To build assets into an AssetBundle, you must assign assets to an AssetBundle, either in the Unity Editor or through a script. You can then create and use a script to build the AssetBundles. For information on the best approaches for organizing assets into AssetBundles, refer to Preparing assets for AssetBundles.
Note: This workflow describes the creation of AssetBundles with the built-in BuildPipeline.BuildAssetBundles API. A more user-friendly alternative is to use the Addressables package.
To assign a given asset to an AssetBundle in the Unity Editor, perform the following steps:
Assets folder (Project tab) More info/ character. For example, use the AssetBundle name environment/forest to create an AssetBundle named forest under an environment subfolder.You can assign an AssetBundle to a folder in your project. By default, all assets in that folder are assigned to the same AssetBundle as the folder. However, the AssetBundle assignments for individual assets takes precedence. To assign an AssetBundle to a folder:
You can also select multiple assets and assign them to an AssetBundle. However, assigning assets to an AssetBundle in this way overrides any existing AssetBundle assignments for those assets.
To assign assets to AssetBundles in your code, use the BuildPipeline.BuildAssetBundles method with an array of AssetBundleBuild structures. This approach overrides any AssetBundle assignments made in the Inspector.
If you want your script to respect AssetBundle assignments made in the Inspector, use AssetDatabase.GetAllAssetBundleNames and AssetDatabase.GetAssetPathsFromAssetBundle to retrieve the necessary information and populate the AssetBundleBuild array.
To build AssetBundles, you must create a build script and place it a folder called Editor in the Assets folder.
The following script is an example of an AssetBundle build script. It adds a menu item at the bottom of the Assets menu called Build AssetBundles. When you select Build AssetBundles the BuildAllAssetBundles method is called. A progress bar appears while the build takes all the assets you labeled with an AssetBundle name and uses them to populate AssetBundles at the path that assetBundleDirectory defines.
using UnityEditor;
using System.IO;
public class CreateAssetBundles
{
[MenuItem("Assets/Build AssetBundles")]
static void BuildAllAssetBundles()
{
string assetBundleDirectory = "Assets/AssetBundles";
if(!Directory.Exists(assetBundleDirectory))
Directory.CreateDirectory(assetBundleDirectory);
BuildPipeline.BuildAssetBundles(assetBundleDirectory,
BuildAssetBundleOptions.None,
BuildTarget.StandaloneWindows);
}
}
The script has the following arguments:
assetBundleDirectory: The directory to output the AssetBundles to within the current Unity project. The folder doesn’t need to be in the Assets folder. In the code example, it creates the folder on demand if it doesn’t exist.BuildAssetBundleOptions.None: The default value for the build options argument. You can use this argument to specify one or more flags to enable a variety of optional behaviours. For example, this argument controls the choice of compression algorithm. For a full list of options available refer to the BuildAssetBundleOptions API documentation.BuildTarget.StandaloneWindows: Defines the target platform for the AssetBundles. Alternatively, you can call EditorUserBuildSettings.activeBuildTarget, which returns the platform profile currently set as active in the Build ProfilesA set of customizable configuration settings to use when creating a build for your target platform. More infoYou should perform a clean build when you do an official AssetBundle release. To perform a clean build, pass the BuildAssetBundleOptions.ForceRebuildAssetBundle flag as an option to BuildPipeline.BuildAssetBundles.
In some projects, you can delete the Library/ShaderCache directory to decrease the time required for the next Player or AssetBundle build, especially for projects where shaderA program that runs on the GPU. More info
See in Glossary compilation is a lengthy process. This cache isn’t cleared when you specify BuildAssetBundleOptions.ForceRebuildAssetBundle.
An alternative way to perform a clean build is to stop Unity, delete your project’s Library directory, then reopen Unity. This process is time consuming because all the project assets need to be reimported and other data is regenerated.
For more information, refer to Incremental build pipeline.
The BuildPipeline.BuildAssetBundles API allows you to specify the target and subtarget platform for deploying AssetBundles.
If the specified target platform differs from the one configured in Build Profiles, Unity must recompile Editor scriptsA piece of code that allows you to create your own Components, trigger game events, modify Component properties over time and respond to user input in any way you like. More info
See in Glossary and reimport assets such as textures that have platform-specific representations. After the build is complete, Unity restores the original target platform settings.
This process can significantly increase build times. Additionally, the script containing the BuildPipeline.BuildAssetBundles call continues to execute as compiled for the current target platform, not the specified build target. This can cause issues if the build script or callback scripts rely on platform-specific code or assemblies.
To avoid this issue, ensure that any code executed during a build dynamically checks the target platform (for example, using if statements) rather than relying on platform-specific conditional compilation (such as, #ifdef statements).
For command line builds, use the --buildTarget command line argument to align the target platform with your build requirements.
You can distribute AssetBundles in the following ways:
UnityWebRequestAssetBundle to download them.To load AssetBundles and access the AssetBundle object in your runtime code, either use the load methods in AssetBundle or UnityWebRequestAssetBundle.
To reclaim memory used by a loaded AssetBundle, call AssetBundle.Unload(bool) or AssetBundle.UnloadAsync(bool).
For more information on APIs that load and unload AssetBundles, refer to Loading assets from AssetBundles.