Building Subsystem¶

UBuildingSubsystem is a UGameInstanceSubsystem responsible for loading, caching, and querying the project's Building Data Asset assets.

It shares the same lifetime as the GameInstance and can persist across level transitions. Building Entities, Chunks, and runtime representations in the current world are managed by UBuildingWorldSubsystem.

Getting the Subsystem¶

Blueprint¶

Get Game Instance Subsystem
→ Building Subsystem

C++¶

UBuildingSubsystem* BuildingSubsystem =
    GetGameInstance()->GetSubsystem<UBuildingSubsystem>();

if (!IsValid(BuildingSubsystem))
{
    return;
}

Building Asset Queries¶

API	Description
`GetAllBuildings`	Returns all loaded building assets.
`GetBuildingsByCategory`	Returns building assets belonging to a specified category.
`GetBuildingDataByAssetId`	Returns a building asset by Primary Asset ID.

GetAllBuildings¶

TArray<UBuildingDataAsset*> GetAllBuildings() const;

Returns all loaded building data assets.

GetBuildingsByCategory¶

TArray<UBuildingDataAsset*> GetBuildingsByCategory(
    FName Category
) const;

Returns the building data assets that belong to the specified Category.

The category value comes from UBuildingDataAsset::Category.

GetBuildingDataByAssetId¶

UBuildingDataAsset* GetBuildingDataByAssetId(
    FPrimaryAssetId AssetId
) const;

Returns the loaded building asset associated with the specified Primary Asset ID. Returns nullptr if no matching asset is found.

This API is commonly used during building creation, network synchronization, and save restoration.

Loading State¶

API	Return Type	Description
`AreBuildingAssetsLoaded`	`bool`	Whether all building assets have finished loading.
`GetLoadProgress`	`float`	The loading progress, from `0.0` to `1.0`.
`GetLoadedBuildingCount`	`int32`	The number of building assets currently loaded.
`GetTotalBuildingCount`	`int32`	The total number of building assets found during the current scan.

If no building assets are found, the loading state should immediately be treated as complete:

Loaded Count = 0
Total Count = 0
Load Progress = 1.0
Assets Loaded = true

Loading Events¶

Event	Description
`OnBuildingAssetLoadProgressChanged`	Triggered when the loading progress or asset counts change.
`OnBuildingAssetLoaded`	Triggered when an individual building asset becomes available.
`OnBuildingAssetsLoaded`	Triggered when all building assets have finished loading.
`OnBuildingAssetLoadingCanceled`	Triggered when the current asynchronous loading request is canceled.

OnBuildingAssetLoadProgressChanged¶

Parameters:

Parameter	Type	Description
`Progress`	`float`	The current loading progress.
`LoadedCount`	`int32`	The number of assets currently loaded.
`TotalCount`	`int32`	The total number of assets in the current load operation.

This event can be used to update a loading progress bar.

OnBuildingAssetLoaded¶

Parameters:

Parameter	Type	Description
`BuildingData`	`UBuildingDataAsset*`	The building asset that has become available.
`LoadedCount`	`int32`	The number of assets currently loaded.

OnBuildingAssetsLoaded¶

Triggered after all building assets have finished loading.

After receiving this event, call GetAllBuildings() to refresh the building menu.

Usage Workflow¶

Get Building Subsystem
→ Check Are Building Assets Loaded

If loading is complete:

Get All Buildings
→ Refresh the building menu

If loading is still in progress:

Bind the loading progress event
→ Update the loading interface

Bind the loading completed event
→ Get All Buildings
→ Refresh the building menu

Cost Checking Toggle¶

UBuildingSubsystem provides a runtime toggle for building cost validation.

Default state:

Enable Check Cost = true

GetEnableCheckCost¶

bool GetEnableCheckCost() const;

Returns whether building cost validation is currently enabled.

SetEnableCheckCost¶

void SetEnableCheckCost(bool bEnabled);

Enables or disables building cost validation.

This value is valid only for the current GameInstance lifetime. It is not automatically written to project settings or save data.

For the complete cost workflow, see Building Cost System.

Asset Sorting¶

After building assets finish loading, they are sorted by SortIndex in ascending order:

Lower SortIndex
→ Displayed earlier

Subsystem Responsibilities¶

Subsystem	Lifetime	Responsibility
`UBuildingSubsystem`	`GameInstance`	Building asset loading, caching, and queries.
`UBuildingWorldSubsystem`	`World`	Building Entities, Chunks, save data, and runtime representations.

Do not store the following in UBuildingSubsystem:

Actors from the current world
Render Chunk Actors
HISM Components
HISM Instance Indexes
Runtime Building Entity data

For world-level building management, see Building World Subsystem.

Troubleshooting¶

Issue	What to Check
The building list is empty	Check whether building asset loading has completed.
`TotalCount` is `0`	Check the Asset Manager scan configuration.
Category queries return no results	Check the `Category` configured in the building assets.
Asset ID lookup fails	Check the Asset ID and loading state.
The UI does not refresh	Check whether the loading completed event is bound.
No buildings are available in a packaged build	Check the Primary Asset scan and packaging rules.

For building asset configuration, see Building Data Assets.