Version: 2017.3
public ParticleSystem.MinMaxCurve startSize ;

Description

The initial size of particles when emitted.

See Also: MinMaxCurve.

using UnityEngine;
using System.Collections;

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

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

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

void OnGUI() { hSliderValue = GUI.HorizontalSlider(new Rect(25, 45, 100, 30), hSliderValue, 0.0F, 10.0F); } }