Abstract: One method of directly rendering a three-dimensional volume of scalar data is to project each cell in a volume onto the screen. Rasterizing a volume cell is more complex than rasterizing a polygon. A method is presented that approximates tetrahedral volume cells with hardware renderable transparent triangles. This method produces results which are visually similar to more exact methods for scalar volume rendering, but is faster and has smaller memory requirements. The method is best suited for display of smoothly-changing data.

Abstract: This paper describes a system architecture that supports realtime generation of complex images, efficient generation of extremely high-quality images, and a smooth trade-off between the two.Based on the paradigm of integration, the architecture extends a state-of-the-art rendering system with an additional high-precision image buffer. This additional buffer, called the Accumulation Buffer, is used to integrate images that are rendered into the framebuffer. While originally conceived as a solution to the problem of aliasing, the Accumulation Buffer provides a general solution to the problems of motion blur and depth-of-field as well.Because the architecture is a direct extension of current workstation rendering technology, we begin by discussing the performance and quality characteristics of that technology. The problem of spatial aliasing is then discussed, and the Accumulation Buffer is shown to be a desirable solution. Finally the generality of the Accumulation Buffer is explored, concentrating on its application to the problems of motion blur, depth-of-field, and soft shadows.

Abstract: The large size of many volume data sets often prevents visualization algorithms from providing interactive rendering. The use of hierarchical data structures can ameliorate this problem by storing summary information to prevent useless exploration of regions of little or no current interest within the volume. This paper discusses research into the use of the octree hierarchical data structure when the regions of current interest can vary during the application, and are not known a priori. Octrees are well suited to the six-sided cell structure of many volumes.A new space-efficient design is introduced for octree representations of volumes whose resolutions are not conveniently a power of two; octrees following this design are called branch-on-need octrees (BONOs). Also, a caching method is described that essentially passes information between octree neighbors whose visitation times may be quite different, then discards it when its useful life is over.Using the application of octrees to isosurface generation as a focus, space and time comparisons for octree-based versus more traditional “marching” methods are presented.

Abstract: As computer graphics technique rises to the challenge of rendering lifelike performers, more lifelike performance is required. The techniques used to animate robots, arthropods, and suits of armor, have been extended to flexible surfaces of fur and flesh. Physical models of muscle and skin have been devised. But more complex databases and sophisticated physical modeling do not directly address the performance problem. The gestures and expressions of a human actor are not the solution to a dynamic system. This paper describes a means of acquiring the expressions of real faces, and applying them to computer-generated faces. Such an "electronic mask" offers a means for the traditional talents of actors to be flexibly incorporated in digital animations. Efforts in a similar spirit have resulted in servo-controlled "animatrons," high-technology puppets, and CG puppetry [1]. The manner in which the skills of actors and puppetteers as well as animators are accommodated in such systems may point the way for a more general incorporation of human nuance into our emerging computer media.The ensuing description is divided into two major subjects: the construction of a highly-resoved human head model with photographic texture mapping, and the concept demonstration of a system to animate this model by tracking and applying the expressions of a human performer.

Abstract: Two strategies, pre-computation before display and adaptive refinement during display, are used to combine interactivity with high image quality in a virtual building simulation. Pre-computation is used in two ways. The hidden-surface problem is partially solved by automatically pre-computing potentially visible sets of the model for sets of related viewpoints. Rendering only the potentially visible subset associated with the current viewpoint, rather than the entire model, produces significant speedups on real building models. Solutions for the radiosity lighting model are pre-computed for up to twenty different sets of lights. Linear combinations of these solutions can be manipulated in real time. We use adaptive refinement to trade image realism for interactivity as the situation requires. When the user is stationary we replace a coarse model using few polygons with a more detailed model. Image-level linear interpolation smooths the transition between differing levels of image realism.

