Editing Field map encounter mechanics (section)

== Quirks and other misc. stuff ==

=== Mastered Preemptive Glitch ===

When equipping a Mastered Preemptive Materia, the Mastered Preemptive Flag is always set, no matter what character it is equipped on.

On any of the following conditions, the Mastered Preemptive Flag is recalculated based only on whether the third character has a Mastered Preemptive Materia equipped, ignoring any equipped on either the first or second characters:
* A battle starts (If this is a random encounter, the Mastered Preemptive Flag does affect this battle's generation before it is recalculated)
* The menu is closed and opened again
* The Materia section of the menu is exited and entered again

On any of the following conditions, the Mastered Preemptive Flag is recalculated based only on whether the ''current'' character has a Mastered Preemptive Materia equipped, ignoring any equipped on any of the other characters:
* Any Materia is equipped or unequipped
* A piece of equipment (including an accessory) is equipped or unequipped

In short, the Mastered Preemptive Flag is the least broken when Preemptive Materia are equipped on the third character, but they can still be temporarily broken.

=== Menu Skipping ===

On field maps, it is possible to interrupt the transition from the field to a random encounter, effectively skipping that encounter, by opening the menu on the same frame that the encounter would happen on.

There are two caveats:
# Your danger value gets reset after a random encounter finishes, so that danger reset never happens on a skipped encounter.
# Skipping an encounter and then entering a scripted battle before the next field map encounter will result in the Duplicating Boss Glitch, where that scripted encounter plays again immediately after it finishes, which also sometimes results in the game crashing after that repeated boss.

A similar mechanic is used to perform [[Stinger Skip]] where a random encounter is triggered on the same frame that you enter the Stingers' webs in the Cave of the Gi, resulting in both being skipped.

=== Offset Math ===

You can find the index of any offset value (the number of times you have to overflow stepid and increment offset to get to this offset value) with the following formula:

<pre>
(offset * 197) mod 256
</pre>

so offset 0 has index 0, offset 13 has index 1, offset 177 has index 53, and offset 243 has index 255.

This works because the modular multiplicative inverse of 13 (modulo 256) is 197. Read more about it on wikipedia if you want because math is pretty cool https://en.wikipedia.org/wiki/Modular_multiplicative_inverse

=== 32/64 glitch ===

If an encounter formation has an encounter rate of 32 or greater, it acts as if it has an encounter formation of 64/64. This is due to using signed 16-bit values to store world map encounter data, as opposed to unsigned values.

This affects five encounter tables in the game: [[mtnvl3]] encounter table 2, [[junin2]] encounter table 2, [[junsbd1]], [[mtcrl_4]], and [[mtcrl_9]].

https://pastebin.com/yJ6N0H9d 

=== Reroll 6 / Bump 6 glitch ===

When determining a field map encounter formation, if you get bumped and then the game rolls the encounter formation in slot 6 on the reroll, your last encounter formation is NOT updated. You can trace a path through the codepath above and see that this is the case. This should almost never actually affect anything. <youtube>https://www.youtube.com/watch?v=kGMXu0k7nGo</youtube>