  Eight years of optical photometry from OGLE-III are presented of the optical
counterpart to the High Mass X-ray Binary system, SMC X-1. The optical data
provide the best view to date of the modulation of the light from the system at
the binary period of 3.9d. In addition, it is shown for the first time that the
light is also modulated at the superorbital period - a period associated with
the precessing of a warped accretion disk around the neutron star partner. The
implications for the sources of the various components of the optical light in
this system are discussed.
