?