@ -83,11 +83,28 @@ struct AccelerationContext {
Vector math and gravity calculations. RK4 (Runge-Kutta 4th order) integration with `rk4_step()` .
### Bodies (bodies.cpp/h)
Simulation state management and updates. SOI detection using Hill sphere: `r_soi = a * (m/M)^(2/5)`
Simulation state management and updates. SOI detection using Hill sphere: `r_soi = a * (m/M)^(2/5)` .
**Key functions:**
- `find_dominant_body()` - determines which body has gravitational dominance
- `update_soi()` - calculates sphere of influence radius using Hill sphere
- `update_simulation()` - runs one physics step: finds dominant parent, calculates gravity, applies RK4 integration
- Dynamic parent switching when bodies cross SOI boundaries (with hysteresis)
### Config Loader (config_loader.cpp/h)
TOML-based config parser using tomlc17 library. Auto-calculates circular orbit velocities and SOI radii.
**Key functions:**
- `parse_toml_body()` - parses individual body entries
- `calculate_initial_velocities()` - sets circular orbit velocities using vis-viva equation
- `calculate_soi_radii()` - computes sphere of influence for all bodies
**Config format details:**
- TOML array of tables: `[[bodies]]`
- Comments start with `#`
- `parent_index = -1` indicates root bodies (stars)
- Supports binary/multiple star systems with barycentric orbit calculation
**Config format (TOML):**
```toml
[[bodies]]
@ -114,6 +131,42 @@ semi_major_axis = 1.496e11
### Renderer (renderer.cpp/h)
Raylib 3D visualization with logarithmic distance scaling and size scaling for visibility.
### Main Program (main.cpp)
GUI-only application with interactive 3D visualization.
- Initializes simulation with MAX_BODIES=100, TIME_STEP=60 seconds
- Runs 100 physics steps per frame (adjustable with speed multiplier)
- Game loop: input handling → camera update → physics update (if not paused) → rendering
- Supports speed multiplier (2x/0.5x per keypress, min 0.125x)
**Controls:**
- Arrow keys: Rotate and zoom camera
- Space: Pause/Resume
- +/-: Speed up/slow down simulation
- I: Toggle info display
- ESC: Quit
## Data Flow
### Initialization Sequence
1. Configuration file → `load_system_config()` → populates `SimulationState`
2. `calculate_initial_velocities()` → sets circular orbit velocities for all bodies
3. `calculate_soi_radii()` → computes sphere of influence for each body
### Main Simulation Loop
1. `update_simulation()` → for each body:
- `find_dominant_body()` → determine gravitational parent based on SOI
- `evaluate_acceleration()` → compute gravitational force from parent
- `rk4_step()` → update position/velocity using Runge-Kutta 4th order
2. `render_simulation()` → for each body:
- `scale_position()` → convert to render coordinates using logarithmic scaling
- `scale_radius()` → convert to render size using exponential scaling
- `render_body()` → draw sphere with color
### SOI Transition Mechanics
- Bodies dynamically switch gravitational parents when crossing SOI boundaries
- Uses 0.5x distance hysteresis to prevent oscillation between parents
- `find_dominant_body()` checks all bodies and selects most dominant influence
## Implementation Status
### ✅ Completed
@ -134,15 +187,25 @@ Raylib 3D visualization with logarithmic distance scaling and size scaling for v
## Technical Notes
### Code Style and Architecture
- C-style C++: structs and functions only, no classes or templates
- All headers use include guards
- Memory management uses malloc/free
- Layer separation: Physics, Simulation, Configuration, Rendering layers
### 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
- Both distance_scale and size_scale are configurable in RenderState
### Physics Considerations
- Timestep: ~ 60 seconds for solar system scale
- Timestep: 60 seconds for solar system scale
- Circular orbit velocity: `v = sqrt(G * M / r)`
- May need multiple physics sub-steps per render frame
- Physics steps per frame: 100 (default) with speed multiplier adjustment
- Simulation time per frame: 60s * 100 = 6000 seconds at 1x speed
- SOI (Sphere of Influence) uses Hill sphere approximation: `r_soi = a * (m/M)^(2/5)`
- SOI transitions use 0.5x distance hysteresis to prevent oscillation
## Future Enhancements
- More accurate integration methods (Newton-Raphson propagation)
