ParticleSystem.CollisionModule.radiusScale

Description

A multiplier that Unity applies to the size of each particle before collisions are processed.

Useful for improving the visual accuracy of collisions, for example when there is an alpha border in the particle texture. Additional resources: ParticleSystem.collision.

using UnityEngine;
using System.Collections;

[RequireComponent(typeof(ParticleSystem))]
public class ExampleClass : MonoBehaviour
{
    private ParticleSystem ps;
    public float hSliderValue = 8.0F;

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

        var collision = ps.collision;
        collision.enabled = true;
        collision.type = ParticleSystemCollisionType.World;
        collision.mode = ParticleSystemCollisionMode.Collision3D;
        collision.dampen = 1.0f;

        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);
    }

    void Update()
    {
        var collision = ps.collision;
        collision.radiusScale = hSliderValue;
    }

    void OnGUI()
    {
        hSliderValue = GUI.HorizontalSlider(new Rect(25, 40, 100, 30), hSliderValue, 0.0F, 2.0F);
    }
}