Language:
Page Info
Engine Version:

3. Program and Bind Game Actions

Choose your OS:
  1. In Visual Studio, open MyPawn.h and add the following code to the bottom of MyPawn's class definition:

    //Input functions
    void Move_XAxis(float AxisValue);
    void Move_YAxis(float AxisValue);
    void StartGrowing();
    void StopGrowing();
    
    //Input variables
    FVector CurrentVelocity;
    bool bGrowing;

    The four input functions are going to be bound to our input events. When they run, they will update the values stored in our new input variables, which MyPawn will use to determine what it should do during in the game.

  2. We'll switch over to MyPawn.cpp and program the four functions we just declared. Add the following code:

    void AMyPawn::Move_XAxis(float AxisValue)
    {
        // Move at 100 units per second forward or backward
        CurrentVelocity.X = FMath::Clamp(AxisValue, -1.0f, 1.0f) * 100.0f;
    }
    
    void AMyPawn::Move_YAxis(float AxisValue)
    {
        // Move at 100 units per second right or left
        CurrentVelocity.Y = FMath::Clamp(AxisValue, -1.0f, 1.0f) * 100.0f;
    }
    
    void AMyPawn::StartGrowing()
    {
        bGrowing = true;
    }
    
    void AMyPawn::StopGrowing()
    {
        bGrowing = false;
    }

    We use FMath::Clamp to constrain the values we get from our inputs to the range of -1 to +1. Although it's not an issue in this example, if there were multiple keys that could affect an axis in the same way, the values would be added together if a player pressed those inputs at the same time. For example, if both W and Up Arrow were mapped to MoveX with scales of 1.0, pressing both would result in an AxisValue of 2.0, which would let the player move at double speed if we didn't clamp it.

    You may notice that the two "Move" functions take axis values as floats, while the "Grow" functions do not. This is because they will be mapped to MoveX and MoveY, which are Axis Mappings, and therefore will have a floating-point parameter. Action Mappings do not have this parameter.

  3. Now that we have our input functions defined, we'll need to bind them so that they will react to the appropriate inputs. Add the following code inside of AMyPawn::SetupPlayerInputComponent:

    // Respond when our "Grow" key is pressed or released.
    InputComponent->BindAction("Grow", IE_Pressed, this, &AMyPawn::StartGrowing);
    InputComponent->BindAction("Grow", IE_Released, this, &AMyPawn::StopGrowing);
    
    // Respond every frame to the values of our two movement axes, "MoveX" and "MoveY".
    InputComponent->BindAxis("MoveX", this, &AMyPawn::Move_XAxis);
    InputComponent->BindAxis("MoveY", this, &AMyPawn::Move_YAxis);
  4. We now have variables that are updated by the inputs we configured. All we have left to do is write code to do something with them. Let's add the following code to AMyPawn::Tick:

    // Handle growing and shrinking based on our "Grow" action
    {
        float CurrentScale = OurVisibleComponent->GetComponentScale().X;
        if (bGrowing)
        {
            // Grow to double size over the course of one second
            CurrentScale += DeltaTime;
        }
        else
        {
            // Shrink half as fast as we grow
            CurrentScale -= (DeltaTime * 0.5f);
        }
        // Make sure we never drop below our starting size, or increase past double size.
        CurrentScale = FMath::Clamp(CurrentScale, 1.0f, 2.0f);
        OurVisibleComponent->SetWorldScale3D(FVector(CurrentScale));
    }
    
    // Handle movement based on our "MoveX" and "MoveY" axes
    {
        if (!CurrentVelocity.IsZero())
        {
            FVector NewLocation = GetActorLocation() + (CurrentVelocity * DeltaTime);
            SetActorLocation(NewLocation);
        }
    }
  5. After compling our code, we can return to the Unreal Editor and press Play. We should have control of our Pawn with the WASD keys, and we should be able to make it grow by holding Space Bar, and watch it shrink when we let go.

PlayingGame1.png PlayingGame2.png


Finished Code

MyPawn.h

// Copyright 1998-2017 Epic Games, Inc. All Rights Reserved.

