In modern optical engineering the simulation of imaging and non-imaging optical systems on the basis of wave optics is of increasing importance. A simulation based on wave optics means on one hand to use everywhere in the optical system a wave-optical description of light. This allows the evaluation of more general merit functions for the description of the system quality which requires, for example, access to amplitude, phase, polarization, coherence information of light. On the other hand, including wave optics in optical simulations means to model the light propagation exact enough to describe wave-optical propagation effects. That means in general not to perform all simulations without physical approximations but to use light propagation models that work with sufficient physical precision within the optical system. The authors will discuss which needs follow for modern optical simulation software. This discussion includes a flexible handling of different models for simulation of light propagation, descriptions of different wave-optical light representations and considerations of numerical and physical simulation precision.