// Define the variables used in the script, the Corresponding collider is the wheel collider at the position of
// the visible wheel, the slip prefab is the prefab instantiated when the wheels slide, the rotation value is the
// value used to rotate the wheel around it's axel.
var CorrespondingCollider : WheelCollider;
var SlipPrefab : GameObject;
private var RotationValue : float = 0.0;

function Update () {

  // define a hit point for the raycast collision
  var hit : RaycastHit;
  // Find the collider's center point, you need to do this because the center of the collider might not actually be
  // the real position if the transform's off.
  var ColliderCenterPoint : Vector3 = CorrespondingCollider.transform.TransformPoint( CorrespondingCollider.center );
   
  // now cast a ray out from the wheel collider's center the distance of the suspension, if it hit something, then use the "hit"
  // variable's data to find where the wheel hit, if it didn't, then se tthe wheel to be fully extended along the suspension.
  if ( Physics.Raycast( ColliderCenterPoint, -CorrespondingCollider.transform.up, hit, CorrespondingCollider.suspensionDistance + CorrespondingCollider.radius ) ) {
   transform.position = hit.point + (CorrespondingCollider.transform.up * CorrespondingCollider.radius);
  }else{
   transform.position = ColliderCenterPoint - (CorrespondingCollider.transform.up * CorrespondingCollider.suspensionDistance);
  }
   
  // now set the wheel rotation to the rotation of the collider combined with a new rotation value. This new value
  // is the rotation around the axle, and the rotation from steering input.
  transform.rotation = CorrespondingCollider.transform.rotation * Quaternion.Euler( RotationValue, CorrespondingCollider.steerAngle, 0 );
  // increase the rotation value by the rotation speed (in degrees per second)
  RotationValue += CorrespondingCollider.rpm * ( 360/60 ) * Time.deltaTime;
   
  // define a wheelhit object, this stores all of the data from the wheel collider and will allow us to determine
  // the slip of the tire.
  var CorrespondingGroundHit : WheelHit;
  CorrespondingCollider.GetGroundHit( CorrespondingGroundHit );
   
  // if the slip of the tire is greater than 2.0, and the slip prefab exists, create an instance of it on the ground at
  // a zero rotation.
  if ( Mathf.Abs( CorrespondingGroundHit.sidewaysSlip ) > 2.0 ) {
   if ( SlipPrefab ) {
    Instantiate( SlipPrefab, CorrespondingGroundHit.point, Quaternion.identity );
   }
  }
   
}

function OnDrawGizmos () {
  // make a new array of waypoints, then set it to all of the transforms in the current object
  var waypoints = gameObject.GetComponentsInChildren( Transform );
   
  // now loop through all of them and draw gizmos for each of them
  for ( var waypoint : Transform in waypoints ) {
   Gizmos.DrawSphere( waypoint.position, 1.0 );
  }
   
}