LootTweaker Mod Wiki

LootTweaker is an essential utility mod for Minecraft that bridges the gap between the vanilla loot table system and CraftTweaker. While vanilla Minecraft allows loot tables to be overridden using JSON files, LootTweaker provides a dynamic ZenScript API to make surgical changes—such as adding a single item to a dungeon chest or removing a specific drop from a mob—without replacing the entire table.

This mod is primarily used by modpack creators to balance gameplay, integrate modded items into world generation, and customize entity drops. It supports all loot tables, including those from vanilla Minecraft and any mod that utilizes the standard Forge loot system.

To effectively use LootTweaker, it is important to understand the hierarchy of the Minecraft loot system:

• Loot Table: The top-level object (e.g., minecraft:entities/cow or minecraft:chests/simple_dungeon). It contains one or more Loot Pools.
• Loot Pool: A group of potential loot entries. Each pool has a set number of 'rolls' (how many times it attempts to pick an entry).
• Loot Entry: The actual item, loot table, or empty result that can be picked. Entries have weights and qualities.
• Conditions: Requirements that must be met for a pool or entry to be valid (e.g., killed_by_player).
• Functions: Modifications applied to the item after it is picked (e.g., setting stack size, damage, or enchantments).

Weight and Quality

Loot selection is based on Weight. The chance of an entry being picked is its weight divided by the total weight of all valid entries in the pool.

Quality modifies the weight based on the player's Luck attribute using the formula: Effective Weight = floor(weight + (quality * luck))

LootTweaker adds several commands to help identify loot table IDs and structures. All commands are sub-commands of /ct (CraftTweaker).

The mod uses several classes to interact with loot data. You must import these at the top of your script.

import loottweaker.LootTweaker;
import loottweaker.LootTable;
import loottweaker.LootPool;
import loottweaker.Conditions;
import loottweaker.Functions;

LootTable Methods

• LootTweaker.getTable(String tableName): Returns a reference to an existing loot table.
• LootTweaker.newTable(String tableName): Creates a brand new loot table.
• table.addPool(String name, int minRolls, int maxRolls, int minBonusRolls, int maxBonusRolls): Adds a new pool to the table.
• table.getPool(String name): Retrieves an existing pool for modification.
• table.removePool(String name): Removes a pool entirely.
• table.clear: Removes all pools from the table.

LootPool Methods

• pool.addItemEntry(IItemStack stack, int weight): Adds a simple item entry.
• pool.addItemEntry(IItemStack stack, int weight, int quality, LootFunction[] functions, LootCondition[] conditions, String name): Adds a complex item entry.
• pool.addLootTableEntry(String tableName, int weight): Adds an entry that triggers another loot table.
• pool.addEmptyEntry(int weight): Adds a chance for 'nothing' to drop.
• pool.removeEntry(String entryName): Removes a specific entry by name.
• pool.setRolls(int min, int max): Sets the number of times the pool is rolled.
• pool.setBonusRolls(int min, int max): Sets bonus rolls based on luck.

Conditions and Functions allow for fine-tuned control over when loot drops and how it appears.

Common Conditions

Common Functions

LootTweaker allows for entirely custom logic using the Functions.zenscript method. This allows you to modify the item stack based on complex variables like the random number generator or the loot context.

somePool.addItemEntry(<minecraft:potato>, 1, 0, [
 Functions.zenscript(function(input, rng, context) {
 return input.withDisplayName("Super Potato");
 })
], []);

Modifying Mob Drops

This script removes Mutton from Sheep and adds a chance to drop an Apple instead.

val sheep = LootTweaker.getTable("minecraft:entities/sheep");
val main = sheep.getPool("main");

main.removeEntry("minecraft:mutton");
main.addItemEntry(<minecraft:apple>, 20, 0, [Functions.setCount(1, 3)], [Conditions.killedByPlayer]);

Adding Loot to Dungeon Chests

This script adds a 10% chance to find a Diamond in simple dungeon chests.

val dungeon = LootTweaker.getTable("minecraft:chests/simple_dungeon");
val extra = dungeon.addPool("rare_loot", 1, 1, 0, 0);

extra.addItemEntry(<minecraft:diamond>, 10);
extra.addEmptyEntry(90);

LootTweaker is a specialized addon and requires the following to function correctly:

1. CraftTweaker: The base mod required for ZenScript processing.
2. Mixin Loader: As of LootTweaker version 0.4.0, a Mixin loader (such as MixinBootstrap) must be present in the mods folder to prevent crashes during the launch phase.
3. Server/Client: While LootTweaker can be installed on the server only (version 0.1.7+), CraftTweaker generally requires installation on both the client and server for full functionality.