（转）【风宇冲】Unity3D教程宝典之AssetBundles:第一讲

自：http://blog.sina.com.cn/s/blog_471132920101gz8z.html

原创文章如需转载请注明：转载自风宇冲Unity3D教程学院

       

                                     AssetBundles第一讲：基本使用

AssetBundles是从unity导出你选择的assets,它使用特有的压缩格式并且应用可以实时去读取它。包括模型贴图音频等任何asset类型，甚至整个场景。压缩大小基本能达到zip的效果。AssetBundles从设计时就定位为可以很简单就下载到应用里。如果你想包括自定义的binary数据，就要用.bytes后缀，Unity将作为TextAssets导入他们。

 

注意:

AssetBundles并不像Unity官方说的那样，各种unity版本兼容。经测试在unity4中创建的ab,在4中正常使用，但在3.5.0里无法正常使用。说明用AB不能向下兼容。

开发阶段:
(1)创建AssetBundles:
不能是scene objects的objects使用BuildPipeline.BuildAssetBundle 

targetplatform要指定，不能用默认参数，默认模式是webplayer
 

1. using UnityEngine;
2. using UnityEditor;
3. public class ExportAssetBundles {
4.     [MenuItem("Assets/Build AssetBundle From Selection - Track dependencies")]
5.     static void ExportResource () {
6.         // Bring up save panel
7.         string path = EditorUtility.SaveFilePanel ("Save Resource", "", "New Resource","unity3d");
8.         if (path.Length != 0) {
9.             // Build the resource file from the active selection.
10.             Object[] selection = Selection.GetFiltered(typeof(Object), SelectionMode.DeepAssets);
11.             BuildPipeline.BuildAssetBundle(Selection.activeObject, selection, 
12. path, BuildAssetBundleOptions.CollectDependencies |BuildAssetBundleOptions.CompleteAssets
13. ,BuildTarget.StandaloneWindows);
14.             Selection.objects = selection;
15.         }
16.     }
17.     [MenuItem("Assets/Build AssetBundle From Selection - No dependency tracking")]
18.     static void ExportResourceNoTrack () {
19.         // Bring up save panel
20.         string path = EditorUtility.SaveFilePanel ("Save Resource", "", "New Resource","unity3d");
21.         if (path.Length != 0) {
22.             // Build the resource file from the active selection.
23.             BuildPipeline.BuildAssetBundle(Selection.activeObject, Selection.objects, path);
24.         }
25.     }
26. }

bool BuildPipeline.BuildAssetBundleExplicitAssetNames(Object[] assets, string[] assetName, string pathName, BuildAssetBundleOptions assetBundleOptions, Buildtarget targetPlatform)
创建bundle并自定义名称。assetName的长度及排列与assets对应。并不是真正改变物体的名称，只是在assetBundle.Load的时候有个唯一对应的名称

 

对上面代码仅需修改第11行。将BuildPipeline.BuildAssetBundle(Selection.activeObject, selection, 

path, BuildAssetBundleOptions.CollectDependencies | BuildAssetBundleOptions.CompleteAssets

,BuildTarget.StandaloneWindows); 里的第一个参数mainAsset去掉，并在selection也就是Object[]之后加string[] assetName即可

 

1. [MenuItem("Assets/Build AssetBundle From Selection Names- Track dependencies")]
2.     static void ExportResourceWithNames () {
3.         // Bring up save panel
4.         string path = EditorUtility.SaveFilePanel ("Save Resource", "", "New Resource","unity3d");
5.         if (path.Length != 0) {
6.             // Build the resource file from the active selection.
7.             Object[] selection = Selection.GetFiltered(typeof(Object), SelectionMode.DeepAssets);
8. string[] names = new string[selection.Length];
9. for(int i =0;i
10. {
11. names[i] = i+"_"+ selection[i].name;
12. }
13.             BuildPipeline.BuildAssetBundleExplicitAssetNames( selection,names, 
14. path, BuildAssetBundleOptions.CollectDependencies |BuildAssetBundleOptions.CompleteAssets
15. ,BuildTarget.StandaloneWindows);
16.             Selection.objects = selection;
17.         }
18.     }

 

 

 

 

