ParticleCollisionEvent OnParticleCollision

[tooomg]

If you want it to trigger only once per particle, you can store the list of the already-processed particles in a HashSet within the class handling the collision (or anywhere you see fit). For each collision, you would check if contact.particle is not present in the set and then proceed with your collision logic, and then add the contact.particle ID into the HashSet for it to not be proceed ever again

Cheers