unity 2d auto shadow caster 2d at wall-closed tilemap - 2d

Question

https://www.youtube.com/watch?v=0F8boyFinOk&t=12s
While making a roguelike game with Unity2d, I applied an automatic shadow generator to a randomly generated tilemap from the video above. But it doesn't work for tilemaps that are closed due to using the CompositeCollider2d's Path. How do I solve it?
Generated Shadow Shape(outer)
Generated Shadow Shape(inner)

Answer 1

Solved with this code:
using System.Linq;
using System.Reflection;
using UnityEngine;
using UnityEngine.Rendering.Universal;
using System.Collections.Generic;
[RequireComponent(typeof(CompositeCollider2D))]
public class AutoShadowClosedTilemap : MonoBehaviour
{
[Space]
[SerializeField]
private bool selfShadows = true;
private CompositeCollider2D tilemapCollider;
private List<Vector2> unionVertices = new();
static readonly FieldInfo meshField = typeof(ShadowCaster2D).GetField("m_Mesh", BindingFlags.NonPublic | BindingFlags.Instance);
static readonly FieldInfo shapePathField = typeof(ShadowCaster2D).GetField("m_ShapePath", BindingFlags.NonPublic | BindingFlags.Instance);
static readonly MethodInfo generateShadowMeshMethod = typeof(ShadowCaster2D)
.Assembly
.GetType("UnityEngine.Rendering.Universal.ShadowUtility")
.GetMethod("GenerateShadowMesh", BindingFlags.Public | BindingFlags.Static);
[ContextMenu("Generate")]
public void Generate()
{
tilemapCollider = GetComponent<CompositeCollider2D>();
if(tilemapCollider.pathCount != 2) {
print("Shadow must be used in one closed tiles. Please erase the other tiles to other Tilemap.");
return;
}
unionVertices.Clear();
DestroyAllChildren();
Vector2[] pathVertices = new Vector2[tilemapCollider.GetPathPointCount(0)];
tilemapCollider.GetPath(0, unionVertices);
tilemapCollider.GetPath(1, pathVertices);
var index = 0;
var endPath = unionVertices[unionVertices.Count - 1];
var length = Vector2.Distance(pathVertices[0], endPath);
for(var i = 1; i < pathVertices.Length; i++) {
var path = pathVertices[i];
var curLen = Vector2.Distance(endPath, path);
if(curLen < length) {
length = curLen;
index = i;
}
}
for(var i = 0; i < pathVertices.Length; i++) {
var path = pathVertices[(i + index) % pathVertices.Length];
unionVertices.Add(path);
}
for(var i = 0; i < unionVertices.Count; i++) {
var cur = unionVertices[i];
var next = unionVertices[(i + 1) % unionVertices.Count];
Debug.DrawLine(cur, cur + (next - cur) * 0.5f, Color.red);
}
var shadowCaster = new GameObject("ShadowCaster");
shadowCaster.transform.parent = gameObject.transform;
shadowCaster.transform.position = Vector3.zero;
ShadowCaster2D shadowCasterComponent = shadowCaster.AddComponent<ShadowCaster2D>();
shadowCasterComponent.selfShadows = this.selfShadows;
var testPath = new Vector3[unionVertices.Count];
var j = 0;
foreach (var path in unionVertices)
{
testPath[j++] = path;
}
shapePathField.SetValue(shadowCasterComponent, testPath);
meshField.SetValue(shadowCasterComponent, new Mesh());
generateShadowMeshMethod.Invoke(shadowCasterComponent, new object[] { meshField.GetValue(shadowCasterComponent), shapePathField.GetValue(shadowCasterComponent) });
Debug.Log("Shadow Generated");
}
public void DestroyAllChildren()
{
var tempList = transform.Cast<Transform>().ToList();
foreach (var child in tempList)
{
DestroyImmediate(child.gameObject);
}
}
}