Vault-Tec Labs

Worldmap.txt is located in master.dat/data/ and contains information about random encounters and terrain on the world map. The locations of cities are stored in city.txt. Impassible areas (i.e. ocean) are defined by .msk files.

The comments refer to several features that do not exist. These should be ignored and are not included in the excerpts here.

Data Section[]

The file begins with some properties of the worldmap system.

; Encounter frequency percentages:
Forced=100%        ; This shouldn't change
None=0%            ; This shouldn't change

; Terrain types:
;terrain_types=Desert:2, Mountain:4, City:1, Ocean:1
terrain_types=Desert:1, Mountain:2, City:1, Ocean:1

The percentages are presumably the chance of an encounter occurring each time the game checks for one. The frequency of these checks is believed to be based on processor speed, not actual travel time or distance.

It isn't clear what the numbers next to the terrain types are for. Possibly the time it takes to cross a square of that terrain type. The commented out line may have been values left over from Fallout 1.

In Fallout 2 it takes 25 hours to cross a square of desert, city, or ocean, and 32.5 hours (30% more) to cross a square of mountains. In Fallout 1 it took 10 hours for desert and ocean, 20 for mountains, and 6 for city terrain.

;These determine which maps are randomly chosen from for normal random encounters
[Random Maps: Desert]
map_00=Desert Encounter 1
map_01=Desert Encounter 2

[Random Maps: Mountain]
map_00=Cavern Encounter 0
map_01=Mountain Encounter 1

[Random Maps: City]
map_00=City Encounter 1
map_01=City Encounter 2

[Random Maps: Ocean]
map_00=Coast Encounter 1
map_01=Coast Encounter 2

This section is fairly self-evident: a list of maps used for random encounters in the different terrain types.

Encounter Groups[]

These are the groups the encounter tables use to determine what creatures and/or items appear with that group. A single encounter can contain more than one group.


[Encounter: ARRO_Hunting_Party]
type_00=pid:16777418, Item:280(wielded), Item:(0-10)41, Script:484             ; Male Hunter w/ Sharp Spear (Leader)
type_01=ratio:60%, pid:16777418, Item:7(wielded), Item:(0-10)41, Script:484    ; Male Hunter w/ Spear
type_02=ratio:40%, pid:16777419, Item:7(wielded), Item:(0-10)41, Script:484    ; Female Hunter w/ Spear
type_03=Dead, pid:16777296, Distance:7                          ; Dead Silver Gecko
position=wedge, spacing:2

There can be at most 100 type_## entries (numbered 00 to 99). The syntax (adapted from the description in worldmap.txt):

Type Subinfo:
Ratio:#% determines frequency of occurrence
Dead means that the critter starts out in a dead state
pid:<#> determines what this critter's pid is
Script:<#> overrides the default script with a new one
Item:<#> gives an item of a given pid #; may be appended with "(wielded)"
Item:(min-max)<#> gives a random quantity of the item, in the range given
If (<something>) -- conditionals, allows <,>,<=,>=,==,& as well as tests on Player(<stat/attribute/skill/etc.>),
 Enctr(Num_Critters), Time, Global(<variable index>), Rand(Chance%)
 Note - Enctr and Time are never used, may not be implemented
Distance:# -- Forces the distance for a particular critter (if possible)

The sum of all ratios should be 100%; the game's behavior if they do not is unknown. If no ratio is given, exactly one of that critter/item will be generated. From text in fallout2.exe, it appears that items can be marked "(worn)" to indicate that they are worn as armor. Either parens () or curly braces {} can be used around wielded/worn.

Position determines what formation the group assumes when encountered, and has one of the following values:

straight_line - A straight line of creatures.
double_line - Two rows of creatures.
huddle - A cluster of creatures in a circle.
cone - (I believe) a triangular shape with the point away from the player.
wedge - (I believe) a triangular shape with the point facing the player.
surrounding - Surrounds the player.

This is followed by Spacing:<#>, which indicates how far the critters are from each other. There can also be a Distance: field, which indicates how far the critters are from the player.

The default is "position=Surrounding, Spacing:5, Distance:Player(Perception)"

PIDs are described in the File Identifiers document. For critters, subtracting 16777216 gives the critter's proto ID number.

