FISSION Worldmap Modding Mini-Guide

Add Custom Encounter Tables, Named Encounters, and Tile Overrides

This guide assumes you have a working mod folder (e.g., mods/mod_mytown.dat/ from the Quick Start Guide). You’ll extend the worldmap with new random encounters, custom critter groups, and even override specific map tiles.

1. What You Need

Your existing mod folder: mods/mod_mytown.dat/. (a folder for development, compress into actual .dat for release)

You will create one or more of these files:

  • data/worldmap_mytown.txt – defines encounter tables, named encounters, and tile overrides
  • text/english/game/worldmap_mytown.msg – provides custom encounter description text

2. Create the Worldmap Definition File

File: mods/mod_mytown/data/worldmap_mytown.txt

This file can contain three types of sections:

A. Encounter Tables

[Encounter Table 0]
lookup_name=My_Desert_Table
maps=Desert Encounter 4, Desert Encounter 5
enc_00=chance:10%,Map:MyMap,Enc:player,MyRaiders
enc_01=chance:20%,Map:Desert Encounter 1,Enc:MyRaiders

Fields explained:

  • lookup_name – Unique name for this table. Used by subtiles to reference it.
  • maps – Comma‑separated list of map lookup names to use for encounters (from maps.txt or maps_mytown.txt).
  • enc_XX – Encounter entry definitions (XX = 00–40):
    • chance – Percentage chance (e.g., 5%).
    • Map – Which map to load (must match a lookup_name from maps.txt).
    • Enc – Named encounter(s) to spawn. Can list multiple, separated by commas.
    • counter – (optional) Max times this encounter can trigger (-1 = unlimited).
    • special – (optional) Marks this as a special encounter (creates a map marker).

B. Named Encounters

[Encounter: MyRaiders]
type_00=ratio:100%, pid:16777317, Script:764, Item:(2-6)365
position=Wedge, Spacing:2, distance:15

[Encounter: MyBoss]
type_00=ratio:50%, pid:16777221
type_01=ratio:50%, pid:16777222, distance:5

Fields explained:

  • type_XX – Each line defines a critter or group:
    • ratio – Percentage of total critters this type represents.
    • pid – Prototype ID (full ID for critters, short ID for items).
    • Script – Script index (1‑based, from scripts.lst or scripts_mytown.lst).
    • Item – Item to equip or add, with optional quantity range.
    • distance – Spawn distance from player.
    • tile – Specific tile number (override).
  • position – Formation type: Surrounding, Straight_Line, Double_Line, Wedge, Cone, Huddle.
  • spacing – Distance between units in the formation.
  • team_num – Team ID for combat (default = -1 = hostile to player).

C. Tile Overrides

[Tile 5]
art_idx=350
walk_mask_name=mynewmask
encounter_difficulty=-10
3_3=Desert,No_Fill,Common,Common,Common,My_Desert_Table
6_5=Mountain,Fill_N,Rare,Rare,Rare,My_Mountain_Table

Fields explained:

  • art_idx – Override the tile’s appearance (FRM index from art/intrface/).
  • walk_mask_name – Override the walkability mask (from data/*.msk).
  • encounter_difficulty – Modifier to player’s Outdoorsman skill for detecting encounters.
  • X_Y – Subtile coordinates (X = 0..6, Y = 0..5). Value format:
    • terrain – Desert, Mountain, Ocean, Forest, etc. (from worldmap.txt).
    • fill – No_Fill, Fill_N, Fill_S, Fill_E, Fill_W, Fill_NW, Fill_NE, Fill_SW, Fill_SE.
    • morning_chance – Encounter frequency: None, Rare, Uncommon, Common, Frequent, Forced.
    • afternoon_chance – Same as above.
    • night_chance – Same as above.
    • type – The lookup_name of the encounter table to use.

Note: Tile overrides are partial – you only need to specify the subtiles you want to change. All other subtiles keep their original values.

3. Create the Message File (Optional)

File: mods/mod_mytown/text/english/game/worldmap_mytown.msg

For custom encounter descriptions, add entries starting at local number 100:

{100}{}{You spot a group of raiders looting a caravan.}
{101}{}{A massive radscorpion emerges from the sand!}
{102}{}{You find a wounded traveller in need of help.}

Rules:

  • Local numbers 0–99 are reserved for entrance labels (if your mod adds towns).
  • Local numbers 100–499 are for encounter entry texts.
  • Each table gets 50 consecutive IDs: Table 0 uses 100–149, Table 1 uses 150–199, etc.
  • The first entry (enc_00) of Table 0 uses local number 100, enc_01 uses 101, etc.

Why 100? To avoid overlap with entrance labels (0–99). If your mod doesn’t add entrances, you can start at 0 instead, but we recommend the standard offset.

4. Where to Put Everything

mods/mod_mytown/
    ├─ data/
    │   ├─ worldmap_mytown.txt
    │   └─ ... (other files)
    └─ text/
        └─ english/
            └─ game/
                ├─ worldmap_mytown.msg
                └─ ... (other message files)

5. Test Your Worldmap Content

  1. Run the game and load your save (or start a new game).
  2. Check the debug reports in data/lists/:
    • encounter_tables_list.txt – shows all tables (vanilla + mod) with their stable slots.
    • named_encounters_list.txt – shows all named encounters (vanilla + mod).
  3. Travel to the tile/subtile you overrode and trigger encounters. Your custom table should appear.

If your encounter doesn’t trigger:

  • Verify the subtile’s type field matches your table’s lookup_name.
  • Ensure the table has at least one enc_XX entry with a valid Map.
  • Check that Map references an existing map lookup name (from maps.txt or maps_mytown.txt).

6. Important Notes

  • Stable IDs – All encounter tables and named encounters get deterministic hashed slots based on your mod name and the table/encounter name. This means they won’t change between game sessions or conflict with other mods.

  • Partial Tile Overrides – You only need to specify subtiles you want to change. All other subtiles on that tile remain original.

  • Message Blocks – The base ID for your mod’s worldmap messages is computed automatically from your mod name. You only provide local numbers in the .msg file.

  • Collision Detection – If two mods accidentally generate the same hash slot, a warning message box appears and the conflicting table/encounter is skipped. Rename your mod or the table/encounter to resolve it.

  • Vanilla Encounter Tables – You can override existing tables by using the same lookup_name as a vanilla table (e.g., Desert). Your table will replace it globally.

7. Quick Troubleshooting

Problem Likely Fix
Table not in encounter_tables_list.txt Check worldmap_mytown.txt syntax. Missing lookup_name or malformed enc_XX.
Named encounter not in named_encounters_list.txt Section name must be [Encounter: Name]. Check spelling and brackets.
Encounter doesn’t trigger Subtile’s type doesn’t match your table’s lookup_name. Or the table has no valid Map.
Message shows “Error!” Missing worldmap_mytown.msg file, or local number is outside 100–499 range.
Tile override not applied Check tile index is valid (0–19). Or art_idx points to a non‑existent FRM.
“Hash collision” popup Another mod uses the same slot. Change your mod name or table/encounter name.

8. What’s Next?

Once your worldmap content works, combine it with other modding features:

  • Add custom maps via maps_mytown.txt to use as encounter locations.
  • Add custom critters via critters_mytown.lst to populate your encounters.
  • Add custom areas via city_mytown.txt to place towns or special locations on the map.

The full FISSION modding suite gives you complete control over the worldmap ecosystem!