I was wondering earlier if anyone has experimented with precisely how far apart Nether Portals have to be in the overworld to prevent them opening to the same portal in the nether. Until now I've just played with a portal in each corner of the map after my first attempt with portals turned into a pain festival.
On a new map, I've got one portal in the NE corner at X255 Z-391 and quite high in the sky.
I just played with making a second portal to the south, just reloading over and over to find the closest boundary. The portal worked at z-5 but not at z-15.
Now I'm thinking it might be possible to have up to 9 portals in the overworld, at eight points around the outside and one in the centre. Which would be a pretty great shortcut network. I'll continue to work on it, but surely someone has tried all this already?
