firestorm/MW4COMPARE/README.md

MW4COMPARE -- FireStorm source tree vs. the FS_Build_V4H binary build

Comparison of our source repository against FireStorm Battletech SMT Build Four (v4h), a parallel, independently-maintained binary-only build of the same game, located at /home/rich/Repositories/FS_Build_V4H (1.7 GB, dated Oct/Nov 2021).

Goal: work out what each side has that the other does not, so the two can eventually be merged into one build containing all the mechs, maps, game types and variants.

Status: Part 1 (survey) complete. Part 2 (extraction + pruning) complete. Nothing has been merged into the repo. Every V4H asset is unpacked to a parallel tree outside the repo at /home/rich/Repositories/FS_Build_V4H_extracted, reduced to differences only -- 5,385 files / 65 MB out of an original 46,707 files / 1.24 GB -- and reshaped to mirror Gameleap/mw4. See section 5.

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0. TL;DR

	V4H has, we don't	We have, V4H doesn't
Mechs	6 new chassis (IDs 65-70): Champion, Jenner IIC, Dasher, Marauder, Thunderbolt, Griffin -- full geometry, textures, HUD/MFD/radar art, footsteps	Source for ~25 unregistered/experimental chassis (Blackheart, Bowman, Canis, Crab, Gargoyle, koto, locust2c, marauder2, pitbull, privateer, razorback, reaper, reaver, shadowhawk, strider, urbanmech_iic, ursus, vulture2, vulturec, ...) plus 4 Elite_* pilot variants
Variants	797 saved mechlab variants (resource/Variants/*.mw4); we ship 1	--
Maps	none	19 maps (conroe01-03, desert, doneg01, gage, minerl01, mountn01/03, ngoth, ruin03, scrub01, scrub06, volcan01/03, ddc_msl, freezer, ...)
Missions	none	17 missions + 5 UserMissions (aspen, canyon, conroe01-03, gagetown, gladiatorpit, lakeside, mechworks, minehq, newgothem, rubble, sanddunes, spaceport, vbase, editortemplate)
Skies	missing entirely -- no skies.mw4	skies.mw4 (40 MB, 2975 entries)
Shell scripts	reworked MechLab + 11 loose script/header files we don't have at all	our own console/lobby work (RookieMission, -tmfds, etc.)
Engine	binary only -- cannot be recovered	full source

The single most important structural finding:

Mech IDs 0-64 are byte-for-byte identical in both forks. V4H appended its six new mechs as IDs 65-70. There is no re-indexing to do -- a merge is additive on both sides.

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1. What FS_Build_V4H is

A deployed game folder, not a source tree. Notable contents:

FS_Build_V4H/
  MW4.exe                 3,633,152 B  2021-09-08   (their fork; no source available)
  ScriptStrings.dll         163,840 B  2021-02-03   (has the 6 new mech display names)
  MissionLang.dll           188,416 B  2021-09-01
  content/                  14 loose files (shell scripts + 1 ABL header)
  hsh/                      279 files -- the "block HUD" set introduced in v4f
  hshoriginal/              447 files -- the pre-v4f HUD set, archived
  resource/
    core.mw4                12,709 entries
    props.mw4               10,779 entries
    textures.mw4            10,419 entries
    maps/         27 maps    Missions/  29 missions
    Variants/    797 saved mechlab loadouts
    Pilots/Tesla/options.mw4
    (no skies.mw4)
  stats/zWorldStats/        stock 2001-era MS stats uploader, logs end 2001 -- dead weight
  uploadbuildv4h/           777 MB self-extracting installer of this same build
  firestorm build V4h.txt   changelog for v4 -> v4h (also in uploadbuildv4h/)

Their own changelog (firestorm build V4h.txt) is worth reading; it documents the six new mechs, the 3-ton-per-weapon ammo cap, the MechLab save crash, and the fact that corrupt variants can corrupt the whole build.

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2. Method

The .mw4 files are GameOS Stuff::Database packages (magic #VBD) -- a flat directory of named records, each optionally LZW-compressed. See tools/mw4db.py for the format and a faithful port of gos_LZDecompress.

Two comparison levels were used:

1. Index-only (mw4index.py + diffindex.py) -- parses the directory, no decompression. ~1 s for the whole 780 MB tree. Gives an exact entry-name diff.
2. Decoded (pkgcmp.py) -- decompresses every record and compares plaintext bytes. Slower (~2 MB/s) but is the only trustworthy content test.

