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;
    [Header("是否使用GPU实例化")]
    public bool isInStance = false;
    
    
    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
    void LateUpdate()
    {
        //目标为空就不渲染
        if(TargetChange()==false) return;
        
        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.renderQueue = 3000;
        
        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] = Matrix4x4.TRS(position, rotation, scale);
        }
     
    }
    
    //使用GPU实例化
    void UpDateInstance()
    {
       
        if (skinHasValue)
        {
            skinnedMeshRenderer.BakeMesh(mesh);
        }
        
        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);
        }
        
    }


    
}