lightRelated: dark, heavy, SUN, truth E=mc^2 -> Energy=Mass*Light^2 Arachnoid.com/OpticalRayTracer >>OpticalRayTracer is a free (GPL) Linux (Xwindows GUI-based) utility that analyzes systems of lenses. It uses optical principles and a virtual optical bench to predict the behavior of many kinds of ordinary and exotic lens types. OpticalRayTracer includes an advanced, easy-to-use interface that allows the user to rearrange the optical configuration by simply dragging lenses around using the mouse.