StateTree Integration

Documentation Unreal Engine AI StateTree

Guide to StateTree tasks, structure, and integration with the combat system.

Available StateTree Tasks

Task	Purpose	When to Use
`STTask_BuildDecisionContext`	Gathers combat data	Every tick in root state
`STTask_AIMovement`	Evaluates and applies movement	Every tick in root state
`STTask_PollAction`	Scores and selects action	On entering decision state
`STTask_DoAction`	Triggers execution of chosen action	On entering execute state
`STTask_UpdateActionSet`	Swaps ActionSet	When changing AI behavior
`STTask_PollCombatRole`	Polls current combat role	Every tick, outputs role tag
`STTask_PollFocusActor`	Polls controller focus actor	Every tick, outputs target reference
`STTask_SyncActionSet`	Syncs ActionSet from pawn's SECActionSetComponent	On entering role state
`STTask_SyncMovementProfile`	Syncs MovementProfile for current role	On entering role state

All StateTree tasks work with any AAIController that has a SECCombatControllerComponent. They use the component's static resolution helpers to find AIConfig and combat role data.

Typical StateTree Structure

Root (Always Active)
├─ BuildDecisionContext [Tick]
├─ AIMovement [Tick]
│
├─ Idle State
│  └─ Transition → Combat (when target acquired)
│
└─ Combat State
   ├─ Decision State
   │  ├─ PollAction [Enter]
   │  └─ Transition → Execute (when action chosen)
   │
   └─ Execute State
      ├─ DoAction [Enter]
      └─ Transition → Decision (when complete)

Task Details

STTask_BuildDecisionContext

Inputs:

AIController (Object)
DefaultAggressionLevel
WindowIdIntervalSeconds

Attribute Inputs (Optional):

HealthAttribute (FGameplayAttribute)
MaxHealthAttribute (FGameplayAttribute)
StaminaAttribute (FGameplayAttribute)
MaxStaminaAttribute (FGameplayAttribute)

Point these at your GAS AttributeSet properties (e.g. UMyAttributeSet::GetHealthAttribute()). When set, the task reads live values from the pawn's ASC every tick. When left empty, it falls back to BasicHealthComponent (if present) or safe defaults (health percentage 1.0, max health 100).

Outputs:

OutDecisionContext (FDecisionContext struct)

What it does:

Calculates distance and angle to target
Reads health and stamina from GAS attributes (or BasicHealthComponent fallback)
Evaluates health percentages
Gathers gameplay tags from target

STTask_PollAction

Inputs:

AIController
Context (FDecisionContext)
EvaluationCooldown
DebugLog

Outputs:

ChosenAction (FChosenAction)

What it does:

Scores all actions in ActionSet
Applies evaluators
Checks cooldowns
Selects best valid action

STTask_DoAction

Inputs:

Actor
AIController
InChosenAction (FChosenAction)
DebugLog

What it does:

If Ability: Activates via ASC
If BT: Runs behavior tree sequence
Waits for SEC.Action.End event
Completes when action finishes