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Shadowthrall Centipede Controller Brain

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

Overview​

This brain component acts as a controller for multi-headed centipede entities (e.g., Shadow Thrall centipedes), determining which head holds active control and switching control when appropriate. It evaluates all head segments for their control_priority, selects the highest-priority head, and delegates control via CentipedeBody:GiveControlToHead(). If multiple heads share equal priority, it uses a progressive probabilistic mechanism (SWITCH_CHANCES) to introduce variety in head rotation. The brain integrates with the Behavior Tree system and the CentipedeBody component, ensuring dynamic and responsive control transitions.

Usage example​

This brain is typically assigned internally to centipede entities via the game's entity definitions. A modder would not usually add it manually, but an example of its integration is shown below:

local centipede = Entity("centipede")
centipede:AddComponent("centipedebody")
centipede:AddBrain("brains/shadowthrall_centipede_controller_brain")

Once attached, the brain automatically manages control transitions between heads based on priority and internal logic. Modders may interact indirectly by setting head.control_priority on head entities.

Dependencies & tags​

Components used: centipedebody — accessed via self.inst.components.centipedebody, calling GiveControlToHead() and GiveControlToOtherHead().

Tags: None identified (does not manipulate entity tags directly).

Properties​

PropertyTypeDefault ValueDescription
switch_chance_indexnumber1Index into SWITCH_CHANCES array; tracks current probability of head rotation when priorities are equal. Incremented on equal-priority detection, reset after a switch or priority change.

Main functions​

IncreaseSwitchChance()​

  • Description: Increments switch_chance_index, moving to a higher entry in SWITCH_CHANCES (i.e., increasing the probability of a future head rotation). capped at the array's maximum index.
  • Parameters: None.
  • Returns: None.
  • Error states: None; safely caps at #SWITCH_CHANCES.

ResetSwitchChance()​

  • Description: Resets switch_chance_index to 1, the baseline low-probability state (0% chance of switching on next check).
  • Parameters: None.
  • Returns: None.
  • Error states: None.

RollSwitchChance()​

  • Description: Evaluates whether a head switch should occur based on SWITCH_CHANCES[self.switch_chance_index]. If the random roll succeeds, triggers ResetSwitchChance() and calls GiveControlToOtherHead().
  • Parameters: None.
  • Returns: None.
  • Error states: No-op if SWITCH_CHANCES index is out of bounds (though constructor ensures it is initialized to 1, and IncreaseSwitchChance enforces bounds).

OnStart()​

  • Description: Constructs and sets the behavior tree root node. Evaluates which head should be in control by scanning all heads for highest control_priority. If a higher-priority head is found, grants it control. If two heads share equal priority (the first and second heads), initiates probabilistic switching logic (IncreaseSwitchChance() + RollSwitchChance()). Behavior tree re-runs every UPDATE_RATE = 3 seconds.
  • Parameters: None.
  • Returns: None.
  • Error states: Assumes centipedebody.heads has at least one entry; if fewer than two heads exist, equal-priority logic is skipped.

Events & listeners​

This brain does not register or dispatch any events via inst:ListenForEvent() or inst:PushEvent().