attrib dat Format

attrib dat Format

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Per-screen map attribute table that parallels map.dat (tiles) and supplies environment, world-adjacency, and roof data for each of the 60 map screens.

• File size: 3840 bytes = 60 screens * 64 bytes.
• Record size: 64 bytes (0x40), indexed by area * 64.
• Endianness: the few multibyte fields are read byte-wise by the engine; the legacy Amiga build is big-endian. The 16-bit "complex id" (0x15-0x16) is stored big-endian here.

Sources

• Legacy reverse code: b3dmm2/mm2ed.bb load_map() (reads +0x03, +0x04, +0x15, +0x20..0x3F) and b3dmm2/main.bb loadmap().
• Disassembly: EXTRACTED/mm2.capstone.asm (env/roof use in the screen loader and map view).
• Data-driven analysis of all 60 records (adjacency table verified symmetric).

Record Layout

Offset	Size	Field	Status	Notes
0x00	1	area_id	confirmed	Always equals the record index (0..59).
0x01	1	map_category	confirmed	1=town/surface-A, 2=cavern/surface-B, 3=dungeon, 4=castle; 5..8 used by elemental planes (41..44).
0x02	1	tileset_id	confirmed	Graphics/wall set. Constant per environment: town 0x21, cavern 0x32, dungeon 0x53, castle 0x44; 0x03/0x04/0x06 for surface, 0x00 for planes.
0x03	1	env_type	confirmed	0x11=town, 0x12=cavern, 0x13/0x14=castle, else outside/surface. (Used by mm2ed.bb.)
0x04	1	surface_flag	confirmed	0=interior. Nonzero ⇒ outside/overland; the value is a terrain/biome class (0xAA,0xBB,0xCC,0x99...). mm2ed.bb treats >0 as "Outside Area".
0x05	1	neighbor_0 (N)	confirmed	Adjacent screen id.
0x06	1	neighbor_1 (E)	confirmed	Adjacent screen id.
0x07	1	neighbor_2 (S)	confirmed	Adjacent screen id.
0x08	1	neighbor_3 (W)	confirmed	Adjacent screen id.
0x09	1	field_09	observed	Mostly 0x64 (100); 0xC8/0x96/0xFA/0x32 on some. Read at 0x10A2.
0x0A..0x0C	3	params	observed	Compared against runtime values (0x12124, 0x11FA2, 0x11FB2).
0x0D	1	field_0D	observed	Multiples of 10 (30..200). Compared at 0x116CA/0x13148.
0x0E	1	entry_coord / in-map safe square	asm-confirmed	Packed `(Y<<4)
0x0F	1	era_gate	asm-confirmed	Compared against the current era index (-$79B5, low byte of -$79B6) in the event interpreter at 0x172BC; mismatch skips the screen's event record. Usually 0x09. See 13-time-era-calendar.md.
0x10	1	pad	confirmed-zero	0x00 in every record.
0x11..0x14	4	sublayout params	observed	Read/compared during screen setup (0x12F58, 0x9C2A, 0x20D6E, 0x1A8B4). 0x12/0x13 look like a second coordinate pair.
0x15	1	label / transition hi	strong	Outside: legacy "Outside Area: XX" label byte. Interior: high byte of the town↔cavern complex_id.
0x16	1	recall_coord	asm-confirmed	Packed `(Y<<4)
0x17	1	level/floor (interior)	strong	0x01 for town/upper level, 0x02 for its cavern; higher for deeper castle floors. 0x00 outside.
0x18	1	recall_screen	asm-confirmed	Destination screen id: copied into the current-screen index -$79F2 at 0xB2F2 by a command handler (family at 0xA816–0xB3B6) gated by flag bit 6. Interior screens point to their overland location (Surface / Town-Portal style recall); outside: equals own area_id.
0x19	1	pad	confirmed-zero	0x00 in every record.
0x1A	1	flags	asm-confirmed	Screen behaviour bitfield; bits individually btst-tested: bit0 (0xBCCA), bit3 (0xBB98), bit4 (0xADE8), bit5 (0xB006), bit6 (0xB2C2/0xAAEE/0xB102). Bit 6 gates the 0x18 transition. Often 0x80 in caverns/castles.
0x1B	1	flags2	observed	Nonzero on a few screens (0xB0,0xD0,0xE0).
0x1C..0x1F	4	tail	mostly-zero	Set only on elemental planes (41..44: 0x1E/0x1F) and a few others.
0x20..0x3F	32	roof_bits	confirmed	256-bit roof bitmap, 1 bit per tile of the 16×16 screen. Bit order: tile t ⇒ byte 0x20 + (t>>3), bit t&7. (mm2ed.bb reads LSB-first per byte and reverses tile order.)