Two traps that cost time -- do not repeat them

• Case. V4H's packer lowercased every entry name (ablscripts\bots\0-bot.abl vs our ablscripts\bots\0-Bot.abl). A case-sensitive comparison reported 5,909 "new" and 5,155 "missing" entries in core.mw4 that were the same files. Always compare through mw4db.norm().
• Stored-byte md5 is not an equality test. Comparing the compressed payloads over-reports massively: maps/peaks.mw4 showed 9 differing blobs by stored bytes but only 1 after decompression. Use pkgcmp.py before believing any difference.

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3. Findings

3.1 The six new mechs (the headline)

core.mw4 in V4H is a strict superset of ours: 754 extra entries, zero entries we have that they lack. All 754 belong to six new chassis and their destroyed models:

chassis	core entries	textures	props (animation)
marauder	63 armaturedata + 49 root + 21 armaturevideo + 5 destroyed	37 + 1	reuses existing
griffin	57 + 54 + 19 + 5	38 + 1	reuses existing
champion	57 + 51 + 19 + 5	36 + 1	reuses existing
thunderbolt	54 + 48 + 18 + 5	33 + 1	reuses existing
dasher	45 + 48 + 15 + 5	29 + 1	reuses existing
jenner2c	45 + 46 + 15 + 5	30 + 1	155 new entries under mechs/jenner2c/animation

Each chassis brings the full set: .contents (+ per-joint {armature} / {sites} pages), .damage, .data (+ {element} {footsteps} {gamemodel} {hierarchicalobb} {solidobb}), .engine, .instance, .subsystems, .torso.

textures.mw4 adds 299 entries: the six mechs' skins, six sets of textures/@a{chp,grf,jec,mar,thu,...}0-5.tga cockpit/pilot art, and textures/footsteps/<mech>_{default,dirt,snow}.tga.

Nothing else is new in core.mw4. No new weapons, no new subsystem types, no new tables. Whatever balance changes V4H made live in the per-mech .subsystems records and in their MW4.exe.

3.2 Mech ID space -- identical for 0-64

content/ABLscripts/mwconst.abi differs from ours by exactly this:

-LastMechID = 64 ;
-NoMechID   = 65 ;
+M_Champion = 65 ;
+M_Jenner2c = 66 ;
+M_Dasher = 67 ;
+M_Marauder = 68 ;
+M_Thunderbolt = 69 ;
+M_Griffin = 70 ;
+LastMechID = 70 ;
+NoMechID   = 71 ;
+LastMP1MechID = M_Solitaire;

Corroborated three ways:

• content/shellscripts/mechbay/mechnames.script and buildmechnames.script list mech_name[0..64] exactly matching our mechnames[] in CoreTech/Libraries/GameOS/render.cpp, then append 65-70.
• core.mw4 defines 65 *.subsystems on our side, 71 on theirs; the extra six are champion, dasher, griffin, jenner_2c, marauder, thunderbolt.
• ScriptStrings.dll (UTF-16) gains display strings Champion, Jenner2c, Dasher, Marauder, Thunderbolt, Griffin.

Note the naming inconsistency in their own build: the chassis directory is jenner2c but the subsystems record is jenner_2c, while three of their variants still reference jenner_iic1 (see section 3.3).

3.3 797 mech variants

resource/Variants/*.mw4 -- saved MechLab loadouts. We ship exactly one (MW4/Resource/Variants/Argus Variant1.mw4).

Each variant package is 4 records:

[0] 'Resource\Variants\<name>'   4 B    raw
[1] '{Mech}'                     ~350 B
[2] '<chassis>{Subsystem}'       ~4 KB   <- names the chassis it needs
[3] '<8-char token>'             16 B

Because the chassis is named in record 2, dependency analysis needs no decompression (tools/variants-report.py). Result:

loadable in our build TODAY : 727
blocked on the 6 new chassis:  67   (thunderbolt 22, griffin 15, marauder 15,
                                      dasher 10, champion 5)
broken / orphaned           :   3   (chassis 'jenner_iic1' does not exist even in V4H --
                                      Jenner2c 1 / Jenner2c 4 / Jenner2c Pharaoh)

Top chassis by variant count: warhammer 36, rifleman 30, nova 24, madcat 23, atlas 23, thunderbolt 22, hunchback 21, battlemaster 21, archer 21, thor 20.

Full table: reports/variants-inventory.txt.

