Behavior trees

The behavior-tree editor: a Selector root over a Sequence (Condition seesPlayer → Action chase) with a fallback patrol action.

A behavior tree ticks from its root every frame and returns a Status. Composite nodes control flow; decorators transform one child’s result; leaves are your registered actions and conditions. Attach a BehaviorTreeAgent:

import { BehaviorTreeAgent } from 'esengine';

cmds.spawn()
  .insert(NavAgent, {})
  .insert(Perception, {})
  .insert(BehaviorTreeAgent, { bt: 'assets/ai/enemy.esbt' });   // an editor-authored asset

BehaviorTreeAgent field	Description
bt	Key of the tree to run: a registerBt name or an .esbt asset path.
status	Last root status, written each tick (read-only).

Author the tree visually in the editor, or build it in code with registerBt:

import { registerBt } from 'esengine';

registerBt('guard', {
  root: {
    type: 'selector',            // try children left→right until one succeeds
    children: [
      {
        type: 'sequence',        // all must succeed, in order
        children: [
          { type: 'condition', name: 'seesPlayer' },
          { type: 'action', name: 'chase' },
        ],
      },
      { type: 'action', name: 'patrol' },
    ],
  },
});

Node types:

Category	Type	Behavior
Composite	sequence	Ticks children in order; fails on the first failure, succeeds if all succeed.
	selector	Ticks children in order; succeeds on the first success, fails if all fail.
	parallel	Ticks all children; policy: 'one' succeeds when any does, 'all' (default) when all do.
Decorator	inverter	Inverts its child’s Success/Failure.
	succeeder	Always reports Success.
	repeater	Re-runs its child count times (0 = forever).
	wait	Runs for seconds before reporting Success.
Leaf	action	Runs the registered action name; its Status (or Success on void) propagates up.
	condition	Returns Success when the registered condition name is true, else Failure.