# Verlet Integration & Constraints

**Track:** Simulation & Complexity — Advanced Creative Coding — proposed (50)
**Framework / surface:** p5.js
**Level:** Medium
**Prerequisites:** Forces & Acceleration, Vectors: Magnitude & Direction

**In one line:** Position-based motion; distance constraints as the building block.

## Theory, aesthetics & inspiration

Verlet integration tracks a particle by its current and previous positions; velocity lives implicitly in the gap between them, so motion emerges without ever being stored explicitly. Loup Verlet introduced the scheme for molecular dynamics in 1967, and Thomas Jakobsen's 2001 GDC paper "Advanced Character Physics" recast it for games, pairing it with iterative constraint relaxation. The atomic unit is the distance constraint: hold two points a fixed length apart, project them back when stretched, and repeat until the system settles. From this single rule, rope, cloth, and ragdolls assemble. The aesthetic is one of settling weight — overshoot, sag, and a convincing inertia that feels observed rather than scripted.