3.4 Maps and missions -- we are ahead, they changed a little

• Maps: V4H has 27, we have 46. Zero V4H-only maps. Common maps are effectively identical -- file sizes differ by 0-2 bytes and peaks.mw4 decodes to exactly one differing record (peaks.data{gamemodel}, an internal reference blob).
• Missions: V4H has 29, we have 46 + 5 UserMissions. Zero V4H-only missions. Every common mission decodes to 2-4 differing records, always the same shape:
  • <name>.lights and <name>night.lights -- 3 bytes differ out of 33 KB. Noise.
  • <name>.contents -- real. Coliseum: 11,588 of 52,954 bytes differ, and the differing region contains new ASCII entity names. Their mission layouts have been edited. Worth a proper look before merging either direction.
  • Missions/freezer.mw4 additionally has 30 V4H-only records: stadium crowd VO (audio/vo/generic/mp/{cheer1-9,boo1-3,jeers,roar,ahh,aww,stadamb}.wav) and a rewritten scripts/freezer_teamattrition.abl (10,710 B vs our 832 B).
• All 71 loose .nfo / .tga / .txt files in resource/ (mission metadata, game-type definitions, thumbnails) are byte-identical. No game-type divergence.
• skies.mw4 is absent from V4H entirely. 40 MB / 2,975 entries that only we have.

3.5 Shell scripts -- V4H has a diverged MechLab and 11 files we don't have at all

props.mw4 decodes to 419 differing records, only 3 entries missing on their side (lobbydecals/decal_46/47/49.tga) and 155 extra (jenner2c animation). The interesting differences (V4H size vs ours):

script	V4H	ours	delta
mechbay/mechbay_main.script	94,517	61,432	+33 KB
mechbay/weapons.script	102,025	83,653	+18 KB
mechbay/armor.script	64,539	61,807	+2.7 KB
mechbay/infobox.script	43,875	41,595	+2.3 KB
listboxes.script	30,785	29,269	+1.5 KB
scriptstrings.h	71,608	70,811	+797 B
netlobby.script	163,740	163,088	+652 B
multiplayer/buildrestriction.script	16,443	15,713	+730 B
mechbay/chassis.script	82,596	81,881	+715 B
conlobby.script	141,044	140,532	+512 B
...plus ~15 more with small deltas

Also: 24 mechbay/graphics/installed/weapon_-1_*.tga slot images are much smaller in V4H (1,036 B vs 6,540 B etc.) -- this is the "weapon box sizes set to minimum" change from their v4 changelog.

Eleven loose files in content/shellscripts/ exist in V4H and nowhere in our repo:

clock.script                    wall-clock overlay
cm_listboxes.script             console mech list box
firestorm.h                     20 console callsigns
firestorm64.h                   64 Dragon-MP callsigns
globals.script                  shared script globals
options.h                       USE_ALLOWED_MECHS, Battle_Ammo, USE_OBSERVER, ...
mechbay/buildmechnames.script   71-entry mech name table
mechbay/mechnames.script        71-entry mech name table
mechbay/mechdescriptions.script 74 KB of mech description text
mechbay/old mechdescriptions.script
graphics/multiplayer/lobbydecals/decal_.tga

These are loaded loose from disk (they are in neither core.mw4 nor props.mw4 on either side). Their computerplayer.script #includes firestorm.h where ours #includes callsign.h -- so this is a genuinely diverged shell-script codebase, not just extra data.

3.6 HUD art (hsh/)

V4H maintains two HUD sets:

• hshoriginal/ (447 files) -- the detailed paper-doll set, close to ours.
• hsh/ (279 files) -- the "block HUD" compromise introduced in v4f so the new mechs would have something to display. Their changelog admits HUDs do not always match the mech actually in use.

Against our hsh/ (456 files):

	identical	differ	V4H-only	ours-only
hsh/	182	68	29	206
hshoriginal/	275	148	24	33

V4H-only files are the six new mechs' hud/, MFD/, radar/hud/ and Mechs/ art, decals/DDC.bmp, plus Mechs/battlemasteriic.bmp and Mechs/mad cat mk.ii.bmp (pre-rename spellings of files we renamed).

Colour depth differs systematically: their Mechs/*.bmp are 24-bpp 500x400 (600,054 B), ours are 8-bpp palettised (201,080 B). Same for MFD/rifleman.bmp (43,256 vs 15,476).

hsh/hud/Convert.txt and hsh/radar/hud/Convert.txt are the authoring recipe for the paper-doll art and explicitly say the coordinates go into coord.cpp under GameOS/External dependencies. Independent corroboration of MFD-RADAR-MAPPINGS.md. They are reproduced verbatim in reference/Convert-hud.txt / reference/Convert-radar.txt.

