Virtual reality is a popular term generally used to refer to real-time visual simulation system
capabilities that provide the viewer with a high degree of interaction. More recently, the concept
of “interaction” has expanded to include both tactile and visual interaction. Virtual reality
applications often employ a helmet-mounted display system which provides the viewer with an
unlimited overall field of view, but usually at the expense of a rather small instantaneous field of
view. The effectiveness of virtual reality is often defined in terms of how effectively the viewer can
be ‘immersed’ within the virtual environment.