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Data maps

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A data map attaches a value to registry entries: a radiation level to an item, a fuel value to a fluid, a damage resistance to an entity type. HBM keeps most of 1.7’s per-item tables this way, so a datapack can change them. The format is NeoForge’s data-map format, and Golem Core provides it on every loader and Minecraft version.

Where the files go

Section titled “Where the files go”
data/<map namespace>/value_maps/<registry>/<map>.json

The map hbm:hazards over items is data/hbm/value_maps/item/hazards.json. The registry folder is item, block, fluid or entity_type; HBM has one map keyed by material name, under material. The folder names are the same on every Minecraft version.

File format

Section titled “File format”
data/hbm/value_maps/item/hazards.json (a datapack's copy)
{
  "replace": false,
  "values": {
    "#c:ingots/uranium": { "mutex": 1, "entries": [{ "type": "hbm:radiation", "level": 0.35 }] },
    "hbm:ingot_pu238": {
      "mutex": 1,
      "entries": [{ "type": "hbm:radiation", "level": 10.0 }, { "type": "hbm:hot", "level": 3.0 }]
    }
  },
  "remove": ["hbm:ingot_u235"]
}
Field Type Meaning
replace boolean, optional true drops every value that lower-priority copies of this file gave. Default false.
values object, optional Keys are an entry id ("hbm:ingot_pu238") or a tag ("#c:ingots/uranium"). The value’s shape depends on the map.
remove list, optional Entry ids or #tags to take away from what lower-priority copies gave.

Inside one file, replace is applied first, then values, then remove. A remove or replace only affects what was loaded before it, so a later file can add the entry back.

A value that does not decode is skipped with a log line (Data map hbm:hazards: skipping <key>: <reason>); the rest of the file still loads.

How copies merge

Section titled “How copies merge”

Every pack’s copy of a map file is read, lowest priority first, the same way vanilla tags merge. So HBM’s jar, an addon mod and a server datapack can all add to one map without one file replacing another. A later copy that names the same key overrides its value.

When the game looks up an entry:

  1. The entry’s own id wins.
  2. Otherwise, the tags are tried from the last one given to the first, and the first that holds the entry wins. A tag keeps the place where it was first given: a later file that gives it a new value changes the value, not the place.
  3. Otherwise there is no value, and the code’s default applies (often 1.7’s own rule for unlisted items).

The hazards map is an exception: every tag that matches applies, plus the item’s own value.

To add an entry, ship a file at the map’s path with only your values:

data/hbm/value_maps/item/difurnace_fuel.json
{
  "values": {
    "minecraft:blaze_rod": 400
  }
}

Patching another mod’s map

Section titled “Patching another mod’s map”

A copy at the map’s own path merges in pack order. Pack order between mods is not the same on every loader (Fabric 1.20.1 serves all mods as one pack, in mod list order). So when a mod or a modpack changes another mod’s values, especially with remove or by overriding a value, it should ship a patch in its own namespace:

data/<your ns>/value_maps/patches/<map namespace>/<registry>/<map>.json

The format is the same. Patches apply after every copy of the map’s own file, sorted by the patching namespace, each namespace’s copies lowest priority first. A remove or an overridden value in a patch therefore always wins over the map’s own files.

data/mypack/value_maps/patches/hbm/item/difurnace_fuel.json
{
  "values": {
    "minecraft:feather": 50
  },
  "remove": ["hbm:briquette_wood"]
}

When values are read

Section titled “When values are read”

HBM reads a map value at the moment it needs it, so a /reload changes behaviour at once. The bundled values are loaded when the game starts, so menus and tooltips have them before a world is open. Each datapack load replaces them with the merged values of all packs, and clients receive the same values.

Many maps only describe items of a matching kind. An rbmk_fuel value on an item that is not an RBMK fuel rod does nothing, for example. A datapack can change the values of existing items; a new fuel rod item needs an addon mod.

HBM’s maps

Section titled “HBM’s maps”
Page Maps
Hazards and radiation item/hazards, item/hazard_multiplier, fluid/cell_hazards, block/radiation_emission
Armor and protection item/radiation_resistance, item/protection_classes, item/faraday_armor, item/armor_sets, item/damage_resistance, entity_type/damage_resistance, item/lockpick_jacket
Reactor fuels item/rbmk_fuel, item/pwr_fuel, item/zirnox_fuel, item/watz_pellet, item/pile_rod, item/rtg_pellet, item/betavoltaic, item/plate_fuel, item/research_reactor_fuel, item/radgen_fuel, fluid/icf_fuel, material/icf_fuel
Machine parts item/pa_coil, item/drill_bit, item/piston, item/machine_upgrade, item/plasma_forge_booster, item/battery_pack
Fuels and containers item/fuel_category, item/difurnace_fuel, item/brick_furnace_speed, fluid/autosaw_fuel, fluid/gas_turbine_fuel_consumption, item/fluid_container, fluid/fluid_containers
World block/erosion, block/radiation_decay, block/fluid_deposit, block/fluid_deposit_states
Weapons and satellites item/custom_nuke, fluid/custom_nuke, item/satellite

The data map reference lists them all in one table. HBM’s own files, with every value, are in the NTM - Continuum jar under data/hbm/value_maps/.