Why won't my portals link up properly?
Before you say this is a duplicate, I am well versed in the normal operation of portals, and understand how to link portals that are very close to each other. This problem is occurring in spite of my understanding.
I have two portals - the main access to my base, at y=66, and a portal which is supposed to take me to the top of my mob spawner tower, which is at y=230+. I've calculated the exact locations for each portal in the nether and placed them accordingly, but no matter what, the portal that is supposed to take me to the top of the tower just spawns me at my main overworld portal. I tried raising the tower portal in the nether slightly in hopes that that would help, but it didn't.
Coordinates of main portal pair: -3653, 66, -2722; -456, 70, -340
Coordinates of tower portal pair: -3736,, 238, -2739; -466, 77, -342
It seems like these should be far enough apart to link properly... Any ideas why they aren't? I hope I don't have to raise the tower portal a lot, that would defeat the purpose...
Images showing relative locations of the portals:
Best Answer
As you said it yourself, portals do take the vertical distance into account. This means you cannot make a sky portal higher than y~=192 if your ground portal is at sea level, as distance from Nether ceiling (your top portal) to sky portal must be less than from Neither ceiling to level of your ground entrance portal.
Overworld|Nether
Sky [@] 192
^
A|
v
[@] Nether top 128
[@] Nether bottom
^
B|
v
Ground [@] 64
But there is a solution!
By moving your ground entrance away horizontally, you can increase distances just enough to fix all the portals (after moving Nether portals to the ceiling, of course).
I have written this handy spreadsheet to easily calculate all distances for two pairs of portals (coordinates in frames are editable). By just moving ground portal from x=-3653 to x=-3623, thirty meters away, you can fix everything! Well, maybe a couple meters more to be sure :-) Again, note I've assumed your Nether portals to be at y=110 and 120, otherwise your Ground portal would have to be much farther.
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How do you fix the nether portal not linking?
The key is that the game looks for the closest portal in the destination dimension, so if you build both portals in the "right" places (overworld x and z divided by 8 in the nether), before lighting either of them (Obviously you need an original set of portals to do this), then you can connect them properly.Why do all my nether portals go to the same place?
The distance that your new portal needs to be away from the old one isn't terribly large, only 128 blocks, but it's measured in terms of the destination world; every block in the Nether is worth eight in the overworld, meaning you'll need to move around 1024 blocks or so away to keep a new portal from joining the one ...Why Won't You
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Answer 2
Ok, I have had problems with this same subject. Sometimes the position of the first portal affects where the sister portal appears. For example, if the original portal is facing east to west and the sister portal is facing north to south you will have very different outcomes. Just keep in mind, one block in the nether is equal to eight blocks in the overworld. Also, if the portals are at different "Y" levels the outcome can greatly change. Try this from the wiki: http://minecraft.gamepedia.com/Nether_portal
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Images: Alice Castro, Chris F, Pawan kumar Photograpry, Sebastiaan Stam