The radiosity approach to rendering has its basis in the theory
of heat transfer. This theory was applied to computer graphics in 1984 by Goral
Surfaces in the environment are assumed to be perfect (or Lambertian)
diffusers, reflectors, or emitters. Such surfaces are assumed to reflect incident
light in all directions with equal intensity.
A formulation for the system of equations is facilitated by dividing
the environment into a set of small areas, or patches. The
radiosity over a patch is constant.
The radiosity, B, of a patch is the total rate of energy leaving
a surface and is equal to the sum of the emitted and reflected energies:
Radiosity was used for Quake II