The goal of the ELI (Extreme Light Infrastructure) project is to build a laser centre with the worlds highest power output
pulsed laser in the locality of Dolní Břežany near Prague. Presented paper offers first glance to the insight into
continuous and pulsed beam interaction with various optical systems which causes beam's spatial and temporal
transformation. Complexity of this problem is illustrated in need of geometrical and physical optics knowledge,
numerical simulations, material engineering and many others. This paper is focused on the field trace simulations in
various software environments for both simple and more complex optical systems.