The reflection of light from most materials consists of two major terms: the specular and the diffuse. Specular reflection may be modeled from first principles by considering a rough surface consisting of perfect reflectors, or micro-facets. Diffuse reflection is generally considered to result from multiple scattering either from a rough surface or from within a layer near the surface. Accounting for diffuse reflection by Lambert's Cosine Law, as is universally done in computer graphics, is not a physical theory based on first principles. This paper presents

We present a method for the efficient re-rendering of a scene under a directional illuminant at an arbitrary orientation. We take advantage of the linearity of the rendering operator with respect to illumination for a fixed scene and camera geometry. Re-rendering is accomplished via linear combination of a set of pre-rendered "basis" images. The theory of steerable functions provides the machinery to derive an appropriate set of basis images. We demonstrate the technique on both simple and complex scenes illuminated by an approximation to natural skylight. We show re-rendering simulations under conditions of varying sun position and cloudiness.

The purpose of these notes is to describe some of the physical and mathematical properties of the equations occurring in global illumination. We first examine the physical assumptions that make the particle model of light an appropriate paradigm for computer graphics and then derive a balance equation for photons. In doing this we establish connections with the field of radiative transfer and its more abstract counterpart, transport theory. The resulting balance equation, known as the equation of transfer, accounts for large-scale interaction of light with participating media as well as complex reflecting surfaces. Under various simplifying assumptions the equation of transfer reduces to more conventional equations encountered in global illumination. 1 Introduction Global illumination connotes a physically-based simulation of light appropriate for synthetic image generation. The task of such a simulation is to model the interplay of light among large-scale objects of an environment in...

This dissertation is a discussion and development of hierarchical algorithms for illumination. These algorithms operate through recursive, adaptive refinement of the environment into hierarchical meshes --- rather than computing light transport only between elements at the finest level of refinement, the algorithms allow computation of transport between higher level subpatches, as controlled by user specified error bounds. As discussed in this dissertation, employment of hierarchical methods yields significant savings in computation. The initial work in hierarchical methods was that of Hanrahan and Salzman for the computation of radiosity over unoccluded environments. In this dissertation, we discuss extension of the algorithm to occluded environments, incorporating visibility heuristics and acceleration via radiosity weighting. Given an environment consisting of k polygonal patches and n elements at the finest level of refinement, the algorithm requires at most O(n + k 2 ) transpor...

Abstract not found

We present a new framework for rendering virtual environments. This framework is proposed as a complete scene description, which embodies the space of all possible renderings, under all possible lighting scenarios of the given scene. In effect, this hypothetical rendering space includes all possible light sources as part of the geometric model. While it would be impractical to implement the general framework, this approach does allow us to look at the rendering problem in a new way. Thus, we propose new representations that are subspaces of the entire rendering space. Some of these subspaces are computationally tractable and may be carefully chosen to serve a particular application. The approach is useful both for real and virtual scenes. The framework includes methods for rendering environments which are illuminated by artificial light, natural light, or a combination of the two models. 1 Introduction The emerging field of visualization in computer science combines calculations with c...

Abstract not found