  We study routing for massively dense wireless networks, i.e., wireless
networks that contain so many nodes that, in addition to their usual
microscopic description, a novel macroscopic description becomes possible. The
macroscopic description is not detailed, but nevertheless contains enough
information to permit a meaningful study and performance optimization of the
network. Within this context, we continue and significantly expand previous
work on the analogy between optimal routing and the propagation of light
according to the laws of Geometrical Optics. Firstly, we pose the analogy in a
more general framework than previously, notably showing how the eikonal
equation, which is the central equation of Geometrical Optics, also appears in
the networking context. Secondly, we develop a methodology for calculating the
cost function, which is the function describing the network at the macroscopic
level. We apply this methodology for two important types of networks: bandwidth
limited and energy limited.
