cod2.md

Call of Duty 2

vcod plays and hosts Call of Duty 2, patch 1.3 (protocol 118). It needs a CoD2 install: main/ with the stock iw_*.iwd files. Put the binaries in it, or point --game-dir or COD_DIR at it (COD2_DIR is only for tests and tools). The game is detected from main/iw_*.iwd or CoD2MP_s.exe; --game cod2 forces it. How to run each mode is in usage.md.

Research docs live in docs/research; the links below name the section that measured each claim.

What works

Client

Front end. Bare vcod --game cod2 runs CoD2's stock main menu, its rects placed by their screen alignment (cod2-fonts-menus.md 4).

• The server browser lists LAN servers (a getinfo broadcast), master.cod.pm's protocol 118 list and favourites, in CoD2's eleven columns, maps by their arena long name. It joins the server picked.
• Start New Server runs vcod-server --game cod2 beside vcod.
• The options screens set binds, mouse, graphics (the monitor's video modes and refresh rates) and snd_volume.
• Player profiles are created, picked and deleted as retail's (players/<name>/, active.txt), each with its own vcod_mp.cfg.

Join, download, spectate, play. --connect ip:port, the browser or connect on the console:

• Decodes the gamestate and delta snapshots and sends the pure cp checksums (cod2-protocol.md 11).
• Downloads the non-stock iwds the server references and the install lacks (cl_allowDownload; UDP, or a www redirect's HTTP under cl_wwwDownload) into main/ or the server's fs_game, with progress on the connect screen, then reopens the search path over them (cod2-protocol.md 17.5). A refused download or a map that will not load returns to the menu with retail's message.
• Shows the server's script menus (server info, team, weapon, Esc's ingame, mute and vote) for the player to answer. --team and --weapon answer them on their own.
• Spectates (free flight through usercmds, or following a player) or plays. A player sends CoD2's buttons through the console binds (default_mp.cfg's): fire, sight toggle, melee, hold breath, frag, smoke, binoculars, use, reload, lean, gocrouch, goprone, +gostand, weapnext. The weapon byte is the client's own pick. X opens changeweapon for the next spawn.
• Follows a map change, keeps the map through map_restart, fast_restart and sd rounds, and returns to the main menu with the server's reason on a kick, a server quit or cl_timeout.
• Forwards say, callvote and other unknown commands to the server. rcon login, rcon logout and rcon host stand in for 1.3's missing rconPassword (usage.md, "Console").

Netcode and prediction.

• The clock is CoD2's CL_AdjustTimeDelta, one snapshot behind the newest. The last 32 snapshots are kept and each entity is drawn between the two around the frame's time.
• One packet a frame on a LAN, 30 a second off it, each repeating the last packet's cmds (cl_packetdup 1). Connection Interrupted and the net_disconnect icon show when the server stops running cmds; cg_drawLagometer draws the lagometer. A changed name, rate or snaps goes out as userinfo (cod2-protocol.md 18).
• Our own body is predicted through the server's own pmove and weapon code: the sight's rise, zoom and clips, shots and reloads at the frame rate, retail's error decay, first-person bob and lean, mantles, and other players' bodies clipped a unit inside the server's box as the cgame does. Brush models and item pickups are left out of the prediction (cod2-movement.md 18, cod2-hud.md 18.1).
• VCOD_NETSIM simulates a bad link; F3 adds net, clock, lerp and prediction lines.

Rendering.

