We discuss an algorithm for capturing the shadow boundary in the
context of simplied high frequency wave propagation.
This requires solving efficiently a non-standard Hamilton-Jacobi
equation. We present the corresponding analysis, algorithms, and
extensions. This type of algorithms is potentially useful in locating
the shadow boundaries in a simple and robust way.
The second part of the talk focusses on our results in optimization of
visibility. This includes, for example, finding the shortest path to
see multiple objects at once, and path design under visual
surveillance considerations.