A method of computing wave propagation similar to the finite difference time domain method. The region of interest is broken up into a collection of small cubic elements, each of which contains information about the fields and material parameters at that point. However, instead of a calculation directly on the field components, an analogue to transmission lines is invoked where the fields are translated into voltages and currents and the material parameters are translated into capacitances and inductances. A three-dimensional network of transmission lines is then modelled using these parameters, with signals being applied and propagated at successive small time steps. When the calculation is terminated, the voltages and currents are then translated back to fields where desired.