Using an efficient data representation and a fast rendering method volumetric data can be displayed at an average desktop PC at frame rates which are comparable with those which are achieved by consumer 3D hardware. The software approach provides significantly more flexibility, like object-wise transfer functions, shading models and compositing methods (MIP, DVR, ...). Taking into account peculiarities of Java, all those capabilities can be made available to users with standard desktop hardware using different operating systems. Using a compact volume representation, the RTVR library can be also exploited to provide highly interactive and flexible presentations of visualization results over networks, like the Internet. For sample visualizations using RTVR see http://www.vrvis.at/vis/research/rtvr/.