ParticleSystem.CollisionModule.type

Description

The type of particle collision to perform.

Here is an example of plane collsiion:

using UnityEngine;
using System.Collections;

[RequireComponent(typeof(ParticleSystem))]
public class ExampleClass : MonoBehaviour
{
    private ParticleSystem ps;

    void Start()
    {
        ps = GetComponent<ParticleSystem>();

        var collision = ps.collision;
        collision.enabled = true;
        collision.type = ParticleSystemCollisionType.Planes;
        collision.mode = ParticleSystemCollisionMode.Collision3D;

        var collider = GameObject.CreatePrimitive(PrimitiveType.Plane);
        collider.transform.parent = ps.transform;
        collider.transform.localPosition = new Vector3(0.0f, 0.0f, 5.0f);
        collider.transform.localScale = new Vector3(20.0f, 20.0f, 20.0f);
        collider.transform.localRotation = Quaternion.Euler(new Vector3(-90.0f, 0.0f, 0.0f));

        collision.SetPlane(0, collider.transform);
    }
}

Here is an example of world collision:

using UnityEngine;
using System.Collections;

[RequireComponent(typeof(ParticleSystem))]
public class ExampleClass : MonoBehaviour
{
    private ParticleSystem ps;

    void Start()
    {
        ps = GetComponent<ParticleSystem>();

        var collision = ps.collision;
        collision.enabled = true;
        collision.type = ParticleSystemCollisionType.World;
        collision.mode = ParticleSystemCollisionMode.Collision3D;

        var collider = GameObject.CreatePrimitive(PrimitiveType.Sphere);
        collider.transform.parent = ps.transform;
        collider.transform.localPosition = new Vector3(0.0f, 0.0f, 13.0f);
        collider.transform.localScale = new Vector3(20.0f, 20.0f, 20.0f);
    }
}