Hierarchical N-body solver

Fast Multipole Gravity Lab

Softened Newtonian gravity in 2D, solved every frame with an adaptive-quadtree Cartesian FMM — far fields travel through multipole and local Taylor expansions, near fields are summed exactly.

M2M → M2L → L2L → P2P

Particles0

FPS–

FMM solve–

Quadtree nodes0

M2L interactions0

Sample force err–

Scene

Particle count 1024

FMM solver

Expansion order 3

Separation ratio 1.60

Leaf capacity 32

Physics

Gravity G 0.65

Softening ε 0.018

Timestep dt 0.0030

View

Particle trails Quadtree overlay Acceleration vectors Sampled error check

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