unity 3d 之合并网格和贴图(combine mesh and texture)

　　本人是个小白，但是有个做技术的理想。

　　关于合并网格和贴图这个问题困扰了我好久，问群友，逛论坛，翻帖子，或者说是我的愚笨吧，不过经过努力还是我解决了，测试通过，一个8drawcall的模型，合并后降到2drawcall，当然现在移动设备的性能都比较高了，不必过多纠结于drawcall，如果没这需要请路过吧。。。

　　好的，废话不多说，我把代码贴出来。

using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using System.IO;

public class CombineMesher : MonoBehaviour
{
    // Use this for initialization
    void Start()
    {
        Combine(transform);
    }

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

    }


    public Transform Combine(Transform root)
    {
        float startTime = Time.realtimeSinceStartup;

        // The SkinnedMeshRenderers that will make up a character will be
        // combined into one SkinnedMeshRenderers using one material.
        // This will speed up rendering the resulting character.
        // note:each SkinnedMeshRenderer must share a same material
        List<CombineInstance> combineInstances = new List<CombineInstance>();
        List<Material> materials = new List<Material>();
        Material material = null;
        List<Transform> bones = new List<Transform>();
        Transform[] transforms = root.GetComponentsInChildren<Transform>();
        List<Texture2D> textures = new List<Texture2D>();
        int width = 0;
        int height = 0;

        int uvCount = 0;

        List<Vector2[]> uvList = new List<Vector2[]>();

        foreach (SkinnedMeshRenderer smr in root.GetComponentsInChildren<SkinnedMeshRenderer>())
        {
            if (material == null)
                material = Instantiate(smr.sharedMaterial) as Material;
            for (int sub = 0; sub < smr.sharedMesh.subMeshCount; sub++)
            {
                CombineInstance ci = new CombineInstance();
                ci.mesh = smr.sharedMesh;
                ci.subMeshIndex = sub;
                combineInstances.Add(ci);
            }

            uvList.Add(smr.sharedMesh.uv);
            uvCount += smr.sharedMesh.uv.Length;

            if (smr.material.mainTexture != null)
            {
                textures.Add(smr.renderer.material.mainTexture as Texture2D);
                width += smr.renderer.material.mainTexture.width;
                height += smr.renderer.material.mainTexture.height;
            }

            // we need to recollect references to the bones we are using
            foreach (Transform bone in smr.bones)
            {
                foreach (Transform transform in transforms)
                {
                    if (transform.name != bone.name) continue;
                    bones.Add(transform);
                    break;
                }
            }
            Object.Destroy(smr.gameObject);
        }

        // Obtain and configure the SkinnedMeshRenderer attached to
        // the character base.
        SkinnedMeshRenderer r = root.gameObject.GetComponent<SkinnedMeshRenderer>();
        if (!r)
            r = root.gameObject.AddComponent<SkinnedMeshRenderer>();
        
        r.sharedMesh = new Mesh();

        //only set mergeSubMeshes true will combine meshs into single submesh
        r.sharedMesh.CombineMeshes(combineInstances.ToArray(), true, false);
        r.bones = bones.ToArray();
        r.material = material;

        Texture2D skinnedMeshAtlas = new Texture2D(1024, 512);
        Rect[] packingResult = skinnedMeshAtlas.PackTextures(textures.ToArray(), 0);
        Vector2[] atlasUVs = new Vector2[uvCount];

        //as combine textures into single texture,so need recalculate uvs

        int j = 0;        
        for (int i = 0; i < uvList.Count; i++)
        {
            foreach (Vector2 uv in uvList[i])
            {
                atlasUVs[j].x = Mathf.Lerp(packingResult[i].xMin, packingResult[i].xMax, uv.x);
                atlasUVs[j].y = Mathf.Lerp(packingResult[i].yMin, packingResult[i].yMax, uv.y);
                j++;
            }
        }
        
        r.material.mainTexture = skinnedMeshAtlas;
        r.sharedMesh.uv = atlasUVs;

        Debug.Log("combine meshes takes : " + (Time.realtimeSinceStartup - startTime) * 1000 + " ms");
        return root;
    }
}