Ue Enhanced Input

Enhanced Input

Enhanced Input is the modern UE input system. It is data-driven: Input Actions define what a player can do, Input Mapping Contexts map physical keys to actions (with optional modifiers and triggers on each mapping), and the Enhanced Input Local Player Subsystem pushes and pops contexts at runtime. Legacy DefaultInput.ini axis/action mappings still compile but are deprecated and should be avoided in new code.

When to use this skill

• Setting up player controls on a Pawn, Character, or PlayerController.
• Binding movement, look, jump, interact, or any other player action in C++.
• Adding, removing, or reprioritizing mapping contexts at runtime (context switching: on-foot, in-vehicle, UI, etc.).
• Reading analog values from FInputActionValue in an action handler.
• Replacing legacy BindAxis/BindAction input bindings.

Mental model

Copy code
Physical key press
   → IMC mapping (modifiers applied first, triggers evaluated)
   → FInputActionValue delivered to handler on matching ETriggerEvent

The system is entirely data-asset-driven. UInputAction and UInputMappingContext are UDataAsset subclasses created in the Content Browser. C++ code holds UPROPERTY pointers to them and uses the subsystem and component to wire them up.

Setup checklist

1. Verify the Enhanced Input plugin is enabled (on by default in 5.x new projects).
2. Add "EnhancedInput" to PrivateDependencyModuleNames in your Build.cs.
3. Set defaults in Project Settings → Engine → Input:
   • Default Player Input Class → EnhancedPlayerInput
   • Default Input Component Class → EnhancedInputComponent
4. Create a UInputAction asset per action; set the value type (Boolean, Axis1D, Axis2D, Axis3D).
5. Create a UInputMappingContext asset; add key→action mappings, plus any per-mapping modifiers/triggers.
6. On possession/spawn: push the context via the subsystem.
7. In SetupPlayerInputComponent: cast to UEnhancedInputComponent, call BindAction.

Core types

Adding a mapping context

Push contexts from a point where the local player exists — typically APlayerController::BeginPlay or APawn::PawnClientRestart:

cppCopy code
// In AMyPlayerController::BeginPlay or APawn::PawnClientRestart
#include "EnhancedInputSubsystems.h"

if (ULocalPlayer* LP = GetLocalPlayer())  // APlayerController has GetLocalPlayer()
{
    auto* Subsys = LP->GetSubsystem<UEnhancedInputLocalPlayerSubsystem>();
    if (Subsys && DefaultMappingContext)
    {
        Subsys->AddMappingContext(DefaultMappingContext, /*Priority*/ 0);
    }
}

Higher-priority values take precedence when two active contexts map the same key to different actions. Remove with Subsys->RemoveMappingContext(IMC). A context can be added/removed any number of times (e.g. entering/leaving a vehicle).

Binding actions in C++

SetupPlayerInputComponent runs on the Pawn after the input component is created. Cast it to UEnhancedInputComponent (safe once the default class is set in Project Settings):

cppCopy code
// AMyCharacter.h
#pragma once
#include "CoreMinimal.h"
#include "GameFramework/Character.h"
#include "AMyCharacter.generated.h"

class UInputAction;
class UInputMappingContext;
struct FInputActionValue;

UCLASS()
class MYGAME_API AMyCharacter : public ACharacter
{
    GENERATED_BODY()
public:
    virtual void SetupPlayerInputComponent(UInputComponent* PlayerInputComponent) override;

protected:
    void OnMove(const FInputActionValue& Value);
    void OnLook(const FInputActionValue& Value);

    UPROPERTY(EditAnywhere, BlueprintReadOnly, Category = "Input")
    TObjectPtr<UInputMappingContext> DefaultMappingContext;

    UPROPERTY(EditAnywhere, BlueprintReadOnly, Category = "Input")
    TObjectPtr<UInputAction> MoveAction;   // Axis2D

    UPROPERTY(EditAnywhere, BlueprintReadOnly, Category = "Input")
    TObjectPtr<UInputAction> LookAction;   // Axis2D

    UPROPERTY(EditAnywhere, BlueprintReadOnly, Category = "Input")
    TObjectPtr<UInputAction> JumpAction;   // Boolean
};

cppCopy code
// AMyCharacter.cpp
#include "AMyCharacter.h"
#include "EnhancedInputComponent.h"
#include "EnhancedInputSubsystems.h"
#include "InputActionValue.h"

void AMyCharacter::SetupPlayerInputComponent(UInputComponent* PlayerInputComponent)
{
    Super::SetupPlayerInputComponent(PlayerInputComponent);

