Pak File Workflow Tutorial

This guide explains how to use UnrealCV’s Pak file management system for dynamic asset loading at runtime.

Overview

Pak files are UE’s archive format for shipping assets separately from the main application. UnrealCV’s Pak system enables:

Runtime asset loading without recompilation
Dynamic asset pools for dataset generation
Modular content management
On-demand asset registration

Key Components:

UPakMountBPLib - Blueprint library for Pak operations
FPakHandler - TCP command handler
FAssetPoolManager - Asset registration and retrieval

Workflow

::

Pak File Mount Scan Register Asset Pool ──────── ────── ──────── ────── ──────── ────── ──────────── ───────────── Create ─────> Mount ─────> Scan ─────> Register ─────> Available for (.pak) Pak Assets to Pool Spawning

Create Pak files via UE Editor packaging
Mount Pak at runtime
Scan for assets in the mounted Pak
Register to AssetPoolManager
Spawn assets via SceneCompositionBPLib

Creating Pak Files

Editor Method:

Open Package Project dialog: File > Package Project > Pak
Select output directory
Name the Pak file (e.g., Assets.pak)
Result: Assets_Win64.pak

Python/Automation Method:

Use UE’s automation tools for batch Pak creation.

Mounting Pak Files

Blueprint API:

.. code-block:: cpp

UFUNCTION(BlueprintCallable, Category = “UnrealCV|PakMount”) static bool MountPakFile(const FString& PakFilePath, int32 PakOrder = 0);

Example:

.. code-block:: cpp

bool bMounted = UPakMountBPLib::MountPakFile( TEXT(“D:/Paks/Assets_Win64.pak”), 0 // PakOrder for loading priority );

TCP Command:

.. code-block:: bash

vset /pak/mount D:/Paks/Assets_Win64.pak 0 ok Mounted: D:/Paks/Assets_Win64.pak (Order: 0)

Parameters:

PakFilePath - Absolute path to the Pak file
PakOrder - Loading priority (higher = loaded later, overrides)

Unmounting Pak Files

.. code-block:: cpp

UFUNCTION(BlueprintCallable, Category = “UnrealCV|PakMount”) static bool UnmountPakFile(const FString& PakFilePath);

TCP:

.. code-block:: bash

vset /pak/unmount D:/Paks/Assets_Win64.pak ok Unmounted: D:/Paks/Assets_Win64.pak

Scanning Assets

After mounting, scan to discover available assets:

.. code-block:: cpp

UFUNCTION(BlueprintCallable, Category = “UnrealCV|PakMount”) static void ScanMountedAssets(const FString& MountPoint, bool bForceRescan = true);

TCP:

.. code-block:: bash

vset /pak/scan /Game/Assets 1 ok Scanned: /Game/Assets

Parameters:

MountPoint - Virtual path prefix (e.g., /Game/Assets)
bForceRescan - Force re-scanning cached assets

Listing Assets

Get All Assets in Path:

.. code-block:: cpp

UFUNCTION(BlueprintCallable, Category = “UnrealCV|PakMount”) static TArray GetAllAssetsInPath(const FString& PackagePath, UClass* AssetClass = nullptr);

TCP:

.. code-block:: bash

vget /pak/assets /Game/Assets ok /Game/Assets/Character1 /Game/Assets/Character2 /Game/Assets/Prop1

Filter by Class:

.. code-block:: cpp

// Get only StaticMesh assets TArray Meshes = UPakMountBPLib::GetAllAssetsInPath( TEXT(“/Game/Assets”), UStaticMesh::StaticClass() );

Loading Assets

Load Single Asset:

.. code-block:: cpp

UFUNCTION(BlueprintCallable, Category = “UnrealCV|PakMount”) static UObject* LoadAssetFromPak(const FString& AssetPath, UClass* AssetClass);

TCP:

.. code-block:: bash

vget /pak/load /Game/Assets/Character1 ok Loaded: /Game/Assets/Character1 (Class: AActor)

Example - Spawn Loaded Actor:

.. code-block:: cpp

UObject* LoadedObj = UPakMountBPLib::LoadAssetFromPak( TEXT(“/Game/Assets/Character1”), AActor::StaticClass() );

if (LoadedObj) { AActor* NewActor = GetWorld()->SpawnActor(LoadedObj->GetClass()); }

Registering to Asset Pool

Assets can be registered to the AssetPoolManager for random selection:

.. code-block:: cpp

UFUNCTION(BlueprintCallable, Category = “UnrealCV|PakMount”) static bool RegisterAssetsToAssetPool(const FString& PackagePath, const FString& Category);

TCP:

.. code-block:: bash

vset /pak/register /Game/Assets/ foreground ok Registered assets from ‘/Game/Assets/’ to category ‘foreground’

Parameters:

PackagePath - Path to scan (e.g., /Game/Assets)
Category - Asset pool category (foreground, occluder, scene)

Asset Pool Categories:

Checking Mount Status

Is Pak Mounted:

.. code-block:: cpp

UFUNCTION(BlueprintCallable, Category = “UnrealCV|PakMount”) static bool IsPakFileMounted(const FString& PakFilePath);

TCP:

.. code-block:: bash

vget /pak/ismounted D:/Paks/Assets_Win64.pak ok 1

List All Mounted:

.. code-block:: cpp

UFUNCTION(BlueprintCallable, Category = “UnrealCV|PakMount”) static TArray GetMountedPakFiles();

TCP:

.. code-block:: bash

vget /pak/mounted ok D:/Paks/Assets1_Win64.pak D:/Paks/Assets2_Win64.pak

Complete Workflow Example

Step 1: Mount Pak

.. code-block:: cpp

void LoadDatasetAssets() { // Mount asset Pak bool bSuccess = UPakMountBPLib::MountPakFile( TEXT(“D:/Datasets/HumanCharacters_Win64.pak”), 0 );

   if (!bSuccess)
   {
       UE_LOG(LogTemp, Error, TEXT("Failed to mount Pak"));
       return;
   }

}

Step 2: Scan and Register

.. code-block:: cpp

// Scan for all human character assets UPakMountBPLib::ScanMountedAssets(TEXT(“/Game/Characters/Humans”));

// Register to asset pool UPakMountBPLib::RegisterAssetsToAssetPool( TEXT(“/Game/Characters/Humans”), TEXT(“foreground”) );

Step 3: Use in Scene Generation

.. code-block:: cpp

// Later, spawn random from pool FAssetHandle AssetHandle; bool bFound = USceneCompositionBPLib::SpawnRandomForeground( GetWorld(), TEXT(“foreground”), FVector(0, 0, 0), AssetHandle );

Common Issues

Pak won’t mount:

Verify file path exists and is accessible
Check Pak was created for correct platform
Ensure no other process has file locked

Assets not found after scan:

Confirm MountPoint matches Pak’s virtual paths
Try bForceRescan = true
Check Pak was properly created with assets

Registration fails:

Verify AssetPoolManager is initialized
Check category name is valid
Ensure scanned path contains assets

LoadAsset returns nullptr:

Verify asset path is correct
Check asset wasn’t already loaded
Ensure class type matches asset type