Global Element Method for Radiosity Calculation

Szirmay-Kalos László
Department of Process Control, Technical University of Budapest,
Budapest, Muegyetem rkp. 11, H-1111, HUNGARY


Traditional radiosity methods decompose surfaces into planar surface elements that can be supposed to have uniform radiosity and emittance, that is they approximate the unknown radiosity distribution by piecewise constant functions. This paper, on the other hand, develops a general framework to solve the radiosity equation numerically for any kind of function series approximation. Having derived the general formulae, three special cases are discussed: piecewise constant functions which lead to the traditional methods, linear finite elements and harmonic approximations where the basis functions are not of finite element type because they can approximate the radiosity distribution everywhere, and thus fall into the category of global element methods. Global element methods are able to work on the original geometry and they can be speeded up by effective techniques, such as Fast Fourier Transform.


Radiosity method, finite-element and global-element techniques, linear finite elements, variational method, Fast Fourier Transform, Ritz method.