AbstractCurrent 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
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