Use this skill to inspect Blitz3D game code with B3DDecomp, understand runtime behavior and animated models, and port eligible content to another engine. It also explains when protected builds or usage rights mean the work must stop.
Decompile a Blitz3D game to readable Blitz source with B3DDecomp and port what it does to another engine. Covers SCP - Containment Breach-era and other .bb games, B3DDecomp, Blitz3D runtime behaviour (fixed tick, Animate, CurveValue, Euler angles, quaternions, Rnd), animated .b3d models (viewmodels with bones and keyframes) into Roblox, and where to stop (builds protected against decompiling, games and assets the user has no rights to). Use when a Blitz3D game's code or animated models are needed.
Run score Not tested
See how to installReview the instructions the agent will receive before you install.
Blitz3D games ship as one exe: the runtime in .text and the compiled game in a resource module that
the runtime links at load. Ghidra on the exe shows only the runtime. The route that works:
B3DDecomp disassembles the module and decompiles it to Blitz source. Then the source is the spec for the
port, and the original game stays the oracle.
Keep every disassembly and decompile outside any repo (convention: ~/<game>-decomp/), and never
publish them; the scripts here are fine to keep. Leave proprietary DLLs that forbid decompiling alone: their
export names in the exe are enough. Journal in the mod's MODLOG.md.
Read the source when there is one: SCP: Containment Breach (Regalis11/scpcb) and its Ultimate Edition Reborn fork (Jabka666/scpcb-ue-my) are open source under CC BY-SA 3.0.
What a port may use. A port that re-expresses a game's logic, or converts its models, keyframes, textures or sounds, redistributes that game once it is published or uploaded (to Roblox too). Port only what the user has the rights to: their own game, or an openly licensed one on its terms (SCP: Containment Breach: credit it and keep the port under CC BY-SA 3.0, and check each asset's credits, since fan games mix licences). Anything else stays a private study: nothing from it is uploaded or published.
dotnet build Blitz3DDecomp.sln -c Release. It needs a .NET 8 SDK; a user-local one installs without admin
(dotnet-install.ps1 -Channel 8.0 -InstallDir <dir>). Run with DOTNET_ROLL_FORWARD=Major and
bin/Release/net8.0 on PATH: the decompiler starts Blitz3DDisasm by name.git apply; made on
commit 2b3148b): the decompiler then skips a function it can't finish, with a step5 failed line, instead
of stopping.Done when Blitz3DDecomp.exe and Blitz3DDisasm.exe build.
Blitz3DDecomp.exe <copy of game.exe> writes <game>_disasm/ (Code/ per function, Type/, Strings.txt,
BuiltIn/, Libs/, BuiltInSymbols.txt), then decompiles it to <game>_decomp/. Games built from SCP:
Containment Breach's code need the game's fmod.decls as a second argument (B3DDecomp's README: the shipped
decls drop a parameter from FSOUND_Stream_Open).
When it still aborts, the exception names the construct. Never make a type setter silently ignore writes to get past one: the type propagation then loops forever with no output.
Protected builds: stop. Some builds are protected against this step: a modified compiler and runtime
hash every function, type and builtin name (B3DDecomp stops with Unrecognized function: @_builtIn_f<garbled>; SCP: Containment Breach 2's client is built this way), or the module is encrypted.
Those are protections the developer added against decompiling. Don't reverse them: tell the user and stop
(skills/mod-any-game/references/safety.md). Current B3DDecomp undoes one of them by itself, without saying
so: an XOR on a .b3dmod section. List the exe's sections first (objdump -h, or any PE viewer) and stop if
it has one.
Done when <game>_decomp/ holds Main.bb, Functions/, Types/ and Decls/ and the run prints
at most a handful of step5 failed lines.
grep -l StringConstant_<n> Code/*).Done when every number the port will use is traced to the line that sets it and the line that reads it.
Read references/blitz-runtime.md before writing port code: Blitz3D's clock,
Animate, CurveValue, Euler angles, Rnd and entity calls behave in ways a straight transcription gets wrong.
For animated .b3d models (viewmodels, rigs, keyframes) into Roblox, follow
references/b3d-to-roblox.md; its scripts are in scripts/roblox/.
Port step for step: same order, same constants, same tick. Mark every deviation in a comment with the reason. The rights rule above covers the code as much as the models.
Measure the port against the decompiled numbers in the engine, not by eye: rates (shots per second at the fixed tick), durations (frames / speed / ticks per second), aim (the sight's dot on the screen centre), ammo on the server. Record each check and its result in the journal.
Done when every ported behaviour has a measured number next to the decompiled one.
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Prepare generated or hand-drawn artwork for a game's required file layout, dimensions, colors, and transparency. Create sprite sheets, assemble animation frames, and render 3D models into consistent views for use as game images.
Create game assets through fal.ai, including sprites, textures, 3D models, sound effects, music, voices, and video clips. Guides consistent visual variations, file conversion, model selection, and generation records so assets can be traced and regenerated.
Launch and control a real game to verify mods through screenshots and logs. Automate menus, keyboard and mouse input, and repeatable test scenes, with guidance for connecting an agent to game state through a JSON bridge.
Investigate an installed game before making a mod. Identify its engine, available mod loaders, save locations, anti-cheat protection, and compatibility issues, then record a practical approach and unresolved questions in MODDING_PLAN.md.
Research game modding methods and tools across public websites and archived pages. Recover information from dead forum links, compare reports, and produce findings with source URLs, version details, credibility notes, and clearly identified gaps.
Build mods that combine content or gameplay from different games. Choose between content ports, two games exchanging data, embedded game engines, or rewritten rules, with clear integration plans and checks against the original behavior.