vehicle-physics

Basic Setup

```lua

-- 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

1. Network Ownership: Always SetNetworkOwner(driver) when player enters vehicle
2. Friction: Set wheelPart.CustomPhysicalProperties with specific friction values
3. Anti-Roll: Use RodConstraint between left/right suspension attachments
4. Steering Ackermann: Inner wheel turns sharper than outer: innerAngle = atan(L / (R - W/2))

Gear System

```lua

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

```

Lift and Control

```lua

-- 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

```lua

-- 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

```

Buoyancy Implementation

```lua

-- 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

```lua

-- 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

```

Lift and Drag

```lua

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

```

```lua

-- 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

```

```lua

-- 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

```

Network Ownership Transfer

```lua

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

```lua

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

```