FusionAssetLite

A fast, low-memory asset dumper for Windows Clickteam Fusion 2.5 games.

Point it at a game EXE (or raw CCN data) and it extracts images, sounds, packed runtime files, and shaders. It is built around two goals:

• Speed — a parallel decode/encode pipeline, libdeflate for both decompression and PNG compression, SIMD pixel translation, and single-write in-memory PNG assembly. A 509 MB FNaF-class game dumps in about 2 seconds.
• Low memory — asset banks are streamed from the game file through bounded queues of compressed payloads; the whole game is never loaded into RAM.

This is an asset extractor, not a decompiler. Events, frames, and object data are out of scope.

What it extracts

Asset	Details
Images	Graphic modes 4 (24-bit masked), 6 (15-bit), 7 (16-bit), and 8 (32-bit RGBA), including RLE variants and the Fusion 2.5+ optimized LZ4 image format. Written as PNG — RGB for fully opaque images, RGBA otherwise.
Sounds	Standard (compressed) Windows sound banks. File type detected from content: wav, ogg, aiff, mp3, it, xm, s3m, mod, or bin fallback.
Packed data	Embedded runtime files (Packed Data/), inflated when zlib-compressed.
Shaders	.fx source or .fxc compiled blobs plus an .xml parameter manifest per shader.

Input formats: Fusion 2.5 PAME/PAMU payloads inside a Windows EXE, or a raw CCN/data stream. The payload is located automatically after the PE sections (with a fallback scan for the package header).

Known limitations:

• Fusion 1.x legacy pack data is detected but skipped.
• Mobile/Flash/HTML sound banks are detected but skipped.
• Graphic modes other than 4/6/7/8 are reported as failures per image.

Quick start

FusionAssetLite.exe "C:\Games\SomeGame.exe"

Assets land in extracted_assets_lite\<App Name>\ next to the game by default. Pass a second argument to choose the output root:

FusionAssetLite.exe "C:\Games\SomeGame.exe" "D:\dumps"

Options

Flag	Effect
--zip	Write everything into a single stored (uncompressed) .zip instead of one file per asset. Fastest mode on most systems — it replaces thousands of file creations with one, which also sidesteps antivirus per-file scan overhead.
--no-images	Skip the image bank.
--no-sounds	Skip the sound bank.
--no-pack	Skip packed runtime files.
--no-shaders	Skip shader banks.

PNG compression

Controlled by the FUSION_ASSET_LITE_PNG_COMPRESSION environment variable (case-insensitive). The default is libdeflate level 1, which is the best speed/size tradeoff; a managed zlib path is used automatically if the native libdeflate binary is unavailable.

Value	Meaning
(unset), fastest, libdeflate	libdeflate level 1 (default)
optimal	libdeflate level 6 — smaller PNGs, slower
zlib_fastest	force the managed zlib path, fastest level
zlib_optimal	force the managed zlib path, optimal level
none / stored	no compression — very fast, but expect ~3× the output size

Unknown values print a warning and fall back to the default.

Performance

Measured on Five Nights at Candy's 3.exe (509 MB, 3,270 images, 138 sounds, 16 packed files, 16 shaders), Release build:

Tool	Peak RAM	Dump time
CTFAK	~8.7 GB	46 s
NebulaFD	~7.0 GB	2 m 13 s
FusionAssetLite (folder output)	~856 MB	~2.1 s
FusionAssetLite (--zip)	~856 MB	~1.8 s

How: images are decoded and PNG-encoded by one worker per core fed from a bounded channel; compressed banks stream straight off disk; source inflation and PNG deflation both go through libdeflate; pixel translation is SSSE3 vectorized and writes directly into pre-filtered PNG scanlines; each PNG is assembled in pooled memory and written with a single preallocated write.

Tip for folder output on Windows: exclude the output directory from Defender real-time scanning, or just use --zip — per-file scan overhead is the single largest external cost.

The optimization history (13.3 s → 1.8 s on the same game) is charted in docs/fnac3-optimization-timeline.svg.

Building from source

Requires the .NET 10 SDK on Windows (pinned by global.json).

dotnet build .\FusionAssetLite.sln -c Release

Projects:

Path	Description
src/FusionAssetLite	The CLI dumper (single-file source, net10.0).
src/FusionAssetLite.Gui	WPF desktop front-end (net10.0-windows).
tests/FusionAssetLite.Tests	Golden-dump integration tests.

Run the GUI from source:

dotnet run --project .\src\FusionAssetLite.Gui\FusionAssetLite.Gui.csproj -c Release

Dependencies: LibDeflate.NET (fast inflate/deflate), K4os.Compression.LZ4 (Fusion 2.5+ optimized images), System.IO.Hashing (hardware CRC-32 for PNG chunks).

Tests

The integration tests dump nine reference FNaF EXEs and compare the results against golden fingerprints in tests/FusionAssetLite.Tests/Reference. Every emitted PNG is structurally validated and fingerprinted by its decoded RGBA pixels (so compressor changes don't break the goldens); other assets are fingerprinted by SHA-256.

The tests need the game files locally. Point them at your set:

$env:FUSION_ASSET_LITE_FNAF_ROOT = "D:\path\to\fnaf\games"
dotnet test .\FusionAssetLite.sln -c Release

Test environment variables:

Variable	Effect
FUSION_ASSET_LITE_FNAF_ROOT	Root folder containing the reference games.
FUSION_ASSET_LITE_TEST_KEEP_OUTPUT=1	Keep temporary dumps from passing tests for inspection.
FUSION_ASSET_LITE_TEST_PARALLELISM	Lower the parallel dump count if disk or antivirus is the bottleneck.

Output layout

extracted_assets_lite\
└── <App Name>\
    ├── Images\        00000.png, 00001.png, ...
    ├── Sounds\        <name>.<wav|ogg|...>
    ├── Packed Data\   original relative paths, sanitized
    └── Shaders\       <name>.fx|.fxc + <name>.xml

With --zip, the same layout is written as entries of extracted_assets_lite\<App Name>.zip.