How to add friction to a Wheel of Fortune in Unity3D - unity3d

Question

First of all I am new to unity as will as C#. I want to create a Wheel of Fortune for my game using C# where you can rotate it with the mouse. I wrote this code in C# - it works well, the only problem is I don’t know how to add friction to it so that if I release the mouse button it still continues rotating and slows down until it is fully stopped (Just like a realistic Fortune Wheel).
using UnityEngine;
using System.Collections;
public class RotateCSharp : MonoBehaviour
{
public int speed;
public float lerpSpeed;
float xDeg;
float yDeg;
Quaternion fromRotation;
Quaternion toRotation;
void Update()
{
if (Input.GetMouseButton(0))
{
xDeg -= Input.GetAxis("Mouse X") * speed;
fromRotation = transform.rotation;
toRotation = Quaternion.Euler (yDeg,xDeg,0);
transform.rotation = Quaternion.Lerp(fromRotation, toRotation, Time.deltaTime * lerpSpeed);
}
}
}
How can I accomplish this?

Answer 1

Full Disclosure--I don't do Unity, and not much C#, but this is mostly math.
Friction from sliding or rolling is almost exactly constant deceleration. Deceleration is negative acceleration, and acceleration is (velocity change)/(elapsed time).
Figure out how long you want the wheel to spin at a the maximum initial angular speed you'll allow, and that speed/time ratio is your deceleration rate. That's a constant for the wheel.
Now, in the code either before or after adjusting the angular position, decrease the speed by the deceleration rate * time interval, being careful not to overshoot 0:
if (speed > 0)
speed = Math.max(0, speed - decelRate*Time.deltaTime);
else
speed = Math.min(0, speed + decelRate*Time.deltaTime);
That assumes that decelRate is a positive value, and will handle spins in either direction.
You may have to adjust the syntax a bit, but that's the basic idea.

Answer 2

I've put together a behaviour that applies friction on a hinge joint. Here it is:
using UnityEngine;
public class JointFriction : MonoBehaviour {
[Tooltip("mulitiplier for the angular velocity for the torque to apply.")]
public float Friction = 0.4f;
private HingeJoint _hinge;
private Rigidbody _thisBody;
private Rigidbody _connectedBody;
private Vector3 _axis; //local space
// Use this for initialization
void Start () {
_hinge = GetComponent<HingeJoint>();
_connectedBody = _hinge.connectedBody;
_axis = _hinge.axis;
_thisBody = GetComponent<Rigidbody>();
}
// Update is called once per frame
void FixedUpdate () {
var angularV = _hinge.velocity;
//Debug.Log("angularV " + angularV);
var worldAxis = transform.TransformVector(_axis);
var worldTorque = Friction * angularV * worldAxis;
_thisBody.AddTorque(-worldTorque);
_connectedBody.AddTorque(worldTorque);
}
}
You can apply this as a separate behaviour to the object with the hinge joint, or you can take bits of it and incorporate them into your behaviour.
This code assumes the hinge joint has a connected rigidbody that it is rubbing against, if that is not the case, simply remove the lines that refer to the _connectedRigidbody.