nether9

A little program to search for favorable 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.

Features

Now available as a self contained web app – no more compilation required!

https://spadix0.github.io/nether9 (requires a relatively recent browser)
Still no dependencies – just save that index.html file and run it locally, even without internet access.
Adjust the search parameters: start location, radius and number of matching locations to report.
The search pattern is now fully customizable within a 5x4x5 block match volume. Use the widget under "Advanced Options" in the web app to search for an optimal location to install whatever crazy contraption you can dream up.

Building

To build the command line application, 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 program:

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

For really advanced users, it is also possible to build the web app; your compiler must support WebAssembly (eg, a modern clang) and there is a small Python script to embed the result in the HTML template. Check the Makefile for details.

Running

You must specify a world seed, eg:

$ nether9 8371793346352930225
seed=8371793346352930225 around (0,, 0)
search radius 60
found @ (-72,, 67)
       x=       -72               -72               -72               -72
       y=[123]   |         [124]   |         [125]   |         [126]   |
           . . . . . . .     . # . . . . .     # # # # # . .     . # # # . # #
           . . # . . . .     # # . . . # .     # . # . # . #     # # # . # # #
       z=  # . . . . . .     # # # # # . #     . # # # # . .     . . # # . # #
      67 - . . . . . . .     . . # # # . #     # # # # # # #     # # # # . # #
           . . # . . . .     . . # # # # .     # # # # # # #     # # # # . # #
           . # . # . . #     . . # # # . .     . # . . # # #     . # # # # . #
           . . . . . . .     . . . . # . .     # . # # # . .     # . # # # # #

…

found 4 locations within 420 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.

Note that the command line version supports neither advanced configuration nor pattern customization – just hack the source or use the library API.

Details

Recent versions of Minecraft (currently 1.21, 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 5x4x5 cubes of bedrock that match a customizable pattern. The default pattern is good for making a Wither killer:

            x           x           x           x
    y=[123] |     [124] |     [125] |     [126] |
          ? ? ?       # # #       # # #       ? ? ?
    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 adjust these thresholds in the web app or hack them in 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!

Nether9

Install / Use

README