Interactive direct volume rendering with physically - based lighting

The field of volume visualization has undergone rapid development during the past years, both due to advances in suitable computing hardware and due to the increasing availability of large volume datasets. Recent work has focused on increasing the lighting realism in interactive raycasting by integrating a number of visually plausible but often effect-specific optimizations. These improvements yield impressive results, but often rely on certain assumptions, such as for example a fixed light-source, or a limited number of light-sources. On the other hand, stochastic Monte Carlo ray-tracing, coupled with physically based light transport, is able to synthesize highly realistic images. It has been successfully applied to boundary surfaces and participating media, applying either BRDF shading or phase functions. However, it has not yet been applied to interactive DVR. With this work, we present an interactive DVR approach integrating ray-traced lighting. Our method enables the configuration of any number of arbitrarily shaped and textured area lights, models a real-world camera, including its lens and aperture, and incorporates complex materials, whilst still maintaining interactive display updates. In addition, our method is able to shift dynamically between BRFDF and phase function shading to cope with heterogeneous volumetric data, and also alleviates the unwanted start-up noise usually associated with progressive rendering. Finally, we have made our complete implementation available in source and binary forms under a permissive free software license.