ParticleSystem.LightsModule.alphaAffectsIntensity

Description

Toggle whether the system multiplies the particle alpha by the light intensity when it computes the final light intensity.

This is useful to fade the Lights out at the same time as the particles, to avoid popping.

using UnityEngine;
using System.Collections;

// For best results, use Deferred Rendering (see Camera settings)
[RequireComponent(typeof(ParticleSystem))]
public class ExampleClass : MonoBehaviour
{
    private ParticleSystem ps;
    public Light lightPrefab;     // Provide a light Prefab in the inspector (eg a default Point Light)
    public float hSliderValueA = 1.0f;
    public bool alphaAffectsIntensity = true;

    void Start()
    {
        ps = GetComponent<ParticleSystem>();
        ps.transform.localRotation = Quaternion.Euler(0.0f, 0.0f, 45.0f);

        var shape = ps.shape;
        shape.shapeType = ParticleSystemShapeType.Circle;

        var lights = ps.lights;
        lights.enabled = true;
        lights.light = lightPrefab;
        lights.ratio = 1.0f;
        lights.maxLights = 1000;

        // plane to receive lights
        var plane = GameObject.CreatePrimitive(PrimitiveType.Plane);
        plane.transform.parent = ps.transform;
        plane.transform.localPosition = new Vector3(0.0f, 0.0f, 3.0f);
        plane.transform.localScale = new Vector3(20.0f, 20.0f, 20.0f);
        plane.transform.localRotation = Quaternion.Euler(-90.0f, 0.0f, 0.0f);

        var material = new Material(Shader.Find("Standard"));
        material.color = new Color(0.1f, 0.1f, 0.1f, 1.0f);
        plane.GetComponent<MeshRenderer>().material = material;
    }

    void Update()
    {
        var lights = ps.lights;
        lights.alphaAffectsIntensity = alphaAffectsIntensity;

        var main = ps.main;
        main.startColor = new Color(1.0f, 1.0f, 1.0f, hSliderValueA);
    }

    void OnGUI()
    {
        GUI.Label(new Rect(25, 40, 100, 30), "Alpha");

        hSliderValueA = GUI.HorizontalSlider(new Rect(95, 45, 100, 30), hSliderValueA, 0.0f, 1.0f);
        alphaAffectsIntensity = GUI.Toggle(new Rect(25, 85, 200, 30), alphaAffectsIntensity, "Particle Alpha Affects Light Intensity");
    }
}