Calling SpawnActor() using GetSocketLocation() does not spawn the actor at the right location

Development Programming & Scripting Multiplayer & Networking
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1

Currently trying to spawn a projectile at gun’s static mesh’s muzzle socket location. However, it has resulted in the projectile being spawned at the player character’s foot like shown here

Here’s a picture of the muzzle socket in the static mesh

And here’s the code for spawning the projectile,

for (int i = 0; i < Components.Num(); i++) {
    if (Components[i]->GetName() == "Weapon") {
        UStaticMeshComponent* WeaponComponent = Components[i];

        FVector MuzzleLocation = WeaponComponent->GetSocketLocation("muzzle");
                        
        APlayerController* PlayerController = Cast<APlayerController>(GetController());
        FRotator CameraRotation = PlayerController->PlayerCameraManager->GetCameraRotation();
        FVector CameraLocation = PlayerController->PlayerCameraManager->GetCameraLocation();
        PlayerController->GetPlayerViewPoint(CameraLocation, CameraRotation);
        FVector ShootDirection = CameraRotation.Vector();

        const FVector StartTrace = FollowCamera->GetComponentLocation();
        const FVector EndTrace = StartTrace + ShootDirection * 100000.0;
        FHitResult Impact;
        FCollisionQueryParams CollisionParams;
        GetWorld()->LineTraceSingleByChannel(Impact, StartTrace, EndTrace, ECC_Visibility, CollisionParams);

        if (Impact.bBlockingHit) {
            FTransform SpawnTransform(ShootDirection.Rotation(), MuzzleLocation);
            auto Bullet = Cast<AProjectileActor>(UGameplayStatics::BeginDeferredActorSpawnFromClass(this, CurrentWeapon->BulletClass, SpawnTransform));
            if (Bullet != nullptr)
            {
                //spawnactor has no way of passing parameters so need to use begindeferredactorspawn and finishspawningactor
                Bullet->Weapon = CurrentWeapon;
                Bullet->WeaponHolder = this;

                UGameplayStatics::FinishSpawningActor(Bullet, SpawnTransform);
            }
        }
        break;
    }
}

Not sure what’s causing this, any help would be appreciated!

EDIT
The code above is in a server rpc. Oddly enough, the bullet spawns on the muzzle socket on the server, but when replicating this back to the client the location is incorrect. I’ve also experienced a similar issue with AttachtToComponent attaching in different rotations on server vs client.

2

Have you tried drawing a debug sphere at the MuzzleLocation just to test if that one is correct.

that would be that

other things I see is that you don’t set the ESpawnActorCollisionHandlingMethod for BeginDeferredActorSpawnFromClass which you should set to AlwaysSpawn so that the position doesn’t get changed on spawn.

3

Failed to GetSocketTransform from weapon, so the Bullet spawned on ZeroVector.

4

+1, you should log the MuzzleLocation value ( or put breakpoint ) to check the returned value

THe weapons doesn’ tlooks like to be the same, make sure all meshes have the socket setup

5

I have tried doing drawdebugsphere and the bullet spawns on the socket location on the server but not on the clients. This code is currently in a server rpc. And weirdly enough it does spawn normally in a single player game. Do you think there’s a problem with spawning things server side?

6

Unfortunately I did try logging the muzzle location value and it’s not a zero vector. However, one thing i found out is that the bullet spawns at the socket location in a single player game but not in a multiplayer game. This code is in a server rpc currently. Do you think there’s something wrong with spawning server side? Because on the server it spawns fine but it doesn’t replicate currently to the clients.

7

Anyway, the code you post looks like suit only for local running. If it is in server rpc as you said, you may need to SetOwner of the bullet.

Normally, using a local function to calculate the start pose of bullet, and call a server function to spawn bullet with certain pose, would be suit for most of needs of sync-bullet. ShooterGame could be a good reference for you.

8

Hi Henry, sorry for the late response. It seems that SetOwner doesn’t change the result either. However, when you say use a local function to calculate the start pose, then call a server rpc to spawn the bullet, how would I pass the start pose from the local client function to the server rpc? Thanks for your help so far.

1 Like
9

Nevermind I’m stupid, for some reason I thought you couldn’t pass parameters to server rpcs. Calculating the location client side did work. Thank you henry.