ai-behavior-trees-utility-ai

1# Behavior Trees & Utility AI
2 
3Two complementary ways to structure NPC decision-making, plus how to combine them. A
4**behavior tree (BT)** expresses *structured, prioritized, reactive* logic as a tree that is
5"ticked" each step. **Utility AI** answers *"how much do I want each option right now?"* by
6scoring actions with normalized curves and picking the best. Ship believable agents by using a
7BT for structure and Utility AI where graded trade-offs matter.
8 
9This skill is the **implementation** companion to `game-ai` (which helps you *choose* between
10FSM / BT / steering / pathfinding). Read `game-ai` to pick a model; read this to build the
11runtime.
12 
13## When to use
14 
15- Use to build a **reusable BT runtime**: a `Blackboard`, `Node` base, action/condition leaves,
16  `Sequence`/`Selector`/`Parallel` composites, and decorators (Inverter, Cooldown, Repeat).
17- Use to build a **Utility AI** decider: response curves, considerations, and an evaluator that
18  scores and selects actions (max, softmax, or weighted-random for variety).
19- Use to build **hybrid AI** — a BT whose leaf delegates the "which attack / which target"
20  choice to a utility evaluator.
21 
22**When *not* to use:** to *choose* between FSM, BT, steering, or pathfinding, and for A*/navmesh
23routing, use `game-ai`. For Unreal's asset-based `BehaviorTree`/`Blackboard`, `BTTask`/`BTService`
24and `AIController`, use `unreal-behavior-trees`. For the navmesh agent that *moves* the NPC, use
25`unity-navmesh` or the engine's navigation node.
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