randar_n0p_2022.txt

Randar/ResetFinder - block game military grade radar 2

written by pcm1k - 2022-10-21

In Minecraft versions < 1.13 there exists a glitch known as "world RNG reset".

Whenever a chunk loads, for each structure, the game tries to figure out if
that structure should be there by generating a certain Java Random seed based
on the world seed, structure type, and the approximate chunk location, and
using that to calculate if the structure should be considered to be in that
location.

The problem is that instead of using a separate Random object for this purpose,
it actually uses the global world Random object that is used for many other
gameplay actions. The world RNG seed ends up being the seed used for checking
the last structure, which in 1.12, happens to be woodland mansions (overworld)
or end cities (end). The nether is not affected by this glitch AFAIK.

The seed it generates is the same every time, this means it is possible to
force the world RNG state to be a certain value just by loading a specific
chunk.

This is already publicly documented, however what is not documented as of
writing (AFAIK) is that you can also do this in the "reverse".

By performing a certain action, we can calculate the current world RNG state.
Then by advancing the RNG state backwards, and undoing the seed generation
algorithm, we can get that approximate chunk location. We then look for
"reasonable-looking" locations (locations outside of the world are clearly
invalid). This allows us to find the approximate location of the last loaded
chunk, and thus find player locations.