OT — Static Object Definition (.OT)

FA_2.LIB contains 170 .OT files. Each defines one static (non-moving) scenery or target object — buildings, bridges, trees, flags, runways, radar dishes, etc. BRF plain text (NOT a Win32 PE DLL); decompressed sizes vary (e.g. BLDG1.OT = 1256 bytes).

Tools

fx

fx ot info   <file.OT>               # human-readable field dump
fx ot unpack <file.OT> [-o out.txt]  # editable text
fx ot pack   <in.txt>  -o out.OT     # write back (byte-identical)

File Layout

Plain text; BRF syntax (see BRF.md for the token grammar). Single-section structure (OBJ_TYPE only — no NPC_TYPE or PROJ_TYPE).

OBJ_TYPE

[brent's_relocatable_format]

;---------------- START OF OBJ_TYPE ----------------
;---------------- general info ----------------

    byte 1                  ; object category (1 = static object)
    word 166                ; hitpoints (durability)
    word 0                  ; object subtype ID
    ptr ot_names
    dword $521              ; capability flags
    word $100               ; flags2
    ptr shape               ; 3D model reference
    dword 0 ... (reserved fields, same layout as JT/NT)
    dword 1956              ; year placed / era introduced
    word 195                ; (param)
    word 0
    word 100 ... word 100   ; (performance/damage-resistance params)
    byte 35                 ; (armor/hardness)
    byte 15
    dword 0
    word 0

;---------------- movement info ----------------
    word 0 ... (all zeros — static objects do not move)
    symbol _OBJProc         ; static object callback

;---------------- sound info ----------------
    dword 0 ... (all zeros — most static objects have no ambient sound)

Labels Section

:ot_names
    string "Factory 3"
    string "Factory 3"
    string "BLDG1.OT"
:shape
    string "bld1.SH"
    end

Notes:

• Static objects have no loopSound ptr, no secondSound, and no hardpoints.
• The movement info block is all zeros.
• _OBJProc handles collision detection, destruction events, and visibility only.
• The ~ prefix has two distinct uses: (1) destruction state replacement — ~BNK5.OT is "Damaged Shelter 5" with a destroyed model (dbk5.SH), zeroed dmg_armor, and bit 5 of ot_flags cleared; placed by the engine at the same world position after the base object is destroyed. (2) campaign/theater variant — ~COLTWR.OT is an enhanced version of COLTWR with an added loop sound and bit 22 set, used in a specific campaign. Check the ~ prefix section in architecture.md for the full list.

obj_class word — confirmed values

Value	Class	Representative files
$40	Scenery / terrain feature	TREE1-2, ROAD, LOT, CITY1-3, CRATER, CROPA/B, FLAG, RES1-2, HOUS*, HOOCH, MOOSEA/B
$100	Ground structure	BLDG1-3, BNK1-9, STRIP1-7, HANGR, SILO, TOWER, COMM, BUNKER, SHELT

$40 covers both pure scenery (TREE, ROAD) and targetable-but-civilian structures (CITY blocks, urban terrain). $100 covers all military and airfield structures. Naval and vehicle classes appear in NT files only ($2000 = ship, $1000 = SAM, etc.).

ot_flags dword — observed bit map

Full survey of all 170 OT files. Bit positions confirmed by cross-category comparison.

Bit	Mask	Label	Status	Notes
0	$1	targetable	confirmed	Absent on TREE, ROAD, LOT, CRATER, DEST, REACTB (pure scenery / already-destroyed states)
5	$20	armed / valid combat target	confirmed — FUN_0043df7b	Hard gate in targeting acquisition: entity with bit 5 clear is immediately rejected as a valid target. Absent on civilian variants (BLDG2 $501) and ~ destroyed-state replacements.
8	$100	has collideable oriented geometry	confirmed — FUN_0042c9b0	When set with a non-zero heading, uses angle-based hit detection (calls Rotate2). Present on bridges, most structures, rocks; absent on flat terrain tiles (ROAD, LOT, TREE).
10	$400	civilian or dual-use infrastructure	confirmed — _Reaction_12 (0x464040), _MaskEvents_4 (0x463ea0)	Set on BLDG, HOUS, urban blocks, airport buildings (APTLA/B/C), NUCOB, REACTR; also on SAM infrastructure sites (SA3SITE, HAWKSITE) — not exclusively civilian. Drives the event-system handlers; also toggles bay-door actuator.
11	$800	animated / non-static scenery	confirmed — FUN_0042c9b0	OBJ_TYPE+9 & 0x800 sets a ground-mobile state flag in the targeting/collision resolver. Set on FLAG, CROP, CITY1-3, BR*END (bridge endpoints), SUPPLY, PRDR1/2 (rotating radar dish), MOOSEA/B, MICRO/MICROM (comm dish), CRANE, COMM, BRD1.
15	$8000	airfield surface	confirmed — FUN_00425196	When set, forces targeting category to 4 (flight deck special class), bypassing normal flags2-based lookup. Also tested combined with bit 22 (& 0x408000) in targeting eligibility. Exclusive to STRIP1-7 and DTSTRP.
17	$20000	military / hardened structure	confirmed	Set on BNK, HANGR, COMM, NUCCT, PRDR, RELAY, TOWER, COLTWR, CTWR, and other military targets.
20	$100000	damaged runway surface	inferred	DTSTRP only; contrasts with bit 21 on intact STRIP*.
21	$200000	intact runway surface	inferred	STRIP1-7; absent on DTSTRP (damaged variant).
22	$400000	prominent/large variant	confirmed — FUN_0042c9b0	When set, collision geometry uses hit-point count of 16 (0x10); when clear, uses full default geometry. Also tested combined with bit 15 (& 0x408000) for targeting eligibility. Set on SHELT, BUNKER, HANGRB, CTOWR, FUEL, OILW, DOCK1, COMM, REACTR, CTYBKA/B, APTLA, ~COLTWR.

