Irradiance Gradients

by Greg Ward and Paul Heckbert

ABSTRACT

A new method for improving the accuracy of a diffuse interreflection calculation is introduced in a ray tracing context. The information from a hemispherical sampling of the luminous environment is interpreted in a new way to predict the change in irradiance as a function of position and surface orientation. The additional computation involved is modest and the benefit is substantial. An improved interpolation of irradiance resulting from the gradient calculation produces smoother, more accurate renderings. This result is achieved through better utilization of ray samples rather than additional samples or alternate sampling strategies. Thus, the technique is applicable to a variety of global illumination algorithms that use hemicubes or Monte Carlo sampling techniques.


Unfortunately, we do not have an HTML version of this paper to offer. Instead, we have a set of PostScript files that together comprise the original submission.

The PostScript files are bundled in a compressed tar archive, paper.tar.Z (1799K). A README file contained in this archive describes its contents.

We have also put these together, somewhat haphazardly, in an Adobe Acrobat document, paper.pdf (217K).