The most critical issue in the radiosity method is efficient form factor calculation, and thus it is not surprising that considerable research effort has gone into various algorithms to evaluate or approximate the formula which defines the form factors:
As in the solution of the shading problem, the different solutions represent different compromises between the conflicting objectives of high calculation speed, accuracy and algorithmic simplicity.
In our survey the various approaches are considered in order of increasing algorithmic complexity, which, interestingly, does not follow the chronological sequence of their publication.