Underworld

The underworld refers to all indoor locations; including dungeons, caves, and houses.

Important Hex Addresses

Room Headers

• $027502-$027781 - Pointer Table, 2 byte local addresses, indexed by room.
• $027781-$027FEF - Data

Headers are $0E (Decimal: 14) bytes formatted thusly:

• byte 0: aaab bbcd
  • the a bits are transformed into 0000 0aaa and stored to $0414 ("BG2" in Hyrule Magic)
  • the b bits are transformed into 0000 0bbb and stored to $046C ("Collision" in Hyrule Magic)
  • the c bit is unused
  • the d bit is stored to $7EC005 (If set, use a lights out routine in the room transition)

• byte 1: aabb bbbb
  • the a bits are unused
  • the b bits are transformed into bbbb bb00, thus making them a multiple of 4.

This value is used to load 4 different palettes for the dungeon, and corresponds to, you guessed it, Palette # in Hyrule Magic!

The resulting index is used to load values for $0AB6, $0AAC, $0AAD, and $0AAE

• byte 2: gets stored to $0AA2 (GFX # in Hyrule Magic)

• byte 3: value + #$40 gets stored to $0AA3 (Sprite GFX # in Hyrule Magic)

• byte 4: gets stored to $00AD ("Effect" in Hyrule Magic)

• byte 5: gets stored to $00AE ("Tag1" in Hyrule Magic)

• byte 6: gets stored to $00AF ("Tag2" in Hyrule Magic)

These are the planes to use for bytes 9 through D. This determines which BG you appear on, and possibly more.

• byte 7: aabb ccdd
  • the a bits are transformed into 0000 00aa and stored to $063F
  • the b bits are transformed into 0000 00bb and stored to $063E
  • the c bits are transformed into 0000 00cc and stored to $063D
  • the d bits are transformed into 0000 00dd and stored to $063C

Note, the only safe values for a plane seem to be 0,1, or 2. Hyrule Magic appears to violate this rule by letting you put 3 down, but nothing higher.

• byte 8: aaaa aabb
  • the a bits are unused
  • the b bits are transformed into 0000 00bb and stored to $0640

• byte 9: stored to $7EC000 These are all room numbers that you could possibly exit to.
• byte A: stored to $7EC001
• byte B: stored to $7EC002
• byte C: stored to $7EC003
• byte D: stored to $7EC004

Sprite Data

• $04D62E-$04D92E - Pointer Table, 2 byte local addresses, indexed by room.
• $04D92E-$04EC9D - Data

Sprite data is formatted thusly:

• First Byte: Stored to $0FB3. Not sure what the purpose of that is yet.

After the first byte, you will see 3 byte clusters that break down thus:

• First Byte:
  • Bits 4,3,2,1,0 - Y coordinate (in pixels from the top, starting at 0) of the sprite divided by 16.
  • Bits 6,5 - If these are set, they will be used to generate a subtype, stored to $0E30, X.
  • Bit 7 - If set, the sprite is on BG2, if not it's on BG1

• Second Byte:
  • Bits 4,3,2,1,0 - X coordinate (in pixels from the far left, starting at 0) of the sprite divided by 16.
  • Bits 7,6,5 - If all these bits are set then this is an Overlord, otherwise it's a normal sprite. If only some of them are set they can be used to generate a subtype, stored at $0E30, X

• Third Byte: Sprite or Overlord type. If a sprite, this will get loaded into a slot at $0E20, X. If an Overlord, will get loaded to $0B00, X.

The array is terminated with a byte of $FF.

Object Data

• $0F8000-$0F83BF - Pointer Table, 3 byte long addresses, indexed by room.

Dungeon Secrets Data

• $00DB69 - $00DDE8 - Pointer Table

Push Block Data

• $0271DE-$027369 - Pointer Table

(Inter Room) Torch Data

• $02736A-$027489 - Pointer Table

Chest Contents

• $00E96E - $00EB65 - Data

Rooms

Main Map

The main underworld map consists of $FF (decimal: 256) rooms.