IN THIS ARTICLE

Creating a Content Patch Update Package

This topic explains the process for creating a content patch update package for your Open 3D Engine (O3DE) project with Asset Bundler. This includes a patch bundle that contains just the asset updates, and a patched release bundle that contains all the game assets including the asset updates.

Prerequisites

To follow along, you’ll need a project with a release build that has been created through the steps in the previous topic, Creating a Project Game Release Layout for Windows.

Conventions used in this topic

This topic makes some assumptions about your project for clarity:

Your project has a seed list file and an asset list for game only assets.
You are using a source engine build within your project.

The following conventions are used in this topic as substitutions for your own directory and file names:

Project name and directory: C:\MyProject
Source engine build directory: C:\MyProject\build\windows\bin\profile
Game asset seed list : game_seed_list.seed
Game asset list: game_v1.assetlist

Make asset changes to your project

Make a visual change to your project that simulates a content update. For demonstration purposes, you might add an asset to a level that is easy to spot when you test the update bundle. Save the changes to your level.

Create an update package

There are four steps to creating an update package:

Ensure all assets are processed.
Generate new asset lists based on the changes.
Create a patched release asset bundle that contains all the game assets and updates.
Create a patch asset bundle that contains just the game asset updates.

Process all project assets

For most updates, only the game assets will change. When upgrading to a new version of O3DE and pushing an update, you should regenerate all of the existing content to ensure it’s properly updated, including the engine assets and auxiliary content.

To process the assets, run Asset Processor or Asset Processor Batch by following the steps in the process assets section of the Windows release layout topic.

Create a patched release asset list

Create a new version of the game asset list containing all the assets that are in the original game_v1.assetlist as well as the changes you saved to the level. This new asset list serves as the asset list for the patched release, and is used to generate a patch for existing distributions of your project in the next section.

Asset Bundler GUI
Asset Bundler command

Run AssetBundlerBatch.exe from the source engine build directory.
In the Seeds tab, select the game_seed_list by checking the box to its left. The seeds in the list appear in the main list view.
Choose Generate Asset Lists in the upper-right.
In the Generate Asset List Files dialog, choose Browse….
In the new file dialog, enter game_v2.assetlist for the name, and choose Open.
In the Generate Asset List Files dialog, choose pc from the platform list.
Choose Create New File.

Alternatively, you can run this command to generate the asset list for a patched release.

AssetBundlerBatch.exe assetLists --seedListFile game_seed_list.seed ^
    --assetListFile game_v2.assetlist

After a short time, a dialog notifies you that the asset list has been created successfully. You can verify your changes have been added to the new patched release asset list by choosing the Asset List tab, selecting game_v2 from Asset list files, and examining the contents in the main list window.

Note:
You don’t need to update the game_seed_list.seed file because it already contains a reference to the level you updated. Changes to the level’s dependencies are included when the asset list is generated.

Create a patch asset list

The patch asset list is applied to an existing distribution and only contains new and updated assets. To create a patch, you need to compare the v2 list against the v1 list and save the delta to a new asset list.

Asset Bundler GUI
Asset Bundler command

In Asset Bundler, choose the Rules tab.
Choose Create new Rules file.
In the file dialog, enter generate_v1_to_v2_patch.rules for the file name, and choose Open.
Select generate_v1_to_v2_patch from the Rules list.
Choose Add Step from the Comparison Steps list.
Enter a name for the new step such as Generate V1 to V2 Delta.
Set the Comparison Type to Delta.
Choose Browse… under Input A and select the game_v1.assetlist.
Choose Browse… under Input B and select the game_v2.assetlist.
Choose Run Selected Rule.
In the Run Rule dialog, choose Browse….
In the new file dialog, enter game_v1_to_v2_patch.assetlist for the name, and choose Open.
In the Generate Asset List Files dialog, choose pc from the platform list.
Choose Create New File.

Alternatively, you can run this command to generate the patch asset list.

AssetBundlerBatch.exe compare --comparisonType delta ^
    --firstAssetFile game_v1.assetlist ^
    --secondAssetFile game_v2.assetlist ^
    --output game_v1_to_v2_patch.assetlist

After a short time, a dialog notifies you that the asset list has been created successfully. You can verify that the patch asset list contains only the new changes by choosing the Asset List tab, selecting game_v1_to_v2_patch from Asset list files, and examining the contents in the main list window.

Create asset bundles

Now you must create asset bundles (.pak files) for the new asset lists.

Asset Bundler GUI
Asset Bundler command

To generate the patched release asset bundle, do the following:

In the Asset Lists tab, select the game_v2 asset list.
Choose Generate Bundle.
In the Generate Bundles dialog, choose Browse….
In the file dialog, enter game_v2.pak for the file name and choose Open.
Choose Generate Bundles.

To generate the patch asset bundle, do the following:

In the Asset Lists tab, select the game_v1_to_v2_patch asset list.
Choose Generate Bundle.
In the Generate Bundles dialog, choose Browse….
In the file dialog, enter game_v1_to_v2_patch.pak for the file name and choose Open.
Choose Generate Bundles.

Alternatively, you you can run these commands to generate bundles from the asset lists.

Use the following command to generate the patched release bundle containing all the game assets:

AssetBundlerBatch.exe bundles --assetListFile game_v2.assetlist ^
    --outputBundlePath game_v2.pak

Use the following command to generate the patch bundle containing only the changed assets:

AssetBundlerBatch.exe bundles --assetListFile game_v1_to_v2_patch.assetlist ^
    --outputBundlePath game_v1_to_v2_patch.pak

In the next section, you’ll test the new bundles with your project’s release build.

Test the asset bundles

You can test the asset bundles by simulating two user scenarios.

Because your release build currently has the original v1 asset bundle, start by testing the scenario where a user has your project installed and applies the patch asset bundle containing just the updated assets. Copy the patch asset bundle to your release asset directory.

copy C:\MyProject\AssetBundling\Bundles\game_v1_to_v2_patch.pak ^
    C:\MyProject\install\bin\Windows\release\Monolithic\Cache\pc\

Launch the release build and check that your updates appear in the level.

C:\MyProject\install\bin\Windows\release\Monolithic\MyProject.GameLauncher.exe

If the content patch was applied successfully, you’ll see your updated content in the level.

Now you can simulate a user downloading a new release with the content patch already applied.

Delete the patch asset bundle and the v1 asset bundle from your game release:

del C:\MyProject\install\bin\Windows\release\Monolithic\Cache\pc\game_v1_to_v2_patch.pak
del C:\MyProject\install\bin\Windows\release\Monolithic\Cache\pc\game_v1.pak

Copy the v2 asset bundle to the release:

copy C:\MyProject\AssetBundling\Bundles\game_v2.pak ^
    C:\MyProject\install\bin\Windows\release\Monolithic\Cache\pc\

Relaunch the release build and check that your updates appear in the level:

C:\MyProject\install\bin\Windows\release\Monolithic\MyProject.GameLauncher.exe

Conclusion

You’ve learned how to generate a content patch to apply to an existing release. You can use these steps to create any number of updates through various releases of your project.