GunSystem/Assets/particleSystem/Almgp_particle_vol_1/script/sprite_sheet.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

[ExecuteInEditMode]
public class sprite_sheet : MonoBehaviour 
{
	public int _uvTieX = 1;
	public int _uvTieY = 1;
	public int _fps = 10;
 
	private Vector2 _size;
	private Renderer _myRenderer;
	private int _lastIndex = -1;
 
	void Start () 
	{
		_size = new Vector2 (1.0f / _uvTieX , 1.0f / _uvTieY);
		_myRenderer = GetComponent<Renderer>();
		if(_myRenderer == null)
			enabled = false;
	}
	// Update is called once per frame
	void Update()
	{
		// Calculate index
		int index = (int)(Time.timeSinceLevelLoad * _fps) % (_uvTieX * _uvTieY);
    	if(index != _lastIndex)
		{
			// split into horizontal and vertical index
			int uIndex = index % _uvTieX;
			int vIndex = index / _uvTieY;
 
			// build offset
			// v coordinate is the bottom of the image in opengl so we need to invert.
			Vector2 offset = new Vector2 (uIndex * _size.x, 1.0f - _size.y - vIndex * _size.y);
 
			_myRenderer.material.SetTextureOffset ("_MainTex", offset);
			_myRenderer.material.SetTextureScale ("_MainTex", _size);
 
			_lastIndex = index;
		}
	}
}