3.7 Per-mech .subsystems differ for every single chassis

Every one of the 65 shared chassis has a differing .subsystems record -- same length, different content (Atlas: 1,830 of 6,082 bytes). This is the compiled form, not the source text, so it is not directly readable. It is consistent with V4H's documented changes: 3-ton ammo cap per weapon, revised default weapon groups, restricted hardpoints on the new mechs.

This is the one area where merging is genuinely risky -- see the open questions.

Also differing in core.mw4 for essentially every mech: .data{gamemodel}, .torso{gamemodel}, and the contents[joint_torsoabove]{armature} / contents[joint_*belowankle]{armature} records. Byte inspection of atlas.data{gamemodel} shows one side stores an inline path string where the other stores a numeric reference -- i.e. a packer/format difference, most likely benign. Confirm before treating any of these as content changes.

3.8 Root config and binaries

Identical: 37 root files, including all three ctcl-*.ini.

Differing binaries (theirs older/forked, ours newer): MW4.exe, autoconfig.exe, Launcher.exe, mw4print.exe, ctcls.dll, Language.dll, MissionLang.dll, ScriptStrings.dll.

V4H-only root files: Console launcher.bat (mw4.exe -window), optionssmt.ini, optionssmtv4.ini, options.ini.rp411old, pre-uninstall.bat, RMTSHARE.EXE, SetNetworkAccess.reg, firestorm build V4h.txt.

options.ini differences worth flagging:

key	V4H	ours
bitdepth	32	16
ruletype	17	2
unlimitedammo	0	1
friendlyfirepercentage	100	0
heaton	1	0
allowedbeam1	fffffffd	ffffffff
allowedmissile1	ff3bffff	ffffffff
allowedprojectile1	ffffdfff	ffffffff
playericon / teamicon	decal_49 / decal_50	decal_48 / decal_48
[RookieMission] section	absent	present (ours)
RuleBook/DawnWar/BiggieSizeIt/CanYouHearTheFootSteps	absent	present (ours)

bitdepth=32 is interesting given all the DWM8And16BitMitigation work recorded in the repo memory -- V4H apparently runs the console at 32 bpp.

optionssmtv4.ini additionally carries a full [cameraship params] block (over-shoulder offsets, death-sequence camera, HUD name/chat toggles) that ours does not.

3.9 What we have that V4H does not

Besides the maps/missions/skies above, Gameleap/mw4/Content/Mechs contains 93 non-destroyed chassis directories, of which 27 are not in V4H's 71-mech roster:

Blackheart  Bowman  Canis  Crab  Duangung  Gargoyle  Gesu  Grimreaper_DNU
koto  locust2c  marauder2  pitbull  privateer  razorback  reaper  reaver
shadowhawk  strider  urbanmech_iic  ursus  vulture2  vulturec
Elite_Daishi_Castro  Elite_Daishi_William  Elite_Madcat_James  Elite_Thor_Duncan
jenner2c   (chassis 'jenner2c' -- V4H spells theirs 'jenner_2c')

Two of these matter immediately:

• Dasher_DNU/ -- chassis dasher, 71 source files including .subsystems, .damage, .animscript, geometry. We already have Dasher source; it is simply not registered in the roster or packed into core.mw4.
• jenner2c/ -- 80 source files, plus jenner2c_destroyed/. Likewise unregistered.

So of V4H's six new mechs we may already hold source for two. marauder2 is Marauder II, a different chassis from their marauder.

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4. Tools

All under tools/. Python 3, no dependencies.

file	what it does
mw4db.py	#VBD package reader + gos_LZDecompress port. Import this; everything else builds on it. Documents the on-disk format.
mw4index.py	mw4index.py <resourceRoot> > manifest.tsv -- directory-only manifest of every *.mw4. ~1 s for 780 MB.
diffindex.py	diffindex.py A.tsv B.tsv [labelA] [labelB] -- case-insensitive package/entry-name diff.
pkgcmp.py	pkgcmp.py A.mw4 B.mw4 -- authoritative decoded content diff of one package.
dumprec.py	dumprec.py pkg.mw4 "entry/name" [out] -- extract one decoded record; --list lists entries.
treediff.py	treediff.py dirA dirB [labelA] [labelB] -- case-insensitive loose-file tree diff by md5.
variants-report.py	chassis-dependency inventory of resource/Variants, flags variants that cannot load.
extract-all.py	extract-all.py <resourceRoot> <outDir> -- unpack every package into a real directory tree. See section 5.
prune-identical.py	prune-identical.py <extractedDir> [--apply] -- delete everything we already have byte-for-byte. Dry-run by default.
classify-survivors.py	classify-survivors.py <prunedDir> -- split what is left into NEW vs DIFFERS.
restructure.py	restructure.py <extractedDir> [--apply] -- reshape a pruned tree to the repo's layout and casing. Refuses to run if any two packages would collide.
split-source.py	split-source.py <extractedDir> [--apply] -- separate repackable source from compiled records and rename the .obbs.

