  Light scattering from self-affine homogeneous isotropic random rough surfaces
is studied using the ray-optics approximation. Numerical methods are developed
to accelerate the first-order scattering simulations from surfaces represented
as single-connected single-valued random fields, and to store the results of
the simulations into a numerical reflectance model. Horizon mapping and
marching methods are developed to accelerate the simulation. Emphasis is given
to the geometric shadowing and masking effects as a function of surface
roughness, especially, to the azimuthal rough-surface shadowing effect.