1. using System;
2. using System.IO;
3. using UnityEngine;
5. public class LoadAssetBundle : MonoBehaviour {
6. private AssetBundle assetBundle;
7. private AssetBundleCreateRequest request;
9. void Update () {
10. }
11. void OnGUI()
12. {
13. if(GUI.Button(new Rect(0,0,100,50),"Load"))
14. {
15. byte[] bs = File.ReadAllBytes(Application.dataPath+ "/withNames.unity3d");
16. request = AssetBundle.CreateFromMemory(bs);
17. }
18. if(GUI.Button(new Rect(0,50,100,50),"Check"))
19. {
20. if(request.isDone == true)
21. {
22. assetBundle = request.assetBundle;
23. UnityEngine.Object obj = assetBundle.Load("0_Cube");
24. Instantiate(obj);
25. }
26. }
27. }

将场景做成AB时，BuildPipeline.BuildStreamedSceneAssetBundle

将一个或者多个场景打包到asset bundle里，可以为任何平台，并总创建单一的压缩.unity3d文件。

在下载后，可以用WWW.LoadFromCacheOrDownload从缓存里读取。 

1. using UnityEngine;
2. using UnityEditor;
4. public class BuildScene : MonoBehaviour {
5. [MenuItem ("Build/BuildWebplayerStreamed")]
6. static void BuildScenes()
7. {
8. string [] levels = new string[1];
9. levels[0] = "Assets/scene.unity";
10. BuildPipeline.BuildStreamedSceneAssetBundle(levels, "Assets/myLevel.unity3d",BuildTarget.StandaloneOSXIntel);
11. }
12. }

兼容性

Platform compatibility for AssetBundles
	Standalone	Webplayer	iOS	Android
Editor	Y	Y	Y	Y
Standalone	Y	Y
Webplayer	Y	Y
iOS			Y
Android				Y

(2)上传AssetBundles: 基于你所使用的服务器决定如何上传。

使用阶段：
(1)下载AssetBundles:
1 AssetBundle.CreateFromFile： 

   (1)只能用于pc和mac standalone

   (2)只支持Uncompressed：也就是在build的时候buildoption还要加上UncompressedAssetBundle 。

   (3)必须得是绝对路径。

       AssetBundle assetBundle = AssetBundle.CreateFromFile("D:/myBundle4.unity3d");

2 AssetBundle.CreateFromMemory(bs);

1. using System;
2. using System.IO;
3. using UnityEngine;
4. public class LoadAssetBundle : MonoBehaviour {
5.     private AssetBundle assetBundle;
6.     private AssetBundleCreateRequest request;
7.     void Update () {
8.         if(request!=null)
9.             print(request.progress);
10.     }
11.    
12.     void OnGUI()
13.     {
14.         if(GUI.Button(new Rect(0,0,100,50),"Load"))
15.         {
16.             byte[] bs = File.ReadAllBytes("D:/myBundle.unity3d");
17.             request = AssetBundle.CreateFromMemory(bs);
18.         }
19.        
20.        
21.         if(GUI.Button(new Rect(0,50,100,50),"Check"))
22.         {
23.             if(request.isDone == true)
24.             {
25.                 print("name: "+request.assetBundle.mainAsset.name);
26.                 Instantiate(request.assetBundle.mainAsset);
27.             }
28.         }
29.     }
30. }

3 AssetBundle bundle = www.assetBundle;

注：WWW也是可以读取本地文件的，

只需要在路径前file://即可，如

WWW myWWW = new WWW("file://E://LSY/wamp/www/cat.jpg");

1. using System;
2. using System.IO;
3. using UnityEngine;
4. using System.Collections;
5. public class LoadAssetBundle : MonoBehaviour {
6.     private AssetBundle assetBundle;
7.     private string address = "http://127.0.0.1/AssetBundles/myBundle.unity3d";
8.    
9.     void OnGUI()
10.     {
11.         if(GUI.Button(new Rect(0,0,100,50),"Load web"))
12.         {
13.             StartCoroutine(Load());
14.         }
15.     }
16.    
17.     IEnumerator Load() {
18.        // Download the file from the URL. It will not be saved in the Cache
19.        string    AssetName="";
20.        WWW www = new WWW(address);
21.        yield return www;
22.        if (www.error != null)
23.            throw new Exception("WWW download had an error:" + www.error);
24.        AssetBundle bundle = www.assetBundle;
25.        if (AssetName == "")
26.            Instantiate(bundle.mainAsset);
27.        else
28.            Instantiate(bundle.Load(AssetName));
29.                // Unload the AssetBundles compressed contents to conserve memory
30.                bundle.Unload(false);
31.    }
32. }