run-comparison.sh regenerates every report:

cd MW4COMPARE
./run-comparison.sh                                   # uses the default paths
./run-comparison.sh /path/to/OTHER_BUILD /path/to/our/mw4

Runtime is a few minutes; textures.mw4 dominates.

There is an older, standalone version of the same decompressor at build-env/extract-mw4.py. tools/mw4db.py supersedes it and is the one to extend.

5. The extracted asset tree

Every record of every V4H package, unpacked to real files at /home/rich/Repositories/FS_Build_V4H_extracted -- deliberately outside the repo. Nothing has been merged; this is derived data and is regenerable:

python3 MW4COMPARE/tools/extract-all.py \
    /home/rich/Repositories/FS_Build_V4H/resource \
    /home/rich/Repositories/FS_Build_V4H_extracted

857 packages -> 46,707 files, 1.24 GB, about 3 minutes.

directory	files	size	from
core/	12,709	3.4 MB	core.mw4
props/	10,779	178 MB	props.mw4
textures/	10,419	358 MB	textures.mw4
maps/<map>/	7,219	576 MB	27 map packages
Missions/<name>/	2,391	60 MB	29 mission packages
Variants/<name>/	3,188	4.8 MB	797 saved loadouts
Pilots/Tesla/options/	2	5 KB
_merged/	42,100	hardlinks	flattened Content-shaped view

Extraction is per package, because 842 entry paths are claimed by more than one package and 70 of those hold genuinely different content (mostly a mission packing its own copy of a global props.mw4 asset -- 29 are Coliseum/Freezer crowd VO). A single flat tree would silently lose data.

_merged/ is a convenience view built with hardlinks (no extra disk) that mirrors Gameleap/mw4/Content, so it diffs directly against our source tree. Conflicts resolve props > core > textures > maps > missions and every one is listed in _conflicts.tsv. Variants and Pilots are excluded from it -- their records have no directory part ({Mech}, <chassis>{Subsystem}) so all 797 variants would collide. Treat _merged/ as read-only; hardlinks mean editing there edits the per-package copy.

Full details, including the duplicate-entry handling, are in the tree's own _README.txt.

How close packed records are to real source

Verified against mechs/jenner2c:

• Recovered as-is -- .contents, .damage, .data, .engine, .instance, .subsystems, .torso, .animscript, every *.erf geometry part, *_cage.erf, runninglights.erf, armaturedata/, armaturevideo/. Decoded TGAs are valid (Targa image data - RGB 512 x 512 x 32); core/ablscripts/mwconst.abi extracts byte-identical to V4H's loose copy, which independently validates the decompressor.
• Recoverable by renaming a qualified record -- X.data{solidobb} -> X_skeleton_SOLID.obb and X.data{hierarchicalobb} -> X_skeleton.obb. Both carry the #BBO magic and byte-identical headers to our source .obb files.
• Not directly present -- X.armature. The packer splits it into per-joint X.contents[joint_*]{armature} records.

Also worth knowing before any merge: V4H's Jenner IIC is not a rename of ours. Their part prefix is jec_ and chassis files are jenner_2c.*; ours are j2c_ and jenner2c.*. Zero files in common. They are separately authored assets.

Pruning to differences only

Our own packages were extracted the same way to /home/rich/Repositories/FS_Ours_extracted (102 packages, 51,382 files, 1.76 GB), then everything V4H has that we already hold byte-for-byte was deleted:

python3 MW4COMPARE/tools/prune-identical.py  /home/rich/Repositories/FS_Build_V4H_extracted --apply
python3 MW4COMPARE/tools/classify-survivors.py /home/rich/Repositories/FS_Build_V4H_extracted

46,707 files / 1.24 GB -> 5,385 files / 66 MB. 41,322 deleted (88.5%), 1,912 empty directories removed. _pruned.tsv logs every deletion and which rule matched.

package group	NEW	DIFFERS
Variants	3,188	0	797 loadouts x 4 records; we ship 1
core	746	440	6 new mechs + per-chassis changes
props	155	419	jenner2c animation + reworked MechLab
textures	297	2	new mechs' skins / footsteps
Missions	1	114	.contents, .lights, freezer crowd VO
maps	0	21
Pilots	0	2
total	4,387	998

