modelling and electromagnetic propagation modelling. In both of these applications, beams are used as an efficient way to track deep reflections from a source to a receiver (or vice versa). Beams can provide a convenient and compact way to represent visibility. Once a beam tree has been calculated, one can use it to readily account for moving transmitters or receivers. Beam tracing is related in concept to cone tracing. See also Pat Hanrahan Ray tracing (graphics) References Global illumination algorithms