Proximity Radiosity : Exploiting Coherence to Accelerate Form Factor Computations

Abstract

This paper introduces a new acceleration principle for the zonal method. The core concept resides in exploiting the coherence that exists between form factors of two close voxels (or patches). Primarily, we dissociate the radiometric part of the form factors form the geometrical part, the remaining geometrical expressions including volume integrals can be then developed with the Green-Ostrogradski theorem in terms of double surface integrals. These new expressions are less complex and allow us to divide computational time by a factor of about 4. Secondary, we show how all voxels in the neighborhood of a given “reference” voxel, have form factors (with another patch or voxel) that are weighted sums of the reference voxel form factor and a series of associated integrals of generalized orthogonal polynomials. Subsequently, calculation time decreases while a control of the generated error is maintained.