Custom assets

This page describes the creation of custom asset classes.

Module structure

Creating custom asset classes usually means adding runtime support (UObjects that are used by the actual game runtime code) and editor support (editor utilities like a dedicated asset editor or asset actions like creation/import/export etc.). An example could be a dialogue system where runtime classes are UDialogueAsset and UDialogueComponent, and editor support involves a node-based dialogue editor. Since editor utilities are not needed by the actual game, they are placed into a separate module, resulting in the following module structure:

• DirectorySource

  • DirectoryMyProjectName

    • DirectoryPrivate/

      • …
    • DirectoryPublic/

      • …
    • MyProjectName.Build.cs
  • DirectoryMyProjectNameEditor

    • DirectoryPrivate/

      • …
    • DirectoryPublic

      • …
      • MyProjectNameEditor.h editor module startup and shutdown
    • MyProjectNameEditor.Build.cs
• MyProject.uproject has to correctly point to MyProjectNameEditor module as an editor module

Editor support for the custom asset class

Asset actions

Asset actions like creation, import/export, duplication, and context actions applicable to selected assets, are managed by the AssetTools singleton, available from the AssetToolsModule. The singleton provides many Blueprint-callable asset actions and registers new aset types and actions applicable to the asset types. For example, registering asset actions and new asset category for a custom asset in the module startup:

class FMyModule : public IModuleInterface {
    TSharedPtr<FCustomActionsClass> CustomActionsSingleton;

public:
    virtual void StartupModule() override;
    virtual void ShutdownModule() override;
}

void FMyModule::StartupModule() {
    // get the asset tools module
    IAssetTools& AssetTools = FAssetToolsModule::GetModule().Get();

    // registering a new advanced asset category will return the new category's id
    uint32 AssetCategoryId = AssetTools.RegisterAdvancedAssetCategory(
        FName{"NewCategoryKey"},
        FText::FromString("New Category Title")
    );

    // register the actions class (we pass the category id on to it)
    CustomActionsSingleton = MakeShared<FCustomActionsClass>(AssetCategoryId);
    AssetTools.RegisterAssetTypeActions(CustomActionsSingleton.ToSharedRef());
}

void FMyModule::ShutdownModule() {
    // unregsitering the custom actions
    if (!FModuleManager::Get().IsModuleLoaded("AssetTools")) return;
    FAssetToolsModule::GetModule().Get().UnregisterAssetTypeActions(CustomActionsSingleton.ToSharedRef());
}

FCustomActionsClass must implement IAssetTypeActions (you can extend the helper class FAssetTypeActions_Base though). It decides multiple things regarding asset behavior in editor:

• coloration of the asset’s icon (GetTypeColor())
• menu that appears on the right-click on the asset (GetActions(...))
• which asset editor will open when double-clicking the asset (OpenAssetEditor(...))
• which actions can be performed on the asset (CanRename(), CanDuplicate(), CanFilter(), CanLocalize(), CanMerge() etc.)
• asset’s thumbnail (GetThumbnailInfo(), GetThumbnailOverlay(), GetThumbnailBrush(), GetIconBrush() etc.)