Synchronizing Destruction Events with Gameplay Triggers

In this lesson, you will learn how to bridge the gap between gameplay logic—like a projectile impact—and the Chaos Physics engine to trigger specific destruction effects.

The Bridge: Linking Logic to Chaos

Up until now, you have used Field System Actors as standalone objects placed in the world. To make destruction feel reactive, you must move that logic into your Gameplay Blueprint (e.g., your Projectile class). Instead of placing a Radial Falloff Field in the level, you will spawn it dynamically at the moment of impact.

When a projectile hits a Geometry Collection, you shouldn't just play a sound; you should execute a sequence that communicates with the Chaos system. You can achieve this by creating a reference to a Field System Actor or, more efficiently, spawning a Field System Component at the impact location using the Spawn Actor from Class node.

Implementing the Trigger

When your projectile’s OnComponentHit event fires, you need to pass the hit location into the Field System to ensure the physics force originates exactly where the impact occurred.

Conceptual Blueprint Logic:

1. Hit Event: Triggered by OnComponentHit of your projectile.
2. Location Data: Use the Hit Result pin to get the Impact Point.
3. Spawn Field: Use Spawn Actor from Class (selecting your custom Field System Actor) at the Impact Point.
4. Force Application: The Field System Actor, upon spawning, will immediately evaluate its internal Radial Vector Field or Radial Falloff against any Geometry Collections within its radius.

// Logic flow for an impact-triggered field
void AMyProjectile::OnHit(UPrimitiveComponent* HitComp, ...) {
    // Spawn the field at the exact point of impact
    GetWorld()->SpawnActor<AFieldSystemActor>(FieldClass, HitLocation, Rotation);
    
    // Destroy the projectile to prevent repeat triggers
    this->Destroy();
}

By spawning the field dynamically, you ensure that the destruction logic is localized, resource-efficient, and perfectly synchronized with gameplay events. This transforms a static destructible object into a reactive environment where every bullet strike can cause a unique, physics-driven fracture based on the impact location.

Key Takeaway: By spawning Field System Actors dynamically at the site of a gameplay collision, you allow physics-driven destruction to react precisely to player interaction.