Unity游戏开发——画出有物理效果的线

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

namespace Starry
{
    public class DrawLine : MonoBehaviour
    {
        public Material line;
        public bool gravity;
        public Color lineColor = Color.white;
        
        private List<GameObject> lineList = new List<GameObject>();
        private List<Vector2> pointList = new List<Vector2>();
        private GameObject currentLine;
        private LineRenderer currentLineRenderer;

        private bool stopHolding;
        private static readonly int EmissionColor = Shader.PropertyToID("_EmissionColor");

        private void Update()
        {
            if (Input.GetMouseButtonDown(0))
            {
                pointList.Clear();
                CreateLine();
            }

            if (Input.GetMouseButton(0))
            {
                Vector2 item = Camera.main.ScreenToWorldPoint(Input.mousePosition);
                if (!pointList.Contains(item))
                {
                    pointList.Add(item);
                    currentLineRenderer.positionCount = pointList.Count;
                    currentLineRenderer.SetPosition(pointList.Count - 1, pointList.Last());
                    if (pointList.Count >= 2)
                    {
                        Vector2 vector1 = pointList[pointList.Count - 2];
                        Vector2 vector2 = pointList[pointList.Count - 1];

                        GameObject currentCollierObject = new GameObject("Collider");
                        currentCollierObject.transform.position = (vector1 + vector2) / 2f;
                        currentCollierObject.transform.right = (vector2 - vector1).normalized;
                        currentCollierObject.transform.parent = currentLine.transform;
                        BoxCollider2D currentBoxCollider2D = currentCollierObject.AddComponent<BoxCollider2D>();
                        currentBoxCollider2D.size = new Vector3((vector2 - vector1).magnitude, 0.1f, 0.1f);
                        currentBoxCollider2D.enabled = false;
                    }
                }
            }
            
            if (Input.GetMouseButtonUp(0))
            {
                if (currentLine.transform.childCount > 0)
                {
                    for (int i = 0; i < currentLine.transform.childCount; i++)
                    {
                        currentLine.transform.GetChild(i).GetComponent<BoxCollider2D>().enabled = true;
                    }

                    lineList.Add(currentLine);

                    if (gravity)
                    {
                        currentLine.AddComponent<Rigidbody2D>().useAutoMass = true;
                    }
                }
                else
                {
                    Destroy(currentLine);
                }
            }
        }

        private void CreateLine()
        {
            currentLine = new GameObject("Line");
            currentLineRenderer = currentLine.AddComponent<LineRenderer>();
            currentLineRenderer.material = line;
            currentLineRenderer.material.EnableKeyword("_EMISSION");
            currentLineRenderer.material.SetColor(EmissionColor, this.lineColor);
            currentLineRenderer.positionCount = 0;
            currentLineRenderer.startWidth = 0.1f;
            currentLineRenderer.endWidth = 0.1f;
            currentLineRenderer.startColor = lineColor;
            currentLineRenderer.endColor = lineColor;
            currentLineRenderer.useWorldSpace = false;
        }

        public void ClearAll()
        {
            foreach (var obj in lineList)
            {
                Destroy(obj);
            }
            lineList.Clear();
        }
    }
}