In this lesson, you will learn how to architect your Unreal Engine project to decouple content from the base game installation, allowing you to ship and update assets as independent DLC packages.
The Logic of Asset Chunking
Modular packaging relies on the Primary Asset ID system. Instead of including every asset in the main build, you define "Primary Assets" that act as anchors for specific content packages. Unreal Engine uses these anchors to identify which dependencies (textures, meshes, blueprints) must be included in a "Chunk."
To begin, navigate to Project Settings > Packaging. Ensure Generate Chunks is enabled. By default, the engine puts everything in Chunk 0 (the base game). To create modular DLC, you must map specific assets to higher chunk IDs (e.g., Chunk 1 for a "Desert Expansion," Chunk 2 for a "Winter DLC").
Implementing Chunk Assignments
You can assign assets to chunks via the Asset Manager or the Data Asset system. By creating a PrimaryDataAsset that references your DLC’s top-level assets, you can instruct the cooker to group everything referenced by that asset into a specific chunk ID.
You can verify your assignments using the Reference Viewer. If an asset in your DLC chunk relies on an asset in the base game, the engine handles the dependency, but if your base game relies on a DLC asset, you will encounter a circular dependency error. Always maintain a "bottom-up" dependency flow:
// Example: Registering a DLC Chunk in the Asset Manager
// In your GameInstance or a dedicated Module initializer:
TArray<FPrimaryAssetId> AssetsToPackage;
AssetsToPackage.Add(FPrimaryAssetId("PrimaryAssetType", "MyDLC_Content_PrimaryAsset"));
// The cooker uses these IDs to pull dependencies into the specific chunk
Cooking for DLC
Once your assets are assigned to a chunk ID, you must package the project using the "Build DLC" setting in the Project Launcher. This process creates a separate .pak file that contains only the data assigned to that specific chunk ID. When the player launches the game, the IPlatformFile system dynamically mounts these additional .pak files, allowing the engine to stream the new assets into the existing world seamlessly.
Key Takeaway: Modular DLC is achieved by assigning content to unique Chunk IDs via the Asset Manager, ensuring that your secondary pak files remain lightweight and independent of the primary game executable.