The algorithms discussed in the previous chapter directly compute the intensity of light passing though the pixels of the virtual screen. In contrast, this chapter covers methods that compute a so-called world space representation of the illumination in a three-dimensional scene. Very often, this object space representation consists of the average diffuse illumination on triangles or convex quadrilaterals into which a three-dimensional model has been tessellated. There are, however, plenty of other possibilities, too. Since diffuse illumination is best modeled by a quantity called radiosity (see Section 2.3.1), such methods are usually called radiosity methods.
The main advantage of computing the illumination in ...