1 AcknowledgmentsI would like to thank Professor Stefan Bruckner for supervising this thesis and for the great discussions we frequently had giving rise to the solutions presented in this thesis. I would also like to thank Itai Kallos for informative discussions giving insight in the physics behind our light model. In recent years, significant progress has been made in developing high-quality interactive methods for realistic volume illumination. However, refractiondespite being an important aspect of light propagation in participating media -has so far only received little attention. In this thesis, we present a novel approach for refractive volume illumination including caustics capable of interactive frame rates. By interleaving light and viewing ray propagation, our technique avoids memory-intensive storage of illumination information and does not require any precomputation. Propagation of refracted illumination is realized by employing a Semi-Lagrangian backward integration scheme, inspired by texture advection from the field of texture-based flow visualization. It is fully dynamic and all parameters such as light position and transfer function can be modified interactively without a performance penalty.