Abilities

In SeinARTS, everything is an ability. Movement, attack, harvest, build, patrol, garrison — all player-issuable commands are abilities. There is no hardcoded command enum.

Why?

A hardcoded command system forces you to modify C++ every time you add a new unit behavior. With abilities:

• Designers create new behaviors entirely in Blueprint
• Each ability encapsulates its own logic, targeting, and FX
• Abilities compose naturally (an ability can activate other abilities)
• The command buffer is uniform — every command is "activate ability X on target Y"

Ability Classes

Abilities are USeinAbility subclasses — Blueprint classes, not data assets.

UCLASS(Blueprintable, Abstract)
class USeinAbility : public UObject
{
    UPROPERTY(EditAnywhere, Category = "SeinARTS|Ability")
    FText AbilityName;

    UPROPERTY(EditAnywhere, Category = "SeinARTS|Ability")
    FGameplayTag AbilityTag;

    UPROPERTY(EditAnywhere, Category = "SeinARTS|Ability")
    FFixedPoint Cooldown;

    UPROPERTY(EditAnywhere, Category = "SeinARTS|Ability")
    TMap<FName, FFixedPoint> ResourceCost;

    UPROPERTY(EditAnywhere, Category = "SeinARTS|Ability")
    ESeinTargetType TargetType;  // None, Point, Entity, PointOrEntity

    UPROPERTY()
    FFixedPoint CooldownRemaining;

    UPROPERTY()
    bool bIsActive;

    UPROPERTY()
    bool bIsPassive;
};

Key Properties

Property	Description
AbilityTag	Unique gameplay tag identifying this ability (e.g., Ability.Attack.Ranged)
Cooldown	Fixed-point cooldown duration in sim ticks
ResourceCost	Map of resource name → cost (e.g., {"Manpower": 50, "Munitions": 25})
TargetType	What kind of target the ability needs
bIsPassive	If true, auto-activates and stays active (auras, passive buffs)

Latent Execution

Abilities don't execute in a single tick. They run as latent actions — cooperative coroutines managed by USeinLatentActionManager.

An ability's execution graph might look like:

MoveToAction (reach target)
  → WaitAction (wind-up time)
    → Apply Damage
      → WaitAction (cooldown)
        → Loop back to MoveToAction (for auto-attack)

Each latent action runs for as many ticks as it needs, then yields to the next. The latent action manager ticks all active actions each sim tick (Phase 3: Ability Execution).

Built-in Latent Actions

Action	Purpose
USeinMoveToAction	Pathfind and move to a target point or entity
USeinWaitAction	Wait for N sim ticks

Designers can create custom latent actions in Blueprint for complex behaviors.

Ability Component

Entities hold abilities via FSeinAbilityComponent:

USTRUCT(BlueprintType)
struct FSeinAbilityComponent
{
    UPROPERTY(EditAnywhere, Category = "SeinARTS|Ability")
    TArray<TSubclassOf<USeinAbility>> GrantedAbilityClasses;

    UPROPERTY()
    TArray<USeinAbility*> AbilityInstances;
};

GrantedAbilityClasses is set on the archetype. At spawn, instances are created from these classes. Abilities can also be granted/revoked at runtime (e.g., veterancy unlocks a new ability).

Querying Abilities

Function	Description
FindAbilityByTag(Tag)	Find an ability instance by its gameplay tag
HasAbilityWithTag(Tag)	Check if entity has a specific ability

From the UI ViewModel:

EntityViewModel → GetAbilities() → TArray<FSeinAbilityInfo>
EntityViewModel → GetAbilityByTag(Tag) → FSeinAbilityInfo
EntityViewModel → HasAbilityWithTag(Tag) → bool

FSeinAbilityInfo is a display-friendly struct with name, icon, cooldown percent, active state, and resource cost already converted to floats.

Command Flow

sequenceDiagram
    participant Player as Player Input
    participant PC as PlayerController
    participant Buf as Command Buffer
    participant Sim as Sim Tick (Phase 2)
    participant Ability as Ability System

    Player->>PC: Right-click on enemy
    PC->>Buf: FSeinCommand{ActivateAbility, AttackTag, TargetHandle}
    Note over Buf: Buffered until next sim tick
    Sim->>Buf: Dequeue commands
    Sim->>Ability: FindAbilityByTag(AttackTag)
    Sim->>Ability: CanActivate? (cooldown, cost, target valid)
    Ability->>Ability: Activate → Start latent action chain

Designing Abilities in Blueprint

1. Create a new Blueprint class derived from USeinAbility
2. Set the ability tag, cooldown, cost, target type in defaults
3. Override the execution graph using latent action nodes
4. Add the ability class to a unit's GrantedAbilityClasses array on its archetype

The ability automatically:

• Appears in the unit's ability bar (via GetAbilities())
• Shows cooldown state in UI (via FSeinAbilityInfo)
• Validates resource costs before activation
• Enters the latent action manager when activated
• Fires visual events for the render layer

Tips

Tag hierarchy for ability categories

Use tag hierarchy for organization: Ability.Movement.Move, Ability.Attack.Ranged, Ability.Special.Heal. This lets you query by category (e.g., "does this unit have any attack abilities?") using tag matching.

Abilities are sim-side objects

USeinAbility instances live in the simulation. They use FFixedPoint for cooldowns and costs. The FSeinAbilityInfo struct in the UI Toolkit is the render-friendly mirror — don't confuse the two.