Radiance is a suite of tools for performing lighting simulation originally written by Greg Ward.
It uses ray tracing to perform all lighting calculations, accelerated by the use of an octree data structure.
It also implements global illumination using the Monte Carlo method to sample light falling on a point.
Greg Ward started developing Radiance in 1985 while at Lawrence Berkeley National Laboratory.
One study found Radiance to be the most generally useful software package for architectural lighting simulation.
[citation needed] The file starts with the signature '#?RADIANCE' and then several lines listing the commands used to generate the image.
Radiance calculates light values as floating point triplets, one each for red, green and blue.
It can specify individual geometric objects, as well as call programs by starting a line with an exclamation point '!'.
Generators simplify the task of modelling a scene, they create certain types of geometry from supplied parameters.