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

public class CombineSkinMesh : MonoBehaviour
{
    public SkinnedMeshRenderer Body;
    public SkinnedMeshRenderer Kuzi;
    public SkinnedMeshRenderer Shangyi;

    public SkinnedMeshRenderer[] Clothes;
    
    // Start is called before the first frame update
    void Start()
    {
        //StartCombine();
    }

    // Update is called once per frame
    void Update()
    {
        
    }

    public void StartCombine()
    {
        Debug.Log("Combine");
        //SkinnedMeshRenderer[] meshes = new SkinnedMeshRenderer[] {  Shangyi };
        CombineObject(Body.rootBone.gameObject, Clothes);
    }

    /// <summary>
    /// Only for merge materials.
    /// </summary>
    private const int COMBINE_TEXTURE_MAX = 512;
    private const string COMBINE_DIFFUSE_TEXTURE = "_MainTex";

    /// <summary>
    /// Combine SkinnedMeshRenderers together and share one skeleton.
    /// Merge materials will reduce the drawcalls, but it will increase the size of memory. 
    /// </summary>
    /// <param name="skeleton">combine meshes to this skeleton(a gameobject)</param>
    /// <param name="meshes">meshes need to be merged</param>
    /// <param name="combine">merge materials or not</param>
	public void CombineObject(GameObject skeleton, SkinnedMeshRenderer[] meshes, bool combine = false)
    {

        // 收集所有关于skeleton的骨骼
        List<Transform> transforms = new List<Transform>();
        transforms.AddRange(skeleton.GetComponentsInChildren<Transform>(true));

        List<Material> materials = new List<Material>();//材质
        List<CombineInstance> combineInstances = new List<CombineInstance>();//网格
        List<Transform> bones = new List<Transform>();//骨骼

        // 下面的信息只用来合并材质(bool combine = true)
        List<Vector2[]> oldUV = null;
        Material newMaterial = null;
        Texture2D newDiffuseTex = null;

        // 收集网格部分信息
        for (int i = 0; i < meshes.Length; i++)
        {
            SkinnedMeshRenderer smr = meshes[i];
            // 收集材质
            materials.AddRange(smr.sharedMaterials);
            // 收集网格
            for (int sub = 0; sub < smr.sharedMesh.subMeshCount; sub++)
            {
                CombineInstance ci = new CombineInstance();
                ci.mesh = smr.sharedMesh;
                ci.subMeshIndex = sub;
                combineInstances.Add(ci);
            }
            // 收集骨骼
            for (int j = 0; j < smr.bones.Length; j++)
            {
                int tBase = 0;
                for (tBase = 0; tBase < transforms.Count; tBase++)
                {
                    if (smr.bones[j].name.Equals(transforms[tBase].name))
                    {
                        bones.Add(transforms[tBase]);
                        break;
                    }
                }
            }
        }

        // 合并材质
        if (combine)
        {
            newMaterial = new Material(Shader.Find("Mobile/Diffuse"));
            oldUV = new List<Vector2[]>();
            // 合并贴图
            List<Texture2D> Textures = new List<Texture2D>();
            for (int i = 0; i < materials.Count; i++)
            {
                Textures.Add(materials[i].GetTexture(COMBINE_DIFFUSE_TEXTURE) as Texture2D);
            }

            newDiffuseTex = new Texture2D(COMBINE_TEXTURE_MAX, COMBINE_TEXTURE_MAX, TextureFormat.RGBA32, true);
            Rect[] uvs = newDiffuseTex.PackTextures(Textures.ToArray(), 0);
            newMaterial.mainTexture = newDiffuseTex;

            // 重置uv贴图
            Vector2[] uva, uvb;
            for (int j = 0; j < combineInstances.Count; j++)
            {
                uva = (Vector2[])(combineInstances[j].mesh.uv);
                uvb = new Vector2[uva.Length];
                for (int k = 0; k < uva.Length; k++)
                {
                    uvb[k] = new Vector2((uva[k].x * uvs[j].width) + uvs[j].x, (uva[k].y * uvs[j].height) + uvs[j].y);
                }
                oldUV.Add(combineInstances[j].mesh.uv);
                combineInstances[j].mesh.uv = uvb;
            }
        }

        // 创建新的SkinnedMeshRenderer
        SkinnedMeshRenderer oldSKinned = skeleton.GetComponent<SkinnedMeshRenderer>();
        if (oldSKinned != null)
        {

            GameObject.DestroyImmediate(oldSKinned);
        }
        SkinnedMeshRenderer r = skeleton.AddComponent<SkinnedMeshRenderer>();
        r.sharedMesh = new Mesh();
        r.sharedMesh.CombineMeshes(combineInstances.ToArray(), combine, false);// 合并网格
        r.sharedMesh.name = "newMesh";
        r.bones = bones.ToArray();// 使用新骨骼
        if (combine)
        {
            r.material = newMaterial;
            for (int i = 0; i < combineInstances.Count; i++)
            {
                combineInstances[i].mesh.uv = oldUV[i];
            }
        }
        else
        {
            r.materials = materials.ToArray();
        }
    }
}