Radiance
Highly accurate ray-tracing software system for UNIX computers
Radiance is a free, highly accurate ray-tracing software system for UNIX computers. It is a suite of programs designed for the analysis and visualization of lighting in design.
Radiance is superior to simpler lighting calculation and rendering tools in that there are no limitations on the geometry or the materials that may be simulated. Scene geometry, materials, luminaires, time, date and sky conditions (for daylight calculations) are specified; spectral radiance (ie. luminance + color...