Skyrim Mod:Mod File Format/WRLD

WRLD records contain the data for a 'world', which can be all of Tamriel or a handful of cells.

In the WRLD GRUP, following each WRLD record is a nested GRUP which contains a single CELL record (presumably the starting location for the world) and a number of Exterior Cell Block groups (see the group table). Each Exterior Cell Block group contains Exterior Cell Sub-Block groups, each of which contain CELL records.

Record header flags:

0x80000 - Can't Wait

C	Field	Name	Type/Size	Info
+	EDID	EditorID	zstring	The name of this worldspace used in the construction kit
*	RNAM	unknown	struct	(int16's look like coordinates, formids are REFRs) int16[2] uint32 - count of pairs following: formID int16[2]
-	MHDT	unknown	ubyte[??]	unknown
-	FULL	Name	lstring	The name of this worldspace used in the game
-	WCTR	center cell	int16[2]	X, Y
-	LTMP	unknown	formID	Interior Lighting LGTM
-	XEZN	unknown	formID	Encounter Zone ECZN
-	XLCN	exit location	formID	Location LCTN
-	CNAM	Climate	formID	CLMT reference.
-	NAM2	unknown	formID	Water WATR
-	NAM3	LOD Water Type	formID	LOD water-type, always a WATR form ID
-	NAM4	LOD Water Height	float	LOD oceanwater-level (-14000.0 for Tamriel)
-	DNAM	Land Data	float[2]	Default land- and oceanwater-levels (-27000 & -14000.0 for Tamriel)
-	MODL	cloud model	MODL	Cloud Model - Includes optional field MODT
-	MNAM	Map size	struct	16 or 28 byte structure
		width	uint32	The usable width of the map
		height	uint32	The usable height of the map
		NW cell X	int16
		NW cell Y	int16
		SE cell X	int16
		SE cell Y	int16
		Min Height	float	Camera Data (default 50000), new as of Skyrim 1.8, purpose is not yet known.
		Max Height	float	Camera Data (default 80000)
		Initial Pitch	float	Camera Data (default 50)
+	NAMA	unknown	float	Distant LOD Multiplier
-	DATA	flags	uint8	Flags 0x01 - Small World 0x02 - Can't Fast Travel From Here 0x04 0x08 - No LOD Water 0x10 - No Landscape 0x20 - No Sky 0x40 - Fixed Dimensions 0x80 - No Grass
-	NAM0	unknown	int32[2]	Coordinates for the bottom left corner of the worldspace (assumed from Oblivion)
-	NAM9	unknown	int32[2]	Coordinates for the top right corner of the worldspace (assumed from Oblivion)
-	WNAM	Parent worldspace	formID	Form ID of the parent worldspace.
-	PNAM	unknown	uint16	Use flags - Set if parts are inherited from parent worldspace WNAM 0x01 - Use Land Data (DNAM) 0x02 - Use LOD Data (NAM3, NAM4) 0x04 - Use Map Data (MNAM, MODL) 0x08 - Use Water Data (NAM2) 0x10 - unknown 0x20 - Use Climate Data (CNAM) 0x40 - Use Sky Cell
-	ONAM	unknown	float[4]	This field specifies where map markers will appear in relation to the parent World Map Scale - -1=Hide Map Markers Cell X Offset * 4096 Cell Y Offset * 4096 Cell Z Offset * 4096
-	TNAM	HD LOD Diffuse	zstring	The name of a texture file.
-	UNAM	HD LOD Normal	zstring	The name of the normals file matching the TNAM.
+	ZNAM	music	formID	always a MUSC form ID
-	XWEM		zstring	Water Environment Map
-	OFST	unknown	unknown	unknown large struct (tamriel = 45600) offset? apparently, contains absolute file offsets to cells, for debugging purposes.

It isn't entirely clear what effect the map size field has on the game. Many map sizes simply contain zero in these fields. The landscape can be larger than this size, although the outer areas of the landscape appear to be less well defined.