    // Push mapping context (Pawn path: via controller's local player)
    if (APlayerController* PC = Cast<APlayerController>(GetController()))
    {
        if (ULocalPlayer* LP = PC->GetLocalPlayer())
        {
            auto* Subsys = LP->GetSubsystem<UEnhancedInputLocalPlayerSubsystem>();
            if (Subsys && DefaultMappingContext)
                Subsys->AddMappingContext(DefaultMappingContext, 0);
        }
    }

    auto* EIC = CastChecked<UEnhancedInputComponent>(PlayerInputComponent);

    // Continuous actions use ETriggerEvent::Triggered (fires every tick while held)
    EIC->BindAction(MoveAction, ETriggerEvent::Triggered, this, &AMyCharacter::OnMove);
    EIC->BindAction(LookAction, ETriggerEvent::Triggered, this, &AMyCharacter::OnLook);

    // Jump: Started fires on first press, Completed fires on release
    EIC->BindAction(JumpAction, ETriggerEvent::Started,   this, &ACharacter::Jump);
    EIC->BindAction(JumpAction, ETriggerEvent::Completed, this, &ACharacter::StopJumping);
}

void AMyCharacter::OnMove(const FInputActionValue& Value)
{
    const FVector2D Axis = Value.Get<FVector2D>();  // matches IA_Move's Axis2D type
    AddMovementInput(GetActorForwardVector(), Axis.Y);
    AddMovementInput(GetActorRightVector(),   Axis.X);
}

void AMyCharacter::OnLook(const FInputActionValue& Value)
{
    const FVector2D Delta = Value.Get<FVector2D>();
    AddControllerYawInput(Delta.X);
    AddControllerPitchInput(Delta.Y);
}

Key rules:

• Action UPROPERTY members are assigned in a Blueprint subclass (or in asset defaults). Assign DefaultMappingContext, MoveAction, etc. via EditAnywhere.
• CastChecked asserts in Debug builds if the cast fails — a fast failure on misconfiguration.
• The handler signature must exactly match one of the four overloads: no args, const FInputActionValue&, const FInputActionInstance&, or the dynamic four-param form.
• BindAction returns a FEnhancedInputActionEventBinding& if you need to remove the binding later; store the handle or use RemoveBindingByHandle.

Reading FInputActionValue

cppCopy code
// Match the value type declared on the UInputAction asset:
bool     bPressed = Value.Get<bool>();
float    Analog   = Value.Get<float>();       // Axis1D
FVector2D Axis2D  = Value.Get<FVector2D>();   // Axis2D
FVector   Axis3D  = Value.Get<FVector>();     // Axis3D

Reading the wrong type silently returns zero (e.g. Get<bool>() on an Axis2D action returns false). The correct type is whatever EInputActionValueType the action asset declares.

Trigger events — choosing the right one

Note: Started fires once on the frame the key passes the actuation threshold. Triggered fires every tick while held. Completed fires the frame the key is released (or the trigger condition is fully met and then ends).

WASD as an Axis2D — modifier pattern

A single IA_Move (Axis2D) action can be driven by four keyboard keys using per-mapping modifiers in the IMC:

At runtime, Enhanced Input accumulates all active mappings for an action per frame (default TakeHighestAbsoluteValue; Cumulative is the alternative, set on the UInputAction asset).

Gotchas

• Missing "EnhancedInput" in Build.cs → unresolved symbols for all Enhanced Input classes.
• Default input classes not set → CastChecked<UEnhancedInputComponent> crashes on start; Cast returns null and nothing fires.
• Mapping context not added → actions never fire; the subsystem must have the IMC before any key can reach an action.
• Adding context before local player exists → GetLocalPlayer() returns null; always add from PawnClientRestart/BeginPlay (after possession), not the constructor.
• Value type mismatch → Get<FVector2D>() on a Boolean action yields (0, 0); align the handler type with the action asset's ValueType.
• Legacy bind calls on UEnhancedInputComponent → BindAxis/BindAction(FName, ...) are deleted (compile error) unless ENHANCED_INPUT_ALLOW_LEGACY_BINDING=1 in Build.cs.
• Action fires on context add when key is held → default FModifyContextOptions sets bIgnoreAllPressedKeysUntilRelease = true; the key must be released and re-pressed. Set bIgnoreAllPressedKeysUntilRelease = false to override.
• Priority conflicts — add 0 for most contexts; reserve higher values for overlay contexts (e.g. UI) that must win over gameplay.