Two sub-layouts (selected by surface_flag at 0x04)

• Interior (surface_flag == 0): env_type gives town/cavern/castle; the four neighbor bytes all equal area_id (no overland wrap); 0x15-0x18 carry the town/cavern complex linkage and floor.
• Outside / overland (surface_flag != 0): the four neighbor bytes are the real adjacent screen ids; 0x15 is the overland label; 0x18 == area_id.

Confirmed: World Adjacency Table (0x05–0x08)

For overland screens, bytes 0x05..0x08 are the four neighbouring screen ids. This was verified to be fully symmetric across all 60 records: opposite pairs are (0x05, 0x07) and (0x06, 0x08). If screen A names B in slot s, B names A in the opposite slot — 0 asymmetries over the whole file. Interior screens set all four neighbours to themselves.

The precise compass assignment (which slot is North) is provisional; the proven fact is the two opposite-direction pairs.

Runtime field usage (asm-confirmed)

• The whole file is read into a buffer whose pointer is stored at A4-$79F6 (allocated as 0xF00 bytes at 0x2655A/0x266AE; filename string "attrib.dat" at 0x92E6).
• On entering a screen, the loader at 0x923E takes the current screen index from A4-$79F2, multiplies by 64 (asl.w #$6), and copies that 64-byte record into the current-screen attrib buffer at A4-$561A.
• Field reads therefore appear as A4-$561A + offset. Mapping: byte 0x05 = -$5615 … byte 0x18 = -$5602 … byte 0x1A = -$5600, roof bytes start at -$55FA.

Notable confirmed reads: neighbours 0x05-0x08 drive screen-to-screen movement (0x2606+), 0x0E sets party entry coords, 0x0F gates events by era, 0x16/0x18 form a transition (coord + dest screen), and 0x1A is a flag bitfield.

Safe square / recall model (interpretation)

The two coordinate fields line up with MM2's two kinds of "safe square":

• 0x0E (in-map safe square): where the party spawns on the screen, and the likely landing square for combat run and same-map recall.
• 0x16 + 0x18 (cross-map recall): the destination screen + coords used by a relocation command handler (0xB2BE, gated by flag bit 6). For interior screens this points at the screen's overland location, matching the Surface (dungeon→overland), Town Portal (→town) and Fly (overland) spells, which all teleport the party to a per-map fixed square. Example: Middlegate (area 0) and Middlegate Cavern (area 17) both recall to overland screen 11 at (7,3).

Relationship to the time/era system

attrib.dat is static — one record per screen, identical across all game eras. The current era/year is runtime world state in the A4 globals (see 13-time-era-calendar.md). The link between the two is byte 0x0F: the event interpreter compares it against the current era index before running a screen's event record (0x172BC), which is how the same screen can behave differently across eras. attrib.dat itself only describes the screen's fixed geometry/environment/transition data.

Codecs

• C: EXTRACTED/decomp/mm2_attrib_codec.h / .c — byte-exact decode/encode/load/save plus named accessors for the confirmed fields.
• Python: tools/attrib_codec.py — same field model, round-trips byte-exact.