Setup Guide

Auto-Configure (Recommended)

1. Create the Root GameObject

VehicleRoot (Rigidbody + OffroadVehicle)

1. Create an empty GameObject
2. Add a Rigidbody component
3. Add the OffroadVehicle component — it auto-adds OffroadInputSystem if no OffroadInput component exists

2. Run the Wizard

Prefab Note: If the root GameObject or any of its children (body, wheels) come from a prefab, unpack the prefab first (right-click in the Hierarchy > Prefab > Unpack). The wizard re-parents scene objects and creates new children — this breaks prefab connections. Unpack before running the wizard.

In the OffroadVehicle inspector, click Auto-Configure.

Step 1: Body (Optional)

• Drop a body mesh (prefab or scene object) into the Body field
• Scene objects are reparented (not copied); prefabs are instantiated
• The body receives a BoxCollider only if no colliders already exist
• All body renderers are set to the Ignore Raycast layer (so the suspension raycasts pass through)
• Adjust Scale if needed

Step 2: Wheel Selection

• Assign all 4 wheel meshes — Left Front, Right Front, Left Rear, Right Rear
• Radius and width are auto-detected from mesh bounds
  • The middle dimension becomes the radius
  • The smallest dimension becomes the width
• Manual overrides are available

Step 3: Axle Positions

The wizard calculates:

• Front Axle — midpoint between the two front wheel positions
• Rear Axle — midpoint between the two rear wheel positions
• Wheelbase — distance between front and rear axles
• Track Width — average of front and rear track widths

Create Vehicle

Click Create Vehicle — the wizard creates:

Created Item	Details
FrontAxle	SolidAxle with FrontWheel + RearWheel OffroadWheel children
RearAxle	SolidAxle with OffroadWheel children
OffroadWheel (×4)	Per-wheel components with preset radius/width
Wheel Pivot	Per-wheel pivot transform for spin + steer rotation
CenterOfMass	Empty transform positioned low (60% of half-height below body center)
Body	Reparented or instantiated with BoxCollider if needed

3. Configure the Vehicle

After wizard setup, configure the OffroadVehicle in the inspector:

Engine Presets

Preset	Max Torque	Max RPM	Idle RPM	Character
V8	650 Nm	5,500	750	Diesel-like low-end torque, 60% at idle
V6	500 Nm	6,500	800	Balanced, builds from 30% at idle
I4	400 Nm	7,500	850	Peak at high RPM, 15% at idle
I6	550 Nm	6,000	800	Broad flat curve, 40% at idle

Transmission Presets

Preset	Ratios	Final Drive
4-Speed	4.0 / 2.5 / 1.7 / 1.0	4.1
5-Speed	4.0 / 2.5 / 1.7 / 1.2 / 0.9	4.1
6-Speed	4.0 / 2.5 / 1.7 / 1.3 / 1.0 / 0.8	3.9

Vehicle Presets

One-click buttons that set weight, engine, transmission, suspension, differential, and aerodynamics:

Preset	Weight	Wheels	Suspension	Diff	Best For
Rock Crawler	2,400 kg	5.5 / 3.5 / 2.2 / 1.5 / 1.0 × 5.3 (×2.0 LO)	0.6m ride, 0.5m travel, 42k spring	Locked	Technical rock crawling
Trail Rig	2,000 kg	5.0 / 2.8 / 1.8 / 1.3 / 1.0 × 4.1 (×2.0 LO)	0.5m ride, 0.36m travel, 49k spring	LimitedSlip	General offroad
Overlander	3,200 kg	5.0 / 3.0 / 2.0 / 1.4 / 1.0 × 4.5 (×2.0 LO)	0.55m ride, 0.4m travel, 70k spring	Locked	Heavy expedition
Baja Racer	1,800 kg	4.0 / 2.2 / 1.6 / 1.2 / 0.9 × 3.7 (×2.0 LO)	0.6m ride, 0.6m travel, 26k spring	Open	High-speed desert

4. Configure Each Axle

Each SolidAxle has these per-axle settings:

Setting	Description
Drive	Axle receives engine torque
Steer	Wheels on this axle steer
Differential	Open, Locked, or LimitedSlip
Ride Height (m)	Distance from axle center to wheel center at rest
Travel Up (m)	How far the wheel compresses from rest (bump travel)
Travel Down (m)	How far the wheel droops from rest
Spring Rate (N/m)	Suspension stiffness
Damper Rate (N·s/m)	Suspension damping
Track Width (m)	Distance between left and right wheel centers
Traction Coefficient	Friction multiplier (1.2 = 20% more grip)
Cornering Coefficient	Slip-angle stiffness (5–15 typical). Higher = more lateral force.
Max Steer Angle (°)	Maximum steering angle (steerable only)
Steer Smooth Speed	Base response speed for steering
Sensitivity	0–2. Multiplier on steering response. Lower = less twitchy.
Auto Return	On: steering returns to center. Off: holds last position (manual return).
Invert Steer	Flip steering direction for this axle
Force Response	Lateral force build rate (1 = slow, 10 = instant)
High Speed Reduction	0–1. Reduces steering angle at high speed (arcade feel). 0 = off.
Reference Speed (m/s)	Speed at which High Speed Reduction reaches full effect

Stiffen/Soften buttons multiply both spring and damper rates by 1.2× / ÷1.2.

