Current radiosity methods rely on the calculation of geometric factors, known as form-factors, which describe energy exchange between pairs of surfaces in the environment. The most computationally efficient method for form-factor generation is a numerical technique known as the hemi-cube algorithm. Use of the hemi-cube is based on assumptions about the geometry of the surfaces involved. First, this paper examines the types of errors and visual artifacts that result when these assumptions are

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... lated. Second, the paper shows that these errors occur more frequently in progressive refinement radiosity than in the originally proposed full matrix radiosity solution. Next, a new analytical technique for determining form-factors that is immune to the errors of the hemicube algorithm is introduced. Finally, a hybrid progressive refinement method that invokes the new technique to correctly compute formfactors when hemi-cube assumptions are violated is presented.