Why our source tree alone is not a sufficient baseline

A .mw4 is not a zip of Content/. Measured:

• 17,683 records (42%) are qualified derivatives the packer generates and that have no source file at all -- foo.data{gamemodel}, foo.contents[joint_hip]{armature}, bar.tga{hint}.
• ~7,400 more have a source path but the packer rewrites the bytes. Proven by comparing our own Content/ against our own .mw4 output: 3,238 .data, 2,320 .video, 583 .instance, 361 .contents, 345 .audio, 235 .damage, 117 .torso, 103 .subsystems, 65 .engine, 58 .lights.

Matching against Content/ alone would have "kept" roughly 24,000 files we already have. So each candidate is tested in order: (1) same package + entry path in our extracted packages, (2) same entry path in any of our packages, (3) unqualified name at the same path in Content/. In practice 41,320 matched rule 1 and 2 matched rule 3.

Case warning. V4H's packer lowercased every entry name; ours did not. The same record is core/mechs/longbow/longbow.data{element} in V4H and core/Mechs/Longbow/longbow.data{Element} in ours. Every comparison here is case-insensitive -- a plain diff -r between the two trees is meaningless.

Reading the 998 DIFFERS

By extension: 352 data{gamemodel}, 96 torso{gamemodel}, 93 subsystems, 114 contents[joint_*]{armature}, 55 lights, 54 audio, 38 instance, 37 contents, 29 script, 28 tga, 15 wav.

• Probably packer noise -- the {gamemodel} records encode cross-package references (one side stores an inline path string where the other stores a numeric id), and the .lights differences measured 3 bytes out of 33 KB. Verify before treating as content.
• Real, needs a design decision -- the 93 .subsystems (V4H's balance pass) and the 37 mission .contents (substantial layout edits).
• Real, straightforward -- the 29 .script files (their MechLab rework) and the freezer crowd VO.

Reshaped to the repo layout

Once pruned, the V4H tree has zero cross-package collisions -- 5,385 files map to 5,385 distinct destinations -- so it was flattened to the repo's shape:

python3 MW4COMPARE/tools/restructure.py /home/rich/Repositories/FS_Build_V4H_extracted --apply

FS_Build_V4H_extracted/
  Content/                        same shape and casing as Gameleap/mw4/Content
  Resource/Variants/<name>/       797 saved loadouts (records have no path)
  Resource/Pilots/Tesla/options/

Path components are re-cased against the repo wherever a counterpart exists, so mechs/longbow/longbow.data{element} became Content/Mechs/Longbow/longbow.data{Element}. Components with no counterpart keep the packer's spelling -- which is why the six new chassis sit at Content/Mechs/champion, dasher, griffin, jenner2c, marauder, thunderbolt in lower case. _layout.tsv records the originating package and entry name for every file, so the per-package view can be reconstructed at any time.

FS_Ours_extracted is deliberately left in per-package form. Unpruned it still has 60 genuine collisions (mission-local copies of shared Culturals/ props, e.g. arena_debris_large01.data differing across Coliseum / Reduex / StormCanyon) plus 2,617 harmless duplicate paths. Flattening it would lose data, and it is regenerable in ~4 minutes anyway. restructure.py refuses to run on a tree with collisions for exactly this reason.

Source vs compiled -- only 502 of the 2,195 files are repackable

A .mw4 does not store the source tree. Some records are the source file byte for byte; others are what the packer produced from it. Which is which was established empirically by hash-matching every record of our own packages against Gameleap/mw4/Content (22,138 matched a source file, 28,728 did not):

repackable source	.tga .erf .mw4anim .bid .wav .bsp .material .abl .obb .ebf .bounds .animscript .fgd .tcf .mlr .d3f .gaf .script .h .abi
compiled	.data .instance .subsystems .damage .torso .engine .audio .video .lights .mw4, and every {hint} {handle} {gamemodel} {element} {footsteps} {zones} {nametable} [shadow] [joint_*]{armature} [joint_*]{sites} record

The decisive evidence: our source Content/Mechs/Atlas/atlas.data is 4,891 bytes of text; the record packed under that name is a 12-byte binary stub. The real payload went into the {gamemodel} / {element} records. So a mech's .data, .damage, .subsystems, .instance, .contents, .torso and .engine cannot be recovered from any package -- they must be re-authored. .armature does not exist in a package either; the packer splits it into per-joint X.contents[joint_*]{armature} records.

