ABSTRACT
This chapter deals with rendering speed. We cover how frame-to-frame coherence can be exploited in order to more rapidly render computer animation movies or walk-throughs of nondiffuse static environments. Very recently, a number of approaches have appeared that go even further on this track and achieve interactive global illumination, without predefined animation script or camera path. The rendering participating media has received quite some attention since the end of the 1980s. The proposed approaches include deterministic methods and stochastic methods. Classic and hierarchical radiosity methods have been extended to handle participating media by discretizing the volume integral above into volume elements and assuming that the radiance in each volume element is isotropic. Many other deterministic approaches have been proposed as well, based on spherical harmonics (PN methods) and discrete ordinates methods. Deterministic approaches are valuable in relatively “easy” settings, for instance, homogeneous media with isotropic scattering, or simple geometries.
