# HowTo_PlayerCamera

**Repository Path**: wblong/how-to_-player-camera

## Basic Information

- **Project Name**: HowTo_PlayerCamera
- **Description**: 学会使用玩家输入同时操控摄像机和Pawn。
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2021-07-30
- **Last Updated**: 2021-10-21

## Categories & Tags

**Categories**: Uncategorized

**Tags**: Cpp, UE4

## README

# Player-Controlled Cameras

学会使用玩家输入同时操控摄像机和Pawn。

## 创建相机

创建一个 SpringArmComponent，并在末端绑定一个 CameraComponent。弹簧臂是一种绑定摄像机（或其它 组件 ）的简单方式，能让摄像机跟随拍摄对象时平稳自然。

```cpp
    UPROPERTY(EditAnywhere)
    class USpringArmComponent* SpringArmComp;

    UPROPERTY(EditAnywhere)
    class UCameraComponent* CameraComp;

    UPROPERTY(EditAnywhere)
    UStaticMeshComponent* StaticMeshComp;
```

```cpp
#include "GameFramework/SpringArmComponent.h"
#include "Camera/Component.h"
//创建组件
RootComponent = CreateDefaultSubobject<USceneComponent>(TEXT("RootSceneComponent"));
StaticMeshComp = CreateDefaultSubobject <UStaticMeshComponent>(TEXT("StaticMeshComponent"));
SpringArmComp = CreateDefaultSubobject<USpringArmComponent>(TEXT("SpringArmComponent"));
CameraComp = CreateDefaultSubobject<UCameraComponent>(TEXT("CameraComponent"));

//绑定组件
StaticMeshComp->SetupAttachment(RootComponent);
SpringArmComp->SetupAttachment(StaticMeshComp);
CameraComp->SetupAttachment(SpringArmComp,USpringArmComponent::SocketName);

//为SpringArm类的变量赋值。
SpringArmComp->SetRelativeLocationAndRotation(FVector(0.0f, 0.0f, 50.0f), FRotator(-60.0f, 0.0f, 0.0f));
SpringArmComp->TargetArmLength = 400.f;
SpringArmComp->bEnableCameraLag = true;
SpringArmComp->CameraLagSpeed = 3.0f;
```
## 配置输入及处理输入
创建函数来跟踪输入。
```cpp
//输入变量
FVector2D MovementInput;
FVector2D CameraInput;
float ZoomFactor;
bool bZoomingIn;

// 输入函数
void MoveForward(float AxisValue);
void MoveRight(float AxisValue);
void PitchCamera(float AxisValue);
void YawCamera(float AxisValue);
void ZoomIn();
void ZoomOut();

```
```cpp
// 输入函数
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;
}
```
把Pawn的输入事件和函数相绑定。
```cpp
// 绑定"ZoomIn"的事件
InputComponent->BindAction("ZoomIn", IE_Pressed, this, &APawnWithCamera::ZoomIn);
InputComponent->BindAction("ZoomIn", IE_Released, this, &APawnWithCamera::ZoomOut);

//为四条轴绑定事件（每帧调用）
InputComponent->BindAxis("MoveForward", this, &APawnWithCamera::MoveForward);
InputComponent->BindAxis("MoveRight", this, &APawnWithCamera::MoveRight);
InputComponent->BindAxis("CameraPitch", this, &APawnWithCamera::PitchCamera);
InputComponent->BindAxis("CameraYaw", this, &APawnWithCamera::YawCamera);
```
使用 Tick 函数中的这些值来每帧更新 Pawn 和 Camera。
```cpp
void APawnWithCamera::Tick(float DeltaTime)
{
	Super::Tick(DeltaTime);
	//如果按下了放大按钮则放大，否则就缩小
	{
		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);

		//根据ZoomFactor来设置摄像机的视场和弹簧臂的长度
		CameraComp->FieldOfView = FMath::Lerp<float>(90.0f, 60.0f, ZoomFactor);
		SpringArmComp->TargetArmLength = FMath::Lerp<float>(400.0f, 300.0f, ZoomFactor);
	}
	//旋转Actor的偏转角度，这样摄像机也能旋转，因为摄像机与Actor相互绑定
	{
		FRotator NewRotation = GetActorRotation();
		NewRotation.Yaw += CameraInput.X;
		SetActorRotation(NewRotation);
	}

	// 旋转摄像机的俯仰角度，但要对其进行限制，这样我们就能始终俯视Actor
	{
		FRotator NewRotation = SpringArmComp->GetComponentRotation();
		NewRotation.Pitch = FMath::Clamp(NewRotation.Pitch + CameraInput.Y, -80.0f, -15.0f);
		SpringArmComp->SetWorldRotation(NewRotation);
	}

	// 基于"MoveX"和 "MoveY"坐标轴来处理移动
	{
		if (!MovementInput.IsZero())
		{
			// 把移动轴的输入数值放大100倍
			MovementInput = MovementInput.GetSafeNormal() * 100.0f;
			FVector NewLocation = GetActorLocation();
			NewLocation += GetActorForwardVector() * MovementInput.X * DeltaTime;
			NewLocation += GetActorRightVector() * MovementInput.Y * DeltaTime;
			SetActorLocation(NewLocation);
		}
	}
}
```

## Result
![HowToPlayerCamera](./Images/HowToPlayCamera.png)

## Reference
1. [PlayerCamera - https://docs.unrealengine.com/4.26/zh-CN/ProgrammingAndScripting/ProgrammingWithCPP/CPPTutorials/PlayerCamera/](https://docs.unrealengine.com/4.26/zh-CN/ProgrammingAndScripting/ProgrammingWithCPP/CPPTutorials/PlayerCamera/)