Forget what the megacorps are doing. I'm fairly certain that, if a true artificial intelligence ever does spring from a digital chrysalis and kill us all some day, it'll be because someone got a bit too enthusiastic twiddling the dials in Garry's Mod. I say this because I've just finished fooling around with the sandbox's user-created 1:1 Multiverse (2048 Universes) map, and I'm more convinced than ever that mankind is playing with forces the gods usually keep for themselves.
Billed as "probably the biggest ever map in videogame history," 1:1 Multiverse comes courtesy of a modder named Alexandrovich, and claims to feature "2048 different rotated universes 880000000000000000000000000000km EACH". Don't worry, I've got your back: that's eight hundred and eighty octillion kilometres. Multiplied by two thousand and forty eight. Alexandrovich says the next update will add 2,048 solar systems to occupy it. Here it is in action.
If you're anything like me, you're probably a tad suspicious of that claim, but I'm increasingly convinced it's true (or true enough) having messed around with the 1:1 Multiverse map myself. Firstly, there's the system requirements: the map says it would very much prefer running on a machine with 128GB of RAM (although it can deal with 12GB and runs mostly fine on my own 16GB PC).
Then there's the fact that it really does feel quite large once you're loaded in, as asinine as that might sound. There's no real sense of movement even if you set your NoClip speed to some ridiculous nine-digit number. The only way to really grasp how far and how fast you're moving—at least that I discovered—was to spawn a car and watch it zoom off into the black. A map posted in the mod's screenshot gallery also gives some inkling as to how it's all laid-out, though I admit my grasp on it is a little shaky.
But what persuaded me that the map probably is what it says on the tin is learning how it works. 1:1 Multiverse uses another mod as its basis. That mod is InfMap, and was created by a modder named Mee. In a video on YouTube, Mee gives a pretty good explanation as to how their masterpiece works. It's part magician's trick, part quantum superposition experiment, basically.
You can see the whole explanation above. But in essence, InfMap works like this: once you hit the boundary wall in a Source map, you get teleported to the other side, Portal-style. You can actually see this working in 1:1 Multiverse just by firing a rocket: it'll exit the top of the map before jetting past you from below, a process it will repeat indefinitely.
That'd be a huge letdown if that was the whole trick, but it's in dealing with objects within the map that InfMap gets properly clever. Obviously, if you leave a big cube smack-dab in the centre of your map, the illusion of infinity will end up broken as soon as you hit the edge and come in from the other side, seeing a cube that was behind you appear in front of you.
InfMap handles that by changing the properties of map objects in such a way (and I confess I'm operating at the boundaries of my understanding here) that they become invisible and un-collidable once you hit that boundary transition, but still appear visible when you look back at where you came from, maintaining the illusion of forward progress.
Or, to boil it down, what makes InfMap interesting isn't that it changes the map, but that it changes the objects within the map. That's how it keeps its infinite illusion going.
That's probably a little hard to grasp in abstract, but you can see that in effect in one of Alexandrovich's other mods, the 1:1 Solar System. This one also uses InfMap, but unlike the 1:1 Multiverse, which is pretty much barren at the moment, it uses InfMap's basis to recreate our solar system. You can travel between the Moon, the Earth, Neptune, Venus, or whatever you like.
Or you can if you have a few months or years to spare: they're all as far apart in the map as they are in real life, because the magic InfMap does to objects lets that happen even though you are—when you get right down to it—just teleporting from one side of the map to another ad nauseum.
It's a doozy to wrap your head around but also incredibly rad, or at least I think so. It's amazing that GMod users are still coming up with these mind-bending ways to exploit the engine this far into Source's lifespan, and I'm not convinced one of them isn't going to accidentally create life if we keep letting them tinker with it. On the plus side, with a universe made up of—let me check—thousands of 8.8e29km squares, it'll probably be a while before anyone finds it.