The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.

Novel Illumination Algorithms for Off-Line and Real-Time Rendering

Janne Kontkanen

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Computer Science and Engineering for public examination and debate in Auditorium TU1 at Helsinki University of Technology (Espoo, Finland) on the 9th of February, 2007, at 12 noon.

Overview in PDF format (ISBN 978-951-22-8610-2)   [5449 KB]
Dissertation is also available in print (ISBN 978-951-22-8609-6)


This thesis presents new and efficient illumination algorithms for off-line and real-time rendering.

The realistic rendering of arbitrary indirect illumination is a difficult task. Assuming ray optics model of light, the rendering equation describes the propagation of light in the scene with high accuracy. However, the computation is expensive, and thus even in off-line rendering, i.e., in prerendered animations, indirect illumination is often approximated as it would otherwise constitute a bottleneck in the production pipeline.

Indirect illumination can be computed using Monte Carlo integration, but when restrained to a reasonable amount of computation time, the result is often corrupted by noise. This thesis includes a method that effectively reduces the noise by applying a spatially varying filter to the noisy illumination.

For real-time performance, some components of indirect illumination can be precomputed. Irradiance volume and many variations of it precompute reflections and shadowing of a static scene into a volumetric data structure. This data is then used to shade dynamic objects in real-time. The practical usage of the method is limited due to aliasing artifacts. This thesis shows that with a suitable super-sampling approach, a significant quality improvement can be obtained.

Another direction is to precompute how light propagates in the scene and use the precomputed data during run-time to solve both direct and indirect illumination based on the known incident lighting. To keep the memory and precomputation costs tractable, these methods are typically restricted to infinitely distant lighting. Those that are not, require a very long precomputation time. This thesis presents an algorithm that adopts a wavelet-based hierarchical finite element method for the precomputation. A significant performance improvement over the existing techniques is obtained.

When full global illumination cannot be afforded, ambient occlusion is an attractive alternative. This thesis includes two methods for real-time rendering of ambient occlusion in dynamic scenes. The first method models the shadowing of ambient light between rigid moving bodies. The second method gives a data-oriented solution for rendering approximate ambient occlusion for animated characters in real-time. Both methods achieve unprecedented efficiency.

This thesis consists of an overview and of the following 5 publications:

  1. J. Kontkanen, J. Räsänen and A. Keller. Irradiance Filtering for Monte Carlo Ray Tracing. In Monte Carlo and Quasi Monte Carlo Methods 2004, pages 259-272. Springer-Verlag, 2004.
  2. J. Kontkanen and S. Laine. Ambient Occlusion Fields. In Proceedings of ACM SIGGRAPH 2005 Symposium on Interactive 3D Graphics and Games, pages 41-48. ACM Press, 2005.
  3. J. Kontkanen and S. Laine. Sampling Precomputed Volumetric Lighting. In Journal of Graphics Tools, volume 11, number 3, pages 1-16. A K Peters, 2006.
  4. J. Kontkanen, E. Turquin, N. Holzschuch and F. X. Sillion. Wavelet Radiance Transport for Interactive Indirect Lighting. In Rendering Techniques 2006 (Eurographics Symposium on Rendering), pages 161-171. Eurographics Association, 2006.
  5. J. Kontkanen and T. Aila. Ambient Occlusion for Animated Characters. In Rendering Techniques 2006 (Eurographics Symposium on Rendering), pages 343-348. Eurographics Association, 2006.

Keywords: computer graphics, shading, global illumination, indirect illumination, ambient occlusion

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© 2007 Helsinki University of Technology

Last update 2011-05-26