I'm fairly sure portals in that case only refers to how the Build engine determined potentially visible areas. As far as I know there was no mechanism to seamlessly connect far-away parts of a map in that way. If there was, I'd be pissed, because I never used that to built my own maps and it would allow neat non-euclidean geometry (like in Antichamber) :-)
Re:Duke Nukem 3D Mirror Universe
by captainmuon on Wednesday March 24, 2021 @11:55AM
(#26568856)
Yeah, you are right. I think the engine I recall was the successor of Genesis3D, some ActiveX-thing from WildTangent. Whole different beast. I remember making a Stargate using that feature :-D. Must have been around 2000.
I was always got a kick of out of the swimming sections simply being teleporters. Step on top of the water a get teleported to a room filled with water and then swim to the top of the room to get teleported back to the area around the pool.
I just remembered, because of what you wrote, that I thought mirrors worked the same way! That they were a portal glued to itself, or something.
This made a lot of sense to my teenage brain : )
One cool thing about die Build engine is portals, you can build two different rooms and identify a wall in one with another wall in the other and "glue" the rooms together, IIRC. I think that is what is behind most of the "teleportation". I always thought that the mirror was just a wall portaled to itself, I wonder why the "physical" mirror space is necessary?
Edit: or maybe I'm misremembering what portals did? Here is a really detailed article by Fabien Sanglard about the engine: https://fabiensanglard.net/duke3d/build_engine_internals.php