Hierarchical N-body solver

Fast Multipole Gravity Lab

Adaptive quadtree Cartesian FMM in 2D with softened gravity. Far field via multipole & local expansions, near field exact.

M2M → M2L → L2L → P2P

Particles–

FPS–

FMM solve–

Nodes–

M2L pairs–

Force error–

Preset Particles 1024

M2M: child moments → parents
M2L: far cells → local fields
L2L: parent fields → leaves
P2P: exact neighbouring forces

Expansion order 3 Separation ratio 1.60 Leaf capacity 32

Gravity G 0.65 Softening ε 0.018 Timestep 0.0030

Particle trails

Quadtree overlay

Acceleration vectors

Auto sampled error

Click to inject a particle cloud · Shift-click to add a massive body · Space pauses