• Script models, turrets aimed by their controllers, weapon and health items, missiles, brush models, player bodies with the weapon in hand, and corpses, under the server's fog (cod2-protocol.md 12).
• Bodies posed off legsAnim and torsoAnim with the j_* rig's controls (cod2-player-anims.md).
• The view weapon of our own or a followed body: hands and gun animated off the playerstate, swaying, bobbing, tilting and lagging the turn as CG_AddViewWeapon places it. The sight clips crossfade over 0.5 s; a main clip change cuts, as retail's does (cod2-weapons.md 6-7).
• Static props draw their normal and specular maps per pixel. Flags wave. An objective material on a static prop is not drawn (cod2-materials.md 9.2, 9.6, 9.7).
• Retail's shadow cookies: players, corpses and entity models (the nearest 12 by default, up to 24) take the sun off the lit world and models under them, under sc_enable and the other sc_* dvars (9.8).
• r_glow bloom and sky bleed (9.9); the shellshock trail's quarter desaturation (9.10); blurWorld menus blur the 3D view (9.13).
• mp_harbor's water runs retail's wave simulation: a Phillips spectrum through an FFT into a height map each frame, under its cube reflection, the sun's highlight and the fog (9.12).
• Snow on mp_downtown, mp_harbor, mp_leningrad and mp_railyard falls as retail's particle clouds, a thousand flakes a cloud, stopping at roofs (9.14).
• The effect_zfeather* sprites fade into the world behind them (9.5).

HUD. The playerstate's hudelems and the stock hud.menu (cod2-hud.md):

• Ammo counter, weapon name and mode icon, grenade counts, stance icon and the prone-blocked line.
• Compass with north (sprung as it turns), teammates (a talking one flashing), objectives and fire pings, an MG42 gunner's included.
• Use and pickup hints, fading as retail's. The cursor hint names the item, gun or use trigger in front, from retail's one use list (cod2-gsc-diff.md 5.4).
• Low-health overlay, red damage flash, damage direction icons.
• Crosshair spread with the weapon. A scope's overlay with its zoom (adsZoomFov, the gun hidden under it); an iron sight zooms the gun with the world.
• Gametype hudelems: timers, clocks (sd's bomb stopwatch), plant and defuse bars, world waypoints (ctf flags, sd bomb sites, hq radios, death icons).
• Head icons, the disconnected icon and the talk balloon. The killcam's "you" icon over the local player. A teammate's name under the crosshair, coloured by health (cg_drawCrosshairNames).
• A spectator's SPECTATOR, follow keys and following <name> (19).
• The scoreboard on +scores, scrolled by the wheel and page keys; chat lines, the say field, kill lines with icons flipped as each weapon says, the centre print (13-15). The vote lines off configstrings 15..18.
• cg_drawMantleHint, cg_hudStanceHintPrints, cg_chatHeight, cg_chatTime, cg_hudChatPosition, cg_hudSayPosition.
• No health bar, as retail's default.

View effects. Damage kick, the scope's idle sway and bob, the shot's kick roll, a landing dip, earthquakes and MG42 shake. Shellshock from shock/*.shock: screen blend, view kick, mouse scale and turn caps, sound mix and the cmd's 0x800 (cg_shellshock <secs> [file] on the console too). A held breath down a scope plays its breaths, heartbeat and hold_breath.shock mix (cod2-hud.md 16-18).

Mounted guns. A gunner sees from the gun's tag_player with the view held inside its arcs, and so does a spectator following one. Other gunners draw on their guns in the gunner anims (cod2-turrets.md 9, 15).

Sound (cod2-sound.md). CoD2's aliases and falloff curves: footsteps, fire, reloads, impacts, passing rounds, explosions, playSound, entity and missile loops, playLocalSound (the announcer), musicPlay, soundFade, the level's ambient crossfaded between tracks, sound blend entities, slave ducking under a master, setReverb's wet level, alias subtitles. Fire sounds and whizbys come from the shooter's tag_flash.

Effects (cod2-efx.md 6). Bullet impacts from the impact table, explosions, playFx, playLoopedFx, the map's ambient effects, other players' muzzle flashes and their tracers from their gun's tag_flash.

Demos (cod2-demos.md). record and stoprecord write CoD2's .dm_1 in a game. demo <name> and timedemo <name> play one through the session's frame, unpredicted. Retail's demos play in vcod and vcod's in retail.

Server

vcod-server <map> --game cod2 runs cod2::Cod2Server over game::cod2::Cod2Level (cod2-protocol.md 14).

