README.md

nether9

A little program to search for favorable 3x3 patches of bedrock in the ceiling of the Nether where an endless parade of Wither may be quickly and safely dispatched for your beacon farm.

Building

You will need a C compiler. If you also have make, you can:

$ make
cc nether9.c -o nether9

Or just compile it; this is a single C99 source file with no dependencies – you can figure it out! 😜

Then run the compiled command line program:

$ nether9
usage: nether9 [-q] world_seed [start_x start_z]

Running

You must specify a world seed, eg:

$ nether9 8371793346352930225
seed=8371793346352930225 around (0,, 0)
search radius [32:93]
found @ (-72,, 67)
            x=       -72                 -72                 -72
            y=[123]   |           [124]   |           [125]   |
                . . . . . . .       . # . . . . .       # # # # # . .
                . . # . . . .       # # . . . # .       # . # . # . #
            z=  # . . . . . .       # # # # # . #       . # # # # . .
           67 - . . . . . . .       . . # # # . #       # # # # # # #
                . . # . . . .       . . # # # # .       # # # # # # #
                . # . # . . #       . . # # # . .       . # . . # # #
                . . . . . . .       . . . . # . .       # . # # # . .

…

found 4 locations within 465 blocks

You should probably verify in game that the ceiling matches the little map before spawning a Wither. Note that the map is top down, so when staring up at the ceiling it will look mirrored… 😵‍💫

Optionally, add x and z block coordinates to search a specific area.

Add the -q if you want quiet – just the found coordinates without the little maps or other cruft.

Details

Recent versions of Minecraft (currently 1.20, possibly going back to 1.18?) use the world seed to randomize the ceiling of the Nether, so the old tables and search programs are no longer usable. nether9 uses your world seed to generate the ceiling using the new approach. It looks for 3x3x3 cubes of bedrock that match the pattern:

            x           x           x
    y=[123] |     [124] |     [125] |
          ? ? ?       # # #       # # #
    z -   ? . ?       # # #       # ? #
          ? ? ?       # # #       # # #

Where # is bedrock, . is not bedrock (usually netherrack), and ? is don't care.

It will stop after finding at least 4 of those locations or if it gets farther than 1024 blocks from the start. You can hack these thresholds at the top of the source.

So what do you do at these locations anyway‽ Panda's old video is still very relevant, just use the new locations found by nether9.

Issues

This code is not well tested and the approach is brittle – it may break if the world generator changes too much. If you do find a problem or an inconsistency with the game, feel free to let us know by reporting it, but please check first to avoid dups!