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The underworld refers to all indoor locations; including dungeons, caves, and houses.
 
The underworld refers to all indoor locations; including dungeons, caves, and houses.
  
==Important Hex Addresses==
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{{box|[[Underworld:Important Hex Addresses|Important Hex Addresses]]}}
  
===Room Headers===
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{{box|[[Underworld:Rooms|Rooms]]}}
*$027502-$027781 - Pointer Table, 2 byte local addresses, indexed by room.
 
*$027781-$027FEF - Data
 
  
<blockquote>
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{{toc}}
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
 
</blockquote>
 
 
 
===Sprite Data===
 
*$04D62E-$04D92E - Pointer Table, 2 byte local addresses, indexed by room.
 
*$04D92E-$04EC9D - Data
 
<blockquote>
 
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.
 
</blockquote>
 
 
 
===Object Data===
 
*$0F8000-$0F83BF - Pointer Table, 3 byte long addresses, indexed by room.
 
<blockquote>
 
Byte layout:
 
 
 
*byte0: aaaa bbbb.
 
**The a bits are transformed to aaaa0000 and select the type of empty space to fill in. Hyrule Magic calls this 'Floor 1' - Gets stored to $7E0490
 
**The b bits are transformed to bbbb0000 and are the what Hyrule Magic calls 'Floor 2' - Gets stored to $7E046A
 
 
 
*byte1: aaab bbcd
 
**The a bits are unused and should not be used
 
**The b bits determine the room's layout type, ranging from 0 to 7.
 
**The c and d bits are unknown, but I have a feeling it's related to $AA and $A9
 
 
 
After that the bytes come in 3 or 2 byte object structures, used by routine $01:88E4. Objects are loaded until an object with value 0xFFFF occurs. If a value 0xFFF0 is loaded, the game will start loading Type 2 objects and will not go back to loading Type 1 objects until it is time to load the next layer. (Layer as in HM, not to be confused with the SNES' Backgrounds.) A value of 0xFFFF will also terminate the loading of Type 2 objects. The routine immediately terminates if that happens during the loading of either object type.
 
 
 
Type 1 Object structure: (3 bytes):
 
 
 
*Third Byte: Routine to use. If this byte is >= 0xF8 and < 0xFC, then it is a subtype 3 object. If the index is >= FC, it is a subtype 2 object. If not, it is a subtype 1 object.
 
 
 
*Subtype 1 Objects, first and second byte
 
**High Byte: yyyy yycc
 
**Low Byte: xxxx xxaa
 
***The a bits are stored to $B2
 
***The c bits are stored to $B4
 
***The x and y bits are transformed into:  000y yyyy yxxx xxx0 - This is a tilemap address that indexes into $7E2000 and / or $7E4000
 
 
 
Use the third byte * 2 as an index into the table at $8200. This is the routine that is used to draw and otherwise handle the object. Subtype 1 objects have a maximum width and height of 4. Width and height
 
are measured in terms of 32 x 32 pixels. (<-- last part is questionable)
 
 
 
*Subtype 2 Objects, 1st, 2nd, & 3rd bytes:
 
**Third Byte: ffdd dddd
 
**Second Byte:  eeee cccc
 
**First Byte: aaaa aabb
 
***The a bits are unused, but after all they are the marker for this type of object subtype.
 
***The b, c, e, and f bits are transformed into a VRAM tilemap address: 000c cccf fbbe eee0
 
 
 
Might I add this is one messed up format? The d bits are used as an index into the table at $8470. Since such indices are going to be even, the d bits are transformed into: 0000 0000 0ddd ddd0
 
 
 
*Subtype 3 Objects
 
**Similar to Subtype 1, with a few small exceptions.
 
**The vram address is calculated the same way. However, $B2 and $B4 are not used as length or width dimensions here. The routine that is used is determined as follows:
 
**Take the original index (times two) that a Subtype 1 would have used. AND that with 0x000E. Then shift left 3 times to produce 0000 0000 0eee 0000. Then, OR in $B2 and $B4 and shift left once, so the final result is: 0000 0000 eeea abb0.
 
**Also, this value indexes into $85F0 instead of $8200.
 
 
 
Type 2 Object Structure: (2 bytes)
 
*High Byte: cccc cccc
 
*Low Byte: bbbb ddaa
 
**The a bits form a 2-bit value (0000 0aa0) that determines the routine to use for the object. In Hyrule Magic, corresponds to the "direction" of the door.
 
**The b bits are transformed into 000b bbb0 and stored to $02 -> X. Corresponds to "Pos" of door objects in the Hyrule Magic. Note that these range from 0x00 to 0x16 (always even) which if you halve those values is 0 - 11 in decimal. This is easily verifiable in Hyrule Magic.
 
**The c bits are shifted into the lower byte and stored to $04 -> A and $0A. This is later used to grab the tiles used to draw the door and the area below it. In Hyrule Magic, corresponds to "type". Note the type is 1/2 of the number listed here. This is because to avoid using an ASL A command, the c bits are always even.
 
**The d bits are unused.
 
 
 
Next I'll go into the nitty gritty of the various types (the value of $04). Again note that we'll only be dealing with even values b/c that's what you'll see in the code. To convert between here [as well as the code] and Hyrule Magic, take the hex value here and divide by two. Convert to decimal and that's your Hyrule Magic "type."
 
 
 
*Types:
 
**0x00 - Basic door. Index = $0460
 
**0x02 - Normal door?
 
**0x04 - ???
 
**0x06 - ???
 
**0x08 - Waterfall door (only used in Swamp palace; in one room at that!)
 
**0x0A - ???
 
**0x0C - Trap door (probably other types but this seems to be most common)
 
**0x12 - Adds a property to some doors allowing you to exit to the overworld (this is accomplished by writing to the tile attribute map)
 
**0x14 - Transition to dark room?
 
**0x16 - Toggles the target BG Link will emerge on. e.g. if Link starts on BG0 in the next room he'll be on BG1.
 
**0x20 - Locked door specifically for BG0.
 
**0x22 - "
 
**0x24 - Locked door for either BG0 or BG1
 
**0x26 - "
 
**0x30 - Large exploded pathway resulting from a switch being pulled (unusual to have as a door as it's huge)
 
**0x32 - Sword activated door (e.g. Agahnim's room with the curtain door you have to slash)
 
**0x46 - warp door?
 
</blockquote>
 
 
 
===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.
 
 
 
===Secondary Map===
 

Latest revision as of 23:07, 23 December 2017

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

Important Hex Addresses
Rooms

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