  We use a 3D Monte Carlo radiative transfer code to study the polarimetric and
photometric variability from stationary corotating interaction regions (CIR) in
the wind of massive stars. Our CIRs are approximated by Archimedean spirals of
higher (or lower) density formed in a spherical wind originating from the star
and we also made allowance for a bright gaussian spot at the base of the CIR.
Comparing results from our code to previous analytical calculations in the
optically thin case, we find differences which we attribute mainly to a better
estimation of the total unpolarized flux reaching the observer. In the
optically thick case, the differences with the analytical calculations are much
larger, as multiple scattering introduces extra complexities including
occultation effects. The addition of a gaussian spot does not alter the shape
of the polarization curve significantly but does create a small excess in
polarization. On the other hand, the effect can be larger on the light curve
and can become dominant over the resulting CIR, depending on the spot
parameters and density of the wind.
