Set Up FModel

FModel is used throughout the PAYDAY 3 modding workflow to browse the installed game’s Unreal Engine archives, inspect assets, and export files such as AssetRegistry.bin.

PAYDAY 3’s archives are encrypted, and many of its Unreal Engine assets use unversioned properties. Because of that, FModel needs both the PAYDAY 3 AES key and a compatible mappings file before it can correctly read many assets.

Install FModel

Download the current version of FModel and launch it.

When FModel opens, select your PAYDAY 3 installation. If the game is not detected automatically, create an undetected game entry and point FModel at the game’s archive directory, normally the PAYDAY3/Content/Paks directory inside the PAYDAY 3 installation.

FModel’s interface can change between releases, but the important settings are the game archive directory, AES key, Unreal Engine version, and local mapping file.

Add the PAYDAY 3 AES key

PAYDAY 3’s game archives require the following AES key:

0x27DFBADBB537388ACDE27A7C5F3EBC3721AF0AE0A7602D2D7F8A16548F37D394

In FModel:

  1. Open Directory > AES.

  2. Enter the PAYDAY 3 AES key shown above as the main encryption key.

  3. Save or confirm the AES configuration.

  4. Reload the PAYDAY 3 archives if FModel does not refresh them automatically.

Once the key is accepted, the encrypted game archives should become readable.

Get a mappings file

FModel also needs a current Unreal mappings file, normally a .usmap file, to deserialize many PAYDAY 3 assets correctly.

The recommended option is to use the mappings file provided with the current PAYDAY 3 modkit release. Check the Releases section of the modkit repository and download the mappings file that matches the current game/modkit version.

If a current mappings file is not available, you can generate one from the game using a compatible dumper such as:

Mappings are version-sensitive. PAYDAY 3 updates can change reflected classes, structs, enums, and properties.

After a game update, use a mappings file generated for the updated game version. An old mappings file may cause missing properties, incorrect data, or package parsing errors.

Configure FModel to use the local mappings file

After obtaining the .usmap file:

  1. Open Settings in FModel.

  2. Open the General settings page.

  3. Find Local Mapping File (drag & drop).

  4. Enable the Local Mapping File option.

  5. Set Mapping File Path to the downloaded or generated .usmap file. You can use the browse button next to the path field, or drag the mapping file into FModel where supported.

  6. Save the settings.

  7. Reload the PAYDAY 3 archives if necessary.

FModel’s current settings expose both the Local Mapping File (drag & drop) toggle and a Mapping File Path field when the local mapping option is enabled.

Why the mappings file is required

Many PAYDAY 3 packages contain unversioned Unreal properties. The package data does not contain enough information by itself for a generic asset reader to reconstruct every property layout.

The mappings file supplies the schema FModel needs for PAYDAY 3 classes, structs, enums, and their properties.

Without a compatible mappings file, FModel may still list archives and some files, but many assets cannot be fully parsed or inspected. You may see errors about a missing mapping file or unversioned properties, and exported/inspected asset data can be incomplete.

This is why the mappings file is required for common workflows such as:

  • Inspecting Blueprint and data asset properties.

  • Reading reflected class and struct data.

  • Examining references inside many cooked packages.

  • Exporting or inspecting assets that depend on unversioned property layouts.

  • Locating and extracting files needed by the modkit setup workflow.

Verify the setup

After configuring the archive directory, AES key, and local mappings file:

  1. Reload the PAYDAY 3 archives.

  2. Browse into the game’s packages.

  3. Open a few Blueprint or data asset packages.

  4. Confirm that FModel displays their properties without mapping-related errors.

If FModel can list the archives but fails to deserialize many assets, first check that the local mapping option is enabled and that the selected .usmap matches your installed PAYDAY 3 version.

FModel mappings, AssetRegistry.bin, and the modkit JMAP are different

These three files serve different purposes in the PAYDAY 3 modding workflow:

  • The FModel .usmap file supplies Unreal property layout information so FModel can deserialize many cooked PAYDAY 3 packages.

  • AssetRegistry.bin is extracted from the game with FModel and placed in the modkit root. The editor uses it to discover which cooked PAYDAY 3 assets exist and which cooked packages can be resolved and loaded.

  • The modkit JMAP is dumped from a running PAYDAY 3 process by GenerateJMAP.bat. Suzie consumes that JMAP to generate the native PAYDAY 3 class stubs used by the modkit.

GenerateJMAP.bat does not use AssetRegistry.bin to generate the JMAP. They are separate parts of the setup process.

The modkit does not ship with the generated JMAP. The next step explains how to place the current AssetRegistry.bin in the modkit root, dump the JMAP from a clean running game, and use it with Suzie.

FModel reference

For additional information about FModel itself, see:

Next: Install the Modkit.