We present an algorithm for real-time level of detail reduction and display of high-complexity polygonal surface data. The algorithm uses a compact and efficient regular grid representation, and employs a variable screen-space threshold to bound the maximum error of the projected image. A coarse level of simplification is performed to select discrete levels of detail for blocks of the surface mesh, followed by further simplification through repolygonalization in which individual mesh vertices are considered for removal. These steps compute and generate the appropriate level of detail dynamically in real-time, minimizing the number of rendered polygons and allowing for smooth changes in resolution across areas of the surface. The algorithm has been implemented for approximating and rendering digital terrain models and other height fields, and consistently performs at interactive frame rates with high image quality.

Abstract not found

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...

Efficiently identifying polygons that are visible from a dynamic synthetic viewpoint is an important problem in computer graphics. Typically, visibility determination is performed using the z-buffer algorithm. As this algorithm must examine every triangle in the input scene, z-buffering can consume a significant fraction of graphics processing, especially on architectures that have a low performance or software z-buffer. One way to avoid needlessly processing invisible portions of the scene is to use an occlusion culling algorithm to discard invisible polygons early in the graphics pipeline. In this paper, we exploit the presence of large occluders in urban and architectural models to design a real-time occlusion culling algorithm. Our algorithm has the following features: it is conservative, i.e., it overestimates the set of visible polygons; it exploits spatial coherence by using a hierarchical data structure; and it exploits temporal coherence by reusing visibility information computed for previous viewpoints. The new algorithm significantly accelerates rendering of several complex test models.

A new and easy-to-implement method for direct volume rendering that uses 3D texture maps for acceleration, and incorporates directional lighting, is described. The implementation, called Voltx, produces high-quality images at nearly interactive speeds on workstations with hardware support for three-dimensional texture maps. Previously reported methods did not incorporate a light model, and did not address issues of multiple texture maps for large volumes. Our research shows that these extensions impact performance by about a factor of ten. Voltx supports orthographic, perspective, and stereo views. This paper describes the theory and implementation of this technique, and compares it to the shear-warp factorization approach. A rectilinear data set is converted into a three-dimensional texture map containing color and opacity information. Quantized normal vectors and a lookup table provide efficiency. A new tesselation of the sphere is described, which serves as the basis for normal-vec...

We present a new algorithm for rendering very large volume data sets at interactive framerates on standard PC hardware. The algorithm accepts scalar data sampled on a regular grid as input. The input data is converted into a compressed hierarchical wavelet representation in a preprocessing step. During rendering, the wavelet representation is decompressed on-the-fly and rendered using hardware texture mapping. The level of detail used for rendering is adapted to the local frequency spectrum of the data and its position relative to the viewer. Using a prototype implementation of the algorithm we were able to perform an interactive walkthrough of large data sets such as the visible human on a single of-the-shelf PC.

We present a system architecture for the 4 th generation of PCclass programmable graphics processing units (GPUs). The new pipeline features significant additions and changes to the prior generation pipeline including a new programmable stage capable of generating additional primitives and streaming primitive data to memory, an expanded, common feature set for all of the programmable stages, generalizations to vertex and image memory resources, and new storage formats. We also describe structural modifications to the API, runtime, and shading language to complement the new pipeline. We motivate the design with descriptions of frequently encountered obstacles in current systems. Throughout the paper we present rationale behind prominent design choices and alternatives that were ultimately rejected, drawing on insights collected during a multi-year collaboration with application developers and hardware designers.

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.

While large investments are made in sophisticated graphics hardware, most realistic rendering is still performed off-line using ray trace or radiosity systems. A coordinated use of hardware-provided bitplanes and rendering pipelines can, however, approximate ray trace quality illumination effects in a user-interactive environment, as well as provide the tools necessary for a user to declutter such a complex scene. A variety of common ray trace and radiosity illumination effects are presented using multi-pass rendering in a pipeline architecture. We provide recursive reflections through the use of secondary viewpoints, and present a method for using a homogeneous 2-D projective image mapping to extend this method for refractive transparent surfaces. This paper then introduces the Dual Z-buffer, or DZ-buffer, an evolutionary hardware extension which, along with current framebuffer functions such as stencil planes and accumulation buffers, provides the hardware platform to render non-refr...

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.