torqueCars

Drivable cars that behave like machines, as one family switched by one setting. Twelve kinds in three looks, each with its own engine character, gearing and drive layout, and every part swappable while you drive. Built on the engine's own vehicle physics: WheelCollider tyres that spin and slip, a ShaftNetwork drivetrain (engine torque curve → clutch → gearbox → differentials → wheels) solved inside the physics step, and a SoftBody shell that crumples where it is hit and stays crumpled until the car is reset.

First example

Install torqueCars (it brings driveSurfaces for ground grip when you install that too). Then, with the world in play, run this from the console (execute) — or paste it into your scene's entrypoint.luau inside function onLoad() ... end:

local Assemble = require("torqueCars.assemble")
local car = Assemble.spawn({ kind = "rally", position = vector.create(0, 0.2, 6) })
-- W/S throttle and brake (S at a stop reverses), A/D steer, Space brake,
-- Ctrl handbrake, E/Q shift, M auto/manual, R reset, Backspace respawn.

The car takes the player's driving controls at once (gamepad and touch too). To make a car each joining player's own body, build it under the scene's player prototype in build.luau:

local Assemble = require("torqueCars.assemble")
local body = entity.spawn("body", { parent = prototype })
Assemble.build(body, { kind = "coupe", look = "real" })
body.component.add("Car", { kind = "coupe", look = "real", control = "player" })
prototype.component.add("PlayerPrototype", { body = body, camera = rig })

Add a Garage component to any scene entity and G opens the parts panel.

The family: one setting each

Every field below is on the Car component and can be changed live (from the garage, from code with car:setPart(slot, name), or in the inspector):

An empty part name means "the kind's own". All data is in torqueCars.catalog.

Measured 0–100 km/h (stock, flat tarmac, assists on, simulated time)

All twelve measured together on a 2 km tarmac strip with Bench.accelerate, full-rate controller.

Measure your own with torqueCars.bench (Bench.accelerate(car, 100), Bench.brake(car, 60), Bench.brakeRolling(car, 60)); the bench turns the car's lod off. The powerful rear-drivers (muscle, coupe) and the kart are traction-limited off the line: traction control holds the driven tyres near their peak slip, and with it off they spin without limit (#20654), so they launch slower than their real twins.

Measured 60–0 km/h braking (stock hatchback, road tyres, ABS, rolling start)

Gravel stops 28 % later than tarmac, ice 6.6× later. Sand and mud stop shorter than their grip alone suggests because the wheels sink and plough (the surface's bogging drag), as they do in a real car. Studded tyres multiply ice grip 4.2×, snow tyres snow grip 1.9×, off-road tyres loose ground 1.35×.

Measured damage

A rally car driven into the valley's concrete crash wall at 60 km/h (crash detector closing speed 44–50 km/h, the rest absorbed in the first instants of contact) kept a permanent crush of 9.5 cm nose-first and 12.7 cm side-on, unchanged 5 s later. The dent stays until reset() or a respawn, which rebuild the shell undamaged. The rigid core spans the cabin (76 % of the length), so the shell's nose and tail are the crumple zones.

Cost

Per car on a desktop (native, in the editor): the driver runs at the physics tick, about 0.3–0.8 ms a step (network inputs are written only when they change; each ShaftNetwork:set costs ~0.2 ms), and the soft-body shell ~0.15–0.2 ms a step at resolution 5 (36–40 particles). Script-driven cars more than 60 m from this peer's own car run their controller every other step (lod, on by default).

