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The 'Progressive' Radiosity Algorithm.

The 'progressive' radiosity solution is an incremental method, yielding
intermediate results at much lower computation and storage costs. 
Each iteration of the algorithm requires the calculation of form factors
between a point on a single surface and all other surfaces, rather than
all n 2 form factors (where n is the number of surfaces in the
environment).  After the form factor calculation, radiosity values for
the surfaces of the environment are updated.

This method will eventually produce the same complete solution as
the 'full matrix' method, though, unlike the 'full matrix' method,it will
also produce intermediate results, each more accurate than the last. 
It can be halted when the desired approximation is reached.  It also
exacts no large (n 2) storage cost.