  Detailed analysis of the lightcurve of CAL 87 clearly has shown that the high
optical luminosity comes from the accretion disc rim and can only be explained
by a severe thickening of the disc rim near the location where the accretion
stream impinges. This area is irradiated by the X-rays where it faces the white
dwarf. Only if the reprocessing rate of X-rays to optical light is high a
luminosity as high as observed can be understood. But a recent detailed study
of the soft X-ray radiation reprocessing in supersoft X-ray sources has shown
that the efficiency is not high enough. We here propose a solution for this
problem. As already discussed in the earlier lightcurve analysis the impact of
the accretion stream at the outer disc rim produces a ``spray'', consisting of
a large number of individual gas blobs imbedded in a surrounding corona. For
the high mass flow rate this constitutes an optically thick vertically extended
screen at the rim of the accretion disc. We analyse the optical properties of
this irradiated spray and find that the multiple scattering between these gas
blobs leads to an effective reprocessing of soft X-rays to optical light as
required by the observations.
