unity实现屏幕上写字效果

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

public class huaxian : MonoBehaviour 
{

private GameObject clone;
private LineRenderer line;
int i;

//带有LineRender物体
public GameObject target;

void Start()
{
  Debug.Log("请开始写字");
} 

// Update is called once per frame 
 void Update()
{
  if (Input.GetMouseButtonDown(0))
  {
    //实例化对象 
    clone = (GameObject)Instantiate(target, target.transform.position, Quaternion.identity);
    //获得该物体上的LineRender组件 
    line = clone.GetComponent<LineRenderer>();
    //设置起始和结束的颜色 
    line.SetColors(Color.red, Color.blue);
    //设置起始和结束的宽度  
    line.SetWidth(0.2f, 0.1f);
    //计数  
    i = 0;
  }
   if (Input.GetMouseButton(0))
  {
    //每一帧检测，按下鼠标的时间越长，计数越多 
    i++;
    //设置顶点数 
    line.SetVertexCount(i);
    //设置顶点位置(顶点的索引，将鼠标点击的屏幕坐标转换为世界坐标) 
    line.SetPosition(i - 1, Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, 15)));
  }
 }
 
}