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Wormwood Carratbrain

Based on game build 714014 | Last updated: 2026-02-27

Overview​

This component implements the AI behavior tree for the Carrat entity (from the Reign of Giants DLC). It orchestrates movement, prey behavior, and leader-following logic using a priority-based behavior tree (BT). The brain integrates with core systems like movement (Wander, Follow, RunAway), pickup handling, and leader detection via the Follower and Eater components. It ensures Carrats flee from players/pets during PVP, follow their leader within a defined distance range, and opportunistically pick up edible items.

Usage example​

This brain is attached automatically by the carrat prefab definition. Typical usage for modders is to extend or replace this brain in custom Carrat variants:

local CarratBrain = require("brains/wormwood_carratbrain")
inst:AddBrain(CarratBrain(inst))

Note: Brains in DST are singleton components per entity; adding it multiple times will override previous instances.

Dependencies & tags​

Components used:

  • follower: To retrieve the leader entity via GetLeader().
  • eater: To determine if an item is edible via CanEat().
  • inventoryitem: To check if an item is currently held via IsHeld().
  • petleash: To identify if a player is the Carrat’s pet owner via IsPet().

Tags:

  • Tags used for run-away behavior: "scarytoprey" (passed to RunAway behavior via NORMAL_RUNAWAY_DATA).
  • Internal checks use "planted" and "held" indirectly (not added/removed tags; only queried).

Properties​

No public properties are declared in the constructor. All configuration is static (module-level constants) and internal to OnStart().

Main functions​

CarratBrain:OnStart()​

  • Description: Initializes the behavior tree root node. Sets up priorities for panic (electric fence, players), leader-following, pickup handling, wandering, and movement. Called automatically when the brain is attached and activated.
  • Parameters: None (self only).
  • Returns: nil.
  • Error states: None documented; relies on valid component presence (e.g., follower, eater, petleash) for correct operation.

Helper Functions (Internal)​

GetLeader(inst)​

  • Description: Retrieves the leader of this entity via the follower component, if present.
  • Parameters:
    • inst: The entity instance (the Carrat).
  • Returns: entity | nil — The leader entity or nil if no leader exists.

GetLeaderLocation(inst)​

  • Description: Returns the leader’s world position, or nil if there is no leader.
  • Parameters:
    • inst: The entity instance.
  • Returns: {x, y, z} | nil — Leader’s 3D position or nil.

ShouldRunFromScary(other, inst)​

  • Description: Determines if other should trigger the Carrat to flee. Excludes fleeing from one’s own leader or owner (even if a player/pet) in PVP mode.
  • Parameters:
    • other: The potential threat entity.
    • inst: The Carrat entity.
  • Returns: boolean — true if the Carrat should flee, false otherwise.

IsItemEdible(inst, item)​

  • Description: Checks if a given item qualifies as edible for pickup by this Carrat. Enforces that the item is edible, not planted, not currently held, and on the same platform/passable point.
  • Parameters:
    • inst: The Carrat entity.
    • item: The item entity to evaluate.
  • Returns: boolean — true if the item is pickable and edible.

PickUpFilter(inst, target, leader)​

  • Description: Filter function used by BrainCommon.NodeAssistLeaderPickUps. Delegates to IsItemEdible(leader, target) — i.e., only edible items for the leader (the Carrat) are considered.
  • Parameters:
    • inst, target, leader: Standard parameters from the pick-up helper node.

Events & listeners​

None. This component does not register or fire events directly; it uses synchronous behavior tree evaluation and component queries.