Higher Quality Volume Rendering on PC Graphics Hardware

Shading and classification are among the most powerful and important techniques used in volume rendering. Unfortunately, for hardware accelerated volume rendering based on OpenGL, direct classification is only supported on SGI platforms and shading could previously only be approximated inaccurately, resulting in shading artifacts mostly visible in darkening artifacts. So far, the combination of classification and shading either required multi-pass rendering or two volumetric textures. This paper presents a novel approach for accurate phong shading using multi-texturing, dependent textures, cube maps, and texture combiners. Furthermore, another novel approach is presented, enabling the interactive change of sample properties such as color, opacity, shading parameters, and gradient magnitude without the need of recomputing the texture every time the classification parameters change requiring no second volumetric texture. Finally, in combination with texture compression, even relatively large volumes can be rendered at interactive frame updates. CR Categories: I.0.3 [Computer Graphics]: General; I.3.1 [Computer Graphics]: Picture and Image Generation—Graphics processors; I.3.3 [Computer Graphics]: Picture and Image Generation—Viewing algorithms;