Use SetActorLocation() for elements in OnConstruction()

Development Programming & Scripting C++
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1

Hello,

I want to move static meshes continuously in one direction. I’m using the OnConstruction() function because I want to dynamically modify in the editor the number of static meshes, the distance between them, and the scale of each.

The problem is that I can’t move the static meshes created with OnConstruction(). I use SetActorLocation(), the actor’s coordinates change but the meshes don’t.

Here’s what I’ve done in my code:

Buildings.h 
private:

UPROPERTY(VisibleAnywhere)
TArray<UStaticMeshComponent*> Pillars;

UPROPERTY(EditAnywhere)
int NumOfPillars = 10;

UPROPERTY(EditAnywhere)
float PillarGap = 500.0f;

UPROPERTY(EditAnywhere)
float MoveSpeed = -10.0f;

UPROPERTY(EditAnywhere)
float PillarHeightMin = 1.0f;

UPROPERTY(EditAnywhere)
float PillarHeightMax = 4.0f;

UPROPERTY(EditDefaultsOnly)
UStaticMesh* PillarMesh;

UPROPERTY(EditDefaultsOnly)
USceneComponent* Root;

UFUNCTION(BlueprintCallable)
void SpawnPillars();

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

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

	// Construction Script
	virtual void OnConstruction(const FTransform& Transform) override;

public:	
	// Called every frame
	virtual void Tick(float DeltaTime) override;
};
Buildings.cpp 
#include "Buildings.h"

void ABuildings::SpawnPillars()
{
	UE_LOG(LogTemp, Warning, TEXT("Spawning Pillars"));

	for (size_t i = 0; i < Pillars.Num(); i++)
	{
		if (Pillars[i])
		{
			Pillars[i]->DestroyComponent();
		}
	}

	Pillars.Empty();

	for (size_t i = 0; i < NumOfPillars; i++)
	{
		UStaticMeshComponent* smc = (UStaticMeshComponent*)AddComponentByClass(UStaticMeshComponent::StaticClass(), false, FTransform(), true);
		
		if (smc)
		{
			smc->RegisterComponent();
			smc->SetMobility(EComponentMobility::Movable);
			smc->AttachToComponent(Root, FAttachmentTransformRules::SnapToTargetNotIncludingScale);
			smc->SetWorldLocation(GetActorLocation() + FVector(0, PillarGap * i, 0));
			smc->SetWorldScale3D(FVector(1, 1, FMath::RandRange(PillarHeightMin, PillarHeightMax))); // Hauteur des meshs randomisés
			smc->SetStaticMesh(PillarMesh);
			Pillars.Add(smc);
		}
	}
}

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

	Root = CreateDefaultSubobject<USceneComponent>(TEXT("Root"));
	SetRootComponent(Root);

}

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

void ABuildings::OnConstruction(const FTransform &Transform)
{
	SpawnPillars();
}

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

	// Moving pillars
	SetActorLocation(GetActorLocation() + FVector(0, MoveSpeed * DeltaTime, 0));

	GEngine->AddOnScreenDebugMessage(-1, 2.0f, FColor::Red, GetActorLocation().ToString());
}

As you can see, I use SetActorLocation(GetActorLocation() + FVector(0, MoveSpeed * DeltaTime, 0));

The actor itself moves well, but my meshs don’t.

Thank you very much for your help.

2

I would suggest using local transform using SetRelativeLocation or AddRelativeLocation. It should behave the same and can be visualized inside blueprints too.

// Set relative location and scale instead of world
			smc->SetRelativeLocation(FVector(0, PillarGap * i, 0));
			smc->SetRelativeScale3D(FVector(1, 1, FMath::RandRange(PillarHeightMin, PillarHeightMax)));
3

I’ve already tried it and unfortunately it makes no difference. The actor himself moves well, but the meshes do not. I really don’t know what I need to change.

4

Hi @Shotendev,

May you be great!

This issue is quite simple to solve, simple call Super on your OnConstruction:

void ABuildings::OnConstruction(const FTransform &Transform)
{
	Super::OnConstruction(Transform);
	SpawnPillars();
}

or even (Depending on your implementation)

void ABuildings::OnConstruction(const FTransform &Transform)
{
	SpawnPillars();
	Super::OnConstruction(Transform);
}

May that help you.

Bye.

5

Hello,

Thank you very much for offering your help. I’ve tried both solutions, but it doesn’t make any difference. I hope it’s not just a bug on my end.

6

It doesn’t make sense, since all changed variables on OnConstruction() are UPROPERTY(), that should update the transformation.

Have you tried reload your blueprint?

7

It just didn’t make sense! I’ve just deleted my blueprint actor and recreated it again from the C++ class and it works. Thanks a lot for your help.