Rust · rapier3d · renders to braille

A physics sandbox in your terminal.

Inertia simulates rigid bodies, orbital gravity, cloth, fluid, and heat in full 3D, then draws the whole scene with Unicode braille. No GPU, no window server. The same engine now compiles to WebAssembly, so it runs in your browser too.

Launch the demo → View source $cargo install inertia-tui

Rust WebAssembly 60 fps No GPU MIT / Apache-2.0

A recording of Inertia in a terminal: picking the rigid body demo from the start menu, then a pyramid of boxes scattering as a ball is launched into it.

Real physics, drawn in text.

Inertia is a real-time playground that lives entirely inside a terminal. Every solid, particle, and spring is simulated in three dimensions and rasterized with braille glyphs, so each character cell doubles as a 2×4 block of pixels. The result is a smooth, shaded 3D scene made of nothing but text.

Rigid-body dynamics run on rapier3d; the n-body gravity, mass-spring cloth, smoothed-particle fluid, and the temperature field on top of it are built from scratch. You orbit the camera, spawn and throw objects, pour water, heat things up, and watch it all settle, sixty times a second.

Because the engine is plain Rust, it also compiles to WebAssembly and renders to a canvas through ratzilla. Every demo below is the exact terminal program, running in the browser.

The simulations

Six sandboxes, one engine.

Five open on a preset scene; the sixth starts empty. Launch any of them in the browser, then take the controls: orbit the camera, spawn objects, and push the parameters around.

A ball mid-flight through a collapsing pyramid of braille boxes on a grid floor.

Rigid bodies

rapier3d

A ball is launched into a pyramid of boxes. Friction, restitution, and stacking, solved in real time.

Three stars tracing a figure-eight orbit with glowing trails.

N-body gravity

brute-force / Barnes-Hut

Three stars trace a figure-eight in mutual gravitation, leaving orbital trails behind them.

Cloth

mass-spring

A hammock of springs stretches and swings as two balls drop into it. Pin it up, blow wind through it.

A tank of blue braille water with a red ball and a yellow box floating in it.

Fluid

SPH

Thousands of smoothed particles splash and settle into a tank, buoying the debris that lands in them.

Water in a tank colored by temperature, warm plumes rising from a hot floor.

Thermal convection

heat transfer

A hot floor warms the water above it. Buoyant plumes rise and cool, shaded by temperature.

Blank sandbox

build your own

Start from nothing. Drop boxes and spheres, switch gravity to n-body, add cloth and water, and mix the systems however you like.

Get it running

In the browser, or in your shell.

Install from crates.io

Needs a recent Rust toolchain. The crate is published as inertia-tui; the installed command is inertia.

$ cargo install inertia-tui
$ inertia

Build the browser demo

The web build uses trunk and the wasm32-unknown-unknown target. Point trunk at this site's demo/ folder and the Launch buttons light up.

$ rustup target add wasm32-unknown-unknown
$ trunk build --release --dist site/demo

Controls

Arrow keysOrbit the camera

Shift + arrowsPan across the scene

+ / -Zoom in and out

Left dragGrab an object and throw it

b · s · nSpawn a box, sphere, or star

dCycle tool: place, grab, pour, heat, build

SpacePause, then m to step one frame

1 – 6Switch between the sandboxes

? · qFull help, and quit