A Geometrical Constraint on Shadowing in Rough Surfaces

By considering a one-dimensional cross-section through the rough surface, we derive a purely geometrical constraint on the statistical distribution of shadowed facet slopes that should be satissed by any model of surface emissivity that includes the eeect of self-shadowing. Our purpose is not to develop a single shadowing model, but to provide a condition that any valid shadowing model should satisfy. Although the emphasis of the presentation is theoretical, some practical ramiications will also be discussed.