Volume rendering is a technique for visualizing 3D arrays of sampled data. It has applications in areas such as medical imaging and scientific visualization, but its use has been limited by its high computational expense. Early implementations of volume rendering used brute-force techniques that require on the order of 100 seconds to render typical data sets on a workstation. Algorithms with optimizations that exploit coherence in the data have reduced rendering times to the range of ten seconds but are still not fast enough for interactive visualization applications. In this thesis we present a family of volume rendering algorithms that reduces rendering times to one second. First we present a scanline-order volume rendering algorithm that exploits coherence in both the volume data and the image. We show that scanline-order algorithms are fundamentally more efficient than commonly-used ray casting algorithms because the latter must perform analytic geometry calculations (e.g. intersecting rays with axis-aligned boxes). The new scanline-order algorithm simply streams through the volume and the image in storage order. We describe variants of the algorithm for both parallel and perspective projections and

This paper presents a forward mapping rendering algo-rithm to display regular volumetric grids that may not have the same spacings in the three grid directions. It takes advantage of the fact that convolution can be thought of as distributing energy from input samples into space. The renderer calculates an image plane footprint for each data sample and uses the footprint to spread the sample's energy onto the image plane. A result of the technique is that the forward mapping algorithm can support perspective without excessive cost, and support adaptive resampling of the three-dimensional data set during image generation.

Procedural solid texturing was introduced fourteen years ago, but has yet to find its way into consumer level graphics hardware for real-time operation. To this end, a new model is introduced that yields a parameterized function capable of synthesizing the most common procedural solid textures, specifically wood, marble, clouds and fire. This model is simple enough to be implemented in hardware, and can be realized in VLSI with as little as 100,000 gates. The new model also yields a new method for antialiasing synthesized textures. An expression for the necessary box filter width is derived as a function of the texturing parameters, the texture coordinates and the rasterization variables. Given this filter width, a technique for efficiently box filtering the synthesized texture by either mip mapping the color table or using a summed area color table are presented. Examples of the antialiased results are shown.

An algebra consists of a set of objects and a set of operators that act on those objects. We treat shader programs as first-class objects and define two operators: connection and combination. Connection is functional composition: the outputs of one shader are fed into the inputs of another. Combination concatenates the input channels, output channels, and computations of two shaders. Similar operators can be used to manipulate streams and apply computational kernels expressed as shaders to streams. Connecting a shader program to a stream applies that program to all elements of the stream; combining streams concatenates the record definitions of those streams.

A whole variety of different techniques for simulating global illumination in virtual environments have been developed over recent years. Each technique, including Radiosity, Monte-Carlo ray- or photon tracing, and directional-dependent Radiance computations, is best suited for simulating only some special case environments. None of these techniques is currently able to efficiently simulate all important lighting effects in non-trivial scenes. In this paper, we describe a new approach for efficiently combining different global illumination algorithms to yield a composite lighting simulation: Lighting Networks. Lighting Networks can exploit the advantages of each algorithm and can combine them in such a way as to simulate lighting effects that could only be computed at great costs by any single algorithm. Furthermore, this approach allows a user to configure the Lighting Network to compute only specific lighting effects that are important for a given task, while avoiding a costly simulation of the full global illumination in a scene. We show how the light paths computed by a Lighting Network can be described using regular expressions. This mapping allows us to analyze the composite lighting simulation and ensure completeness and redundant-free computations. Several examples demonstrate the advantages and unique lighting effects that can be obtained using this technique. 1

Abstract. Previous efforts aimed at improving direct volume rendering performance have focused largely on time-invariant, 3D data. Little work has been done in the area of interactive direct volume rendering of timevarying data, such as is commonly found in Computational Fluid Dynamics (CFD) simulations. Until recently, the additional costs imposed by time-varying data have made consideration of interactive direct volume rendering impractical. We present a volume rendering system based on a parallel implementation of the Shear-Warp Factorization algorithm that is capable of rendering time-varying 128 3 data at interactive speeds. 1

We present an environment in which users can interactively create different visualization methods. This modular and extensible environment encapsulates most of the existing visualization algorithms. Users can easily construct new visualization methods by combining simple, fine grain building blocks. These components operate on a local subset of the data and generally either look for target features or produce visual objects. Intermediate compositions may also be used to build more complex visualizations. This environment provides a foundation for building and exploring novel visualization methods. Key Words and Phrases: interactive, extensible, spray rendering, smart particles, visualization environment. 1 Introduction The diverse needs of scientists demand the development of general purpose, flexible and extensible visualization environments. Flexibility and extensibility are particularly important since no monolithic package can be expected to satisfy every need. Users often need ...

The process of visualizing a scientific data set requires an extensive knowledge of the domain in which the data set is created. Because an in-depth knowledge of all scientific domains is not available to the creator of visualization software, a flexible and extensible visualization system is essential in providing a productive tool to the scientist. This paper presents a shading language, based on the RenderMan shading language, that extends the shading model used to render volume data sets. Data shaders, written in this shading language, give the users of a volume rendering system a means of specifying how a volume data set is to be rendered. This flexibility is useful both as a visualization tool in the scientific community and as a research tool in the visualization community. 1 Introduction As science is a diverse and far reaching topic, scientific visualization must be prepared to deal with diverse requirements when scientific data sets are examined, explored, and analyzed. In m...

: The wealth of details in real scenes is far beyond the capabilities of explicit optical and geometrical modeling. In order to simulate the complex color or shape variations of such scenes, so-called texturing methods are often used. Unfortunately, they have some important drawbacks : specificity to a particular phenomenon, mutual incompatibility, and worse, lack of extensibility and portability. To remove these restrictions, we propose a new methodology for the description of texturing methods, based on the notion of enrichment. The driving idea of the methodology is to enhance a basic description of the scene by using three families of normalized operators (transformations, perturbations and modulations) that can be infinitely combined. Keywords : Realistic Rendering, Texturing Methods 1 Introduction The image rendering process can be divided in two fundamental steps. First, the modeling step for which a numerical description of the scene to be rendered is created by giving severa...

A methodology is presented that enables to express any deformation technique in a unique framework. The driving idea of this paper is that every deformation can be reformulated as combination of three kinds of normalized operators, transformation, modulation and perturbation. Moreover, using some pleasant properties of the methodology, some innovative ways to use, combine and enhance classical techniques are provided. 1 Introduction A challenging goal in computer graphics is to provide powerful techniques for modeling the shape of an object. In order to create softwares that can be used by designers and stylists, a natural idea is to mimic tools they are familiar with. Therefore, on a lot of modeling systems, the creation of an object starts from a rough shape which is then interactively sculpted or moulded. Techniques based on that concept are usually refered as deformation techniques and have represented a main research topic in computer graphics during the last decade. Deformati...