M — Mission File (.M)

.M files define individual missions as plain-text textFormat data — one keyword per line, with obj and waypoint2 blocks closed by a lone . (517 files in FA_2.LIB). The related .MM theater map format is distinct — see MM.md.

Tools

fx

fx mission info   <file.M>              # map name, time, object count
fx mission unpack <file.M> [-o out.txt] # editable text
fx mission pack   <in.txt>  -o out.M    # write back (byte-identical)

Other Tools

.M files require fx mission unpack → edit → fx mission pack. The companion .MT briefing files are plain ASCII and can be opened directly.

• VS Code — free, cross-platform; multi-file search useful for tracking object names and map references across missions
• Notepad++ — free, Windows; lightweight for quick briefing text edits

File Layout

Plain ASCII text, CRLF line endings, one keyword per line — there is no bracket syntax. The first line is textFormat. Top-level keywords stand alone; obj and waypoint2 open blocks that a lone . line closes. Indentation (tabs) is cosmetic — the structure is defined by the keywords, not the layout.

textFormat
brief
map BALTIC.T2
layer BALTIC.LAY 0
time 6 0
wind 270 15
clouds 20
obj
    type F16.PT
    pos 12345 0 67890
    angle 0 0 0
    nationality2 130
    flags $411
    alias -1
    .
      … more obj blocks …
waypoint2 4
    w_index 0
    w_goal 1
    w_pos2 0 0 743800 16000 929588
    w_speed 920
    w_index 1
      …
    .

Token format

• key value… — one keyword per line, space-separated values (string, decimal integer, or $-prefixed hex).
• obj … . — an object block; the lone . closes it.
• waypoint2 N … . — a waypoint block of N waypoints; the lone . closes it.
• sides4 opens the nationality table (indented $XX values follow).

Top-level keys

Key	Value	Description
textFormat	(none)	magic first line
brief / briefmap / armplane / selectplane	(none)	screen flags
map	file	terrain .T2 reference
layer	file index	.LAY reference
clouds	percent	cloud cover 0–100
wind	dir speed	wind conditions
time	hour min	start time of day
sides4	(block)	nationality table
obj	(block)	a placed object
waypoint2	count (block)	a waypoint list

Object block (obj … .)

Key	Value
type	object type name (references .OT/.NT/.PT files)
pos	x y z (world units)
angle	pitch bank roll (degrees)
nationality2	integer country code
flags	$hex behaviour flags
speed	initial speed
alias	signed id; targeted by a waypoint's w_preferredTargetId2
skill	AI skill level
react	reaction triple ($hex $hex $hex)
searchDist	detection range
name	optional label

The field list varies by object type; unknown fields are preserved verbatim. mission_parse_objects (api.md § mission.h) promotes type/pos/angle to typed members and keeps every other field in MissionObj::fields.

Waypoint block (waypoint2 N … .)

N waypoints, each opened by w_index and carrying w_pos2 (position), w_goal, w_next, w_flags, w_speed, w_react, w_searchDist, w_preferredTargetId2 (target link), and w_name. These blocks are emitted after all obj blocks and there are always fewer of them than objects, so which object a block belongs to is not encoded adjacently — the engine's assignment rule is not yet recovered (re-gameplay, #29). mission_parse_objects therefore returns the blocks as a parallel waypoint_blocks list rather than nesting them in objects.

Preferred target system

Waypoints can designate a specific object as their attack target using w_preferredTargetId2. The value is the object's alias field encoded as a negated unsigned 16-bit hex value:

hex_value = uint16_t(alias)      (equivalently: 0x10000 + alias, since alias is negative)

Alias	w_preferredTargetId2
−1	$ffff
−2	$fffe
−255	$ff01
−256	$ff00
−257	$feff
−288	$fee0

The pattern continues linearly; alias −N = $(10000 − N) in hex. Up to 288 preferred target slots are supported ($ffff through $fee0). Does not apply to map objects or the player object.

Example:

; Waypoint
w_preferredTargetId2 $ff01

; Target object with matching alias
obj
    type TRUCK.NT
    alias -255

Round-Trip Notes

• Parse → serialize produces byte-identical files for all 517 .M files in FA_2.LIB; tests/test_mission.cpp asserts byte preservation.
• mission_roundtrip is a verbatim copy (CRLF-normalized), so it preserves the files' tab indentation regardless of whether the parser needs it.
• mission_parse_objects extracts the full object + waypoint-block lists; the object count matches mission_parse_info for all 592 stock missions.

Related

Formats: MM — the theater map format sharing the mission codec; MT — plain ASCII briefing/debrief companion to each .M file; BRF — the .OT/.PT type definitions referenced by type fields.