How it drives

• Engine: full-throttle torque curve per engine (idle, redline, limiter); idle governor; turbo spool lag (turbo four, diesel); a rev limiter that cuts fuel in 70 ms bursts. Engine braking from friction and pumping losses.
• Clutch: automatic — slips to launch, opens for every shift, re-engages (manual ≈0.3 s, sequential 80 ms, automatic slurs like a torque converter).
• Gearbox: auto-shift by rpm and pedal (kickdown included) or manual E/Q; holding brake at a standstill selects reverse.
• Differentials: open, limited-slip (preload + bias) or locked; AWD cars add a biased centre diff.
• Tyres: grip curve per tyre set, multiplied by the ground under each wheel (driveSurfaces) and the set's affinity for that ground — studded tyres on ice, off-road tyres on gravel.
• Body: a plastic soft-body shell held to the chassis along the cabin floor, so the nose and tail are crumple zones. A 60 km/h wall hit leaves about 10 cm of permanent crush (9.5 cm measured nose-first, 12.7 cm side-on). car:reset() (R) repairs it. car.damage counts from the shell's settled shape, so a fresh or respawned car reads 0 %.
• Cockpit: the body draws its inner faces as dark cabin trim and leaves the glass open from inside, and every car carries a steering wheel in front of its seat, so a camera at car.mountSeat sits in a cabin and one at car.mountHood looks over the bonnet.
• Respawn: respawn() (Backspace) takes the car back to where it stood once it had settled after spawning (a spawner that moves the car in its first second moves the spawn point with it), or to setSpawn's point, set down on the ground there.
• Drag: aerodynamic drag, rolling resistance and soft-ground bogging.

Values a car publishes

Gauges, engine sounds, cameras and AI read the car only through named values on the chassis (car.rpm, car.kmh, car.gear, car.load, …). The full list and the Car API are in CONTRACT.md in this package.

Contents

• Car component — the driver (input or script), drivetrain control, assists, damage, values.
• Garage component — the live parts panel (G / d-pad up / touch).
• torqueCars.assemble — builds a car under a chassis entity (build, spawn).
• torqueCars.catalog — kinds, engines, gearboxes, diffs, tyres, paints.
• torqueCars.bodies — the 36 body meshes, wheels and paints (three looks).
• torqueCars.bench — 0–100 and braking measurements.
• torqueCars.cars — registry of live cars (Cars.all(), Cars.localPlayer()).
• driveControls input map — throttle, steer, brake, handbrake, boost, recover (keyboard, gamepad, touch); the car's own, so it does not depend on the engine's vehicle map.
• carControls input map — shift, auto/manual, respawn, garage (keyboard, gamepad, touch).
• carGallery scene — every kind in every look side by side.

Multiplayer

Each car is simulated by the peer that owns it (a player's car by that player, AI cars by the host); every other peer draws it from the owner's poses. The engine replicates the soft-body dents from the owner, so everyone sees the same crumpled panels, including a player who joins later. The values a voice, a gauge or a brake lamp needs (car.rpm, car.load, car.throttle, car.gear, car.shiftCount, car.boost, car.skid, car.brake, car.impactCount, …) are declared with a replication rate, so remote cars sound and light up as they drive. The part fields (kind, engine, tyres, …) are synced: a swap made in one player's garage reaches every peer. Driving intent and network inputs are local to the owner. Verified on one machine with the engine's replication read-outs; a second real client has not been connected yet.

Known engine limits

• #20569 — wheels do not read the ground's named surfaces yet, so each car ray-casts under its wheels itself and asks driveSurfaces for the grip.
• #20610 — rolling resistance is in progress in the engine; the car applies its own rolling resistance and drag as forces and leaves rollingResistance off double-counting.
• #20543 — wheels have no volume and cannot come off: a crash dents the body but never knocks a wheel loose, and a wheel can clip through a wall the body stops at.
• #20654 — held at full throttle a wheel can spin up without limit; the rev limiter and traction control (assists) keep it in check, with assists off a stationary burnout can over-spin.
• #21001 — a drivetrain's cost grows quickly with its parts, so every car uses the smallest network for its layout (7 parts FWD/RWD, 9 AWD) and writes network inputs only when they change.
• #21241 / #21242 — synced entity references and lists with gaps do not reach other players; the car keeps none in synced fields (the shell's attachment is re-made on each peer).