Visibility with reflection

We extend the concept of the polygon visible from a source point S in a simple polygon by considering visibility with two types of reflection, specular and dzffuse. In specular reflection a light ray reflects from an edge of the polygon according to Snell’s law: the angle of incidence equals the angle of reflection. In diffuse reflection a light ray reflects from an edge of the polygon in all inward directions. Several geometric and combinatorial properties of visibility polygons under these two types of reflection are revealed, when at most one reflection is permitted. We show that the visibility polygon VS(S) under specular reflection may be non-simple, while the visibility polygon Vd(S) under diffuse reflection is always simple. We present a @(nz) worst case bound on the combinatorial complexity of both VS(S) and Vd(S) and describe simple 0(n2 log2 n) time algorithms for constructing the sets.

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