Unofficial Fallout 4 Patch

That's a glitch caused by poor visibility data on Bethesda's "precombs", and this, in turn, is a result of the software they use for their calculation (or possibly, the parameters they feed to that software for that purpose; NB: it's likely that the precomb stuff was developed by a third party, like the "compressed mesh shape" collision the used in Skyrim). Problem is that we don't have aceess to that software and can't vary any parameters either. The only thing we can do is to recalculate the precombs in the CK, but this leads to the same results. While we have a basic understanding of what this software does (and why this saves performance on a running game), the details of the operations are pure speculation. Apparently, the algorithms have a problem with narrow gaps, i.e. any opening that allows a look through to the other side only from specific positions and within a narrow range of viewing angles. At a sufficiently large distance therefore, you can ignore the gap entirely; that saves performance (you won't have to render anything behind the gap) and the loss (i.e. what gets hidden from view although a very small slice of it might actually still be visible) is barely perceptible. For some reason however, the game does not properly "switch back" into normal rendering mode when you get closer.

Another place where this can be observed is Evans Way Cul-de-Sac (the small raider camp southeast of Diamond City). There's a barricade with a guard tower and a turret on the south side. When you stand outside of the camp in front of that barricade, there's a narrow gap between two fence pieces left of the turret, and when you look throught that gap, you get the same visual glitches. Fun thing here is that the raiders can shoot at you through that gap, but you'll have great difficulties to shoot back, because they are not properly rendered either.

Unfortunately, we cannot fix that - but it should be reported to Bethesda. They likely won'r fix it either, but they should at least be informed that their precombs suck, so they will hopefully remember (and try to do it better) in future games.