public class LocalGravity:MonoBehaviour {
    public LayerMask gravMeshLayer;
    public float gravityDistance = 10.0f;
    public float rotationSpeed = 4.0f;
    public void Update() {
        RaycastHit hit;
        if (Physics.Raycast(transform.position,-transform.up,out hit,gravityDistance,gravMeshLayer)) {
            float distRatio = hit.distance/gravityDistance;
            transform.up = Vector3.Slerp(transform.up,hit.normal,Time.deltaTime*rotationSpeed);
        }
    }
}