swept-path

Will this car get through that gate, and how many shunts will it take?

swept-path-steel.vercel.app

A swept path simulator for narrow openings — a driveway gate, a courtyard entrance, a parking box. You give it the opening and the vehicle; it returns a drivable trajectory, the clearance left at the tightest point, and where that figure came from.

Swept path is the English term of art; in French the field is called épure de giration. The interface reads in either, and measures in metres or in US units.

• Can this vehicle get in at all, and in how many moves?
• How much room is left at the tightest moment — and is that moment in the gateway, or against a curb six metres short of it? The two mean very different things to a driver, so both are reported.
• How wide would the street have to be for a single-move entry?
• Is the answer proved or merely found? An exhaustive sweep that returns nothing has established something; a heuristic planner that returns nothing has not. Every result carries which one produced it, and the interface never shows a clearance without it.

The one conclusion worth knowing before opening it: width decides everything. Whatever the trajectory, the best clearance on each side is (opening − vehicle) / 2. Extra manoeuvres buy none of it.

Explained in the app, with figures drawn by the same renderer as the plan: How it works and Disclaimer .

In short: the vehicle follows a kinematic bicycle model, a state being the pose of the rear axle. Three solvers run in turn — an exhaustive sweep of Dubins and Reeds-Shepp curves, a hybrid A* planner for multi-move entries, and a bisection for the narrowest usable street. Clearance, not length, is what gets maximised: the shortest path is the one that grazes most. Everything runs in a Web Worker, and budgets are counted in expanded nodes rather than milliseconds, so the same inputs always produce the same answer on any machine.

Requires the Rust toolchain pinned in rust-toolchain.toml, with the wasm32-unknown-unknown target, plus wasm-pack, just and Node 24.

just install # web dependencies
just dev # rebuilds the wasm package, then serves the app
just ci # everything CI runs

just on its own lists every recipe.

Code, identifiers, rustdoc, test names and commit messages are in English; the interface reads in French or English. Inside the core, lengths are metres and angles radians without exception — conversion happens once, where the form is read.

Stated plainly, because a confident wrong answer is worse than no answer. The scene is assumed symmetric about the opening, so the two posts cannot yet be placed independently. Slope, camber, suspension travel and parked vehicles are absent. And most vehicle figures are not measured: in data/vehicles.json, width over the mirrors is often derived and front overhang estimated, where three centimetres of error flips a conclusion — which is why provenance is recorded field by field.

The application — swept-solver, swept-wasm, the web interface — is AGPL-3.0-only, in LICENSE.

The geometric core, swept-core, is MIT OR Apache-2.0, in crates/swept-core/LICENSE-MIT and LICENSE-APACHE, so that it stays reusable on its own. Keeping it free of production dependencies is what makes that possible.

The vehicle data in data/vehicles.json is licensed separately from the code, and comes from manufacturer documents only — never from an aggregator, whose database rights would follow it.