Diffuse Reflection Radius in a Simple Polygon
  It is shown that every simple polygon in general position with $n$ walls can be illuminated from a single point light source $s$ after at most $\lfloor (n-2)/4\rfloor$ diffuse reflections, and this bound is the best possible. A point $s$ with this property can be computed in $O(n\log n)$ time. It is also shown that the minimum number of diffuse reflections needed to illuminate a given simple polygon from a single point can be approximated up to an additive constant in polynomial time. 
Eli Fox-Epstein, Csaba T\'oth, and Andrew Winslow
cs.CG