• Published in/Presented at Eurographics Symposium on Rendering, Leuven, Belgium, 25-27 June 2003
• Also presented at "Hierarchical Methods in Computer Graphics", Dagstuhl Seminar 03271, Dagstuhl, Germany, June 29-July 4, 2003 (by Philip Dutré)

• SIGGRAPH 2002 Sketch, SIGGRAPH, San Antonio, July 2002
• Report CW336, Departement of Computer Science, K.U.Leuven, April 2002.
• Poster presentation at 13th Eurographics Workshop on Rendering, Pisa Italy, 26-28 June 2002

• 13th Eurographics Workshop on Rendering. Pisa Italy, 26-28 June 2002
• SIGGRAPH 2002 Sketch, SIGGRAPH, San Antonio, July 2002
• Report CW335, Department of Computer Science, K.U.Leuven, April 2002

• SIGGRAPH 2001 Course Notes (Course 20), Los Angeles, August 2001
• SIGGRAPH 2002 Course Notes (Course 2), San Antonio, July 2002

Also as:
Ph. Dutré,
Visibility in  Point Clouds,
The Dagstuhl Seminars on 3D Interactive Graphics and Rendering, Schloss Dagstuhl, Germany (June 2000)

Abstract
In this report, we present a simple technique to evaluate the visibility between pairs of points in a scene. In most current rendering algorithms, visibility queries are evaluated exactly. Our approach approximates the visibility value between two points using a point cloud representation of the surfaces in the scene. The computed value is a function of the distance and orientation of points in the point cloud relative to the line segment connecting the two query points.

Dagstuhl PowerPoint presentation
Page at Cornell, includes pdf version of report

Abstract
In this paper we present a technique for computing the direct lighting in a three-dimensional scene containing area light sources. Our method correctly handles partial visibility between luminaires and receivers, and is able to efficiently generate accurate soft shadows in scenes modeled with general bidirectional reflectance distribution functions. In most current algorithms, the form factor between a light source and receiver is computed using a stochastic ray casting approach which evaluates partial visibility. Such an approach often leads to noisy artifacts or aliasing problems. Generating significantly more rays is often the only solution to improving image quality. Our approach first stores visibility information in the image plane, using lazy evaluation of the visibility function. In a second phase, illumination values for each pixel are generated, using analytic or stochastic integration. Soft shadows and other shading effects are generated with high accuracy in less time than with existing shading algorithms. Coherence in specific blocker-light source relationships across the image plane is exploited to amortize the cost of analytic form factor calculations. By storing information in the image plane, our method is currently designed for generating a single image, and is thus view-dependent.

Page at Cornell, includes pdf version of paper

Abstract
In this paper, an improved Monte Carlo based technique is presented to perform a per-pixel final gather step, also referred to as a local pass in radiosity computations. Using importance sampling based on the results from the finite-element radiosity computation, we achieve a very high image quality at a much lower cost compared to other common techniques. The theory in this paper examplifies how finite element and Monte Carlo techniques for rendering can be combined elegantly.

Gzipped postscript (link to K.U.Leuven)
pdf file (K.U.Leuven)

Abstract
In this technical report we present a new method for optimizing the generation of paths in Monte Carlo global illumination rendering algorithms. Ray tracing, particle tracing, and bidirectional ray tracing all use random walks to estimate various fluxes in the scene. The probability density functions necessary to generate these random walks are optimized using a genetic algorithm, such that a significant reduction of the variance, and thus more reliable flux estimates, are obtained. 

Page at K.U.Leuven
pdf file (K.U.Leuven)

Abstract
In this paper we present a new algorithm for solving the global illumination problem, based on the mathematical framework resulting from the dual set of equations that describe light transport in a three-dimensional environment. The proposed method is a finite element algorithm and propagates radiance as well as potential, thereby focusing on the rapid and efficient computation of the flux emitted by selected patches. We will show that the method takes into account all possible light paths, and that a faster solution can be obtained compared to other radiosity algorithms. 

Page at K.U.Leuven

Page at K.U.Leuven

Page at K.U.Leuven

Abstract
A possible method for solving the global illumination problem is to use a Monte Carlo model, where particles are shot from the light sources and perform a random walk through the scene. The proposed algorithm tries to optimise the sampling process by constructing probability functions that closely match the visual potential function. Importance sampling ensures us that, within the given resolution and accuracy of the probability functions, particles are used in an optimal way, thereby lowering the overall variance of the picture. Sampling based on the local potential functions is done at light sources and surface patches, and thus influences every step of the random walk of a particle. 

Page at K.U.Leuven

Abstract
One possible method for solving the global illumination problem is to use a particle model, where particles perform a random walk through the scene to be rendered. The proposed algorithm uses this particle model, but computes the illumination of the pixels in a direct manner. In order to optimise the sampling process, adaptive probability density functions are used. The result is that particles are shot to those regions with a high potential capability. This algorithm has some advantages, such as the absence of a mesh and the possibility to handle all types of light-surface interactions with the same method. 

Page at K.U.Leuven

Abstract
This paper describes a mathematical framework for rendering algorithms. Starting from the rendering equation and the potential equation, we will introduce the Global Reflection Distribution Function (GRDF). By using the GRDF, we are able to compute the behaviour of light in an environment, independent of the initial lighting or viewpoint conditions. This framework is able to describe most existing rendering algorithms. 

Page at K.U.Leuven

Abstract
A possible method for solving the global illumination problem is to use a particle model, where particles perform a random walk through the scene. The proposed algorithm uses this particle model, but computes the illumination of pixels in a direct manner. It will be shown that the algorithm can be derived from a rewritten formulation of the potential equation. This algorithm has some advantages, including the absence of a mesh and the possibility to handle all types of light-surface interactions with the same method. 

Page at K.U.Leuven