ParticleSystem.SizeOverLifetimeModule.sizeMultiplier

Description

Size multiplier.

This method is more efficient than accessing the whole curve, if you only want to change the overall size multiplier.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour
{
    private ParticleSystem ps;
    public float hSliderValue = 1.0f;

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

        var sizeOverLifetime = ps.sizeOverLifetime;
        sizeOverLifetime.enabled = true;
        sizeOverLifetime.sizeMultiplier = 1.0f;

        var psr = GetComponent<ParticleSystemRenderer>();
        psr.material = new Material(Shader.Find("Sprites/Default"));    // this material renders a square billboard, making it easier to see the size
    }

    void Update()
    {
        var main = ps.main;
        main.startLifetimeMultiplier = hSliderValue;
    }

    void OnGUI()
    {
        hSliderValue = GUI.HorizontalSlider(new Rect(25, 45, 100, 30), hSliderValue, 1.0f, 5.0f);
    }
}