Unreal教學（7）——控制玩家相機（Player-Controlled Cameras）

下面這個設置好像只有一個有作用，無法同時控制兩個物體。

    //Take control of the default Player
    AutoPossessPlayer = EAutoReceiveInput::Player0;

這個程序是讓物體附加一個相機，應該移動和視圖都是針對物體的，和之前的Game-Controlled Cameras還是有區別的，Game-Controlled Camera沒有依附特定的物體，直接寫在程序的兩個變量上進行控制，而這個例子使用的是UCameraComponent，attach到根節點。

放上代碼，和之前的例子沒有什麼區別，那麼這個C++ Programming Tutorials中的七個例子還剩下兩個例子，First Person Shooter Tutorial和User Interface With UMG.這兩個例子暫時先不寫，已經能寫基本的程序，需要弄清楚它們的類是幹什麼的。很明顯的tutorial上有個錯誤是編譯不過的，但是自己參考API修改過來了。

Performing 3 actions (4 in parallel)
@progress 'Compiling C++ source code...' 0%
[2/3] Compile PawnWithCamera.cpp
[1/3] Compile PawnWithCamera.gen.cpp
/home/wang/Documents/Unreal Projects/UnrealLearn/Source/UnrealLearn/PawnWithCamera.cpp:75:43: error: 
      no member named 'SafeNormal' in 'FVector2D'
            MovementInput = MovementInput.SafeNormal() * 100.0f;
                            ~~~~~~~~~~~~~ ^
1 error generated.
@progress 'Compiling C++ source code...' 25%
@progress 'Compiling C++ source code...' 50%
@progress 'Compiling C++ source code...' 75%

可以看到編譯的時候SafeNormal編譯提示上說FVector2D沒有這個方法，所以查看Document發現應該使用GetSafeNormal(),所以會查閱還是很重要的，之前就有很多的頭文件都是通過查找獲取來的，這點官網還做得比較好，附上代碼。

PawnWithCamera.h

// Fill out your copyright notice in the Description page of Project Settings.

#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Pawn.h"
#include "GameFramework/SpringArmComponent.h"
#include "Camera/CameraComponent.h"
#include "PawnWithCamera.generated.h"

UCLASS()
class UNREALLEARN_API APawnWithCamera : public APawn
{
	GENERATED_BODY()

public:
	// Sets default values for this pawn's properties
	APawnWithCamera();

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

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

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

protected:
    UPROPERTY(EditAnywhere)
    USpringArmComponent* OurCameraSpringArm;
    UCameraComponent* OurCamera;
	
	//Input variables
    FVector2D MovementInput;
    FVector2D CameraInput;
    float ZoomFactor;
    bool bZoomingIn;

    //Input functions
    void MoveForward(float AxisValue);
    void MoveRight(float AxisValue);
    void PitchCamera(float AxisValue);
    void YawCamera(float AxisValue);
    void ZoomIn();
    void ZoomOut();
};

PawnWithCamera.cpp

// Fill out your copyright notice in the Description page of Project Settings.


#include "PawnWithCamera.h"

// Sets default values
APawnWithCamera::APawnWithCamera()
{
 	// 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;

	//Create our components
    RootComponent = CreateDefaultSubobject<USceneComponent>(TEXT("RootComponent"));
    OurCameraSpringArm = CreateDefaultSubobject<USpringArmComponent>(TEXT("CameraSpringArm"));
    OurCameraSpringArm->SetupAttachment(RootComponent);
    OurCameraSpringArm->SetRelativeLocationAndRotation(FVector(0.0f, 0.0f, 50.0f), FRotator(-60.0f, 0.0f, 0.0f));
    OurCameraSpringArm->TargetArmLength = 400.f;
    OurCameraSpringArm->bEnableCameraLag = true;
    OurCameraSpringArm->CameraLagSpeed = 3.0f;
    OurCamera = CreateDefaultSubobject<UCameraComponent>(TEXT("GameCamera"));
    OurCamera->SetupAttachment(OurCameraSpringArm, USpringArmComponent::SocketName);

