[Dwedit]

No, really. You could make a single sector that was a long tube, it could curve in over itself. And you could do that multiple times. And even though such a construction is physically impossible, the engine would still let you walk through the tube with 'proper' collision, and render it as if it was possible.

[moring]

The editor manual said that you couldn't do that, and I'm pretty sure I tried and the game glitched. You had to split that sector into multiple ones for that to work, even though from a player's perspective it looked like a single corridor.

As a player, you could see the extents of a sector when you looked at the automap, because the map became visible sector-by-sector.

The exact rule of the editor / engine was actually even stricter. Not only could a sector not overlap itself, you had to make sure that at no position you could see two sectors that overlapped, or the graphics would glitch. If you wanted overlapping, you had to split sectors just to please the engine, even if floor/ceiling height, lighting, textures etc. were the same.

[justsomehnguy]

The most notable would be the spiral staircase right in E1M1, leading to the cinema projector booth. It looks perfectly aligned in the 3d view, but if you look at the map you would notice what it consists of the multiple sectors which are misaligned just a bit.

[dividuum]

Not that this contributes a lot to the overall discussion, but from what I remember, the misalignment in that case wasn't necessary. Vertices could have the same coordinate, but it's just easier in the editor to build that stair case if you can actually find and click them.

[moring]

That's how I understood it too. The misalignment was because the editor would automatically turn two one-sided lines (walls) into a single two-sided line and connect the sectors, and mess everything up. The engine itself probably didn't need the misalignment.

The engine DID need the "lots of sectors so you don't see two overlapping sectors at once", which came for free with a spiral staircase.

[justsomehnguy]

You can but you shouldn't, it really mess the engine, making essentially a one-sided... walls-which-arent-till-they-are.

I just made two sectors separately and moved one on top of other.

https://imgur.com/a/uDxMDBp

[justsomehnguy]

https://news.ycombinator.com/item?id=35628351

[justsomehnguy]

Nope.

Just tested it: https://imgur.com/a/uDxMDBp