在Unity中创建可远程加载的.unity3d包

首发：http://blog.csdn.net/u010732148/article/details/8950552

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　　在一个Unity项目中，发布包本身不一定要包括所有的Asset（译为资产或组件），其它的部分可以单独发布为.unity3d，再由程序从本地/远程加载执行，这部分不在本文讨论范围。虽然Unity并没有直接提供.unity3d的导出功能，但可以通过其手册了解到一些，并打开菜单项。
　　翻看Unity关于AssetBundle的手册，有相关的链接：

BuildPipeline.BuildAssetBundle
Building AssetBundles

【注意】导出.unity3d格式需要pro版本，非pro版本可以打开菜单项，但导出时会提示错误：



　　我们可以使用Untiy提供的现成的脚本打开两个导出.unity3d的菜单项，也可以使用API根据自己的需求来写。当项目变得越来越大时，手工导出AssetBundle会越来越吃力，这时可能就需要自己来开发导出功能，自动创建AssetBundle了。

打开菜单项

　　在Unity中创建名为ExprotAssetBundles的C#脚本，放到Editor目录下（必须是这
4000
个目录，以便在编辑器中生效）。把下面的代码复制到ExprotAssetBundles脚本中（可以在Building
AssetBundles中找到这段代码）

// C# Example
// Builds an asset bundle from the selected objects in the project view.
// Once compiled go to "Menu" -> "Assets" and select one of the choices
// to build the Asset Bundle

using UnityEngine;
using UnityEditor;
public class ExportAssetBundles {
[MenuItem("Assets/Build AssetBundle From Selection - Track dependencies")]
static void ExportResource () {
// Bring up save panel
string path = EditorUtility.SaveFilePanel ("Save Resource", "", "New Resource", "unity3d");
if (path.Length != 0) {
// Build the resource file from the active selection.
Object[] selection = Selection.GetFiltered(typeof(Object), SelectionMode.DeepAssets);
BuildPipeline.BuildAssetBundle(Selection.activeObject, selection, path, BuildAssetBundleOptions.CollectDependencies | BuildAssetBundleOptions.CompleteAssets);
Selection.objects = selection;
}
}
[MenuItem("Assets/Build AssetBundle From Selection - No dependency tracking")]
static void ExportResourceNoTrack () {
// Bring up save panel
string path = EditorUtility.SaveFilePanel ("Save Resource", "", "New Resource", "unity3d");
if (path.Length != 0) {
// Build the resource file from the active selection.
BuildPipeline.BuildAssetBundle(Selection.activeObject, Selection.objects, path);
}
}
}

这时，在Assets菜单下可以看到两个新的菜单项：



1. Build AssetBundle From Selection - Track dependencies
　　这个选项会把当前对象打包到一个asset bundle中，并包含所有依赖。
2. Build AssetBundle From Selection - No dependency tracking
　　与前一个相反的选项，只包含所选的asset
　　例：创建一个Cube，拖拽生成一个预置体。右键点击预置体，选择"Build AssetBundle From Selection - Track dependencies"，这时可以看到.unity3d的保存窗口。在项目中创建一个名为AssetBundles的目录，并把选中的预置体存为Cube.unity3d，可以看到窗口显示如下：



现在，就可以把Cube.unity3d放到任意位置，或自己的服务器上。

如何在创建组件包时修改属性
　　可以在调用 BuildPipeline.BuildAssetBundle以后使用 AssetDatabase.ImportAsset来强制导入组件，然后用 AssetPostprocessor.OnPreprocessTexture来设置需要的属性。
　　下面的示例来展示构建组件包时如何设置不同的纹理贴图。

// Builds an asset bundle from the selected objects in the project view,
// and changes the texture format using an AssetPostprocessor.

using UnityEngine;
using UnityEditor;

public class ExportAssetBundles {

// Store current texture format for the TextureProcessor.
public static TextureImporterFormat textureFormat;

[MenuItem("Assets/Build AssetBundle From Selection - PVRTC_RGB2")]
static void ExportResourceRGB2 () {
textureFormat = TextureImporterFormat.PVRTC_RGB2;
ExportResource();
}

[MenuItem("Assets/Build AssetBundle From Selection - PVRTC_RGB4")]
static void ExportResourceRGB4 () {
textureFormat = TextureImporterFormat.PVRTC_RGB4;
ExportResource();
}

static void ExportResource () {
// Bring up save panel.
string path = EditorUtility.SaveFilePanel ("Save Resource", "", "New Resource", "unity3d");

if (path.Length != 0) {
// Build the resource file from the active selection.
Object[] selection = Selection.GetFiltered(typeof(Object), SelectionMode.DeepAssets);

foreach (object asset in selection) {
string assetPath = AssetDatabase.GetAssetPath((UnityEngine.Object) asset);
if (asset is Texture2D) {
// Force reimport thru TextureProcessor.
AssetDatabase.ImportAsset(assetPath);
}
}

BuildPipeline.BuildAssetBundle(Selection.activeObject, selection, path, BuildAssetBundleOptions.CollectDependencies | BuildAssetBundleOptions.CompleteAssets);
Selection.objects = selection;
}
}
}

// Changes the texture format when building the Asset Bundle.
using UnityEngine;
using UnityEditor;
public class TextureProcessor : AssetPostprocessor
{
void OnPreprocessTexture() {
TextureImporter importer = assetImporter as TextureImporter;
importer.textureFormat = ExportAssetBundles.textureFormat;
}
}

也可以使用AssetDatabase.ImportAssetOptions.来控制如何导入组件。

【注】远程加载.unity3d包，可以使用WWW类