# OnParticleTrigger()

> OnParticleTrigger is called when any particles in a Particle System meet the conditions in the trigger module.

## Definition

* **Type:** Method
* **Namespace:** [UnityEngine](/engine/6000.3/script-reference/unityengine.md)

```csharp
public void OnParticleTrigger()
```

### Remarks

This can be used to kill or modify particles that are inside or outside a collision volume.

### Examples

```csharp

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

public class TriggerScript : MonoBehaviour
{
    void OnParticleTrigger()
    {
        ParticleSystem ps = GetComponent<ParticleSystem>();

        // particles
        List<ParticleSystem.Particle> enter = new List<ParticleSystem.Particle>();
        List<ParticleSystem.Particle> exit = new List<ParticleSystem.Particle>();

        // get
        int numEnter = ps.GetTriggerParticles(ParticleSystemTriggerEventType.Enter, enter);
        int numExit = ps.GetTriggerParticles(ParticleSystemTriggerEventType.Exit, exit);

        // iterate
        for (int i = 0; i < numEnter; i++)
        {
            ParticleSystem.Particle p = enter[i];
            p.startColor = new Color32(255, 0, 0, 255);
            enter[i] = p;
        }
        for (int i = 0; i < numExit; i++)
        {
            ParticleSystem.Particle p = exit[i];
            p.startColor = new Color32(0, 255, 0, 255);
            exit[i] = p;
        }

        // set
        ps.SetTriggerParticles(ParticleSystemTriggerEventType.Enter, enter);
        ps.SetTriggerParticles(ParticleSystemTriggerEventType.Exit, exit);
    }
}
```