ThreeJS Rapier3d Physics is a self-running rigid-body playground: colourful boxes, spheres and rounded blocks rain down onto a grid floor, bounce, tumble and pile up under gravity.
How it works. A full physics engine — Rapier, written in Rust and compiled to WebAssembly so it runs at near-native speed in the browser — steps the world forward every frame, pulling bodies down with gravity and resolving collisions between shapes using their mass and restitution (bounciness). three.js simply mirrors each body's computed position and rotation onto its matching mesh, while thin outlines drawn around every collider reveal the physics shapes the engine actually sees. A new random shape is dropped in automatically once a second, and any body that falls past the floor's edge is quietly removed so the scene never overflows.
What you'll see:
- Automatic spawning — a fresh box, sphere or rounded box in a random colour drops from above every second.
- Bouncy collisions — bodies land with springy restitution, so they bounce and jostle before settling into a heap.
- Orbit the scene — drag to rotate and scroll to zoom, with smooth damped camera motion.
- Full screen — fills the display.
A mostly hands-off three.js physics showcase, computed and rendered live on the Switch GPU entirely offline.