RADIANCE is a physically-based lighting simulation program developed by Lawrence Berkeley National Laboratories in the US. It is used for the simulation and analysis of both natural and artificial lighting environments. The program takes a scene description - including light sources, sun position, sky type, buildings, rooms and furnishings - and produces spectral radiance values represented as 'photo-accurate' high resolution colour images. These images can then be post-processed to yield highly accurate images and contour maps of lighting values - clearly showing Lux levels. For more information, visit the Radiance Home Page.