Legacy input (you will still encounter it)

Older projects use DefaultInput.ini axis/action mappings and BindAxis/BindAction(FName, ...) on UInputComponent. These still compile in 5.8 but cannot coexist cleanly with UEnhancedInputComponent (legacy binds are explicitly deleted on the enhanced component by default). Migrate by replacing axis/action map entries with UInputAction + UInputMappingContext assets, and replacing BindAxis/BindAction(FName, ...) calls with UEnhancedInputComponent::BindAction.

Version notes

• Enhanced Input shipped in UE 4.27 as a plugin and became the default system in UE 5.1. In UE 5.7 the Mappings property on UInputMappingContext is deprecated (marked UE_DEPRECATED(5.7)) in favour of the new DefaultKeyMappings struct; use the editor asset instead of editing the Mappings array in C++.
• FModifyContextOptions (the options struct for AddMappingContext) and input mode filtering via FGameplayTagContainer are 5.3+ additions.

References & source material

Engine source (UE 5.8, plugin path prefix: Engine/Plugins/EnhancedInput/Source/EnhancedInput/Public/):

• InputAction.h — UInputAction:55 (UDataAsset subclass), EInputActionValueType (InputActionValue.h:10, Boolean/Axis1D/Axis2D/Axis3D), EInputActionAccumulationBehavior:24, FInputActionInstance:207 (GetValue():259, GetTriggerEvent():256).
• InputActionValue.h — FInputActionValue:23; Get<bool>():205, Get<float>():212, Get<FVector2D>():218, Get<FVector>():224; EInputActionValueType reused here.
• InputMappingContext.h — UInputMappingContext:87 (UDataAsset subclass); DefaultKeyMappings:101 (5.7 replacement for deprecated Mappings).
• EnhancedInputComponent.h — UEnhancedInputComponent:373; BindAction template macro DEFINE_BIND_ACTION:480 (four signature overloads); BindActionValue:553; RemoveBinding:475; BindActionInstanceLambda:539.
• EnhancedInputSubsystems.h — UEnhancedInputLocalPlayerSubsystem:21 (ULocalPlayerSubsystem + IEnhancedInputSubsystemInterface); AddMappingContext:37; RemoveMappingContext:38.
• EnhancedInputSubsystemInterface.h — IEnhancedInputSubsystemInterface:103; FModifyContextOptions:47 (bIgnoreAllPressedKeysUntilRelease, bForceImmediately, bNotifyUserSettings); HasMappingContext:368; ClearAllMappings:256.
• InputTriggers.h — ETriggerEvent:34 (None/Triggered/Started/Ongoing/ Canceled/Completed); UInputTrigger:113 (ActuationThreshold:130); concrete triggers: UInputTriggerPressed:279, UInputTriggerReleased:298, UInputTriggerHold:318 (HoldTimeThreshold:334), UInputTriggerTap:365, UInputTriggerPulse:457, UInputTriggerChordAction:494.
• InputModifiers.h — UInputModifier:16 (ModifyRaw_Implementation); concrete modifiers: UInputModifierDeadZone:170, UInputModifierNegate:253, UInputModifierSwizzleAxis:412 (EInputAxisSwizzle::YXZ), UInputModifierScalar:213, UInputModifierSmooth:275, UInputModifierResponseCurveExponential:306.
• EnhancedActionKeyMapping.h — FEnhancedActionKeyMapping:37 (Action, Key, Modifiers[], Triggers[]).
• EnhancedInputDeveloperSettings.h — UEnhancedInputDeveloperSettings:43 (DefaultMappingContexts, bEnableInputModeFiltering, DefaultInputMode).

Official docs (UE 5.8):

• Enhanced Input — https://dev.epicgames.com/documentation/unreal-engine/enhanced-input-in-unreal-engine
• Input overview — https://dev.epicgames.com/documentation/unreal-engine/input-in-unreal-engine

Deep-dive references in this skill:

• references/actions-and-contexts.md — UInputAction value types, accumulation, UInputMappingContext structure, priority, runtime add/remove.
• references/modifiers-and-triggers.md — all built-in modifiers and triggers, authoring custom ones, trigger type semantics.
• references/binding-and-setup.md — full BindAction overload set, lambda bindings, removing bindings, the FInputActionInstance handler, per-project class defaults, world-subsystem input for non-player actors.