Rotate an sphere by mouse inputs

// speed is the rate at which the object will rotate var speed = 4.0;

function Update () { // Generate a plane that intersects the transform's position with an upwards normal. var playerPlane = new Plane(Vector3.up, transform.position);

 // Generate a ray from the cursor position
 var ray = Camera.main.ScreenPointToRay (Input.mousePosition);

 // Determine the point where the cursor ray intersects the plane.
 // This will be the point that the object must look towards to be looking at the mouse.
 // Raycasting to a Plane object only gives us a distance, so we'll have to take the distance,
 //   then find the point along that ray that meets that distance.  This will be the point
 //   to look at.
 var hitdist = 0.0;
 // If the ray is parallel to the plane, Raycast will return false.
 if (playerPlane.Raycast (ray, hitdist)) {
     // Get the point along the ray that hits the calculated distance.
     var targetPoint = ray.GetPoint(hitdist);

     // Determine the target rotation.  This is the rotation if the transform looks at the target point.
     var targetRotation = Quaternion.LookRotation(targetPoint - transform.position);

     // Smoothly rotate towards the target point.
     transform.rotation = Quaternion.Slerp(transform.rotation, targetRotation, speed * Time.deltaTime);
 }

}