    //Take control of the default Player
    AutoPossessPlayer = EAutoReceiveInput::Player0;

}

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

// Called every frame
void APawnWithCamera::Tick(float DeltaTime)
{
	Super::Tick(DeltaTime);
	
	//Zoom in if ZoomIn button is down, zoom back out if it's not
    {
        if (bZoomingIn)
        {
            ZoomFactor += DeltaTime / 0.5f;         //Zoom in over half a second
        }
        else
        {
            ZoomFactor -= DeltaTime / 0.25f;        //Zoom out over a quarter of a second
        }
        ZoomFactor = FMath::Clamp<float>(ZoomFactor, 0.0f, 1.0f);
        //Blend our camera's FOV and our SpringArm's length based on ZoomFactor
        OurCamera->FieldOfView = FMath::Lerp<float>(90.0f, 60.0f, ZoomFactor);
        OurCameraSpringArm->TargetArmLength = FMath::Lerp<float>(400.0f, 300.0f, ZoomFactor);
    }

    //Rotate our actor's yaw, which will turn our camera because we're attached to it
    {
        FRotator NewRotation = GetActorRotation();
        NewRotation.Yaw += CameraInput.X;
        SetActorRotation(NewRotation);
    }

    //Rotate our camera's pitch, but limit it so we're always looking downward
    {
        FRotator NewRotation = OurCameraSpringArm->GetComponentRotation();
        NewRotation.Pitch = FMath::Clamp(NewRotation.Pitch + CameraInput.Y, -80.0f, -15.0f);
        OurCameraSpringArm->SetWorldRotation(NewRotation);
    }

    //Handle movement based on our "MoveX" and "MoveY" axes
    {
        if (!MovementInput.IsZero())
        {
            //Scale our movement input axis values by 100 units per second
            MovementInput = MovementInput.GetSafeNormal() * 100.0f;
            FVector NewLocation = GetActorLocation();
            NewLocation += GetActorForwardVector() * MovementInput.X * DeltaTime;
            NewLocation += GetActorRightVector() * MovementInput.Y * DeltaTime;
            SetActorLocation(NewLocation);
        }
    }

}

// Called to bind functionality to input
void APawnWithCamera::SetupPlayerInputComponent(UInputComponent* PlayerInputComponent)
{
	Super::SetupPlayerInputComponent(PlayerInputComponent);
	//Hook up events for "ZoomIn"
    InputComponent->BindAction("ZoomIn", IE_Pressed, this, &APawnWithCamera::ZoomIn);
    InputComponent->BindAction("ZoomIn", IE_Released, this, &APawnWithCamera::ZoomOut);

    //Hook up every-frame handling for our four axes
    InputComponent->BindAxis("MoveForward", this, &APawnWithCamera::MoveForward);
    InputComponent->BindAxis("MoveRight", this, &APawnWithCamera::MoveRight);
    InputComponent->BindAxis("CameraPitch", this, &APawnWithCamera::PitchCamera);
    InputComponent->BindAxis("CameraYaw", this, &APawnWithCamera::YawCamera);
}

//Input functions
void APawnWithCamera::MoveForward(float AxisValue)
{
    MovementInput.X = FMath::Clamp<float>(AxisValue, -1.0f, 1.0f);
}

void APawnWithCamera::MoveRight(float AxisValue)
{
    MovementInput.Y = FMath::Clamp<float>(AxisValue, -1.0f, 1.0f);
}

void APawnWithCamera::PitchCamera(float AxisValue)
{
    CameraInput.Y = AxisValue;
}

void APawnWithCamera::YawCamera(float AxisValue)
{
    CameraInput.X = AxisValue;
}

void APawnWithCamera::ZoomIn()
{
    bZoomingIn = true;
}

void APawnWithCamera::ZoomOut()
{
    bZoomingIn = false;
}