Hierarchical N-body solver

Fast Multipole Gravity Lab

Softened 2D gravity with an adaptive quadtree, Cartesian multipole expansions and truncated Taylor kernel jets. Every interaction is either a far-field multipole translation or an exact near-field pair — no all-pairs loop, so a step stays linear in particle count.

P2M → M2M → M2L → L2L → P2P

Telemetry

Particles1024

Frames / s—

Solve + integrate—

Tree nodes (depth)0

M2M upward0 M2L far0 L2L downward0 P2P exact pairs0

Sampled force error—

Step stiffness δ—

Scene

Preset Particles 1024

FMM solver

Expansion order p 4 Separation criterion 2.60 Leaf capacity 24

Physics

Gravity G 0.55 Softening ε 0.036 Timestep dt 0.0045

View

Particle trails Quadtree overlay Acceleration vectors Sampled error check

Click to inject a dust cloud · Shift-click drops a massive body · Space pause · T tree · R reset · error bar compares against direct O(N²) summation