Levels

What a level is made of, how the game gets the player from one PlayerStart to the right one, and the complete list of the game's 32 maps. The byte format behind everything on this page is in assets.md.

A level's files

A level is always a pair of files sharing a name:

File	Format	Holds
<Level>.gmp	Unreal package	The level's objects: its actors, the Level object, and the BSP Model
<Level>.ibt	Ion Storm block file	The level's own resources: static meshes, textures, materials, physics hulls, ragdolls, skeletal meshes and animations, trigger scripts

Every level also loads three kernel block files shared by the whole game, Kernel_GFXALL.ibt, Kernel_PHYALL.ibt and Kernel_TSDALL.ibt (shaders, HUD art, Garrett's own meshes), and the main menu level loads its own kernel set, MainMenu_*ALL.ibt, instead of a per-level .ibt — Entry, the menu level below, has no Entry.ibt of its own for exactly this reason.

What is in a level

Decoded so far, inside the Level object and the package around it, in order:

• The actor list: every actor in the level, starting with the LevelInfo actor and the level's builder Brush.
• The URL: the protocol, host, map name, portal, options, port and a validity flag — the same URL structure used to travel between levels (see runtime.md).
• A reference to the level's Model (the BSP, below).
• Navigation-mesh polygons.
• BSP render blocks: the actual drawable geometry, packed the same way as a static mesh's render data, one block per piece of world geometry. What indexes these blocks — by zone, by BSP leaf, or something else — is not known yet.
• A list of BSP polygons, kept with position, normal, UV and material data per vertex; probably the source surfaces, kept for decals or lighting rather than for drawing.
• Several hundred kilobytes more that are not decoded.

The Model itself is a cooked, stripped-down BSP: nodes (plane, a 256-bit zone mask, flags, bounding sphere, zone and vertex counts) and a zone table, with the actual points, vertices, surfaces and brush polygons removed — they are not needed to render the game's own render blocks. Zones exist in this data (the per-node zone mask, and a zone table), but portals and the navigation mesh's structure are not decoded, so nothing about the level's visibility or AI navigation graph is understood yet beyond their raw presence.

A level's resource file (.ibt) holds, among other things, TriggerScriptDef resources (TS_<n>, not decoded) and, for every static mesh used, its render data and any physics hulls scaled for that placement. See assets.md for the resource-type table.

Player starts and travelling between levels

A PlayerStart actor is where a player can appear when a level loads. Because every level restarts the process (see runtime.md), arriving at the right start is done through the level-change URL: it carries a DestTeleporter argument, and the new level picks the PlayerStart whose own TeleportDestName property matches it. A New Game, for instance, launches the URL Inn?-LoadTravel?-LoadSave?-ObjectFilter=0?DestTeleporter="Inn", landing the player at the PlayerStart in Inn tagged TeleportDestName="Inn".

Like any other actor, a level's PlayerStarts are plain objects with instance-numbered names (PlayerStart__0, PlayerStart__1, ...); a level with several entry points — one per way of reaching it — has one PlayerStart per destination name.

The map list

The install ships 32 maps. Titles are the level's own English name (read from its string tables); file names are the .gmp/.ibt pair's shared name. Several locations are visited more than once, as a separate mission each time; grouped here by their shared file-name prefix, which is the only grouping the files themselves make clear:

Group	Title	File
Auldale	Auldale	Auldale1
	Gamall's Lair	Auldale3
Castle	Castle Front	Castle1
	Inner Quarters	Castle2
Clocktower	Upper Clocktower	Clocktower1
	Lower Clocktower	Clocktower2
Citadel	Outer Citadel	dungeon1
	Citadel Core	dungeon2
Docks	Docks	docks2
	The Abysmal Gale	docks3
Hammerite intro	Cathedral Grounds	HammerIntro1
	Hammer Factory	HammerIntro2
Cradle	Outer Cradle	HauntedHouse1
	Inner Cradle	HauntedHouse2
Keeper Compound	Keeper Compound	KeeperCompound1
	Lower Libraries	KeeperCompound2
Museum	Porter Hall	museum1
	Tesero Hall	museum2
Old Quarter	Old Quarter	OldQuarter1
	Fort Ironwood	OldQuarter3
Pagan intro	Pagan Tunnels	PaganIntro1
	Pagan Sanctuary	PaganIntro2
Overlook	Overlook Grounds	SeasideMansion1
	Overlook Proper	SeasideMansion2
South Quarter	South Quarter	SouthQuarter1
	Garrett's Building	SouthQuarter1_int1
	Pavelock Prison	SouthQuarter3
Stonemarket	Stonemarket Plaza	Stonemarket1
	Stonemarket Proper	Stonemarket2
	Keeper Library	Stonemarket3
—	Entry	Entry
—	The Blue Heron Inn	Inn

Notes on the two ungrouped maps: Entry is the main menu level (its player controller is Entry.Camera__0, per engine.md), not a mission. Inn is the game's hub level — New Game and several mission exits travel back to it (the URL example above lands there).

SouthQuarter1_int1 is an interior reached from SouthQuarter1, per its file name; no other relationship between same-group maps beyond "the same place, at a different point in the story" is established here. No file exists for OldQuarter2 or SouthQuarter2 in the retail install.