Welcome to my home page! I am currently working at Luciad, a company in my home town Leuven, in Belgium.
From April '96 till May '99, I have worked as a postdoctoral associate, here at the Program of Computer Graphics at Cornell University, which is located in Ithaca, NY. You can find an overview of my work on these pages.
I graduated in July '91 and received my PhD in February '96, from the Katholieke Universiteit Leuven in Belgium, as a member of the Computer Graphics Research Group of the Department of Computer Science
Light reflectance functions describe how light is scattered at the surface of an object. The amount of reflected light typically varies with the incident direction of the incoming light and with the measurement direction for the reflected light. As such, the bidirectional reflectance distribution function (BRDF) at given point on a surface and for a given wavelength is 4-dimensional.
In our light measurement lab, we do reflectance measurements using specular and diffuse reflectometers, and using a custom-built gonioreflectometer. I have written most of the software to drive the gonioreflectometer, allowing automatic control of the light source, the motor stages, and the detector. Some of my measurements and corresponding renderings can be found on our measurement page.
The measurement data are quite bulky. I have introduced a new representation for light reflectance functions that is compact and particularly suited for global illumination computations. I've presented this work at Siggraph '97, in a paper entitled "Non-Linear Approximation of Reflectance Functions".
The reflectance data can then be used in global illumination algorithms, to create physically correct renderings. I am mostly interested in algorithms that can render complex scenes in a physically correct way. Image-based Monte Carlo rendering techniques (like Monte Carlo ray tracing) seem well-suited for this purpose, because of their versatility and scalability. Unfortunately, these techniques are also notoriously slow. All sorts of variance reducing techniques are required to make them more practical. In my research, I have looked at basic Monte Carlo rendering techniques such as path tracing and light tracing, and I have introduced their combination, bidirectional path tracing. I have looked into the application of known variance reducing techniques such as stratified sampling, N-rooks sampling, importance sampling, control variates, and Russian roulette to the algorithms.
This study of the underlying physical and mathematical theories has lead to the introduction of the global reflectance distribution function and the derivation of bidirectional path tracing. My papers and my PhD dissertation "Mathematical Models and Monte Carlo Algorithms for Physically Based Rendering" discuss these subjects in some more detail. More information and the complete dissertation are available on-line. You can also just browse through the colour images from the text.
Out of necessity in this far-away country, I've taken up cooking. My preference goes to making desserts, such as chocolate mousse, tiramisu, and Belgian cake. This hobby is highly appreciated by the students in the lab. Occasionally, I continue programming computer games. For quite a while now, I've been working on an arcade puzzle game called Rock Runner for the Acorn Archimedes. At the moment, a lot of my spare time goes to my open source project ProGuard, a Java class file shrinker and obfuscator.