#pragma once

#include "GameFramework/Pawn.h"
#include "MyPawn.generated.h"

UCLASS()
class HOWTO_PLAYERINPUT_API AMyPawn : public APawn
{
    GENERATED_BODY()

public:
    // Sets default values
    AMyPawn();

protected:
    // Called when the game starts or when spawned
    virtual void BeginPlay() override;

public:
    // Called every frame
    virtual void Tick(float DeltaSeconds) override;

    // Called to bind functionality to input
    virtual void SetupPlayerInputComponent(class UInputComponent* InputComponent) override;

    UPROPERTY(EditAnywhere)
    USceneComponent* OurVisibleComponent;

    // Input functions
    void Move_XAxis(float AxisValue);
    void Move_YAxis(float AxisValue);
    void StartGrowing();
    void StopGrowing();

    // Input variables
    FVector CurrentVelocity;
    bool bGrowing;
};

MyPawn.cpp

// Copyright 1998-2017 Epic Games, Inc. All Rights Reserved.

#include "HowTo_PlayerInput.h"
#include "MyPawn.h"

// Sets default values
AMyPawn::AMyPawn()
{
    // Set this pawn to call Tick() every frame.  You can turn this off to improve performance if you don't need it.
    PrimaryActorTick.bCanEverTick = true;

    // Set this pawn to be controlled by the lowest-numbered player
    AutoPossessPlayer = EAutoReceiveInput::Player0;

    // Create a dummy root component we can attach things to.
    RootComponent = CreateDefaultSubobject<USceneComponent>(TEXT("RootComponent"));
    // Create a camera and a visible object
    UCameraComponent* OurCamera = CreateDefaultSubobject<UCameraComponent>(TEXT("OurCamera"));
    OurVisibleComponent = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("OurVisibleComponent"));
    // Attach our camera and visible object to our root component. Offset and rotate the camera.
    OurCamera->SetupAttachment(RootComponent);
    OurCamera->SetRelativeLocation(FVector(-250.0f, 0.0f, 250.0f));
    OurCamera->SetRelativeRotation(FRotator(-45.0f, 0.0f, 0.0f));
    OurVisibleComponent->SetupAttachment(RootComponent);
}

// Called when the game starts or when spawned
void AMyPawn::BeginPlay()
{
    Super::BeginPlay();

}

// Called every frame
void AMyPawn::Tick(float DeltaTime)
{
    Super::Tick(DeltaTime);

    // Handle growing and shrinking based on our "Grow" action
    {
        float CurrentScale = OurVisibleComponent->GetComponentScale().X;
        if (bGrowing)
        {
            // Grow to double size over the course of one second
            CurrentScale += DeltaTime;
        }
        else
        {
            // Shrink half as fast as we grow
            CurrentScale -= (DeltaTime * 0.5f);
        }
        // Make sure we never drop below our starting size, or increase past double size.
        CurrentScale = FMath::Clamp(CurrentScale, 1.0f, 2.0f);
        OurVisibleComponent->SetWorldScale3D(FVector(CurrentScale));
    }

    // Handle movement based on our "MoveX" and "MoveY" axes
    {
        if (!CurrentVelocity.IsZero())
        {
            FVector NewLocation = GetActorLocation() + (CurrentVelocity * DeltaTime);
            SetActorLocation(NewLocation);
        }
    }
}

// Called to bind functionality to input
void AMyPawn::SetupPlayerInputComponent(class UInputComponent* InputComponent)
{
    Super::SetupPlayerInputComponent(InputComponent);

    // Respond when our "Grow" key is pressed or released.
    InputComponent->BindAction("Grow", IE_Pressed, this, &AMyPawn::StartGrowing);
    InputComponent->BindAction("Grow", IE_Released, this, &AMyPawn::StopGrowing);

    // Respond every frame to the values of our two movement axes, "MoveX" and "MoveY".
    InputComponent->BindAxis("MoveX", this, &AMyPawn::Move_XAxis);
    InputComponent->BindAxis("MoveY", this, &AMyPawn::Move_YAxis);
}

void AMyPawn::Move_XAxis(float AxisValue)
{
    // Move at 100 units per second forward or backward
    CurrentVelocity.X = FMath::Clamp(AxisValue, -1.0f, 1.0f) * 100.0f;
}

void AMyPawn::Move_YAxis(float AxisValue)
{
    // Move at 100 units per second right or left
    CurrentVelocity.Y = FMath::Clamp(AxisValue, -1.0f, 1.0f) * 100.0f;
}

void AMyPawn::StartGrowing()
{
    bGrowing = true;
}

void AMyPawn::StopGrowing()
{
    bGrowing = false;
}