WWW.LoadFromCacheOrDownload
下载过程中可以更换下载地址,并保证版本一致, Webplayer的cache限制在50MB以内。
与普通的www下载仅仅是一句代码的区别
WWW www = new WWW(address);
WWW www = WWW.LoadFromCacheOrDownload(address,1);

1. using System;
2. using System.IO;
3. using UnityEngine;
4. using System.Collections;
5. public class LoadAssetBundle : MonoBehaviour {
6.     private AssetBundle assetBundle;
7.     private string address = "http://127.0.0.1/AssetBundles/myBundle.unity3d";
8.    
9.     void OnGUI()
10.     {
11.         if(GUI.Button(new Rect(0,0,100,50),"Load web"))
12.         {
13.             StartCoroutine(Load());
14.         }
15.     }
16.    
17.     IEnumerator Load() {
18.        string    AssetName="";
19.        WWW www = WWW.LoadFromCacheOrDownload(address,1);
20.        yield return www;
21.        if (www.error != null)
22.            throw new Exception("WWW download had an error:" + www.error);
23.        AssetBundle bundle = www.assetBundle;
24.        if (AssetName == "")
25.            Instantiate(bundle.mainAsset);
26.        else
27.            Instantiate(bundle.Load(AssetName));
28.                // Unload the AssetBundles compressed contents to conserve memory
29.                bundle.Unload(false);
30.    }
31. }

(2)使用AssetBundles里的资源:
bool AssetBundle.Contains(string name) bundle中是否含有名为name的asset

Object AssetBundle.Load(string name) 读取bundle中名称为name的asset

Object AssetBundle.LoadAll()
UnityEngine.Object[] objs = assetBundle.LoadAll();
在本例中assetBundle.mainAsset是GameObject,但是并不代表assetBundle.LoadAll();的返回值数组的第一个数据是GameObject即obj[0]等于assetBundle.mainAsset


assetBundle.mainAsset

AssetBundle.Unload（bool unloadAllLoadedObjects）
清空bundle里的所有资源。释放相关内存。清空后不能再通过该bundle创建物体。
unloadAllLoadedObjects为false: AssetBundle里的数据将会被释放，不影响已经scene中已经创建的相关物体。
unloadAllLoadedObjects为true: 不仅AssetBundle里的数据将会被释放，从该bundle创建的贴图材质等等asset将会被清空。如果scene中已经物体使用这些，连接将丢失。

 

读取场景:

当AssetBundle下载好后，直接Application.LoadLevel("scene");即可

 

1. //******************************************************
2. //AssetBundle.CreateFromMemory -> LoadLevel
3. //******************************************************
4. using System;
5. using System.IO;
6. using UnityEngine;
8. public class LoadAssetBundle : MonoBehaviour {
9. private AssetBundle assetBundle;
10. private AssetBundleCreateRequest request;
12. void Update () {
13. }
14. void OnGUI()
15. {
16. if(GUI.Button(new Rect(0,0,100,50),"Load"))
17. {
18. byte[] bs = File.ReadAllBytes(Application.dataPath+ "/myLevel.unity3d");
19. request = AssetBundle.CreateFromMemory(bs);
20. }
21. if(GUI.Button(new Rect(0,50,100,50),"Check"))
22. {
23. if(request.isDone == true)
24. {
25. Application.LoadLevel("scene");
26. }
27. }
28. }
29. }

 

总结：

制作AssetBundle主要有

1 BuildPipeline.BuildAssetBundle 非场景

2 BuildPipeline.BuildStreamedSceneAssetBundle  场景

 

使用AssetBundle主要有

1 AssetBundle.CreateFromFile   只能是Uncompressed格式

2 AssetBundle.CreateFromMemory    需要处理request

3 AssetBundle bundle = www.assetBundle;  www又分为2种

  （1）WWW www = new WWW(address);
  （2）WWW www = WWW.LoadFromCacheOrDownload(address,1,crc);

          其中网游用的最多的是LoadFromCacheOrDownload，因为第一次下载后就存在本地缓存了，之后就直接从本地缓存读取.crc是用来做数据校验的。

 

其中推荐 LoadFromCacheOrDownload。不推荐CreateFromMemory，因为需要一个解析建AB结构的过程，比较耗时。CreateFromFile也不是很推荐，因为只支持非压缩格式，所以占容量比较多。

预制体打包成AssetBundle时：预制体可以搭脚本，并且指定关系等都可以照常使用。

要求：

(1)但是脚本必须是工程里有的

(2)AssetBundle里预制体上搭载的脚本必须和工程里的脚本一致。

否则会提示错误。