Quaternion.Slerp

static function Slerp (from : Quaternion, to : Quaternion, t : float) : Quaternion

Description

Spherically interpolates between from and to by t.

JavaScript
// Interpolates rotation between the rotations "from" and "to"
// (Choose from and to not to be the same as
// the object you attach this script to)

var from : Transform;
var to : Transform;
var speed = 0.1;
function Update () {
transform.rotation =
Quaternion.Slerp (from.rotation, to.rotation, Time.time * speed);
}