Otterbrain

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

Overview

The OtterBrain component defines the AI logic for the Otter character in Don't Starve Together. It implements a behavior tree (BT) that orchestrates high-priority actions like panic responses and combat, followed by secondary behaviors such as gathering food, looting containers or character inventories, fishing, harvesting kelp, and storing excess items at its home location. The brain dynamically weights its priorities based on internal states (e.g., hunger, inventory load, time of day, season) and external conditions (e.g., presence of burnable or ocean-based targets).

It leverages several components to achieve this: homeseeker for home location tracking, inventory for item management, eater for food validation, locomotor for movement, and timer for cooldown management. Critical behaviors like stealing or fishing are gated by busy state tags and cooldown timers to prevent redundant or unsafe actions.

Usage example

This component is not intended for direct manual instantiation by modders. It is attached to the Otter entity during prefab initialization via:

inst:AddBrain("otterbrain")

The brain is automatically started and stopped with the entity's state graph transitions, and its behavior tree executes in the background during simulation ticks.

Dependencies & tags

Components used: burnable, container, eater, edible, homeseeker, inventory, inventoryitem, knownlocations, locomotor, timer
Tags added: None identified
Tags checked: busy, jumping, INLIMBO, FX, outofreach, fire, burnt, playerghost, catchable, irreplaceable, heavy, spider, player, character, _inventory, _container, pickable, kelp, oceanfishable_creature, fishmeat

Properties

Property	Type	Default Value	Description
max_wander_dist	number	30	Maximum radius around home location for wandering when not engaged in higher-priority tasks.

Main functions

GetHomeLocation(inst)

• Description: Retrieves the position of the Otter's home location. It first checks if homeseeker is present and has a valid home entity; otherwise, it falls back to the known location named "home" stored in knownlocations.
• Parameters: inst — The Otter entity instance.
• Returns: A vector position (x, y, z) or nil if no home data is available.
• Error states: May return nil if both homeseeker:GetHome() and knownlocations:GetLocation("home") are absent or return invalid positions.

HasEnoughItems(inst)

• Description: Determines whether the Otter's inventory is full (or overfilled), based on TUNING.OTTER_MAX_INVENTORY_ITEMS. Prevents picking up more items if no valid home exists to store them.
• Parameters: inst — The Otter entity instance.
• Returns: true if inventory is full or home is unavailable; otherwise false.
• Error states: Returns true early if homeseeker or homeseeker:GetHome() is nil.

FindGroundItemAction(inst)

• Description: Searches within SEE_ITEM_DISTANCE for a suitable item on the ground to pick up (e.g., raw food, non-meat edible). Excludes items held by others, items on the home boat, and blacklisted tags. Returns a BufferedAction to pick it up.
• Parameters: inst — The Otter entity instance.
• Returns: A BufferedAction instance or nil if no valid target found or cooldown/busy state active.
• Error states: Returns nil if target is nil, or if the item is already held (isHeld == true).

FindGroundFoodToEatAction(inst)

• Description: Similar to FindGroundItemAction, but specifically targets meat-type food items (FOODTYPE.MEAT) suitable for immediate consumption. Adds an "ate_recently" cooldown timer upon success.
• Parameters: inst — The Otter entity instance.
• Returns: A BufferedAction instance or nil.
• Error states: Returns nil if no valid meat target found or item is held.

LootContainerFood(inst)

• Description: Scans nearby closed, openable containers (canbeopened == true) for food items and selects one at random to steal via ACTIONS.STEAL. Avoids burning or already-open containers.
• Parameters: inst — The Otter entity instance.
• Returns: A BufferedAction instance or nil.
• Error states: Returns nil if no containers contain suitable food or if the container is open/burning.

StealCharacterFood(inst)

• Description: Searches for nearby characters (player or character tags) within a short radius, scans their inventory for edible items, and attempts to steal one using ACTIONS.STEAL. Only targets characters on passable terrain.
• Parameters: inst — The Otter entity instance.
• Returns: A BufferedAction instance or nil.
• Error states: Returns nil if no character has edible items, or the target item is not currently held.

TryToPickPickables(inst)

• Description: Finds the nearest kelp or other "pickable" entity and generates an ACTIONS.PICK buffered action to harvest it.
• Parameters: inst — The Otter entity instance.
• Returns: A BufferedAction instance or nil.
• Error states: Returns nil if no pickable entity is found in range or the Otter is busy or in cooldown.

GoHomeAction(inst)

• Description: Generates an ACTIONS.GOHOME buffered action to move back to the Otter's home location.
• Parameters: inst — The Otter entity instance.
• Returns: A BufferedAction instance or nil if home is not set.
• Error states: Returns nil if homeseeker.home is nil.

GetNearbyFishTarget(inst)

• Description: Finds a fishable creature (oceanfishable_creature tag) located on the ocean surface, provided the "fished_recently" cooldown timer is not active.
• Parameters: inst — The Otter entity instance.
• Returns: An entity reference or nil.
• Error states: Returns nil if no valid fish is in range, or the "fished_recently" timer is running.

TryToFish(inst)

• Description: If a fish target is found via GetNearbyFishTarget, moves the Otter toward it using locomotor:GoToEntity.
• Parameters: inst — The Otter entity instance.
• Returns: nil. Action is performed via locomotor side effect.
• Error states: No explicit return value; behavior depends on FindEntity and locomotor success.

OtterBrain:OnStart()

• Description: Initializes and starts the behavior tree. Registers listeners for "onreachdestination", defines helper redirect functions for state checking, constructs the full priority-based behavior tree (including panic, hunger, night/winter, inventory dump, and foraging branches), and assigns it to self.bt.
• Parameters: None (instance method).
• Returns: nil.
• Error states: None beyond standard BT construction failures (not explicitly handled in this implementation).

OtterBrain:OnStop()

• Description: Cleans up event listeners when the brain is stopped (e.g., entity killed, state graph changed).
• Parameters: None (instance method).
• Returns: nil.
• Error states: None.

Events & listeners

• Listens to:
  • "onreachdestination" — Triggers on_reach_destination to transition to "toss_fish" state if the reached destination is an ocean-dwelling creature.
• Pushes:
  • None — This component does not directly fire events; it responds to them via the state graph and behavior tree.