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Wx78 Scannerbrain

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

Overview​

This brain component implements the autonomous AI logic for the Wx78 Scanner entity in Don't Starve Together. It orchestrates the scanner's behavior during scanning tasks, including target acquisition, spatial tracking (leashing), orientation, and post-scan return to the player. It relies on the EntityTracker component to manage the scantarget entity and the Follower component to identify the player leader. The brain uses Behavior Tree (BT) constructs with custom action and condition nodes to implement state-dependent decision-making.

Usage example​

Typically attached automatically via the Wx78 Scanner prefab definition during entity initialization. No manual instantiation is required in mod code.

-- Example: How the brain is instantiated in the Wx78 Scanner prefab
inst:AddComponent("wx78scannerbrain")

Dependencies & tags​

Components used: entitytracker, follower
Tags: None identified

Properties​

No public properties are declared or initialized in the constructor. All behavior logic is implemented via function closures and Behavior Tree composition.

Main functions​

The brain provides a single public method inherited from Brain:

OnStart()​

  • Description: Initializes and assigns the Behavior Tree root node to self.bt. Constructs a priority-based tree that prioritizes completing scans over other activities. Handles three main phases: not scanned yet, no scan target, has scan target, and fallback to player proximity.
  • Parameters: None (uses self.inst).
  • Returns: None.
  • Error states: None documented. Tree construction assumes required behavior modules (doaction, faceentity, leash, wander) are correctly loaded.

The following local helper functions are used internally and are critical to behavior correctness:

GetLeader(inst)​

  • Description: Retrieves the scanner's leader (typically the controlling player) via the follower component.
  • Parameters: inst — the scanner entity instance.
  • Returns: Leader instance or nil if no leader exists or follower component is missing.

GetLeaderPosition(inst)​

  • Description: Gets the leader's world position, or the scanner's own position if no leader is available.
  • Parameters: inst — the scanner entity instance.
  • Returns: Vector3 or nil, depending on leader presence.

ReturnToPlayerAfterFinishedScan(inst)​

  • Description: Initiates a buffered walk action to a position near the player after scanning is complete. If scanning isn't finished (inst._donescanning is false), returns nil. Otherwise, computes a walkable offset around the leader or random fallback position and executes the action.
  • Parameters: inst — the scanner entity instance.
  • Returns: nil if scan not finished; otherwise a BufferedAction with success/failure handlers calling OnReturnedAfterSuccessfulScan.
  • Error states: May return nil if FindWalkableOffset fails to find a valid location or no leader is available and random fallback fails.

GetScanTarget(inst)​

  • Description: Queries the entitytracker component for the entity tagged as "scantarget", but only if the stategraph does not have the "scanned" tag.
  • Parameters: inst — the scanner entity instance.
  • Returns: Target entity instance or nil if no target is tracked or scanning is finished.

GetTargetScanFollowDistance(inst)​

  • Description: Calculates the minimum radius the scanner should maintain around the scan target (target radius + TARGET_FOLLOW = 0.1).
  • Parameters: inst — the scanner entity instance.
  • Returns: Numeric distance or TARGET_FOLLOW if no target.

GetMaxScanFollowDistance(inst)​

  • Description: Calculates the maximum radius the scanner may drift from the target before leashing applies, clamped to TUNING.WX78_SCANNER_SCANDIST - 0.05.
  • Parameters: inst — the scanner entity instance.
  • Returns: Numeric distance, clamped, or MAX_TARGET_FOLLOW if no target.

GetScanTargetLocation(inst)​

  • Description: Returns the world position of the scan target, or the scanner’s own position if no target exists.
  • Parameters: inst — the scanner entity instance.
  • Returns: Vector3 or nil.

KeepFacingScanTarget(inst, target)​

  • Description: Callback used by FaceEntity to verify the scanner should continue facing the scan target (i.e., target still exists and is tracked).
  • Parameters:
    • inst — the scanner entity instance.
    • target — the entity being faced (unused directly in logic).
  • Returns: Boolean — true if a scan target exists (via GetScanTarget), false otherwise.

Events & listeners​

No direct event registration (inst:ListenForEvent) is present in this brain. Behavior execution is driven entirely by Behavior Tree state transitions and action node triggers.