We introduce a novel texture-based volume rendering approach that achieves the image quality of the best post-shading approaches with far less slices. It is suitable for new flexible consumer graphics hardware and provides high image quality even for low-resolution volume data and non-linear transfer functions with high frequencies, without the performance overhead caused by rendering additional interpolated slices. This is especially useful for volumetric effects in computer games and professional scientific volume visualization, which heavily depend on memory bandwidth and rasterization power.

Nowadays, direct volume rendering via 3D textures has positioned itself as an efficient tool for the display and visual analysis of volumetric scalar fields. It is commonly accepted, that for reasonably sized data sets appropriate quality at interactive rates can be achieved by means of this technique. However, despite these benefits one important issue has received little attention throughout the ongoing discussion of texture based volume rendering: the integration of acceleration techniques to reduce per-fragment operations.

Interactive direct volume rendering has yet been restricted to high-end graphics workstations and special-purpose hardware, due to the large amount of trilinear interpolations, that are necessary to obtain high image quality. Implementations that use the 2D-texture capabilities of standard PC hardware, usually render object-aligned slices in order to substitute trilinear by bilinear interpolation. However the resulting images often contain visual artifacts caused by the lack of spatial interpolation. In this paper we propose new rendering techniques that signi cantly improve both performance and image quality of the 2D-texture based approach. We will show how multi-texturing capabilities of modern consumer PC graphics boards are exploited to enable interactive high quality volume visualization on low-cost hardware. Furthermore we demonstrate how multi-stage rasterization hardware can be used to eciently render shaded isosurfaces and to compute di use illumination for semi-transparent v...

Direct volume-rendering has proven to be an effective and flexible visualization method for 3D scalar fields. Transfer functions are fundamental

Most direct volume renderings produced today employ one-dimensional transfer functions, which assign color and opacity to the volume based solely on the single scalar quantity which comprises the dataset. Though they have not received widespread attention, multi-dimensional transfer functions are a very effective way to extract specific material boundaries and convey subtle surface properties. However, identifying good transfer functions is difficult enough in one dimension, let alone two or three dimensions. This paper demonstrates an important class of three-dimensional transfer functions for scalar data (based on data value, gradient magnitude, and a second directional derivative), and describes a set of direct manipulation widgets which make specifying such transfer functions intuitive and convenient. We also describe how to use modern graphics hardware to interactively render with multi-dimensional transfer functions. The transfer functions, widgets, and hardware combine to form a powerful system for interactive volume exploration.

We present a multiresolution technique for interactive texture-based volume visualization of very large data sets. This method uses an adaptive scheme that renders the volume in a region-of-interest at a high resolution and the volume away from this region at progressively lower resolutions. The algorithm is based on the segmentation of texture space into an octree, where the leaves of the tree define the original data and the internal nodes define lower-resolution versions. Rendering is done adaptively by selecting high-resolution cells close to a center of attention and low-resolution cells away from this area. We limit the artifacts introduced by this method by modifying the transfer functions in the lower-resolution data sets and utilizing spherical shells as a proxy geometry. It is possible to use this technique to produce viewpoint-dependent renderings of very large data sets. Keywords: multiresolution rendering, volume visualization, hardware texture. 1 INTRODUCTION The capab...

We present two beneficial rendering extensions to the Projected Tetrahedra (PT) algorithm by Shirley and Tuchman. These extensions are compatible with any cell sorting technique, for example the BSP-XMPVO sorting algorithm for unstructured meshes.

For volume rendering of regular grids the display of view-plane aligned slices has proven to yield both good quality and performance. In this paper we demonstrate how to merge the most important extensions of the original 3D slicing approach, namely the pre-integration technique, volumetric clipping, and advanced lighting. Our approach allows the suppression of clipping artifacts and achieves high quality while offering the flexibility to explore volume data sets interactively with arbitrary clip objects. We also outline how to utilize the proposed volumetric clipping approach for the display of segmented data sets. Moreover, we increase the rendering quality by implementing efficient over-sampling with the pixel shader of consumer graphics accelerators. We give prove that at least 4times over-sampling is needed to reconstruct the ray integral with sufficient accuracy even with pre-integration.

One of the most important goals in volume rendering is to be able to visually separate and selectively enable specific objects of interest contained in a single volumetric data set. Using explicit segmentation information is a very powerful way to approach this problem. We show how segmented volume data sets can be rendered interactively on current consumer graphics hardware with high image quality. Pixel-resolution filtering of object boundaries is supported although only a single segmentation volume for all objects is required. In order to enhance object perception, we employ different levels of object distinction. First, each object can be assigned an individual transfer function, multiple of which can be applied in a single rendering pass. Second, different rendering modes such as direct volume rendering, iso-surfacing, and non-photorealistic techniques can be selected for each object. A minimal number of rendering passes is achieved by processing sets of objects that share the same rendering mode in a single pass. Third, local compositing modes such as alpha blending and MIP can be selected for each object in addition to a single global mode, thus yielding a high-quality hardware implementation of two-level volume rendering.

In this paper we present an adaptive approach to volume rendering via 3D textures at arbitrary levels of detail. The algorithm has been designed to enable interactive exploration of large-scale data sets while providing user-adjustable resolution levels. A texture map hierarchy is constructed in a way that minimizes the amount of texture memory with respect to the power-of-two restriction imposed by OpenGL implementations. In addition, our hierarchical levelof-detail representation guarantees consistent interpolation between different resolution levels. Special attention has been paid to the fixing of rendering artifacts that are introduced by non-corrected opacities at level transitions. By adapting the sample slice distance with regard to the desired level-of-detail, the number of texture lookups is reduced significantly.