[shahar2k]

I think duke 3d maps arent strictly laid out on a 2d plane though are they? I know they use some above/below sectors but I"m not sure if those are just portals to other parts of the map (havnt planed as much duke as I have doom)

[Dwedit]

Duke Nukem 3D allows you to create a single sector that intersects itself several times. And you can walk right through the path with no issues.

[dividuum]

Iirc not a single sector, but you could built impossible spaces like that using multiple sectors with the restriction that overlapping sectors must not be visible at the same time. Otherwise you would get rendering glitches.

In addition to that, there’s also teleports used for elevators or water. They move you around then using/jumping in. Multiple elevator transports can move you in impossible ways like getting into an elevator, driving down, only to arrive at other side of the same floor.

So I agree. Might work for some maps, but not in general.

[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.

[justsomehnguy]

Nope.

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