Raycer

Raycer is a lightweight arcade car library. Each car is a single rigid body held up by one raycast spring per wheel, with tire forces computed in code. It uses the same model layout as A-Chassis, so existing A-Chassis-style cars work with it.

Raycer is built for games that prioritize fun driving over realism, like kart racers, party games, etc.

It is not a 1:1 replacement for A-Chassis!

Why Raycer?

• Small. One module of about 400 lines and a config, with no plugins, GUIs or legacy body movers.
• Predictable grip. Tires don't depend on Roblox contact friction, so cars don't slide out in corners or catch on seams between floor parts.
• Tuned in real units. Top speed in studs/s, grip in g, suspension as a bounce frequency. No torque curves or gear ratios.
• One assembly. The car is welded into a single body, so network ownership is one call and there are no joints to break.
• Input for free. Raycer reads the VehicleSeat's ThrottleFloat and SteerFloat, which Roblox's default controls already fill for keyboard, gamepad and touch.
• Per-car tuning. Each car points at its own config, which only needs the values it changes.
• No legacy/deprecated code. Other popular car libraries, such as A-Chassis, use deprecated legacy methods such as :MakeJoints, which do not work well with modern features. Raycer uses only modern APIs.

What it doesn't do

• Exactly four wheels. No three-wheelers, bikes or trucks with extra axles.
• No drifting or handbrake. Tires cancel sliding, which keeps cars controllable but means no oversteer.
• No gearbox or engine simulation. The engine sound's pitch follows speed.
• Only driven cars are simulated. With nobody in the seat, the car rests on its collision hull.

Car layout

The required layout for Raycer is the following:

📦 Car (Model)
├── 💺 DriveSeat (VehicleSeat)
├── 📁 Wheels
│   ├── FL (BasePart)
│   ├── FR (BasePart)
│   ├── RL (BasePart)
│   └── RR (BasePart)
├── 📁 Body (optional, any parts)
└── 🔗 Config (ObjectValue, optional, points at a config ModuleScript)

• The wheels can be any shape. They're only visual and get animated for spin, steering and suspension travel.
• Raycer builds an invisible collision hull from the Body's footprint, sitting just above the ground, so walls and other cars bounce off it. Wheels are made non-collidable. Body parts keep their CanCollide setting, so turn it off unless you want them colliding too.
• The DriveSeat doesn't need to be level. Raycer works out "forward" and "up" from the wheel positions.

Usage

Server

local Raycer = require(ReplicatedStorage.Raycer)

local car = workspace.Car
local chassis = Raycer.new(car)
chassis:Init() -- Welds the car, builds its hull and hands physics to whoever sits in the DriveSeat

-- Later, when the car is removed
chassis:Destroy()

Raycer.new(car, config) also accepts a config ModuleScript, which replaces whatever the car's Config ObjectValue points at.

Client

Call initClient once per client, from a LocalScript. It drives the local player's car and animates every car's wheels and engine sound.

local Raycer = require(ReplicatedStorage.Raycer)

Raycer.initClient()

Collision groups

If your cars use a collision group, pass it in:

Raycer.initClient({ collisionGroup = "Cars" })

The suspension rays then follow the same collision rules as the cars. For example, if characters don't collide with Cars, cars drive straight over players instead of bumping up onto them. Without it, the rays hit anything with CanCollide enabled except the car itself.

Configuration

Every car uses Raycer.DefaultConfig unless its Config ObjectValue points at another ModuleScript. That module only needs the values it changes:

--!strict
return {
	MAX_SPEED = 110,
	GRIP = 2.2,
}

Misspelled keys print a warning, and a config that fails to load falls back to the default.

Key	Default	What it does
MAX_SPEED	90	Top speed, in studs/s.
REVERSE_SPEED	35	Top reversing speed, in studs/s.
ACCELERATION	60	Acceleration, in studs/s².
BRAKE_DECELERATION	130	Braking when holding the opposite direction, in studs/s².
COAST_DECELERATION	20	Slowdown with no throttle, in studs/s².
STEER_ANGLE	30	Front wheel angle at full lock when stopped, in degrees.
HIGH_SPEED_STEER_ANGLE	10	Front wheel angle at full lock at MAX_SPEED, in degrees.
STEER_SPEED	5	How fast the steering moves, in full locks per second.
GRIP	1.8	Max tire force, in multiples of the load on that wheel. Higher means tighter turns before sliding.
SLIP_RATE	25	How fast tires cancel sideways sliding, per second. Lower feels looser.
SUSPENSION_TRAVEL	0.4	Wheel travel each way from rest, in studs.
SUSPENSION_FREQUENCY	3	Suspension bounce speed, in Hz. Higher is stiffer.
SUSPENSION_DAMPING	0.7	1 stops bouncing as fast as possible; lower bounces more.
FLIP_DELAY	2	Seconds upside down before the car flips itself back over.
ENGINE_SOUND_ID	rbxassetid://358130654	Looping engine sound.
ENGINE_VOLUME	0.35	Engine sound volume.
ENGINE_IDLE_PITCH	0.17	Engine sound PlaybackSpeed when stopped.
ENGINE_MAX_PITCH	1.42	Engine sound PlaybackSpeed at MAX_SPEED.

Get started

This project uses Azul, the easiest two-way sync tool.

Use azul push to get the library into your Roblox project:

azul push -s .\sync\ReplicatedStorage -d ReplicatedStorage --from-sourcemap .\raycer.sourcemap.json

This pushes Raycer to ReplicatedStorage. It needs to be somewhere both the server and clients can require it.

License

MIT