Bits 9, 12–14, 16, 18–19, 23+ not observed in any OT file in FA_2.LIB.

Example flag combinations:

Object type	ot_flags	Bits active
TREE1, ROAD	$0	none
SILO	$21	0, 5
ROCKA	$101	0, 8
BLDG2 (Warehouse)	$501	0, 8, 10
BLDG1 (Factory)	$521	0, 5, 8, 10
SA3SITE, HAWKSITE	$401	0, 10
SUPPLY	$820	5, 11
FLAG*	$800	11
CITY1	$900	8, 11
PRDR1/2 (Radar)	$20d21	0, 5, 8, 10, 11, 17
IND1, RES1, HGRP1	$121	0, 5, 8
BNK1	$20121	0, 5, 8, 17
HANGR	$20121	0, 5, 8, 17
HANGRB (large)	$420121	0, 5, 8, 17, 22
BUNKER, SHELT	$400021	0, 5, 22
COMM (C&C)	$400921	0, 5, 8, 11, 22
STRIP1	$208021	0, 5, 15, 21
DTSTRP	$108021	0, 5, 15, 20

Hitpoint scale

All confirmed in the word hitpoints field (field index 23). Values are inferred to be absolute damage points. Compare dmg_armor across JT weapon types against object hit_points to calibrate survivability.

File Inventory

Category	Examples
Structures	BLDG1-3, FACTD, FCTYA/B, FACT1, IND1/2, STORE, HANGR/HANGRB, SHELT, CASTLE
Nuclear facilities	NUCCT, NUCOB, NUCRD, REACTB, REACTR
Runways / Aprons	STRIP1-7 (+ variants), APTB1, APTLA/B/C, APTM, APTOLD, DTSTRP
Bridges	BR1/2/3 END+MID, BRD1-4, BRDEND, BRDMID
Urban	CITY1-3, TWNBKA-F, CTYBKA-G, SLUM01/02, HOUS/HOUSB, HOOCH, RES1/2
Bunkers / Military	BNK1-9 (+ variants), BUNKER, CMHQ1/2, SHELT, SILO
Radar / Comms	PRDR1/2, SRDR1/2, COMM/COMM1/2, RELAY, TOWER, CTOWR, CTWR1/2, COLTWR, KING
Terrain features	ROAD/ROAD2/4/ROADC, ROCKA-E (+ variants), TREE1/2, CROPA/B, WNDMLL, MOOSEA/B
SAM infrastructure	SA3SITE, HAWKSITE
Naval / Port	DOCK1, CONT1-3, CRANE, DKHOS1/2, CGRP1-3, HGRP1-3, SGRP1-3
Misc	CRATER, OILW, SUPPLY, FUEL, WTRBUF, MICRO/MICROM, LOT, REDOM, FLAGO1/2, FLAGR1/2, FLAGY1/2, AV8TNT
Campaign variants (~)	~BNK5, ~BNK6, ~BNK8, ~CLEMT, ~COLTWR, ~KITT, ~MOOSE, ~NIMZ, ~WASP

All 170 live in FA_2.LIB.

Related

Formats: BRF — the family grammar and shared OBJ_TYPE reference; SH — 3D shapes referenced by shape; NT — the moving-unit counterpart; T2 — terrain maps that place OT objects; M — mission files that instantiate OT objects as targets.