Question need help collisionEvents ?

I use a particle system for a rain effect. What I want is when a single particle collides with my floor, a good effect spawns at the position. I attached this script to the floor.
numCollisionEvents is always 0. I have no idea what is going on. oh..!





using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class rainEffect_floor : MonoBehaviour
{
public GameObject effect;
public ParticleSystem ps;
public List<ParticleCollisionEvent> collisionEvents;

void Start()
{
collisionEvents = new List<ParticleCollisionEvent>();

}

void OnParticleCollision(GameObject other)
{



int numCollisionEvents = ps.GetCollisionEvents(other, collisionEvents);
Debug.Log(numCollisionEvents);

for (int i = 0; i < numCollisionEvents; i++)
{

Instantiate(effect, collisionEvents.intersection, Quaternion.identity);
}
}
}

 

I.. really need some help. Cause my brain doesn't work

 

Did u check collision and also send collision messages under it in particle system?