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Shadowthrall Hands Brain

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

Overview​

This brain component implements the behavior tree for the Shadow Thrall's hands entity. It governs coordination with the Shadow Thrall's other body parts (horns and wings) to ensure only one entity attacks at a time, preventing overlapping attacks. It uses a priority-based behavior tree (BT) with a custom attack-turn mechanism, wander logic, and leash constraints to manage movement relative to the target or home location. Key responsibilities include determining attack priority via IsMyTurnToAttack, leash positioning via GetFormationPos, and synchronizing attack events with the host entity's state graph.

Usage example​

This brain is typically attached to a non-player entity (e.g., the "hands" part of the Shadow Thrall boss). It is not meant to be instantiated or used directly in mod code.

-- Example usage in a prefab file (not for modder runtime use)
inst:AddBrain("shadowthrall_hands_brain")

Dependencies & tags​

Components used:

  • combat (InCooldown(), TargetIs(target), target property)
  • entitytracker (GetEntity(name))
  • knownlocations (GetLocation(name))

Tags: None identified.

Properties​

None defined in the constructor. All state is maintained internally in the behavior tree and inst.sg memory.

Main functions​

ShadowThrallHandsBrain:OnStart()​

  • Description: Initializes the behavior tree root node with a priority-based structure that handles waiting for turn order, leashing and positioning, target tracking, chasing/attacking, and wandering. This method must be called during the entity's startup.
  • Parameters: None.
  • Returns: None.
  • Error states: None beyond standard behavior tree execution behavior (bt assignment may fail if parent Brain initialization fails).

Helper Functions (Internal)​

These functions are defined in the script and used internally by the behavior tree:

GetHome(inst)​

  • Description: Returns the spawn point location used for wandering.
  • Parameters: inst (Entity instance).
  • Returns: Position table (x, y, z) or nil if location not set.
  • Error states: Returns nil if knownlocations component is missing or no "spawnpoint" is defined.

GetTarget(inst)​

  • Description: Retrieves the current combat target or, if none, returns the entity currently devoured by the horns (if the state memory exists).
  • Parameters: inst (Entity instance).
  • Returns: Target entity or nil.
  • Error states: May return nil if combat.target and "horns" entity or its state memory are invalid.

IsTarget(inst, target)​

  • Description: Checks whether the given target is the currently tracked combat target or the devoured entity of the horns.
  • Parameters:
    • inst (Entity instance)
    • target (Entity instance or nil)
  • Returns: true if target matches combat.target or the horns' statemem.devoured; false otherwise.
  • Error states: Returns false if either the combat component or horns entity/state memory is missing.

GetTargetPos(inst)​

  • Description: Returns the world position of the current target, or nil if no target exists.
  • Parameters: inst (Entity instance).
  • Returns: Position table or nil.
  • Error states: Returns nil if no target exists.

GetFormationPos(inst)​

  • Description: Computes a position around the target based on the inst.formation angle (in degrees) and FORMATION_DIST. Used to position the hands relative to the target during non-attack phases.
  • Parameters: inst (Entity instance).
  • Returns: Position table or nil if no target or inst.formation is nil.
  • Error states: Uses basic trigonometry with FORMATION_DIST = 6; assumes standard DST coordinate system.

IsTheirTurnToAttack(inst, teammate)​

  • Description: Determines if a specified teammate ( "horns" or "wings") should attack instead of this instance, based on who attacked more recently and whether they share the same target.
  • Parameters:
    • inst (Entity instance)
    • teammate (String identifier, e.g., "horns")
  • Returns: true if teammate has priority; false otherwise.
  • Error states: Returns false if teammate is missing, has no state graph, or no attack time recorded.

IsMyTurnToAttack(inst)​

  • Description: Determines whether this instance may currently attack, based on cooldown status and coordination with teammates.
  • Parameters: inst (Entity instance).
  • Returns: true if allowed to attack; false otherwise.
  • Error states: Always returns false while in a "running" state tag context (per behavior tree structure).

Events & listeners​

This component does not register or push any events directly. It interacts with events indirectly via the behavior tree’s ConditionWaitNode, which calls self.inst:PushEvent("doattack", { ... }) to trigger attacks on the entity's state graph.

  • Pushes (via behavior tree):

    • "doattack" with { target = self.inst.components.combat.target } — triggered from within ConditionWaitNode when it is time to attack.

  • Listens to: None explicitly. The component relies on external listeners (e.g., Combat, StateGraph, EntityTracker) to handle events.