6.1.1 Outline

The basic idea of the classic radiosity method is to compute the average radiosity B _i on each surface element or patch i of a three-dimensional model (see Figure 6.1). The input consists of a list of such patches. Most often, the patches are triangles or convex quadrilaterals, although alternatives such as quadratic surface patches have been explored as well [2]. With each patch i, the self-emitted radiosity (dimensions: [W/m ²]) and reflectivity ? _i (dimensionless) are given. The self-emitted radiosity is the radiosity that a patch emits on its own, even if there were no other patches in the model, or all other patches were perfectly black. The reflectivity is a number (for each considered wavelength) between 0 and 1. It indicates what fraction of the power incident on the patch gets reflected (the rest gets absorbed). These data suffice in order to compute the total emitted radiosity B _i (dimensions: [W/m ²]) by each patch, containing the radiosity received via any number of bounces from other patches in the scene, as well as the self-emitted radiosity.

Figure 6.1: The input of the classic radiosity method consists of a list of patches (triangles, in this example) with their average self-emitted radiosity (left) and reflectivity ? _i (middle) given. These data suffice in order to compute the average total radiosities B _i (right), including...