Unity 预制体烘焙光影丢失，Unity2018 预制嵌套

Unity2018.3测试版发布后支持预制体嵌套……

问题：

1.unity场景烘焙后，再制作预制体后烘焙的光影丢失

2.如何将预制体的更改应用到各个子预制体

解决：

1.这个问题官方有解决，即是给每个需要加载的prefab添加PrefabLightmapData.cs脚本，但是这个脚本没有写完整，它只能在Non-Directional模式下可以正常工作，即没有加载Lightmap-_dir灯光贴图

2.在有嵌套的prefabs中，首先打开嵌套prefabs然后对各个子prefab执行applyAll操作，最后重新保存整个嵌套prefabs

3.本代码是在Unity2018.3.b3版本下编写的，部分api老版本有可能不一样（修改一下即可）

在官方代码基础上修改的代码如下：

using System.Collections;
using System.Collections.Generic;
using System.IO;
using UnityEditor;
using UnityEngine;
using VR403Works.Foundation.Extentions;

[DisallowMultipleComponent]
[ExecuteInEditMode]
public class PrefabLightmapData : MonoBehaviour
{

    [System.Serializable]
    struct RendererInfo
    {
        public Renderer renderer;
        public int lightmapIndex;
        public Vector4 lightmapOffsetScale;
    }

    [SerializeField]
    RendererInfo[] m_RendererInfo;
    [SerializeField]
    Texture2D[] m_LightmapsColor;
    [SerializeField]
    Texture2D[] _lightmapsDir;

    void Awake()
    {
        if (m_RendererInfo == null || m_RendererInfo.Length == 0)
            return;

        var lightmaps = LightmapSettings.lightmaps;
        var combinedLightmaps = new LightmapData[lightmaps.Length + m_LightmapsColor.Length];

        lightmaps.CopyTo(combinedLightmaps, 0);
        for (int i = 0; i < m_LightmapsColor.Length; i++)
        {
            combinedLightmaps[i + lightmaps.Length] = new LightmapData();
            combinedLightmaps[i + lightmaps.Length].lightmapColor = m_LightmapsColor[i];
            combinedLightmaps[i + lightmaps.Length].lightmapDir = _lightmapsDir[i];

        }

        ApplyRendererInfo(m_RendererInfo, lightmaps.Length);
        LightmapSettings.lightmaps = combinedLightmaps;
    }


    static void ApplyRendererInfo(RendererInfo[] infos, int lightmapOffsetIndex)
    {
        for (int i = 0; i < infos.Length; i++)
        {
            var info = infos[i];
            if (info.renderer != null)
            {
                info.renderer.lightmapIndex = info.lightmapIndex + lightmapOffsetIndex;
                info.renderer.lightmapScaleOffset = info.lightmapOffsetScale;
            }
        }
    }

#if UNITY_EDITOR
    [UnityEditor.MenuItem("VR403WorksTools/Bake Prefab Lightmaps")]
    static void GenerateLightmapInfo()
    {
        if (UnityEditor.Lightmapping.giWorkflowMode != UnityEditor.Lightmapping.GIWorkflowMode.OnDemand)
        {
            Debug.LogError("ExtractLightmapData requires that you have baked you lightmaps and Auto mode is disabled.");
            return;
        }
        UnityEditor.Lightmapping.Bake();

        PrefabLightmapData[] prefabs = GameObject.FindObjectsOfType<PrefabLightmapData>();

        foreach (var instance in prefabs)
        {
            var gameObject = instance.gameObject;
            var rendererInfos = new List<RendererInfo>();
            var lightmapsColor = new List<Texture2D>();
            List<Texture2D> lightmapsDir = new List<Texture2D>();

            GenerateLightmapInfo(gameObject, rendererInfos, lightmapsColor, lightmapsDir);

            instance.m_RendererInfo = rendererInfos.ToArray();
            instance.m_LightmapsColor = lightmapsColor.ToArray();
            instance._lightmapsDir = lightmapsDir.ToArray();


            var targetPrefab = PrefabUtility.GetCorrespondingObjectFromOriginalSource(instance.gameObject) as GameObject;
            if (targetPrefab != null)
            {
                GameObject root = PrefabUtility.GetOutermostPrefabInstanceRoot(instance.gameObject);                        // 根结点
                //如果当前预制体是是某个嵌套预制体的一部分（IsPartOfPrefabInstance）
                if (root != null)
                {
                    GameObject rootPrefab = PrefabUtility.GetCorrespondingObjectFromSource(instance.gameObject);
                    string rootPath = AssetDatabase.GetAssetPath(rootPrefab);
                    //打开根部预制体
                    PrefabUtility.UnpackPrefabInstanceAndReturnNewOutermostRoots(root, PrefabUnpackMode.OutermostRoot);
                    try
                    {
                        //Apply各个子预制体的改变
                        PrefabUtility.ApplyPrefabInstance(instance.gameObject, InteractionMode.AutomatedAction);
                    }
                    catch { }
                    finally
                    {
                        //重新更新根预制体
                        PrefabUtility.SaveAsPrefabAssetAndConnect(root, rootPath, InteractionMode.AutomatedAction);
                    }
                }
                else
                {
                    PrefabUtility.ApplyPrefabInstance(instance.gameObject, InteractionMode.AutomatedAction);
                }
            }
        }
    }

    static void GenerateLightmapInfo(GameObject root, List<RendererInfo> rendererInfos, List<Texture2D> lightmapsColor, List<Texture2D> lightmapsDir)
    {
        var renderers = root.GetComponentsInChildren<MeshRenderer>();
        foreach (MeshRenderer renderer in renderers)
        {
            if (renderer.lightmapIndex != -1)
            {
                RendererInfo info = new RendererInfo();
                info.renderer = renderer;
                if (renderer.lightmapScaleOffset != Vector4.zero)
                {
                    info.lightmapOffsetScale = renderer.lightmapScaleOffset;
                    Texture2D lightmapColor = LightmapSettings.lightmaps[renderer.lightmapIndex].lightmapColor;
                    Texture2D lightmapDir = LightmapSettings.lightmaps[renderer.lightmapIndex].lightmapDir;

                    info.lightmapIndex = lightmapsColor.IndexOf(lightmapColor);
                    if (info.lightmapIndex == -1)
                    {
                        info.lightmapIndex = lightmapsColor.Count;
                        lightmapsColor.Add(lightmapColor);
                        lightmapsDir.Add(lightmapDir);
                    }

                    rendererInfos.Add(info);
                }

            }
        }
    }
#endif
}