python3 MW4COMPARE/tools/split-source.py /home/rich/Repositories/FS_Build_V4H_extracted --apply

FS_Build_V4H_extracted/
  Content/     502 files  repackable source, repo shape + casing - drop straight in
  _compiled/  1693 files  packer output, reference only
  Resource/               variants + pilot options (use the original .mw4 files)

Renames applied -- these genuinely are .obb files (#BBO magic, headers byte-identical to ours):

record	becomes
champion.data{solidobb}	champion_skeleton_SOLID.obb
champion.data{hierarchicalobb}	champion_skeleton.obb

(_SOLID.obb / .obb outside Content/Mechs.) The real source spelling is declared inside the .data text we don't have, so a convention was applied and logged in _source-vs-compiled.tsv -- whatever .data gets authored later must reference these names.

What survives in Content/: 208 .erf, 154 .mw4anim, 73 .tga, 29 .script, 17 .obb, 15 .wav, 3 .h, 1 each .animscript .abl .abi.

The resulting Content/Mechs/dasher/ now matches our own Content/Mechs/Dasher_DNU/ naming exactly (das_hip.erf, dasher_cage.erf, dasher_skeleton.obb, dasher_skeleton_SOLID.obb).

For the six new chassis we therefore have all geometry, animation and art, but their definition files must be written by hand. Note we already hold complete source for two of them in our own repo: Content/Mechs/Dasher_DNU and Content/Mechs/jenner2c.

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6. Reports

Written to reports/ by run-comparison.sh. The two manifest-*.tsv files are ~5 MB intermediates and are gitignored.

file	contents
packages-entrydiff.txt	per-package entry-name diff, all 857 V4H packages vs our 102
core-decoded-diff.txt	433 real differences + 754 V4H-only entries in core.mw4
props-decoded-diff.txt	419 real differences + 155 V4H-only in props.mw4
textures-decoded-diff.txt	1 real difference + 299 V4H-only in textures.mw4
maps-decoded-diff.txt	per-map decoded diff (all <=1 real difference)
missions-decoded-diff.txt	per-mission decoded diff (.contents / .lights / freezer)
hsh-diff.txt, hshoriginal-diff.txt	HUD art trees
content-diff.txt	the 11 loose scripts + mwconst.abi
resource-files-diff.txt	package-file and loose-file level diff of resource/
variants-inventory.txt	797 variants grouped by chassis with load status

reference/ holds verbatim copies of small, high-value V4H text files that are not in our tree, so they survive independently of the FS_Build_V4H folder:

file	source
v4h-changelog.txt	firestorm build V4h.txt -- their v4 -> v4h release notes
Convert-hud.txt, Convert-radar.txt	hsh/hud/Convert.txt, hsh/radar/hud/Convert.txt -- paper-doll authoring recipe, points at coord.cpp
mechnames.script, buildmechnames.script	the 71-entry mech name tables
v4h-firestorm.h, v4h-firestorm64.h	20 console / 64 Dragon-MP callsigns
v4h-options.h	USE_ALLOWED_MECHS, Battle_Ammo, USE_OBSERVER, ...
mwconst.abi.diff	the M_Champion..M_Griffin / LastMechID=70 delta
options.ini.diff	ours -> theirs

Not copied (too large, read them from FS_Build_V4H/content/shellscripts/mechbay/): mechdescriptions.script (74,883 B) and old mechdescriptions.script (74,438 B).

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6b. Decompiling the compiled records

Full write-up: DECOMPILING.md. Read that before touching any of this.

The compiled records are not a dead end. The engine source contains both the writer (MWTool::BuildResource -> MWObject::CreateSubsystemStream -> Tool::ConstructCreateMessage -> a per-class factory in one of 51 mw4/Code/MW4/*_Tool.cpp) and the reader, and the message structs are plain PODs declared in our own headers. We also have a closed-loop test harness: 65 chassis where we hold both the source text and the compiled record.

record type	status
.armature	done and verified -- 2,938 of 2,976 pages exact across 65 chassis, 1,849/1,849 child lists exact. All 38 residuals are data the packer itself discarded, so the game never sees them either.
.subsystems	done and verified -- 7,579 of 7,585 keys exact across 63 chassis. The 6 residuals are Behemoth/Behemoth II GroupIndex, changed in source by e45a67a8 after the package was built.
.data .damage .contents .instance .torso .engine	same mechanism, not started

python3 MW4COMPARE/tools/decompile/armature.py --verify          # 65-chassis harness
python3 MW4COMPARE/tools/decompile/armature.py <recordDir> -o out.armature

.armature files have been generated for all six new chassis into FS_Build_V4H_extracted/Content/Mechs/*/.

