Roblox Vehicle Physics Implementation

When implementing vehicle physics, follow these Roblox-specific patterns and constraints.

Car Physics

Basic Setup

-- Use VehicleSeat for driver control -- Connect wheels with HingeConstraint (ActuatorType = Motor) -- Use SpringConstraint for suspension -- CylindricalConstraint for steering column

local function setupWheel(chassis, wheelPart, isSteer, isDrive) local attachment0 = Instance.new("Attachment", chassis) local attachment1 = Instance.new("Attachment", wheelPart)

-- Suspension spring
local spring = Instance.new("SpringConstraint")
spring.Attachment0 = attachment0
spring.Attachment1 = attachment1
spring.Stiffness = 5000  -- Adjust for vehicle weight
spring.Damping = 500
spring.FreeLength = 1
spring.Parent = chassis

-- Wheel rotation
local hinge = Instance.new("HingeConstraint")
hinge.ActuatorType = Enum.ActuatorType.Motor
hinge.MotorMaxTorque = isDrive and 10000 or 0
hinge.Parent = wheelPart

end

Critical Implementation Details

• Network Ownership: Always SetNetworkOwner(driver) when player enters vehicle

• Friction: Set wheelPart.CustomPhysicalProperties with specific friction values

• Anti-Roll: Use RodConstraint between left/right suspension attachments

• Steering Ackermann: Inner wheel turns sharper than outer: innerAngle = atan(L / (R - W/2))

Gear System

local gearRatios = {3.5, 2.5, 1.8, 1.4, 1.0, 0.8} -- 6 gears local finalDrive = 3.7 local maxRPM = 7000

local function calculateWheelTorque(throttle, currentGear, engineRPM) local torqueCurve = 1 - ((engineRPM - 4500) / maxRPM)^2 -- Peak at 4500 RPM return throttle * baseTorque * torqueCurve * gearRatios[currentGear] * finalDrive end

Helicopter Physics

Lift and Control

-- Main rotor provides lift proportional to collective (throttle) -- Cyclic control tilts the rotor disc for directional movement -- Tail rotor counters main rotor torque

local function updateHelicopter(heli, collective, cyclicPitch, cyclicRoll, pedal) local rotorRPM = heli:GetAttribute("RotorRPM") local airDensity = 1.225 -- kg/m³ at sea level

-- Lift = 0.5 * rho * A * Cl * V²
local liftForce = collective * rotorRPM / 500 * heli.Mass * workspace.Gravity

-- Apply forces
local bodyForce = heli:FindFirstChild("LiftForce") or Instance.new("VectorForce", heli)
bodyForce.Force = Vector3.new(
    cyclicRoll * liftForce * 0.3,
    liftForce,
    cyclicPitch * liftForce * 0.3
)

-- Anti-torque from tail rotor
local tailTorque = pedal * rotorRPM * 10
local bodyTorque = heli:FindFirstChild("YawTorque") or Instance.new("Torque", heli)
bodyTorque.Torque = Vector3.new(0, tailTorque, 0)

end

Ground Effect

-- Increase lift when near ground (within 1 rotor diameter) local function groundEffect(altitude, rotorDiameter) if altitude < rotorDiameter then return 1 + (1 - altitude/rotorDiameter) * 0.25 -- Up to 25% lift bonus end return 1 end

Boat Physics

Buoyancy Implementation

-- Sample multiple points below waterline local buoyancyPoints = { Vector3.new(2, 0, 3), -- Front-right Vector3.new(-2, 0, 3), -- Front-left Vector3.new(2, 0, -3), -- Back-right Vector3.new(-2, 0, -3), -- Back-left Vector3.new(0, 0, 0), -- Center }

local function calculateBuoyancy(hull, waterHeight) local totalForce = Vector3.new(0, 0, 0)

for _, localPos in ipairs(buoyancyPoints) do
    local worldPos = hull.CFrame:PointToWorldSpace(localPos)
    local depth = waterHeight - worldPos.Y

    if depth > 0 then
        -- Buoyancy force proportional to submerged depth
        local force = Vector3.new(0, depth * 1000 * hull.Mass / #buoyancyPoints, 0)
        totalForce = totalForce + force
    end
end

return totalForce

end

Wave Response

-- Tilt hull based on wave surface normal local function getWaveHeight(x, z, time) local wave1 = math.sin(x * 0.1 + time) * 2 local wave2 = math.sin(z * 0.15 + time * 1.3) * 1.5 return wave1 + wave2 end

Airplane Physics

Lift and Drag

local wingArea = 20 -- m² local dragCoefficient = 0.02 local liftCoefficient = 0.5

local function calculateAeroForces(velocity, angleOfAttack) local speed = velocity.Magnitude local dynamicPressure = 0.5 * 1.225 * speed^2

-- Lift perpendicular to velocity
local Cl = liftCoefficient * math.sin(2 * angleOfAttack)
local lift = dynamicPressure * wingArea * Cl

-- Stall: lift drops sharply past critical angle
if math.abs(angleOfAttack) > math.rad(15) then
    lift = lift * (1 - (math.abs(angleOfAttack) - math.rad(15)) / math.rad(10))
end

-- Drag opposes velocity
local Cd = dragCoefficient + Cl^2 / (math.pi * 8)  -- Induced drag
local drag = dynamicPressure * wingArea * Cd

return lift, drag

end

Motorcycle/Bike Balance

-- Self-stabilization using BodyGyro with low torque local function setupBikeBalance(bike) local gyro = Instance.new("BodyGyro") gyro.MaxTorque = Vector3.new(5000, 0, 5000) -- Only roll and pitch gyro.P = 1000 gyro.D = 100 gyro.Parent = bike.PrimaryPart

-- Counter-steering: turn bars opposite to initiate lean
local function handleSteering(turnInput, speed)
    if speed > 10 then
        -- At speed, steering input causes lean
        local targetLean = turnInput * math.min(speed / 50, 1) * math.rad(45)
        gyro.CFrame = CFrame.Angles(0, 0, targetLean)
    end
end

end

Train/Rail Following

-- Constrain train to spline path local function followRail(train, spline, distance) local position = spline:GetPositionAtDistance(distance) local tangent = spline:GetTangentAtDistance(distance)

local alignPos = train:FindFirstChild("RailAlign") or Instance.new("AlignPosition", train.PrimaryPart)
alignPos.Position = position
alignPos.RigidityEnabled = true

local alignOri = train:FindFirstChild("RailOrient") or Instance.new("AlignOrientation", train.PrimaryPart)
alignOri.CFrame = CFrame.lookAt(position, position + tangent)

end

Common Patterns

Network Ownership Transfer

vehicleSeat:GetPropertyChangedSignal("Occupant"):Connect(function() local humanoid = vehicleSeat.Occupant if humanoid then local player = game.Players:GetPlayerFromCharacter(humanoid.Parent) if player then for _, part in ipairs(vehicle:GetDescendants()) do if part:IsA("BasePart") and not part.Anchored then part:SetNetworkOwner(player) end end end else -- Return to server ownership for _, part in ipairs(vehicle:GetDescendants()) do if part:IsA("BasePart") then part:SetNetworkOwner(nil) end end end end)

Speedometer/Tachometer

local function getVehicleSpeed(chassis) return chassis.AssemblyLinearVelocity.Magnitude * 3.6 -- Convert to km/h end

local function getRPMFromWheel(hingeConstraint) -- Track angle change over time local currentAngle = hingeConstraint.CurrentAngle local deltaAngle = currentAngle - lastAngle local rpm = (deltaAngle / (2 * math.pi)) * 60 / deltaTime return math.abs(rpm) end