using System;
using System.Collections;
using System.Collections.Generic;
using Unity.VisualScripting;
using UnityEngine;
using UnityEngine.Rendering;
//[ExecuteAlways]
public class RongMaoSkinMesh : MonoBehaviour
{
    public int Count = 0;
    //public Shader shader;
    [Header("渲染目标")]
    [SerializeField]
    private Renderer Target;
    public Shader BaseShader;

    [Header("皮毛物理")]
    public int LayerCount = 10;
    public float FurLength = 0.5f;
    public Vector3 FurFore;
    public Texture2D Noise;
    public Texture2D Noise2;
    public Texture2D MainTex;//毛发颜色
    public Texture2D Mask;//不产生毛发区域的灰度遮罩



    [Header("皮毛渲染")]
    //毛发染色
    public Color FurColor = Color.white;
    public Color ShadowColor = Color.white;
    [Range(0, 1)] public float ShadowStrength = 0.3f;
    [Range(0.01f, 1)] public float R = 0.5f;
    [Range(0, 3)] public float _LengthMut = 1;
    public float Density = 1;
    [Header("是否使用GPU实例化")]
    public bool isInStance = false;

    public bool ZWrite = true;
    public int RenderSort = 0;

    private bool skinHasValue = false;
    private Renderer target;
    //创建毛发
    private Mesh mesh;
    private Material layerMat;
    private SkinnedMeshRenderer skinnedMeshRenderer;
    private MaterialPropertyBlock mpb;

    private ComputeBuffer instanceBuffer;
    private Matrix4x4[] instanceMatrices;

    private bool isInit;
    void OnEnable()
    {
        isInit = Init();
    }
    //更新毛发渲染
    private void Update()
    {
        if (skinHasValue)
        {
            skinnedMeshRenderer.BakeMesh(mesh);
        }
    }
    void LateUpdate()
    {
        //目标为空就不渲染
        if (TargetChange() == false)
        {
            Debug.Log("返回");
            return;
        }
        isInStance = false;
        if (isInStance) UpDateInstance();
        else UpDateMesh();
    }


    bool TargetChange()
    {
        if (Target != target)
        {
            target = Target;
            isInit = Init();
        }
        return isInit;
    }

    //初始化毛发，返回是否初始化成功
    bool Init()
    {
        if (target.IsUnityNull()) return false;
        CreateFur();
        MeshInstancedData();
        if (target.GetType() == typeof(MeshRenderer))
        {
            mesh = target.GetComponent<MeshFilter>().sharedMesh;
            skinHasValue = false;
        }
        else
        {
            skinnedMeshRenderer = target.gameObject.GetComponent<SkinnedMeshRenderer>();
            skinHasValue = true;
        }

        return true;
    }

    //初始化网格、材质、SkinnedMeshRenderer
    void CreateFur()
    {
        mesh = new Mesh();
        layerMat = new Material(BaseShader);
        layerMat.SetTexture("_MainTex", MainTex);
        layerMat.SetColor("_Color", FurColor);
        layerMat.SetFloat("_FurLength", FurLength);
        layerMat.SetTexture("_Noise", Noise);
        layerMat.SetTexture("_Noise2", Noise2);
        layerMat.SetTexture("_Mask", Mask);
        layerMat.SetColor("_ShadowColor", ShadowColor);
        layerMat.SetFloat("_R", R);
        layerMat.SetFloat("_LayerCount", LayerCount);
        layerMat.SetInt("_ZWrite", ZWrite ? 1 : 0);
        layerMat.SetFloat("_Density", Density);
        layerMat.renderQueue = 3000 + RenderSort;

        mpb = new MaterialPropertyBlock();

    }


    void MeshInstancedData()
    {
        instanceMatrices = new Matrix4x4[LayerCount];
        layerMat.enableInstancing = true;
        // 随机生成实例的位置和旋转
        for (int i = 0; i < LayerCount; i++)
        {
            //Vector3 position = target.transform.position;
            //Quaternion rotation = target.transform.rotation;
            //Vector3 scale = Vector3.one;

            instanceMatrices[i] = target.transform.localToWorldMatrix;// //Matrix4x4.TRS(position, rotation, scale);
        }

    }

    //使用GPU实例化
    void UpDateInstance()
    {

       
        for (int i = 0; i < LayerCount; i++)
        {
            instanceMatrices[i] = target.transform.localToWorldMatrix;
        }
        layerMat.EnableKeyword("INSTANCE");
        Graphics.DrawMeshInstanced(mesh, 0, layerMat, instanceMatrices, LayerCount);
    }
    //未使用GPU实例化
    void UpDateMesh()
    {
        //if (skinHasValue)
        //{
        //    skinnedMeshRenderer.BakeMesh(mesh);
        //}

        layerMat.DisableKeyword("INSTANCE");
        float furOffset = 1.0f / LayerCount;
        for (int i = 0; i < LayerCount; i++)
        {
            mpb.SetFloat("_LayerOffset", i * furOffset);
            Graphics.DrawMesh(mesh, target.transform.localToWorldMatrix, layerMat, 0, Camera.main, 0, mpb);
        }

    }



}