vinihcrosaandClaude Sonnet 4.6
dd4e79cbd6
NavalForceModel bridge pattern keeps core::ForceModel interface intact while providing NavalContext (environment, speedToWater, speedToWind, EMA q_avg) to all naval models via bindContext. Force models: Inertial (Coriolis), Restoring (hydrostatic spring), Damping (potential + linear/quadratic), Squat (ICORELS shallow-water), Wind (REGULAR/ACSINKAGE), Current (OBOKATA section-integration and REGULAR with Van der Pol VIM RK4), Thrust (open-water Kt), Rudder (Prandtl lift), Tug (PUSH/PULL/ESCORTING with bilinear table). Wave engine: JONSWAP/PIERSON/REGULAR spectrum, Mitsuyasu cos-2S directional spreading, WAMIT RAO interpolation in WaveForces. NavalSimulation wraps core::Simulation, rebuilds NavalContext each step, maintains EMA (tau=16.5s). 63/63 tests pass. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Ymir
General-purpose physics engine. Designed to simulate the dynamics of physical bodies under arbitrary force systems — extensible to any domain. Coupled with any viewer or simulator via a clean C API.
Current scope: naval domain. First implementation covers 6-DOF hydrodynamics for ships and floating platforms (current, wind, waves, thrusters, rudders, tugs). The architecture is domain-agnostic by design.
What it does (naval module)
- Simulates vessel motion under current, wind, and waves
- Models propulsion (thrusters, rudders), mooring forces, and tug interactions
- Exposes a C API (
DLL/.so/.dylib) for integration with Unity, C#, Python, or any host - Runs in fast-time (pure simulation) or real-time (frame-driven by external host)
Requirements
| Concern | Decision |
|---|---|
| Language | C++17 |
| Mesh library | CGAL |
| ODE solver | SUNDIALS CVODE |
| Build system | CMake ≥ 3.16 |
| Tests | Catch2 |
| Docs | Doxygen |
| Targets | Linux, macOS, Windows — x86_64 & ARM64 |
Architecture
Ports and Adapters. Physics core is pure library — no I/O, no rendering, no file dependencies. Adapters handle JSON input, CSV output, and the public C API.
ymir/
├── core/ # Pure physics — forces, integrator, vessel state
├── adapters/ # JSON I/O, CSV writer, C API (DLL boundary)
├── applications/ # Executables: fasttime, realtime
├── tests/ # Catch2 unit + integration tests
├── docs/ # Architecture docs, design decisions
└── include/ # Public C headers (DLL interface)
Folder structure is provisional — see
docs/as the project evolves.
Building
cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build
Cross-compilation targets and packaging scripts will be documented once the build system is established.
Design principles
- No global state in the physics core
- No runtime allocations inside the integration loop
- Pure C interface at the DLL boundary — no STL, no exceptions crossing the ABI
- Every public function documented with Doxygen
- Every module covered by unit tests before integration