Asset Bundles

The game loads textures, audio, meshes, prefabs, etc. from Unity Asset Bundles at runtime. How these are setup and used has evolved over the years from individual *.unity3d bundles to *.content bundles to *.masterbundle files.

Master Bundles should be used for essentially all new projects.

Tool Setup

Prior to using any of these tools they must be imported into a Unity project

  1. Inside Unity open the Assets > Import Package > Custom Package… wizard.

  2. Find the Unturned installation directory.

  3. Navigate to the Extras/Sources directory.

  4. Import the Project.unitypackage.

Master Bundles

Most official files including curated maps have been transitioned to master bundles (*.masterbundle), and they will be used for the forseeable future.

File Setup for Master Bundles

Master bundles can be loaded from any directory the game loads *.dat files from. Unless an override is specified, the nearest master bundle in the file hierarchy is used. While loading each directory is checked for a MasterBundle.dat file signalling the presence of a master bundle. For example, refer to the core.masterbundle in the Bundles directory.

MasterBundle.dat can set the following keys:

// Name of asset bundle file in the same directory as MasterBundle.dat.
Asset_Bundle_Name core.masterbundle

// Path to the asset bundle within Unity.
// Unity subfolders should match 1:1 with dat subfolders.
Asset_Prefix Assets/CoreMasterBundle

// Version 3 is Unity 2018.4 LTS. Older versions have shader consolidation enabled for backwards compatibility.
Asset_Bundle_Version 3

Individual asset *.dats can set the following keys:

// Name of master bundle to load files from.
Master_Bundle_Override core.masterbundle

// If included, look for an individual *.unity3d asset bundle instead.

// Path within master bundle to load files from.
// Used by notes to share a common object prefab.
Bundle_Override_Path /Objects/Medium/Furniture/Note

Tool Usage for Master Bundles

  1. Follow Tool Setup instructions.

  2. Open the tool from the Window > Unturned > Master Bundle Tool menu.

  3. Select directories of assets in the Project window.

  4. In the Inspector window tag them in any asset bundle.

  5. Click the checkbox next to an asset bundle’s name in the tool to mark it as a master bundle. This filters the list of asset bundles to show, and tracks an export path associated with it.

  6. Click the … to choose a destination for the bundle file.

  7. Click Export.

  8. (optional) When redistributing the asset bundle the “multiplatform” toggle should be enabled. This ensures the appropriate shaders for each platform are included, and exports a “.hash” file so the server can validate client asset bundle integrity.

Motivations for Master Bundles

When upgrading to Unity 2017.4 LTS it became apparent that all asset bundles would have to be re-exported from Unity due to shader compatibility changes. This would be an incredible amount of files, so it was time to re-approach the *.content issue in a way that could quickly convert all existing content. This was handled by keeping the file hierarchy 1:1 and guessing the file extension for the by-name loading.

Individual Asset Bundles

Most official files have transitioned to the master bundle system, but some use individual asset bundles (*.unity3d). For example, the per-map road textures.

Tool Usage for Asset Bundles

  1. Follow Tool Setup instructions.

  2. Open the tool from the Window > Unturned > Bundle Tool menu.

  3. Select individual assets or directories of assets in the Project window.

  4. Click Grab to preview which assets will be exported.

  5. Click Bundle to choose a destination for the asset bundle file.

Motivations for Asset Bundles

When beginning development of 3.0, it was key to support runtime loading of custom modded content. At the time files in asset bundles were loaded by name without extension, so each game type looked for specific names like “Item”, “Object”, “Animal”, etc. The .unity3d extension was chosen for web browser compatibility. Obviously this system did not age well.

Content Bundles (*.content)

Deprecated since version

This format was historically used by terrain, material palettes, and radio songs. After the April 23, 2021 patch (version these assets can all use master bundles instead. As of the February 25, 2022 patch (version any remaining support for content bundles has been removed. New references should use a master bundle name and relative path for the “Name” and “Path” properties.

Reusing Content Bundles

Although it is preferable to properly migrate older assets into master bundles, preexisting content bundles can be easily reused as a master bundle. Rename the *.content file to be *.masterbundle file instead. Then, add a corresponding MasterBundle.dat file as described in the file setup for master bundles.