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In recent years the value of direct volume rendering techniques for the visualization of 3D scalar fields has become evident in many application areas ranging from medicine to natural science and engineering. The applicability of high quality volume rendering, however, was mainly restricted to expensive special purpose hardware or dedicated workstations with high-end graphics subsystem and high-speed memory bus. To these ends this thesis introduces methods for interactive high-quality volume visualization on general purpose hardware such as commodity desktop computers with graphics cards designed for computer games and multimedia. The aim of this work is to achieve a high image quality comparable to traditional ray-casting solutions at interactive frame rates on inexpensive hardware platforms. In this context the benefits and drawbacks of traditional texture based implementations are analyzed with respect to image quality and rendering performance. Based on this analysis, efficient volume rendering techniques are developed targeting the advanced features of modern PC graphics boards such as multi-stage rasterization, pixel shaders and dependent texture lookup. In the context of direct volume rendering, transfer functions are used to specify the emission and absorbtion values which are required for ray integration. Several implementations of transfer functions for pre- and post-classification are presented and analyzed. Automatic image- and data-driven techniques for transfer function design are examined and adapted to different application problems. Advanced features of the graphics hardware are used to include local illumination effects into direct volume rendering and techniques for non-polygonal isosurface display. The lighting effects are achieved as per-pixel illumination with dynamic light sources or as reflection maps, which cache the incident illumination at one point. The analysis of texture based algorithm is completed by a detailed performance measurement on different hardware architectures. As supplements to the 3D-texture based method, volumetric deformation models are introduced which allow the intuitive modeling of volume objects as well as the automatic optimization of deformation parameters for registration purposes. The presented approaches comprise an efficient algorithm for slice decomposition of arbitrary deformed polygonal surfaces and a deformation model based on regular hexahedra structures. A major goal of this work was the improvement of the availability of direct volume rendering for specific visualization problems in medicine and natural science. The application of different techniques in clinical environments are documented in several case studies including the visualization of the inner ear, the examination of tiny vascular structures as well as the functional analysis of the vertebral column.