nbody.h File Reference

N-body gravitational simulation (Velocity Verlet + Plummer softening). More...

#include "nbody_types.h"
#include "sphere_types.h"

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Functions
void	nbody_init_preset (NBodySim *sim)
	Initializes the simulation with a preset solar system configuration.
void	nbody_step (NBodySim *sim, float delta_time)
	Advances the simulation by the given wall-clock delta time.
void	nbody_update_time_scale (NBodySim *sim, float delta_time)
	Smoothly transitions time_scale toward target_time_scale.
void	nbody_write_instances (const NBodySim *sim, SphereInstance *out)
	Writes current body positions and materials into a SphereInstance array.
int	nbody_get_count (const NBodySim *sim)
	Returns the number of active bodies.
float	nbody_total_energy (const NBodySim *sim)
	Computes the total energy (kinetic + gravitational potential).
float	nbody_kinetic_energy (const NBodySim *sim)
	Computes kinetic energy only: Σ ½ m v².
float	nbody_energy_drift (const NBodySim *sim)
	Returns the relative energy drift |E(t) - E₀| / |E₀|.
float	nbody_energy_drift_signed (const NBodySim *sim)
	Signed energy drift.

Detailed Description

N-body gravitational simulation (Velocity Verlet + Plummer softening).

Manages a set of gravitational bodies with position, velocity, and mass. Uses a symplectic Velocity Verlet integrator with per-pair Plummer softening to guarantee long-term energy conservation without ad-hoc damping. Produces SphereInstance data for the instanced renderer.

See also

docs/nbody_physics.md for the full physics reference.

Function Documentation

nbody_energy_drift()

float nbody_energy_drift

(

const NBodySim *

sim

)

Returns the relative energy drift |E(t) - E₀| / |E₀|.

nbody_energy_drift_signed()

float nbody_energy_drift_signed

(

const NBodySim *

sim

)

Signed energy drift.

nbody_get_count()

int nbody_get_count

(

const NBodySim *

sim

)

Returns the number of active bodies.

nbody_init_preset()

void nbody_init_preset

(

NBodySim *

sim

)

Initializes the simulation with a preset solar system configuration.

nbody_kinetic_energy()

float nbody_kinetic_energy

(

const NBodySim *

sim

)

Computes kinetic energy only: Σ ½ m v².

nbody_step()

void nbody_step	(	NBodySim *	sim,
		float	delta_time
	)

Advances the simulation by the given wall-clock delta time.

nbody_total_energy()

float nbody_total_energy

(

const NBodySim *

sim

)

Computes the total energy (kinetic + gravitational potential).

nbody_update_time_scale()

void nbody_update_time_scale	(	NBodySim *	sim,
		float	delta_time
	)

Smoothly transitions time_scale toward target_time_scale.

nbody_write_instances()

void nbody_write_instances	(	const NBodySim *	sim,
		SphereInstance *	out
	)

Writes current body positions and materials into a SphereInstance array.