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