Two things found along the way that matter beyond this section:

• The extracted baseline reflects the packages, not Content/ at HEAD. core.mw4 and textures.mw4 have never been repacked since the initial mirror (2b8ca921); props.mw4 is current as of 8bfaf9b9. Check this before concluding anything is missing. See DECOMPILING.md section 8.
• ResourceID packs the package record id in its high word, which is how Model= references resolve back to a path.

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7. Merge assessment

Ranked by value/risk. None of this has been done.

Low risk, high value -- take from V4H

1. 727 mech variants that reference chassis we already have. Drop-in: they are self-contained .mw4 files in Resource/Variants/, keyed by chassis name, and our chassis names match. Sanity-check a sample in the MechLab first -- their changelog warns that a corrupt variant can corrupt a build.
2. The 11 loose shell scripts -- at minimum mechdescriptions.script (74 KB of mech text we simply do not have) and the two mech-name tables. firestorm.h/firestorm64.h callsign lists are a straight content lift.
3. Freezer stadium crowd VO (17 wavs) and the expanded freezer_teamattrition.abl.
4. HUD/MFD/radar art for the six new mechs, and the 24-bpp Mechs/*.bmp masters if we want higher-quality portraits than our 8-bpp copies.

Medium risk -- the six new mechs

The assets are all extractable from core.mw4/textures.mw4/props.mw4. The blockers are on our side and are all code, not data:

• render.cpp mechnames[] -- append 6 entries (currently 65, "dasher" is commented out).
• coord.cpp -- MFD/radar paper-doll coordinate tables must gain 6 entries.
• mwconst.abi -- apply the M_Champion..M_Griffin / LastMechID=70 delta.
• ScriptStrings.dll (StringResource.rc) -- add DNL_CHAMPION, DNL_JENNER2C, DNL_DASHER, DNL_MARAUDER, DNL_THUNDERBOLT, DNL_GRIFFIN.
• MechLab scripts must learn about IDs 65-70 (this is what their +33 KB mechbay_main.script is doing).
• MW4Shell.cpp / anything else with a hard-coded 65.

Because IDs 0-64 are identical, this is purely additive.

Extracting the mech source (rather than the packed records) is the open question -- the records in core.mw4 are the compiled forms, and we need .erf/.obb/.data sources to rebuild core.mw4 with our own packer. We already hold source for dasher and jenner2c.

High risk -- do not merge blind

• .subsystems for the 65 shared chassis. All 65 differ. Taking theirs imports their entire balance pass (3-ton ammo cap, revised weapon groups) wholesale; taking ours keeps our balance. This is a design decision, not a merge decision.
• Mission .contents. Real, substantial edits on their side for every shared mission. Needs a proper structural diff before any decision.
• MechLab scripts. Their MechLab is documented (by them) as crash-prone on save. Do not import their mechbay_*.script wholesale.

Not worth taking

stats/zWorldStats (dead 2001 telemetry), RMTSHARE.EXE, uploadbuildv4h/ (777 MB installer of the same content), options.ini.rp411old.

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8. Open questions for the project owner

1. Balance. Do we adopt V4H's .subsystems (3-ton ammo cap, their weapon groups) for the 65 shared mechs, keep ours, or merge selectively per mech--
2. Mission layouts. Their .contents differ for every shared mission. Is that deliberate content work on their side (more drop zones? different props?) or drift we should ignore--
3. Mech source. Is there a source tree for V4H anywhere, or is core.mw4 the only copy of the six new mechs? That decides whether we re-pack from source or have to write an unpacker that reconstructs .erf/.obb from packed records.
4. bitdepth=32. V4H runs the console at 32 bpp; we run 16. Given the DWM8And16BitMitigation dependency documented in the repo memory, is their build actually rendering at 32 bpp, and should we try it--
5. The 25 unregistered chassis on our side (Canis, Gargoyle, razorback, reaver, ...) -- are these finished assets that were never wired up, or abandoned work? If usable, the combined roster could be far larger than 71.
6. Variant hygiene. Their changelog warns that corrupt variants can corrupt the build. Do we import all 727 loadable variants, or curate--
7. jenner_iic1. Three variants reference a chassis that exists in neither build. Drop them, or re-point at jenner_2c--

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Generated 2026-08-08 against FS_Build_V4H (Oct/Nov 2021) and branch 5.1.0b-in-progress.