BRUTAL

Rabbet is a from-scratch C++ 3D game engine with a sparse-set entity-component system, versioned entity handles, dense component pools, and a system-and-resource runtime. Its OpenGL 4.1 renderer provides a forward path with metallic-roughness PBR, a Phong fallback, lighting and shadow maps, emissive surfaces, optional image-based lighting, post-processing, CPU particles, and heightmap or noise terrain. The Forge editor provides a dockable ImGui workspace around a render-to-texture viewport, asset thumbnails, hierarchy reparenting, click-to-pick, snapping gizmos, and Play/Pause/Step/Stop controls that snapshot and restore scenes. Assets use stable UUIDs and .import sidecars; models, textures, audio, materials, shaders, prefabs, and scenes are supported, with scenes stored as readable JSON. Lua behaviors run through sol2 with live hot-reload and inspector-editable fields, while physics uses Jolt rigidbodies and audio uses miniaudio. The repository includes the engine, editor, examples, and tests, including the Orb Hunt demo game. It uses CMake 3.24 or later and a C++20 compiler, supports macOS and Linux, fetches pinned dependencies during configuration, and is licensed under Apache License 2.0.

Bevy is a free, open-source data-driven game engine written in Rust. Its engine and game logic use Bevy ECS, an entity-component system in which components are Rust structs and systems are Rust functions, with parallel scheduling, queries, resources, and change detection. It includes 2D and 3D rendering, a render graph for composable and parallel render pipelines, skeletal and blend-shape animation, GLTF loading, audio, scenes, hot reloading, and an ECS-based UI framework with flexbox-style layout. Bevy supports Windows, macOS, Linux, Web, iOS, and Android, and is distributed under the MIT or Apache 2.0 licenses.

Box3D is an open-source 3D physics engine for games, written in portable C17. It provides rigid-body simulation with collision detection, continuous collision detection, contact events, convex hulls, capsules, spheres, triangle meshes, height fields, multiple shapes per body, collision filtering, ray and shape casts, overlap queries, sensors, and a character mover. Its physics system includes a robust Soft Step rigid-body solver, continuous physics, island-based sleeping, and revolute, prismatic, distance, motor, weld, and wheel joints with limits, motors, springs, friction, and force events. The data-oriented system uses multithreading and SSE2 or Neon SIMD, supports cross-platform determinism and recording and replay, and is optimized for large piles of bodies. The core library has no dependencies beyond the C runtime and libm on Unix, can be integrated with CMake as the box3d::box3d target, and builds on Windows, Linux, macOS, and WebAssembly; its samples use sokol and Dear ImGui.

A browser-based first-person shooter built with Three.js r180 and WebGL2. It uses procedurally generated textures, meshes, animations, and Web Audio synthesis rather than external art or sound files; its systems include a market-street world with enterable interiors, custom physics and character movement, procedural weapons and ballistics, GPU visual effects, navmesh-based enemy AI with perception and cover behavior, and a DOM/CSS HUD. The repository also provides a development and testing harness: headless-Chromium screenshot capture, isolated reproducible shotsets with pixel-diff gating, scripted playtesting, and a gameplay profiler that reports frame-time distributions and attributes hitches to per-frame WebGL program compilation. The project is run with npm and has Three.js as its only runtime dependency.

ET is a Unity3D client and C# server framework for distributed online games, including MMOs. It lets client and server code share logic and supports multi-process and multi-threaded server architectures, fiber-based runtimes, actor messaging, service discovery, dynamic room distribution, async/await workflows, hot reload, client and server bots, automated protocol-level tests, and server-side 3D Recast navigation. Its networking layer supports KCP, ENet, TCP, and WebSocket transport with runtime switching, while Unity provides the client runtime and development environment. The ET10 generation adds an AI-assisted development workflow built around analyzers, a Unity runtime bridge, automated compilation and gameplay verification, multi-bot testing, runtime log analysis, and architecture rules covering async safety, entity lifecycles, package dependencies, actor usage, and other runtime constraints. Its Unity bridge exposes operations for scenes, assets, GameObjects, components, prefabs, Play Mode, logs, screenshots, and tests. Additional packages provide behavior trees, configurable condition expressions, spells and buffs, service discovery, .NET Aspire integration, and OpenTelemetry support. The repository distributes the framework as C# and Unity projects and packages. The README states that the ET10 open-source version uses the ET License, is intended for learning and requires a separate license for commercial use.