I am no mapper so bare with me.
Let’s say we had 10 different houses without interiors, just the exterior, with the interiors far below/above the map. Using a script, when a player uses the door they are teleported to the houses interior.
Expanding on this, we duplicate all of the exterior houses as many times as we like, and can change the textures etc but the mesh should stay the same to fit the already existing interior.
Now, all types of houses teleport to the same assigned interior - that can’t work since players will be in each others houses. A fix for that is a virtual world system - all entities, including players, inside the interior are assigned a virtual world when they enter or spawn inside and any entity that is not assigned to the players virtual world is removed to the player(s), or essentially not there. This way, two or more players with different houses share an interior, although they won’t even know it. This allows for a large city map with more than 10 houses without reaching the hammer limits since we’re just using simple exteriors for the most part. This means that windows will be redundant on houses and you will not hear anything or see anything inside the house from the outside.
Am I wrong, mappers? Probably.