Ymir

6-DOF naval physics simulator — rigid-body hydrodynamics for ships and floating platforms under current, wind, waves, thrusters, rudders, and tug interactions.

The engine is domain-agnostic by design. The naval module is the first application.

Repository layout

ymir/
├── apps/
│   ├── server/        real-time server (WebSocket, Protobuf, API handlers)
│   └── fast-time/     batch accelerated simulation (no live clients)
├── libs/
│   ├── common/        math utilities, physical constants, shared types
│   ├── physics/       bodies, force modules, CVODE integrator
│   ├── simulation/    tick orchestration, event system
│   ├── world/         wave engine, environment, terrain state
│   ├── vessel/        vessel config, control modes, actuator state
│   └── persistence/   JSON scenario reader (SQLite planned)
├── tests/             mirrors libs/ structure
└── docs/
    ├── architecture/  architecture wiki and ADR index
    ├── guides/        building.md, contributing.md
    └── adr/           Architecture Decision Records

Bounded contexts

Each context is a CMake static library. The linker enforces dependency rules — no target may link to a context it does not depend on.

Context	CMake target	Include prefix	Directory
Common	ymir_common	ymir/common/	libs/common/
Physics	ymir_physics	ymir/physics/	libs/physics/
Simulation	ymir_simulation	ymir/simulation/	libs/simulation/
World	ymir_world	ymir/world/	libs/world/
Vessel	ymir_vessel	ymir/vessel/	libs/vessel/
Persistence	ymir_persistence	ymir/persistence/	libs/persistence/

Common — shared math, physical constants, and primitive types; no dependencies on other Ymir libraries.
Physics — rigid-body dynamics: state integration, force accumulation, and all force-module implementations.
Simulation — tick orchestration, real-time vs. fast-time loop, deterministic step sequence, pub/sub event system.
World — state repository for all entities and environment; wave engine, terrain, ambient conditions.
Vessel — vessel configuration, mutable actuator/control state, control modes (drift, LOS, berth maneuver).
Persistence — I/O adapters translating between external formats (JSON) and domain objects.

See docs/architecture/bounded-contexts.md for the full dependency table and responsibility breakdown.

Building

Prerequisites

Requirement	Version
C++ compiler	GCC 9+ or Clang 10+ (C++17)
CMake	3.20+
SUNDIALS	6.x (SUNDIALS::cvode)
Catch2	3.x (tests)
nlohmann/json	any recent release (persistence)

Commands

cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build
ctest --test-dir build

Further reading

• docs/architecture/README.md — architecture wiki: bounded-context map, data-flow diagrams, ADR index
• AGENTS.md — contributor rules, coding standards, include conventions, commit discipline

License

MIT — see LICENSE.