The Constant Radiance Term

The proposed method accelerates the computation of multiple interreflections in non-diffuse environments or the solution of the rendering equation. The method is suited for closed environments. It is a generalization of the “constant radiosity step” introduced for diffuse environments and does not require geometrical or visibility information, nor the calculation of form factors. A constant radiance is extracted from the solution in every surface point and every direction. We choose this constant value so that the average selfemitted power of the residuum problem is zero. The self-emitting term of the residuum problem can either be positive or negative. Direction dependency is determined by the albedo function of the characteristic BRDF of the surface. This function can easily be pretabulated and it is used frequently throughout this paper. The residuum problem can be solved faster or with reduced variance by all known non-diffuse methods: different versions of distribution ray tracing, proper methods of radiosity, and hybrid solutions. The acceleration achieved by the proposed method can be significant for bright environments.