The Determination of Form-Factors by Lookup Table

Abstract

Current methods for computer image synthesis using the radiosity algorithm rely heavily on the calculation of geometrical properties, known as form-factors, which quantify the energy exchange between pairs of surfaces in the environment. In this paper, a new method for form-factor calculation is presented, in which form-factors from a differential area to a finite area with various geometric orientations and dimensions can be determined by the summation of three weighted directional form-factors. The three directional form-factors are mutually independent and can be pre-calculated and stored in a lookup table accessed by two indices. Thus, the determination of the generally used complex form-factor integral is greatly simplified and mainly replaced by accessing a pre-established lookup table. Quantitative comparisons of Wallace s ray casting method and the method presented indicate that the new method can provide more accurate form-factors, which implies that the number of sample points necessary on each source patch is comparatively reduced and the process of form-factor calculation can be accelerated.