# HowTo_Components

**Repository Path**: wblong/how-to_-components

## Basic Information

- **Project Name**: HowTo_Components
- **Description**: 学习利用组件将Pawn与物理交互、使用粒子效果等方法。
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2021-08-01
- **Last Updated**: 2021-10-21

## Categories & Tags

**Categories**: Uncategorized

**Tags**: Cpp, UE4

## README

# 组件和碰撞

学习利用组件将Pawn与物理交互、使用粒子效果等方法。

## 粒子系统组件

```cpp
UPROPERTY()
class UParticleSystemComponent* OurParticleSystem;
```
创建与物理场景交互的 球体组件、视觉显示碰撞形态的 静态网格体组件、可随意开关的粒子系统组件，及可用于附加 摄像机组件 控制游戏视角的 弹簧臂组件。

```cpp

    #include "UObject/ConstructorHelpers.h"
    #include "Particles/ParticleSystemComponent.h"
    #include "Components/SphereComponent.h"
    #include "Camera/CameraComponent.h"
    #include "GameFramework/SpringArmComponent.h"

 // 根组件将成为对物理反应的球体
    USphereComponent* SphereComponent = CreateDefaultSubobject<USphereComponent>(TEXT("RootComponent"));
    RootComponent = SphereComponent;
    SphereComponent->InitSphereRadius(40.0f);
    SphereComponent->SetCollisionProfileName(TEXT("Pawn"));

     // 创建并放置网格体组件，以便查看球体位置
    UStaticMeshComponent* SphereVisual = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("VisualRepresentation"));
    SphereVisual->SetupAttachment(RootComponent);
    static ConstructorHelpers::FObjectFinder<UStaticMesh> SphereVisualAsset(TEXT("/Game/StarterContent/Shapes/Shape_Sphere.Shape_Sphere"));
    if (SphereVisualAsset.Succeeded())
    {
        SphereVisual->SetStaticMesh(SphereVisualAsset.Object);
        SphereVisual->SetRelativeLocation(FVector(0.0f, 0.0f, -40.0f));
        SphereVisual->SetWorldScale3D(FVector(0.8f));
    }

    // 创建可激活或停止的粒子系统
    OurParticleSystem = CreateDefaultSubobject<UParticleSystemComponent>(TEXT("MovementParticles"));
    OurParticleSystem->SetupAttachment(SphereVisual);
    OurParticleSystem->bAutoActivate = false;
    OurParticleSystem->SetRelativeLocation(FVector(-20.0f, 0.0f, 20.0f));
    static ConstructorHelpers::FObjectFinder<UParticleSystem> ParticleAsset(TEXT("/Game/StarterContent/Particles/P_Fire.P_Fire"));
    if (ParticleAsset.Succeeded())
    {
        OurParticleSystem->SetTemplate(ParticleAsset.Object);
    }

        // 使用弹簧臂给予摄像机平滑自然的运动感。
    USpringArmComponent* SpringArm = CreateDefaultSubobject<USpringArmComponent>(TEXT("CameraAttachmentArm"));
    SpringArm->SetupAttachment(RootComponent);
    SpringArm->SetRelativeRotation(FRotator(-45.f, 0.f, 0.f));
    SpringArm->TargetArmLength = 400.0f;
    SpringArm->bEnableCameraLag = true;
    SpringArm->CameraLagSpeed = 3.0f;

      // 创建摄像机并附加到弹簧臂
    UCameraComponent* Camera = CreateDefaultSubobject<UCameraComponent>(TEXT("ActualCamera"));
    Camera->SetupAttachment(SpringArm, USpringArmComponent::SocketName);

     // 控制默认玩家
    AutoPossessPlayer = EAutoReceiveInput::Player0;

```

## 移动组件

`UCollidingPawnMovementComponent : public UPawnMovementComponent`

```cpp
void UCollidingPawnMovementComponent::TickComponent(float DeltaTime, enum ELevelTick TickType, FActorComponentTickFunction *ThisTickFunction)
{
    Super::TickComponent(DeltaTime, TickType, ThisTickFunction);

    // 确保所有事物持续有效，以便进行移动。
    if (!PawnOwner || !UpdatedComponent || ShouldSkipUpdate(DeltaTime))
    {
        return;
    }

    // 获取（然后清除）ACollidingPawn::Tick中设置的移动向量
    FVector DesiredMovementThisFrame = ConsumeInputVector().GetClampedToMaxSize(1.0f) * DeltaTime * 150.0f;
    if (!DesiredMovementThisFrame.IsNearlyZero())
    {
        FHitResult Hit;
        SafeMoveUpdatedComponent(DesiredMovementThisFrame, UpdatedComponent->GetComponentRotation(), true, Hit);

        // 若发生碰撞，尝试滑过去
        if (Hit.IsValidBlockingHit())
        {
            SlideAlongSurface(DesiredMovementThisFrame, 1.f - Hit.Time, Hit.Normal, Hit);
        }
    }
};
```

## 使用Pawn和组件

```cpp
UPROPERTY()
class UCollidingPawnMovementComponent* OurMovementComponent;
// 创建移动组件的实例，并要求其更新根。
OurMovementComponent = CreateDefaultSubobject<UCollidingPawnMovementComponent>(TEXT("CustomMovementComponent"));
OurMovementComponent->UpdatedComponent = RootComponent;

UPawnMovementComponent* ACollidingPawn::GetMovementComponent() const
{
    return OurMovementComponent;
}
```

处理Pawn会接收的输入。
```cpp

void MoveForward(float AxisValue);
void MoveRight(float AxisValue);
void Turn(float AxisValue);
void ParticleToggle();
```
```cpp
void ACollidingPawn::MoveForward(float AxisValue)
    {
        if (OurMovementComponent && (OurMovementComponent->UpdatedComponent == RootComponent))
        {
            OurMovementComponent->AddInputVector(GetActorForwardVector() * AxisValue);
        }
    }

    void ACollidingPawn::MoveRight(float AxisValue)
    {
        if (OurMovementComponent && (OurMovementComponent->UpdatedComponent == RootComponent))
        {
            OurMovementComponent->AddInputVector(GetActorRightVector() * AxisValue);
        }
    }

    void ACollidingPawn::Turn(float AxisValue)
    {
        FRotator NewRotation = GetActorRotation();
        NewRotation.Yaw += AxisValue;
        SetActorRotation(NewRotation);
    }

    void ACollidingPawn::ParticleToggle()
    {
        if (OurParticleSystem && OurParticleSystem->Template)
        {
            OurParticleSystem->ToggleActive();
        }
    }
    InInputComponent->BindAction("ParticleToggle", IE_Pressed, this, &ACollidingPawn::ParticleToggle);

    InInputComponent->BindAxis("MoveForward", this, &ACollidingPawn::MoveForward);
    InInputComponent->BindAxis("MoveRight", this, &ACollidingPawn::MoveRight);
    InInputComponent->BindAxis("Turn", this, &ACollidingPawn::Turn);
```
## Result

![1 how to component](./Images/how_to_components.png)

![1 how to component](./Images/how_to_component1.png)

## Reference

1. [组件和碰撞-https://docs.unrealengine.com/4.26/zh-CN/ProgrammingAndScripting/ProgrammingWithCPP/CPPTutorials/Components/](https://docs.unrealengine.com/4.26/zh-CN/ProgrammingAndScripting/ProgrammingWithCPP/CPPTutorials/Components/)