Ymir/docs/architecture

Ymir Architecture

Ymir is a general-purpose 6-DOF physics engine targeting the naval domain. It runs multiple isolated simulations in parallel and exposes a WebSocket + Protobuf API to external clients.

Design Principles

• Domain-agnostic core — the naval module is one application of the engine, not the engine itself.
• Bounded contexts enforced at link time — one CMake static library target per context; linker rejects illegal cross-context dependencies.
• No I/O in physics — all external dependencies (JSON, SQLite, networking) live in adapter libraries.
• Deterministic tick order — every module executes in a fixed sequence each simulation step.

Repository Structure

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

Architecture Pages

Page	Contents
bounded-contexts.md	Responsibilities, CMake target, include prefix, and dependencies for each bounded context
data-flow.md	Simulation tick sequence (12 steps), force execution order, CVODE integration loop

Bounded-Context Map

ymir_common
    └── (no internal deps)

ymir_physics
    ├── ymir_common
    └── SUNDIALS::cvode

ymir_simulation
    ├── ymir_physics
    └── ymir_common

ymir_world
    ├── ymir_physics
    └── ymir_common

ymir_vessel
    ├── ymir_physics
    └── ymir_common

ymir_persistence
    ├── ymir_physics
    ├── ymir_world
    ├── ymir_vessel
    └── nlohmann_json::nlohmann_json

Two Operation Modes

App	Mode	Clients	Isolation
apps/server	Real-time 1×	Manager, Viewer (live events)	Thread per simulation
apps/fast-time	Batch accelerated N×	None live	Process per simulation

ADRs

• ADR-001 — Atomic split reorganization
• ADR-002 — Include namespaces match bounded-context directories
• ADR-003 — One CMake static library target per bounded context