How do I Spawn Actors?

Development Programming & Scripting
1

I am trying to spawn an actor from within my C++ code but can’t seem to get it right without crashing Unreal when loading my project. I setup an actor class called Ball (ABall in C++) and have created a call to the SpawnActor function (from here) and it just doesn’t seem to work.

My current call is:

ABall* SpawnedBall1 = (ABall*)GWorld->SpawnActor(ABall::StaticClass());

which I thought would be substantial in creating a spawn of the object, but clearly not. Any pointers or help would be appreciated.

Thanks

2

It looks like you probably need to check that the world exists before you spawn your actor. Here’s an example from the FPS Tutorial:

UWorld* const World = GetWorld();
            if (World)
            {
                FActorSpawnParameters SpawnParams;
                SpawnParams.Owner = this;
                SpawnParams.Instigator = Instigator;
                // spawn the projectile at the muzzle
                AFPSProjectile* const Projectile = World->SpawnActor<AFPSProjectile>(ProjectileClass, MuzzleLocation, MuzzleRotation, SpawnParams);
                if (Projectile)
                {
                    // find launch direction
                    FVector const LaunchDir = MuzzleRotation.Vector();
                    Projectile->InitVelocity(LaunchDir);
                }
            }
3

Thanks NTG, this has allowed my editor to open with the spawn actor function compiled, however I am still not seeing any type of object appear in the game/hierarchy. I’ll take a look through the FPS tutorial and see if that can give me any pointers when it spawns the projectile object.

4

Try:
ABall* SpawnedBall1 = GWorld()->SpawnActor(ABall::StaticClass());

5

Maybe it will help:
Spawning:
So you need a game Mode as C++ class and then in the Editor under Edit->Project Settings->Maps & Modes: Default Modes you need to set your created GameMode as default game mode. So that this game mode is launched when you start your game.

Or :
open class Viewer from editor and drag your object inside the scene. But i think you want to spawn it.

GameMode cpp:

void AKawummGameMode::BeginPlay()
{
Super::BeginPlay();
UWorld* const World = GetWorld();
if (World)
{
	World->SpawnActor<ASolidBlock>(ASolidBlock::StaticClass());
}
}

SolidBlock cpp:

ASolidBlock::ASolidBlock(const class FPostConstructInitializeProperties& PCIP)
	: Super(PCIP)
{
	MyBlock = PCIP.CreateAbstractDefaultSubobject<UStaticMeshComponent>(this, TEXT("SolidBlock"));

	static ConstructorHelpers::FObjectFinder <UStaticMesh>StaticMesh(TEXT("StaticMesh'/Game/Blocks/SolidBlock.SolidBlock'"));
	static ConstructorHelpers::FObjectFinder<UMaterial> Material(TEXT("MaterialInstanceConstant'/Game/Materials/M_Basic_Floor.M_Basic_Floor'"));

	MyBlock->SetStaticMesh(StaticMesh.Object);
	MyBlock->SetMaterial(0, Material.Object);
}

and SolidBlock .h

UCLASS()
class ASolidBlock : public AActor
{
	GENERATED_UCLASS_BODY()
	virtual void BeginPlay() OVERRIDE;

	// static mesh
	TSubobjectPtr<UStaticMeshComponent> MyBlock;
};

ok. i hope it helps a bit when spawning :slight_smile:

6

I think this shouldn’t be an answer, please instead write a comment as this “answer” doesn’t try to solve the question.