Frontline Forge Engine (FFE)

A custom fork of id Tech 4, derived from the RBDOOM-3-BFG codebase, designed to support the development of a cinematic World War II first-person shooter.

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🎯 Overview

Frontline Forge Engine (FFE) is a restructuring of id Tech 4 focused on building a grounded, narrative-driven FPS experience.

This engine powers:

Crimson Star: Ruins of Ash
A cinematic WWII FPS set during the Battle of Stalingrad.

FFE transforms the original engine by removing DOOM-specific gameplay systems and introducing features suited for human-scale combat, squad-based encounters, and environmental storytelling.

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🧠 Design Philosophy

FFE is built around:

• Cinematic, linear mission design
• Hybrid realism combat (grounded but playable)
• Squad presence as environmental pressure
• Strong atmosphere through lighting and audio
• Controlled, scripted battlefield chaos

This is not a DOOM port, it will be the foundation for a new game.

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🔧 Key Modifications (Planned & In Progress)

• Replacement of monster AI with human combat AI
• Modernized input and player movement
• Weapon systems redesigned for WWII combat
• Mission scripting for cinematic sequences
• Improved audio systems for battlefield immersion
• Cleanup of legacy DOOM-specific systems

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📁 Project Structure

• /engine Core engine code (id Tech 4 fork)
• /game Game-specific logic and systems
• /assets Game content (non-GPL)
• /docs Design documents and technical notes
• /tools Build tools and utilities

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⚙️ Building the Engine

🐧 Linux (Recommended)

1. Install Dependencies

Debian / Ubuntu:

Install ISPC: sudo snap install ispc

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2. Install DirectX Shader Compiler (DXC)

Download from: https://github.com/microsoft/DirectXShaderCompiler/releases

Then:

chmod +x dxc
mv dxc ~/.local/bin/

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3. Build

Preferred repo-root workflow:

./build.sh

This script:

• reuses the existing build/ directory for incremental builds
• runs neo/cmake-linux-release.sh automatically when CMake has not been configured yet
• compiles the engine from build/

Manual equivalent:

cd neo
./cmake-linux-release.sh
cd ../build
make -j"$(nproc)"

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4. Run

Preferred repo-root workflow:

./run.sh

This launcher:

• starts the binary from build/
• mirrors stdout/stderr into log.log
• keeps the repo-root log as the primary runtime debug log

Manual equivalent:

cd build
./RBDoom3BFG

Note: the runtime window title is already Frontline Forge Engine, but the binary name is still RBDoom3BFG.

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📦 Game Data (Required)

FFE requires original DOOM 3 BFG assets for now.

You must provide:

• base/ folder from DOOM 3 BFG Edition

Options:

• Steam install
• GOG install
• SteamCMD

Place in: <repo_root>/base/

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⚖️ License

This project is licensed under:

GNU GPL-3.0-or-later

• Engine code modifications must remain open source
• Game assets (models, audio, maps) are NOT covered by GPL

See:

• LICENSE.md
• LICENSE_EXCEPTIONS.md

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🧱 Credits

• id Software — original id Tech 4 engine
• Robert Beckebans & contributors — RBDOOM-3-BFG

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🚧 Project Status

Early development.

Current focus:

• Engine setup and validation
• System refactoring
• First playable vertical slice (Stalingrad, July 1942)

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🪖 Vision

To create a WWII FPS that emphasizes:

• the confusion of first contact
• the exhaustion of prolonged combat
• the transformation of a city into ruins

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📌 Notes

• This project is in active development
• Many systems are placeholders or under heavy modification
• Expect instability during early stages

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