Voreen (Volume Rendering Engine) is an open source rapid application development framework for the interactive visualization and analysis of multi-modal volumetric data sets. It provides GPU-based volume rendering and data analysis techniques and offers high flexibility when developing new analysis workflows in collaboration with domain experts. Jan Roters and Markus Madeja helped the projects in seminars. They developed a complete label-rendering-system (Jan Roters) in addition to lot's of enhances of the whole system. This includes a additional background-rendering-step, a glow-effect, clipping for volume-data und a measure-system (Markus Madeja).