Handshake and housekeeping (cod2-protocol.md 17):

• getinfo and getstatus answer byte for byte as retail's.
• The pure cp check (sv_pure 0 turns it off), g_password, private slots (sv_privateClients, sv_privatePassword), a full server and sv_minPing / sv_maxPing refuse with retail's replies.
• rate and snaps pace off-LAN clients; a fragmented message goes a fragment a turn; a dropped client is a zombie for sv_zombietime; a silent one times out on sv_timeout; sv_floodProtect.
• Serves a non-stock iwd over UDP (sv_allowDownload) or redirects to sv_wwwBaseURL (sv_wwwDownload).
• --set dedicated=2 heartbeats master.cod.pm:20710 every three minutes.
• g_log writes 1.3's games_mp.log (cod11-map-cycle.md 9).
• Retail CoD2MP_s.exe 1.3 joins it, pure or not: menus, spawn, move, fire, die to a bot, watch the killcam, kill an addTestClient client, scoreboard, chat, iwd download over UDP or HTTP, tdm to its score limit, sd past a round, a map_restart and a map change, with the same console lines as on a retail server (16).

Scripts and gametypes. The stock gsc runs on vcod's VM (cod2-gsc-diff.md). All five stock gametypes (dm, tdm, sd, ctf, hq) run on every stock map: sd's bomb planted and defused on the use key, ctf's flags taken and captured, hq's radios held. --gametype-script <file> runs one off disk.

Movement (cod2-movement.md). Each cmd runs vcod_cod2::pmove over the map's clip map, gated against retail captures (moves_ab, section 17):

• Ladders, the gun put away on the rungs.
• Mantles over flagged walls, the gun down for the high ones, the climb's block keeping others off the ledge (9).
• A prone body's pitch follows the ground; steep ground forces a crouch (10). Foliage rustles (12).
• Players block each other; overlapping ones are pushed apart (cod2-turrets.md 14.2).
• Bodies animate off the anim script's legs and torso picks, the weapon's fire, reload, melee and drop anims, and the hit flinches and stumbles. No turn anims, which retail leaves off (cod2-player-anims.md 9).

Combat (cod2-combat.md, gated against retail captures in section 9):

• Rounds strike the hit boxes of each body posed as retail's server poses it for the trace, through the antilag (9.5).
• Damage through the stock callbacks; death anims; corpses that fall, rest and slide on their death anim's root motion; the respawn.
• Offhand frags and smoke, rockets and their blasts, the script's radiusDamage, damage triggers, binoculars, the sniper's breath hold.
• The weapon a death drops, picked up by touch or swapped on the use key.
• The killcam replays the killer's view out of the engine's frame archive and ends on a use press (cod2-killcam.md).

Mounted guns (cod2-turrets.md 13, 14). Use mounts and lets go; the barrel follows the view inside its arcs; the trigger fires a round a frame. Stand, duck and prone guns (mg42 and 30cal) and the script's spawnTurret ones. A manned gun refuses a second player; a gunner killed on the gun lets it go.

Map cycle (cod2-map-cycle.md). map, devmap, map_restart, fast_restart and map_rotate over sv_mapRotation, the script's map_restart(persist) and exitLevel. Joined clients follow.

Client commands and rcon (cod2-protocol.md 3.4.2, 17.7):

• Chat, score, kill, where, the spectator's follow (follownext, followprev, attack and sight; the follower gets the followed player's playerstate).
• callvote and vote, g_oldVoting's engine vote or the script's. Bots never vote.
• Under sv_cheats: god, demigod, notarget, noclip, ufo, give, take, setviewpos.
• rcon: status, serverinfo, systeminfo, dumpuser, say, tell, kick, clientkick, tempBan* (for sv_kickBanTime), banUser, banClient, unbanUser into ban.txt (--ban-file keeps it), and the map commands.

Bots

--bots N [--bots-shoot] adds bots that join through the stock menus and play every stock gametype with vcod's shared bot brain (bots.md):

• Plant and defuse in sd; take, return and capture flags in ctf; take and hold the radio in hq.
• Throw offhand frags; throw smoke to cover a plant, a defuse or a retreat.
• Man a mounted gun with an enemy in its arc in dm and tdm.
• Climb the ladders and mantles their graph proved.
• Fight from cover with CoD2's leans, retreat when hurt, turn on a hit from out of sight.
• addbot, removebot (kickbot), listbots and the vc_bot_* cvars work as on CoD1.