Encounter Tables[]

After the encounter groups come the encounter tables. Each is a list of possible events, one of which is chosen randomly. The worldmap.txt file contains 76 default encounter types, the first six of which are leftover from Fallout 1 and are unused. An example of the table format:

[Encounter Table 52]
lookup_name=SRNRRN_M                                                    ; San Fran - NCR - Redding - Reno Trade route
 - This is the name used to refer to this table in the Tile sections.
maps=Mountain Encounter 1, Mountain Encounter 2, Mountain Encounter 4, Mountain Encounter 5, Cavern Encounter 0
 - Which maps can be used for encounters in this group.
enc_00=Chance:8%,Enc:(4-7) KLA_Trappers
enc_01=Chance:10%,Enc:(6-10) ARRO_Spore_Plants AMBUSH Player
enc_02=Chance:9%,Enc:(3-8) ARRO_Sm_Scorpions AND (5-8) ARRO_Spore_Plants AMBUSH Player
enc_03=Chance:10%,Enc:(5-8) VPAT_Patrol FIGHTING (4-6) VPAT_Strong_Slavers
enc_04=Chance:3%,Enc:(3-6) KLA_Trappers AND (4-5) KLAD_Caravan FIGHTING (8-12) KLA_Bandits
enc_05=Chance:10%,Enc:(4-7) Morton_Brother, If(Global(386) > 0) And If(Global(386) < 6)
enc_06=Chance:2%,Counter:1,Special,Map:Special Toxic Encounter,Enc:Special1, If(Player(Level) > 5) And If(Global(607) < 1)

There can be up to 100 encounters (enc_00 through enc_99) in a table. Each entry in the list starts with an index number and percentage chance. The chances are probably relative, as they do not necessarily add up to 100%. After Enc: come the encounter groups that will be found. Each is prefixed with a range indicating how many critters from that group should be generated. If no action is given, that group will be neutral. If "AMBUSH Player" is specified, they will be hostile and attack the player. If "FIGHTING" is used, the groups will attack each other. Whether or not they will be hostile to the player is probably determined by their scripts. Two groups connected by "AND" will be on the same team and fight together. Finally, there may be a boolean expression (usually based on global variables and player level) to control whether or not this encounter can occur. "time_of_day" returns the current time, rounded down to the nearest hour.

Special encounters have a slightly different format. The meaning of "Counter:1,Special" is unknown; the number 1 is always used. Map: specifies which special encounter map to use. Enc: is always "Special1", a 'dummy' group with no critters in it.

The limits of the grouping mechanism are unknown. AND is only used to join two groups, and always on the left side of FIGHTING. It is unknown if any of the following would work:

robbers AND highwaymen AND raiders AMBUSH player
geckos AND scorpions FIGHTING mole rats AND spore plants
enclave patrol FIGHTING hubologists FIGHTING master's army

From text in fallout2.exe, it appears that "days_played" can be used similarly to "time_of_day". The keyword "or" also seems to be available, though it is not clear whether it can be applied to the encounter groups or boolean expression.


The Fallout 2 world map consists of 20 tiles. Each each of these tiles consists of 42 squares, arranged 7 wide by 6 high (7x6). This makes for a total of 840 individual squares on the Fallout 2 map. This section contains terrain and encounter information for them.

[Tile Data]

Tiles are laid out left to right, top to bottom, so the number of vertical tiles does not need to be specified. What happens if the total number of tiles is not an even multiple of this value is unknown.

[Tile 0]
; x_offset_yoffset=terrain,morning_chance,afternoon_chance,night_chance,type
  • art_idx indicates which image (/art/intrface/wrldmp**.frm) is to be displayed for this tile.
  • encounter_difficulty is a modifier to the outdoorsman skill check for the player to be able to avoid a random encounter. Normally negative values are used, indicating a penalty.
  • walk_mask_name specifies which mask file (/data/wrldmp**.msk) to use to keep the player from walking across the ocean. If no file is given, the entire tile is passable.

The offset of each square is measured from the upper-left corner. Fill_W indicates that when this square is explored, the square(s) to the left of it become visible as well. Although similar strings exist in fallout2.exe for all eight cardinal directions (n, s, e, w, nw, ne, sw, se), none of the others appear to work. No_Fill is the normal behavior, making only the adjacent squares half-visible. The frequencies for each of the time periods (morning, afternoon, night) are always the same, so it isn't clear if making them different has actually been implemented. The final type field chooses which encounter table to use for this square.

Originally based on the document in TeamX's file section