Java API

For mod makers building on Fundamentum.

Depending on it

Fundamentum publishes com.fundamentum:fundamentum-neoforge:<version>+<minecraft> (for example 1.25.1+26.1.2; fundamentum-forge on 1.20.1). Add the Maven repository it's published to, depend on the artifact, and list fundamentum as a required dependency in your neoforge.mods.toml. Curios is required, so your dev runs need Curios too.

[[dependencies.mymod]]
modId = "fundamentum"
type = "required"
versionRange = "[1.25,)"
ordering = "NONE"
side = "BOTH"

Packages

Everything is under com.fundamentum. Register things while your mod is constructed.

Data

Class	What it's for
data.DataTables / DataTable	your own datapack tables: DataTables.register(id, "mymod/weapons", WeaponDef::fromJson) (or a Codec), then .keyField("item"), .merge(DataTable.Merge.SHALLOW), .builtins(...), .synced(), .onLoad(...). Files merge in file-id order over the built-ins and each other; DEEP merge (the default) merges objects field by field and a null removes a field. Read with get, entries, raw, number(key, field, fallback)
data.StatPatch	ordered stat patches (tiers, upgrades): a field is a value or steps {"set", "add", "multiply", "min", "max"}
item.ItemMatcher	item id or #tag matching (one string or a list) for your data files

Combat

Class	What it's for
attribute.StatAttributes	shared attributes on every living entity: crit_chance, crit_damage, ranged_damage, fire_rate, reload_speed, ammo_conservation, armor_pierce, blast_radius, blast_self_damage, projectile_speed, spread, sickness_duration, wing_flight_time. Fundamentum holds them; the mod that fires or explodes reads and applies them
attribute.HealthCap	max health up to 1,000,000
creature.CreatureTypes	creature type tags and damage rules
damage.Elements	the elements, <e>_damage and <e>_resistance attributes; Elements.add, Elements.variant(id, parent, ...) for a variant that counts as its parent (soul fire is fire; Element.parent(), isA), Elements.registerClassifier for hits no tag can catch
api.SoulFire	soul burning: SoulFire.ignite(entity, ticks), isSoulBurning(entity), clear(entity); the tags SOURCES, PROJECTILES, WEAPONS. Call on the server; see soul fire
damage.DamageClasses	melee, ranger, marksman, mage; <c>_damage attributes; DamageClasses.add
damage.SharedDamage	shared damage types (fundamentum:fire, soul_fire ... arcane, fundamentum:bullet); SharedDamage.source(level, HOLY, projectile, shooter)
element.ElementAuras, ElementAffinities, ElementReactions, ElementRef	auras on a creature, resolved affinities, the loaded reactions, parsing element strings
element.ElementEvents	events on NeoForge.EVENT_BUS: Reaction (cancellable, change the damage), Reacted (after it fired), Affinity (add resistance from code), AuraApply (cancellable)
sickness.Sickness	isBlocked and trigger for items with their own use logic
trigger.Triggers	left click as a trigger: implement Triggers.Handler (press, hold, release, interrupted) or Triggers.register(...)

Equipment

Class	What it's for
curios.Slots	Slots.equipped(entity, slot), Slots.cosmetic(entity, slot)
wings.Wings	wing flight and glide
cosmetic.CosmeticArmor	CosmeticArmor.shown(player, slot) for mods that draw armour themselves
mount.Mounts, MountEntity	mounts; MountEntity is a base class for custom mounts that walk, jump and fly
hook.Hooks, HookModel	grappling hooks and their texture layout
summon.Summons	summons; the fundamentum:summon_damage attribute scales minion hits
whip.Whips	cord whips: register an item with a WhipDefinition (tuning, style, slam, summon tag); WhipHooks, WhipFx.beam / bolt, WhipTags.focus and minionHit for your own minions
arrow.Arrow3DRenderer	Arrow3DRenderer.of(ctx, texture) gives your arrows the 3D look

Nights and skies

Class	What it's for
moon.Moons	addListener (rise, set, while up, kills), registerFlag, registerChance, registerSpawner, registerNight, registerSwitch; current, isUp, raise, clear. Other moon JSON fields are yours through Moon.json()
moon.NightEvents	addListener (start, end with an outcome, while up, kills), registerChance; start(level, id, pos), current, isUp, pos, ticksLeft, raise, end(level, outcome), clear
moon.MoonsClient	client: moon(), event(), fogMix(pt), skyMix(pt), fogColor(), skyColor() for your own skies
sky.FractalSkies	the loaded fractal skies

Client and drawing

Class	What it's for
pose.Poses, PosePlayer, ArmPoses	player poses and clips; Poses.cue(entity, "cast") on the server
pose.FirstPersonHands	first-person arms; register a Frame if you draw the item yourself
glow.Glows	Glows.apply(target, rgb, ticks): a coloured glowing outline
curve.Curve, curve.client.TubeMesh	smooth curves between two ends, and textured tubes along them
client.Tooltips	any item shows its lang lines <item key>.desc, .desc2 and .desc3 under its name

command.Tps and command.Showcase are the commands. Not every package is on every version; see Versions.