Tools and test gates

Retail is the oracle; these replay retail captures on vcod or sweep the stock content. Most need COD2_DIR and pass vacuously without it.

Tool	What it checks
moves_ab (crates/cod2/tests)	pmove against retail move captures (cod2-movement.md 17)
trace_ab, examples/trace_probe.rs	the clip map's traces against retail (cod2-d3dbsp-format.md)
cod2_combat_ab, cod2_hitpose_ab, cod2_antilag_ab, cod2_pickup_ab	shots, hit poses, antilag and pickups (cod2-combat.md 9)
cod2_killcam_ab, cod2_turret_ab	the killcam and mounted guns
cod2::wire_ab	the server's wire against a retail session (cod2-protocol.md 15)
cod2_map_census (ignored)	every stock map through the server, a spectating client, a headless frame and a walk from each spawn
tools/cod2_soak.sh	per map, six bots through dm, tdm, sd, ctf, hq with the client playing (cod2-client-perf.md, "The soak")
GAME=cod2 tools/cod4_perf.sh	client frame time (cod2-client-perf.md)
GAME=cod2 bot_match	seeded bot matches (bots.md)
tools/run_probe_cod2.sh	retail cod2_lnxded with a movement probe gametype

Missing compared to retail

Ranked by how much a player notices, worst first.

1. Voice chat. Neither the client nor the server carries voice. The scoreboard's voice column stays empty and there is no mute list (cod2-hud.md 12). Shout across the room, as LAN parties always did.
2. Muzzle flashes and brass. The view weapon draws no flash or shell eject of its own: its tag_flash and tag_brass are not posed. Another player's flash plays 24 units ahead of his eye, not on his gun. The view weapon's notetrack sounds (noteTrackSoundA..D) do not play.
3. Spread and sway draws. A shot's spread and the gun's sway in its angles use vcod's own random draws, so rounds do not land where retail's would for the same cmds (cod2-combat.md 9.3).
4. Rockets fly true. fire_rocket's destabilization is not modelled, so vcod's bazookas are more accurate than they have any right to be. Weapon_Melee's hit triggers are not either; the melee's 64-unit reach is inferred (cod2-combat.md 8).
5. PunkBuster and CD key checks. vcod runs no PunkBuster. vcod-server never asks the authorize server: an off-LAN client gets its challenge at once and its IP stands in for its ban guid. It does not send the master the status retail sends every 10 minutes. The client reads no CD key from the registry; set VCOD_CDKEY (usage.md, "CD keys").
6. Demo details. timedemo writes no demos/timedemo_*.csv; a demo draws no EV_STEP_VIEW smoothing (cod2-demos.md 7). Retail's front end has no demo list either.
7. Server odds and ends. give all hands over every weapon the level registered, not retail's slot rule. Downloads serve only .iwd files under the game dir, where retail serves any file.

Pending human checks: the in-game script menus have not been checked on a GPU, and sound has not been compared by ear.

Beyond retail

• Bots, on every stock gametype. Their smoke throws are vcod's own rule: CoD1's bots throw none (bots.md).
• The browser asks master.cod.pm for its Internet list.
• VCOD_NETSIM, the F3 net and prediction lines, and the headless --net-probe and --probe-demo clients.
• r_vc_depthprepass (default 1 on CoD2): a depth-only pass before the lit world, same pixels, faster on most GPUs.

Debug and developer modes

• vcod <map> --game cod2 flies a map offline: world and static models, the sky cube, the sun, lightmapped surfaces with their normal, specular and detail maps, and the map script's fog. It runs no game.
• vcod --game cod2 --net-probe ip:port joins headless and prints a line a second; --probe-team / --probe-weapon play a 16 s scripted loop. VCOD_COD2_RECORD=<dir>/<name> records the run.
• vcod --game cod2 --probe-demo <file.dm_1> [--probe-timedemo] plays a demo headless.