A self-levelling Rigidbody-based "vehicle" controller

HoverChassis.cs

using UnityEngine;
using System.Collections;

[AddComponentMenu("Chassis/Hover Chassis")]
public class HoverChassis : Chassis
{
	[SerializeField] protected Transform m_CentreOfMass;
	[SerializeField] protected Transform m_TurningForcePosition;
	[SerializeField] protected Transform m_RaycastPoint;
	
	[SerializeField] protected float m_SteerFactor = 1.0f;
	[SerializeField] protected float m_DriveFactor = 1.0f;
	[SerializeField] protected float m_HoverHeight = 1.0f;
	[SerializeField] protected float m_LiftFactor = 1.0f;
	[SerializeField] protected float m_SelfRightFactor = 1.0f;
	[SerializeField] protected float m_TurnTiltFactor = 1.0f;
	[SerializeField] protected float m_DriveLiftFactor = 0.2f;
	
	protected float m_Altitude;
	
	protected void Start()
	{
		if(m_CentreOfMass)
			m_Rigidbody.centerOfMass = m_CentreOfMass.transform.localPosition;
	}
	
	protected void FixedUpdate()
	{
		if(!m_Takeoff)
			return;
		
		RaycastHit hit;
		if(Physics.Raycast(m_RaycastPoint.position, -m_RaycastPoint.up, out hit))
			m_Altitude = hit.distance;
		
		float steering = m_Steering * m_SteerFactor;
		float drive = m_Drive * m_DriveFactor;

		float lift = Mathf.Clamp((m_HoverHeight - m_Altitude) * m_LiftFactor, -m_LiftFactor, m_LiftFactor);
		
		m_Rigidbody.AddRelativeForce(new Vector3(0.0f, lift + Mathf.Abs(drive), drive));
		m_Rigidbody.AddRelativeTorque(new Vector3(drive * m_DriveLiftFactor, steering * m_TurnTiltFactor, 0.0f));
		m_Rigidbody.AddForceAtPosition(transform.right * -steering, m_TurningForcePosition.position);
		
		float offAngle = Vector3.Angle(transform.up, Vector3.up);
		if(offAngle > 0.001f)
		{
			Vector3 axis = Vector3.Cross(transform.up, Vector3.up);
			m_Rigidbody.AddTorque(axis * offAngle * m_SelfRightFactor);
		}
	}
}