I am continuing the Battery Collector in C++ tutorial from Unreal Engine. This is the 8th video.

This time we will define When to Spawn.

Setting Timers for Spawning

In the SpawnVolume.h header file, we add 3 protected variables: a spawn timer, a minimum spawn delay and a maximum spawn delay.

FTimerHandle SpawnTimer;

/** Minimum spawn delay */
 UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Spawning")
 float SpawnDelayRangeLow;

/** Maximum spawn delay */
 UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Spawning")
 float SpawnDelayRangeHigh;

In the private section, we add the spawn delay variable. It is private, so it can’t be modified by other classes.

/** The current spawn delay */
 float SpawnDelay;

In the source file (SpawnVolume.cpp), we set default values for the spawn delay ranges in the constructor:

// Set the spawn delay range
 SpawnDelayRangeLow = 1.0f;
 SpawnDelayRangeHigh = 4.5f;

We modify the BeginPlay function, to start a timer:

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

	SpawnDelay = FMath::FRandRange(SpawnDelayRangeLow, SpawnDelayRangeHigh);
	GetWorldTimerManager().SetTimer(SpawnTimer, this, &ASpawnVolume::SpawnPickup, SpawnDelay, false);
	
}

We modify also the SpawnPickup function, to restart the timer at the end of the spawning:

void ASpawnVolume::SpawnPickup()
{
	// If we have set something to spawn:
	if (WhatToSpawn != NULL)
	{
		// Check for a valid World:
		UWorld* const World = GetWorld();
		if (World)
		{
			// Set the spawn parameters
			FActorSpawnParameters SpawnParams;
			SpawnParams.Owner = this;
			SpawnParams.Instigator = Instigator;

			// Get a random location to spawn at
			FVector SpawnLocation = GetRandomPointInVolume();

			// Get a random rotation for the spawned item
			FRotator SpawnRotation;
			SpawnRotation.Yaw = FMath::FRand() * 360.0f;
			SpawnRotation.Pitch = FMath::FRand() * 360.0f;
			SpawnRotation.Roll = FMath::FRand() * 360.0f;

			// Spawn the pickup
			APickup* const SpawnedPickup = World->SpawnActor(WhatToSpawn, SpawnLocation, SpawnRotation);

			SpawnDelay = FMath::FRandRange(SpawnDelayRangeLow, SpawnDelayRangeHigh);
			GetWorldTimerManager().SetTimer(SpawnTimer, this, &ASpawnVolume::SpawnPickup, SpawnDelay, false);
		}
	}
}

Back to Unreal Engine Editor, we compile and add a Spawn Volume in the level. We increase its size by 2.25, set the “What to Spawn” as Pickup_BP and the range for the delay between 2 and 6 seconds.

We add another Spawn Volume, increase its Y value by 8.75 and set set the “What to Spawn” as Battery_BP and the range for the delay between 0.5 and 2 seconds. Then we hit play and can see the different pickups spawned:

Next Step

In the next step, we will extend the Character class.