ParticleSystem.LightsModule.alphaAffectsIntensity

Description

Toggle whether the particle alpha gets multiplied by the light intensity, when computing the final light intensity.

Useful for fading 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)
public class ExampleClass : MonoBehaviour
{
    private ParticleSystem ps;
    public Light light;     // 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 = light;
        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");
    }
}