Preventing Overlapping Spawns: Ensuring Enemies Don't Stack Up| Author: Antony Castro| Posted on: July 18, 2025

This week, a noticeable issue emerged when I created the enemy spawner: newly spawned enemies were frequently appearing on top of each other, creating a chaotic and unrealistic pile-up. This wasn't just a visual glitch; it often led to enemies getting stuck, exhibiting strange movement behaviors, or even becoming unhittable due to their overlapping collision volumes. This problem was particularly evident when multiple enemies were spawned in quick succession or when the designated spawn area was slightly constrained. This problem would significantly degrade the end-user experience. Players would encounter enemies that looked unnatural, behaved erratically. It undermined the sense of a believable and challenging combat environment, making the game feel unpolished and frustrating.

The core of the "enemies spawning on top of each other" issue stemmed from the default spawn parameters used by our ACodeSpawner class. Previously, when SpawnActor was called, the SpawnCollisionHandlingOverride was set to ESpawnActorCollisionHandlingMethod::AdjustIfPossibleButAlwaysSpawn. This setting, while ensuring an actor always spawns, would force the new enemy into existence even if its initial spawn location was already occupied by another character or obstacle, leading to the undesirable overlapping.

To address this, I modified the SpawnCollisionHandlingOverride within the ACodeSpawner::SpawnAgent function. I changed it to ESpawnActorCollisionHandlingMethod::AdjustIfPossibleButDontSpawnIfColliding. This crucial change instructs the engine to attempt to adjust the spawn location if there's a minor collision, but if it cannot find a clear spot without colliding, it will simply fail to spawn the actor. This prevents enemies from being forced into overlapping positions. Additionally, I ensured that the spawn location for the enemies was explicitly set to the SpawnPoint component's world location, which is a USceneComponent attached to the SpawnerMesh (the truck model). This SpawnPoint can be precisely positioned in the Blueprint editor to ensure enemies emerge from a clear, designated spot, such as the back of the truck, rather than the truck's main collision.

This solution drastically improves the end-user experience by eliminating the visual and gameplay issues caused by overlapping enemies. Enemies now appear cleanly in the world, behave as expected from the moment they spawn, and contribute to a more polished and believable combat simulation.