  We develop 3-D models of the structured winds of massive hot stars with the
Wind3D radiative transfer (RT) code. We investigate the physical properties of
large-scale structures observed in the wind of the B-type supergiant HD 64760
with detailed line profile fits to Discrete Absorption Components (DACs) and
rotational modulations observed with IUE in Si IV {\lambda}1395. We develop
parameterized input models Wind3D with large-scale equatorial wind density- and
velocity-structures, or so-called `Co-rotating Interaction Regions' (CIRs) and
`Rotational Modulation Regions' (RMRs). The parameterized models offer
important advantages for high-performance RT calculations over ab-initio
hydrodynamic input models. The acceleration of the input model calculations
permits us to simulate and investigate a wide variety of physical conditions in
the extended winds of massive hot stars. The new modeling method is very
flexible for constraining the dynamic and geometric wind properties of RMRs in
HD 64760. We compute that the modulations are produced by a regular pattern of
radial density enhancements that protrude almost linearly into the equatorial
wind. We find that the modulations are caused by narrow `spoke-like' wind
regions. We present a hydrodynamic model showing that the linearly shaped
radial wind pattern can be caused by mechanical wave action at the base of the
stellar wind from the blue supergiant.
