Minimal Enemy

Documentation Unreal Engine AI Tutorial

The smallest enemy the plugin can drive: a plain Character, a plain AI Controller, six components, one action, no StateTree.

Six components on two actors you already own. It walks toward its target and swings. No base class to inherit from, no StateTree to author, no perception to configure.

Set it up

3 minutes
  1. 1

    Add four components to your AI Controller

    Open your existing AI Controller Blueprint and add these four. Nothing here is replicated; they run on the server and decide.
    Components
    + Add
    BP_MyEnemyController (Self)
    SEC Combat Controller
    Add
    Action Evaluation
    Add
    Movement Evaluator
    Add
    SEC Brain
    Add
  2. 2

    Add two components to your pawn

    Open your Character Blueprint and add these two. The Capsule and Mesh are already there.
    Components
    + Add
    BP_MyEnemy (Self)
    Capsule Component
    Mesh
    SEC Action Set Component
    Add
    Ability System Component
    Add
  3. 3

    Make an Enemy AI Config

    Right-click in the Content Browser, SEC, Enemy AI Config.
    Content Browser
    ▸ Content
    Right-click in the Content Browser, SEC, Enemy AI Config.
    Give it an Action Set holding one action and a Movement Behavior Profile. Leave Default State Tree empty: that empty field is what runs the native brain instead.
    DA_AIConfig_Grunt
    ▾Behavior
    Default Action Set
    None▾
    Default Movement Profile
    None▾
    Two assets in. Default State Tree stays empty.
  4. 4

    Have the pawn use that controller

    On the Character's Class Defaults, point it at your controller and let it possess itself. Without both, nothing possesses the pawn and none of the components above ever run.
    BP_MyEnemy
    ▾Pawn
    AI Controller ClassNone
    Auto Possess AI 
    The pawn names its controller and asks to be possessed.
  5. 5

    Point the controller at the config

    Select the SEC Combat Controller component on the controller and hand it the asset you made.
    SEC Combat Controller
    ▾AI
    Default AI Config
    None▾
    A plain Character provides no config of its own, so this field is the one that answers.
  6. 6

    Give it something to fight

    From your player Blueprint on Begin Play, get the AI Combat Role Subsystem and call Register Combat Target with the player pawn, Auto Assign Unassigned ticked.

When to Use This

You have a Character and an AI Controller of your own that you cannot reparent, because they already inherit from something in your project. Nothing here asks you to.
You want to know what the plugin requires, separated from what the demo content happens to ship with.
Something stopped working and you want to find out what. Strip an enemy to this list, confirm it fights, then add your pieces back one at a time until it stops.

The components

Four on the controller, two on the pawn. Everything else in the plugin is an addition to this.
  • SEC Combat Controller resolves the config and hands the settings out.
  • SEC Brain decides what the enemy is doing at any moment.
  • Movement Evaluator works out which way to walk and walks it.
  • Action Evaluation scores the actions and runs the winner.
  • SEC Action Set Component holds which Action Set is live, so clients can read it.
  • Ability System Component runs the ability the winning action names. Adding it is the whole step; no initialization call, no C++.
AdvancedWhat each component would do without the others
The components are tools, so each one answers on its own and none of them drives another.
Drop SEC Brain and nothing calls the other two. The enemy sits still with a perfectly good Action Set and a perfectly good Movement Evaluator, because neither acts unless something asks it to. That is the shape of the whole plugin: a decider calls, components answer.
Drop Movement Evaluator and the enemy attacks whatever wanders into range without ever closing distance. Drop Action Evaluation and it walks to its preferred range and stands there.
Drop SEC Combat Controller and the config never resolves, so the other three run on their own defaults and the Action Set stays empty.

The config

One Data Asset carries the enemy's whole setup, and three of its fields matter here by staying empty.
Default State Tree empty is what selects the native brain, and the native brain is what makes this list short.
Target Selector empty falls back to a built-in one that takes the first target the enemy may fight, even for a target registered long after the enemy started running. Name a real selector once several enemies share a fight or several players are registered. See Targeting.
Leave Awareness Config empty. Without perception settings the brain reads the controller's focus actor, and a focus actor is enough to fight.
Setting Default AI Config on the controller works here because a plain Character does not provide a config of its own. A pawn that provides one wins, and the controller's field is then unreachable.

Give it a target

Register Combat Target, from the last QuickStart step, sets the focus actor the brain reads. Until it happens the enemy stands still, which is correct rather than broken. Auto Assign Unassigned ticked makes an idle enemy pick from the pool on the spot instead of waiting for the reassignment timer.
For the call to reach the enemy it has to be registered with the subsystem, which Auto Register For Combat Roles on the config does by default. Leave it on.

What this enemy does not do

It lands no damage, because it has no melee trace. It answers no hits, because it has no Reaction Set. It knows nothing it cannot see through its focus actor, because it has no perception. It fights anything registered, including other enemies, because nothing has told it who its friends are.
The next four things to add:
  • SEC Melee Trace Component on the pawn, to land hits. See Melee Trace.
  • SEC Reaction Set Component on the pawn, to answer them. See Reaction System.
  • SEC Team Component on both, so enemies leave each other alone. See Targeting.
  • SEC Awareness Component on the controller, for sight, hearing and memory. See Awareness.
AdvancedCombat roles, and why they are absent here
Roles let several enemies share a fight: one presses while others circle and wait. They are worth adding the moment you have a second enemy.
A single enemy does not need them. Without SEC Combat Role Component the pawn's role reads as none, the config's Default Action Set and Default Movement Profile apply for every role, and both the Action Set resolution and the action scoring run as normal.
Add the component and per-role overrides on the config start working. See Combat Roles.
C++Class names and the test that pins this list
The six are USECCombatControllerComponent, UActionEvaluationComponent, UMovementEvaluatorComponent and USECBrainComponent on the controller, plus USECActionSetComponent and UAbilitySystemComponent on the pawn. The pawn is a plain ACharacter and the controller a plain AAIController; neither inherits from AEnemyCharacterBase or AEnemyControllerBase.
USECCombatControllerComponent::ResolveAIConfig branches on whether the pawn implements IEnemyAIConfigProvider. A plain ACharacter does not, which is what leaves the controller's DefaultAIConfig live.
USECBrainComponent::ReconcileBrain selects a StateTree when the config names one and the native loop when it does not. ResolveDesiredPhase falls back to the focus actor when there is no awareness component, or when the one present has neither settings nor recorded data.
UAbilitySystemComponent::InitAbilityActorInfo carries no UFUNCTION, so the handover reaches Blueprint through no node. AEnemyCharacterBase makes the call at EnemyCharacterBase.cpp:142, and every ability lookup in the plugin runs through UAbilitySystemGlobals::GetAbilitySystemComponentFromActor, which finds a plain component without an interface.
SoulslikeEnemyCombat.Recipes.MinimalEnemy builds this exact setup and asserts it fights, so an added requirement fails the test suite rather than a project. It also pins the boundary cases: no ability system means no action starts, and an ability system that never received its actor info still starts one. It possesses the pawn directly rather than through Auto Possess AI, so the possession wiring above is a prerequisite it does not cover.