A fast algorithm for calculation of radiative energy distributions received by pinhole image-formation process from 20 rectangular enclosures

In the fast algorithm the total energy received by pinhole image-formation elements is divided into two parts: the direct part and indirect part. The indirect energy,uas related to the direct part, and the latter was calculat ed through a concept of effective angle factor for image formation. For 2-D systems filled with emitting, absorbing, isotropically scattering medium a nd surrounded by diffusely reflecting wad surfaces, the results through usi ng the fast algorithm approached the statistical average values of those ca lculated using the Monte Carlo method and the computation time can be nearl y 50 times faster.