What causes this very dark areas, that can't be shadows? I'm modelling an indoor scene, but I'm getting these weird shadow-like areas. They can't be shadows though, as they are way too dark and move with my viewports position.
I checked my normals, but they seem all ok (blue) for the faces in the screenshots. I also checked for overlapping faces/edges/vertices but couldn't find any. I do have a couple ngons in the model, but not in the affected floor area of Example 2.
The mesh is &quot;open&quot;(?), so from outside you could see the &quot;inside&quot; of the mesh (red normals). Could this be the cause? I tried adding outside faces as well but it didn't fix the issue.
Any help would be appriciated!
This can be the result of overlapping geometry - causing Z-fighting where two or more faces are in the exact same location and orientation. This can result in the faces shadowing each other and other artefacts  such as banding.
Check your meshes and objects to see if you have a duplicate mesh at the exact same point (try selecting one and move or hide it to see if the other remains) or whether your mesh has multiple overlapping faces (move a vertex and see if another face is in the same place).