Why does my Niagara collision event not spawn debris?

The receiving emitter needs Receive Collision Event Reader in its Event Handler stack and the source emitter must Generate Collision Event. Without the reader, events are emitted but no handler consumes them.

Event names mismatch?

The reader filters by source emitter name. If you renamed the emitter generating the event, update the reader's source field to match. Default lookup is by emitter name string.

Each event spawns once via Spawn Particles From Other Emitter. To produce N particles per collision, set the spawn count parameter on that module.

Fix: Niagara Event Handler No Spawn On Collision

Quick answer: Source emitter: Generate Collision Event. Receiver emitter: Receive Collision Event Reader + Spawn Particles From Other Emitter. Names must match.

Bullet hits wall. Niagara fires a collision event. Debris emitter does nothing. The reader half of the chain is missing or wired to the wrong source.

The Symptom

Event count visible in the Niagara Debugger; receiver emitter never spawns particles.

The Fix

SourceEmitter (sparks):
  Particle Update:
    + Generate Collision Event
        Use Physics Material:  true
        Max Events Per Frame:  16

ReceiverEmitter (debris):
  Event Handler Stack:
    + Receive Collision Event Reader
        Source Emitter Name:   "sparks"   // must match exactly
        Execution Mode:        Spawn
  Particle Spawn:
    + Spawn Particles From Other Emitter
        Source:                "sparks"
        Spawn Count:           8      // per event

Source emits, reader picks up, spawn count fires per event. Stage matters: reader on the receiver, generator on the source.

Verifying

Open Niagara Debugger. Show Event Counts. Source generates events; receiver consumes them. Particle count on debris jumps with each collision.

“Source generates. Reader receives. Names match. Debris spawns.”

Related Issues

For Niagara spawn rate curve, see spawn curve. For RenderTarget2D clearing, see render target.

Generate. Read. Match names. Events flow.