虚幻引擎：如何在循环中创建 UStaticMeshComponent？

Question

我正在尝试使用 for 循环创建多个UStaticMeshComponent ，但虚幻引擎不断在Object.h CreateDefaultSubobject上触发断点（不在我的代码中，它来自 UE4 核心 API）。 当我创建单个组件时，它工作正常。 我对 UnrealEngine 和 C++ 还很陌生，所以我可能会做一些愚蠢的事情，但请放轻松：)

非常感谢你的帮助。

标题

#pragma once

#include "CoreMinimal.h"
#include "GameFramework/Actor.h"
#include "FlowSphere.generated.h"

UCLASS()
class CPP_PRACTICE_3_API AFlowSphere : public AActor
{
    GENERATED_BODY()

public: 
    // Sets default values for this actor's properties
    AFlowSphere();

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

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

private:
    //UPROPERTY()
    //TArray<UStaticMeshComponent*> StaticMeshComponents;

    UStaticMeshComponent* test;

};

C++

#include "FlowSphere.h"

// Sets default values
AFlowSphere::AFlowSphere()
{
    int32 amount = 100;

    RootComponent = CreateDefaultSubobject<USceneComponent>("SceneComponent");

    for (int32 i = 0; i < amount; i++) {

        //WHEN I INCLUDE THE LINE BELOW, UE4 START MAKING BREAKPOINT
        UStaticMeshComponent* item = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("Sphere"));
        item.AttachTo(this->RootComponent);

    }

    //THIS WORKS FINE
    this->test = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("HELLO")); 
    PrimaryActorTick.bCanEverTick = true;

}

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

}

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

}

它从 UE4 API 在Object.h上触发断点的地方

    /**
    * Create a component or subobject
    * @param    TReturnType                 class of return type, all overrides must be of this type
    * @param    SubobjectName               name of the new component
    * @param    bTransient                  true if the component is being assigned to a transient property. This does not make the component itself transient, but does stop it from inheriting parent defaults
    */
    template<class TReturnType>
    TReturnType* CreateDefaultSubobject(FName SubobjectName, bool bTransient = false)
    {
        UClass* ReturnType = TReturnType::StaticClass();
        return static_cast<TReturnType*>(CreateDefaultSubobject(SubobjectName, ReturnType, ReturnType, /*bIsRequired =*/ true, /*bIsAbstract =*/ false, bTransient));
    }

Answer 1

您对 CreateDefaultSubobject 的两个不同调用使用了相同的名称。

我在新的 UE4 C++ 项目中运行您的代码并收到以下错误消息：

致命错误：[File:D:\\Build++UE4\\Sync\\Engine\\Source\\Runtime\\CoreUObject\\Private\\UObject\\UObjectGlobals.cpp] [行：3755] FlowSphere /Script/MyProject 的默认子对象 StaticMeshComponent Sphere 已经存在。默认__FlowSphere。

另外，您发布的代码没有编译。

item.AttachTo(this->RootComponent);

本来应该：

item->AttachTo(this->RootComponent);

并且您还需要包含“Components/StaticMeshComponent.h”。 这是更正后的代码：

#include "FlowSphere.h"
#include "Components/StaticMeshComponent.h"

// Sets default values
AFlowSphere::AFlowSphere()
{
    int32 amount = 100;

    RootComponent = CreateDefaultSubobject<USceneComponent>("SceneComponent");

    for (int32 i = 0; i < amount; i++) {

        FName name = *FString::Printf(TEXT("Sphere %i"), i);
        UStaticMeshComponent* item = CreateDefaultSubobject<UStaticMeshComponent>(name);
        item->AttachTo(this->RootComponent);

    }

    this->test = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("HELLO"));
    PrimaryActorTick.bCanEverTick = true;

}

Answer 2

所以我最近不得不做同样的事情并遇到了很多问题，但要解决的两个主要问题是：

1. 使用 UInstancedStaticMesh 而不是 UStaticMesh。
2. 向静态网格添加属性。

下面是正确的代码。

#include "FlowSphere.h"
#include "Components/StaticMeshComponent.h"
#include "UObject/ConstructorHelpers.h"

// Sets default values
AFlowSphere::AFlowSphere()
{
    int32 amount = 100;

    RootComponent = CreateDefaultSubobject<USceneComponent>("SceneComponent");

    for (int32 i = 0; i < amount; i++) {

        FName name = *FString::Printf(TEXT("Sphere %i"), i);
        FName c_name = *FString::Printf(TEXT("ChildSceneComponent %i"), i);

        UPROPERTY(EditAnywhere)
            USceneComponent* ChildSceneComponent
            = CreateDefaultSubobject<USceneComponent>(c_name);

        // instead of the regular static mesh, create and instance static mesh object with name assigned
        UInstancedStaticMeshComponent* item = CreateDefaultSubobject<UStaticMeshComponent>(name);
        item->RegisterComponent();

        // assign property to mesh if not you'll get a static mesh null property error like i did 
        auto MeshAsset = ConstructorHelpers::FObjectFinder<UStaticMesh>(TEXT("StaticMesh'/Engine/BasicShapes/Sphere.Sphere'"));

        if (MeshAsset.Object != nullptr)
        {
            item->SetStaticMesh(MeshAsset.Object);
        }
        item->SetFlags(RF_Transactional);

        // add instance to actor level
        this->AddInstanceComponent(item);

        // make the scene component for the mesh to be visible
        RootComponent = Root;

        // attach mesh to the scene component of the actor in form of a Hierarchy

        item->AttachToComponent(ChildSceneComponent, FAttachmentTransformRules::KeepWorldTransform, m_name);
        ChildSceneComponent->AttachToComponent(Root, FAttachmentTransformRules::KeepWorldTransform, c_name);

        // set mesh transform based on the ith position
        FTransform t(FVector(250 * i, i, i));

        // activate the new copy of the mesh
        Mesh->AddInstance(t);

        // Offset and scale the child scene from the root scene as a precaution
        ChildSceneComponent->SetRelativeTransform(
            FTransform(FRotator(0, 0, 0),
                FVector(250 * i, i, i),
                FVector(0.1f))
        );


    }


    PrimaryActorTick.bCanEverTick = true;

}