BT Service

Type: Exec (In → Out)
Category: AI_BT
Result: always RUNNING

Executes Python code at regular intervals (not every frame). Useful for periodic update tasks that would be expensive every frame: searching for enemies, recalculating paths, polling data into the blackboard.

Properties

Property	Type	Default	Description
Interval (s)	Float (≥0.016)	0.5	Seconds between code executions
Code	String	"self._bt_bb['service_tick'] = True"	Python executed every Interval seconds

Sockets

Socket	Direction	Type
In	Input	Exec
Out	Output	Exec

Behavior

Every frame: 1. Accumulates deltaTime() into an internal timer (_btsvc_<sid>). 2. If timer ≥ Interval: executes Code and resets timer to 0. 3. Always sets _bt_last_result = 'RUNNING'. 4. Continues through Out.

The code does not execute on the first frame — the timer must accumulate to Interval first.

Variables available in Code

Same as BTCustomTask: self, self.own, self._bt_bb, Range, mathutils.

Difference from BT Simple Parallel and BT Custom Task

Node	Frequency	Result
BT Simple Parallel	Every frame	RUNNING
BT Service	Every N seconds	RUNNING
BT Custom Task	Every frame	Configurable

Typical usage

Search for player every 0.5 seconds

Interval: 0.5
Code:
  player = self.own.scene.objects.get('Player')
  if player:
      diff = player.worldPosition - self.own.worldPosition
      self._bt_bb['enemy_dist']    = diff.length
      self._bt_bb['enemy_visible'] = diff.length < 20.0
  else:
      self._bt_bb['enemy_visible'] = False

Update patrol waypoint every 2 seconds

Interval: 2.0
Code:
  idx = (self._bt_bb.get('waypoint_idx', 0) + 1) % 4
  self._bt_bb['waypoint_idx'] = idx
  self._bt_bb['waypoint'] = 'Waypoint_' + str(idx)

Detect obstacles with a periodic raycast

Interval: 0.25
Code:
  fwd = self.own.worldOrientation.col[1]
  rc  = self.own.rayCast(self.own.worldPosition + fwd * 5.0, None, 5.0)
  self._bt_bb['obstacle_ahead'] = rc[0] is not None

Graph position

Place it at the start of the tree so data is updated before conditions read it:

[OnUpdate] → [BT Service: update perception data]
                    │
                    Out ──► [BT Condition: enemy_visible] → ...

Notes

• Minimum interval is 0.016s (~1 frame at 60fps). For per-frame intervals, use BTSimpleParallel or BTCustomTask.
• Errors in Code are printed to console but don't interrupt the tree — the node returns RUNNING regardless.
• The timer is per node instance. Multiple BTService nodes in the same tree have independent timers.
• Since it always returns RUNNING, don't place it as the sole node before a Selector — the Selector will always go to Failure. Use the Out socket to continue the tree.