GRAVITY // N-BODY

GRAVITY // N-BODY LABORATORY

A direct-summation gravitational N-body simulation. Every particle attracts every other particle — exact O(N²) forces evaluated in a tiled WebGPU compute shader, integrated with a symplectic kick-drift-kick leapfrog scheme. No trees, no approximations, no dependencies.

CAMERA

• drag — orbit  ·  scroll / pinch — zoom  ·  shift-drag — pan

TOOLS

• ATTRACT — hold the pointer to drag a gravitational well through the system. Stir the galaxy.
• SPAWN — drag and release to launch a massive perturber (an intermediate-mass black hole) with the drag direction as its velocity.
• External forcing injects energy — the drift meter re-zeroes when you let go.

KEYS

• space pause   1–5 scenarios   r regenerate   f fullscreen   h hide UI   t trails   ? help

ACCURACY

The HUD tracks total energy E = K + W (kinetic + gravitational potential, including the analytic halo where active) computed on-GPU with the same softened kernel as the forces. A symplectic integrator does not secularly drift — ΔE stays bounded and oscillates. The virial ratio 2K/|W| of a relaxed self-gravitating system settles near 1. Watch both live.

UNITS

G = 1. Each scenario uses natural units (disk scale lengths, Plummer radii). Softening adapts to N as ε ∝ N^-1/3.