claudes_game/docs/implementation_plan.md

Orbital Mechanics Simulation - Technical Reference

Overview

3D orbital mechanics simulation using 2-body gravitational model with sphere of influence (SOI) transitions. Built with C-style C++ and raylib.

Technical Constraints

• C-style C++ only: structs and functions, no classes or templates
• Euler integration for physics
• Simple rotations (quaternions deferred)
• raylib for 3D visualization

Core Data Structures

Vec3 (physics.h)

struct Vec3 {
    double x, y, z;
};

CelestialBody (bodies.h)

struct CelestialBody {
    char name[64];
    double mass;              // kg
    double radius;            // meters
    Vec3 position;            // meters from origin
    Vec3 velocity;            // m/s
    double soi_radius;        // sphere of influence radius (meters)
    int parent_index;         // index of gravitational parent (-1 for root)
    float color[3];           // RGB for rendering
    double eccentricity;      // orbital eccentricity (0 = circular)
    double semi_major_axis;   // meters
};

SimulationState (bodies.h)

struct SimulationState {
    CelestialBody* bodies;
    int body_count;
    int max_bodies;
    double time;              // simulation time (seconds)
    double dt;                // time step (seconds)
};

RenderState (renderer.h)

struct RenderState {
    Camera3D camera;
    double distance_scale;    // Scale factor for distances
    double size_scale;        // Scale factor for body sizes
    bool show_info;           // Display simulation info
};

Module Overview

Physics (physics.cpp/h)

Vector math and gravity calculations. Euler integration with euler_step().

Bodies (bodies.cpp/h)

Simulation state management and updates. SOI detection using Hill sphere: r_soi = a * (m/M)^(2/5)

Config Loader (config_loader.cpp/h)

Text-based config parser. Auto-calculates circular orbit velocities and SOI radii.

Config format:

# name mass(kg) radius(m) x(m) y(m) z(m) parent_index r g b
Sun 1.989e30 6.96e8 0 0 0 -1 1.0 1.0 0.0
Earth 5.972e24 6.371e6 1.496e11 0 0 0 0.0 0.5 1.0

Renderer (renderer.cpp/h)

Raylib 3D visualization with logarithmic distance scaling and size scaling for visibility.

Implementation Status

✅ Completed

• Phase 1-4: Core physics, simulation, config loading, and rendering
• Raylib integration with 3D camera
• Distance and size scaling for visualization
• Config file system with solar_system.txt

🔨 Remaining/Future Work

• Time scaling controls (speed up/slow down)
• Pause/resume functionality
• Additional config files (binary star, etc.)
• Time step tuning for stability

Technical Notes

Scaling for Visualization

• Distance: logarithmic/power-law scaling for solar system scale
• Size: minimum visible radius to prevent tiny bodies from disappearing
• Origin at Sun for simplicity

Physics Considerations

• Timestep: ~60 seconds for solar system scale
• Circular orbit velocity: v = sqrt(G * M / r)
• May need multiple physics sub-steps per render frame

Future Enhancements

• More accurate integration (RK4, Verlet), NOTE: try Newton-Raphson propagation method with testing first
• Interactive body selection
• Reference frame switching