Final Fantasy VI Advance: Border Crossing

On an overworld map, battles are determined by choosing a formation from a group within 32x32 tile zone. The game calculates the zone based on the coordinates of the party.

However, the zone calculation is not run on each step, but rather on each redraw of the map.

Examples of redraws include exiting battle, exiting the menu, and exiting a town.

It is easy to see this bug by entering and exiting the menu at a boundary where the enemy formations change, then walking into the adjacent zone until a battle is triggered. Monsters will appear from the previous zone.

Title: Border Crossing
Author: Imzogelmo, Lenophis, Novalia Spirit
Version: v1.0a
Applies to: FF6us v1.0, FF6us v1.1, FF6j, FF6A (JUE)
Tested on: FF6us v1.0, FF6A (JUE)

Contents: Border Crossing US - header.ips
Border Crossing US - no header.ips
Border Crossing Japan - header.ips
Border Crossing Japan - no header.ips
Border Crossing GBA.ips
Anti Border Crossing US - header.ips
Anti Border Crossing US - no header.ips
Anti Border Crossing Japan - header.ips
Anti Border Crossing Japan - no header.ips
Anti Border Crossing GBA.ips
readme.txt - this thing you are reading.

ROM addresses: C0/C1B2 - C0/C1B4 - US versions
C0/C1B9 - C0/C1BB - US versions
C0/C0E4 - C0/C0E7 - Japanese version
C0/C0EB - C0/C0ED - Japanese version
08001C10 & 08001C11 - GBA versions
08001C14 & 08001C15 - GBA versions

Urgency: A mystery value.

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Description:

On an overworld map, battles are determined by choosing a formation from a group
within 32x32 tile zone. The game calculates the zone based on the coordinates
of the party.

However, the zone calculation is not run on each step, but rather on each redraw
of the map.

Examples of redraws include exiting battle, exiting the menu, and exiting a
town.

It is easy to see this bug by entering and exiting the menu at a boundary where
the enemy formations change, then walking into the adjacent zone until a battle
is triggered. Monsters will appear from the previous zone.

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What this patch does:

Corrects the behavior by loading from variables that are updated every step.

The anti patches effectively remove this patch.

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v1.0a - February 3, 2010
Added patches for GBA versions, patch otherwise unchanged.

v1.0 - January 19, 2010
Initial patch

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Credits:

Mnrogar: For originally discovering this bug.


Final Fantasy VI Advance (USA).gba - NOINTRO
CRC32: D708F5AB
MD5: D1C3D1798A3F347FBAB41F151C99DECE
SHA-1: E9A2A58BC56ACE26CB56D0CF5CDAD1A10AA5DEDF
SHA-256: 1310F2AD3C13F5446CF6C43D01D48AAD640D6B8A4FBBA2B92C776F4F6D90E6FF