5. Add Effects (Optional)

Add OffroadEffects to each wheel GameObject:

1. Create an AudioSource with a tire squeal loop clip on each wheel
2. Assign it to Tire Squeal Source
3. Optionally assign a Skidmark Material and Tire Smoke ParticleSystem
4. Skidmarks auto-create TrailRenderers at runtime

6. Add Audio

Add OffroadAudio to the root GameObject:

1. Create an AudioSource for idle engine sound (assign a clip)
2. Create an AudioSource for running engine sound (assign a clip)
3. Assign both to OffroadAudio

7. Install the Input System Package

This asset uses Unity's New Input System (com.unity.inputsystem).

1. Open Window > Package Manager
2. Search for Input System and click Install
3. When prompted to enable the new input backend, click Yes and let Unity restart

Once installed, the OffroadInputSystem component is enabled by #if ENABLE_INPUT_SYSTEM.

8. Create an Input Action Asset

1. Right-click in your Project window → Create > Input Actions
2. Name it CarInputs.inputactions
3. Open the asset and rename the Action Map to Car
4. Add these actions with the suggested bindings:

Action	Type	Suggested Bindings
Steer	Value / Axis	Left Stick X, A/D keys
Throttle	Value / Axis	Right Trigger, W/Up
Brake	Value / Axis	Left Trigger, S/Down
LowRange	Button	Left Shoulder, Left Shift
Reverse	Button	Right Stick Down, R
Lights	Button	Y, L
CameraSwitch	Button	Right Shoulder, Tab
FourWheelDrive	Button	Left Bumper, F

9. Add PlayerInput to the Vehicle

1. Add a PlayerInput component to the VehicleRoot
2. Drag your CarInputs.inputactions asset into the Actions field
3. Set Default Map to Car
4. Set Behavior to Invoke Unity Events or Send Messages

Freelook: The camera controller reads mouse input directly via Unity's built-in Mouse X/Y axes (no input action setup needed). Move the mouse to orbit the camera; it recenters automatically when you drive.

The vehicle auto-discovers the PlayerInput component and reads actions by name. Hit Play and drive.

For code-driven input (testing, AI), add OffroadInputDelegate instead and set steerOverride, throttleOverride, brakeOverride from code.

10. Add Lights (Optional)

Add OffroadLightManager to the root GameObject:

1. Create child GameObjects with Light components
2. Assign Headlights, Brake Lights, and Reverse Lights to the respective lists
3. Brake lights auto-illuminate when braking
4. Reverse lights auto-illuminate in reverse

11. Add Telemetry (Optional)

Add OffroadInfo to the root GameObject for a real-time HUD overlay showing RPM, gear, speed, torque, compression, articulation, and drivetrain status. Enable Show Gizmo in the inspector to toggle the display.

12. Final Checks

• Verify the Center of Mass position in the Scene view (yellow cross gizmo)
• Check suspension visualization: white center dot, grey axle bar, blue ring (bump stop), red ring (full droop), yellow travel line
• Verify steer cone visualization on steerable axles (blue cone)
• Test drive! Use Max Throttle slider for keyboard-controlled demos
• Enable 4LO for low-range crawling

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Manual Setup (Alternative)

If you prefer to set up the hierarchy manually instead of using the wizard:

Hierarchy

VehicleRoot (Rigidbody + OffroadVehicle + OffroadInputSystem)
├── Body (visual mesh with BoxCollider, layer: Ignore Raycast)
├── CenterOfMass (empty Transform, positioned low)
├── FrontAxle (SolidAxle)
│   ├── Wheel_FL (OffroadWheel → Pivot → wheel_visual)
│   └── Wheel_FR (OffroadWheel → Pivot → wheel_visual)
└── RearAxle (SolidAxle)
    ├── Wheel_RL (OffroadWheel → Pivot → wheel_visual)
    └── Wheel_RR (OffroadWheel → Pivot → wheel_visual)

Key Points

• Each SolidAxle is a child of the root, positioned at the axle center height (Y = rideHeight above wheel center)
• Each OffroadWheel is a child of its axle, positioned at the wheel center in world space
• The wheel visual mesh should be under a Pivot transform (child of OffroadWheel) so spin and steer rotations don't interfere with each other
• The Body must be on the Ignore Raycast layer so suspension raycasts can detect the ground through it

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Suspension Gizmo Reference

Color	Element
White dot	Axle center position
Grey line	Axle bar at rest height
Blue ring	Full bump position (max compression)
Red ring	Full droop position (max extension)
Yellow dotted line	Travel range
Blue/white coilover	Spring zigzag visualization
Blue cone	Steer angle range (steerable axles)

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Common Tuning Tips

Issue	Solution
Vehicle caps at low speed	Decrease rBody.drag — Unity drag is mass × velocity × drag, overpowers heavy vehicles
Vehicle bounces	Increase Damper Rate on SolidAxle
Body rolls too much	Increase Spring Rate, lower Ride Height, widen Track Width
Not enough traction	Increase Traction Coefficient, switch to Locked diff
Won't climb steps	Ensure Travel Up is sufficient (≥0.2m), step detection is active in WheelCast
Engine RPM stuck low	Check gear ratios, increase Shift Down RPM so transmission downshifts earlier
Upshifts too early	Raise Shift Up RPM
Downshifts too late	Raise Shift Down RPM
Oversteers on throttle	Switch diff to Open or LimitedSlip, reduce Traction Coefficient on driven axle
Understeers	Soften front springs, increase rear spring rate
Won't hold on hill	Enable Parking Hold
No power in 4LO	4LO multiplies torque — ensure gear ratios are appropriate for crawling
Wheel clips through steps	Increase Travel Up for more bump travel, verify step detection ray is active