Abstract: We present a rendering method designed to provide accurate, general simulation of global illumination for realistic image synthesis. Separating surface interaction into diffuse plus specular, we compute the specular component on the fly, as in ray tracing, and store the diffuse component (the radiosity) for later-reuse, similar to a radiosity algorithm. Radiosities are stored in adaptive radiosity textures (rexes)1 that record the pattern of light and shadow on every diffuse surface in the scene. They adaptively subdivide themselves to the appropriate level of detail for the picture being made, resolving sharp shadow edges automatically.We use a three-pass, bidirectional ray tracing algorithm that traces rays from both the lights and the eye. The "size pass" records visibility information on diffuse surfaces; the "light pass" progressively traces rays from lights and bright surfaces to deposit photons on diffuse surfaces to construct the radiosity textures; and the "eye pass" traces rays from the eye, collecting light from diffuse surfaces to make a picture.

Abstract: Two strategies, pre-computation before display and adaptive refinement during display, are used to combine interactivity with high image quality in a virtual building simulation. Pre-computation is used in two ways. The hidden-surface problem is partially solved by automatically pre-computing potentially visible sets of the model for sets of related viewpoints. Rendering only the potentially visible subset associated with the current viewpoint, rather than the entire model, produces significant speedups on real building models. Solutions for the radiosity lighting model are pre-computed for up to twenty different sets of lights. Linear combinations of these solutions can be manipulated in real time. We use adaptive refinement to trade image realism for interactivity as the situation requires. When the user is stationary we replace a coarse model using few polygons with a more detailed model. Image-level linear interpolation smooths the transition between differing levels of image realism.

Abstract: We propose a new rendering technique that produces 3-D images with enhanced visual comprehensibility. Shape features can be readily understood if certain geometric properties are enhanced. To achie...

Abstract: This paper describes a 3D object-space paint program. This program allows the user to directly manipulate the parameters used to shade the surface of the 3D shape by applying pigment to its surface. The pigment has all the properties normally associated with material shading models. This includes, but is not limited to, the diffuse color, the specular color, and the surface roughness. The pigment also can have thickness, which is modeled by simultaneously creating a bump map attached to the shape. The output of the paint program is a 3D model with associated texture maps. This information can be used with any rendering program with texture mapping capabilities. Almost all traditional techniques of 2D computer image painting have analogues in 3D object painting, but there are also many new techniques unique to 3D. One example is the use of solid textures to pattern the surface.

Abstract: One method of directly rendering a three-dimensional volume of scalar data is to project each cell in a volume onto the screen. Rasterizing a volume cell is more complex than rasterizing a polygon....

Abstract: This paper describes a system architecture that supports realtime generation of complex images, efficient generation of extremely high-quality images, and a smooth trade-off between the two.Based o...

Abstract: As computer graphics technique rises to the challenge of rendering lifelike performers, more lifelike performance is required. The techniques used to animate robots, arthropods, and suits of armor,...

Abstract: Many techniques for rendering natural objects such as the sea, terrains, and trees have been developed; they are indispensable for flight simulators. In this paper, techniques for rendering road surfaces under various conditions are discussed. Rendering road surfaces is quite useful for the evaluation of driving safety, and it will play an important part in the development of drive simulators. Light sources with high intensity often disturb drivers especially under wet road surface conditions.This paper proposes two models, a reflection model for road surfaces taking into account weather conditions, and a model on streaks of light taking into account both refraction and diffraction of light. Some examples demonstrate the possibility of applications for drive simulators in the future.

Abstract: Most databases for spherically distributed data are not structured in a manner consistent with their geometry. As a result, such databases possess undesirable artifacts, including the introduction of "tears" in the data when they are mapped onto a flat file system. Furthermore, it is difficult to make queries about the topological relationship among the data components without performing real arithmetic. The sphere quadtree (SQT), which is based on the recursive subdivision of spherical triangles obtained by projecting the faces of an icosahedron onto a sphere, eliminates some of these problems. The SQT allows the representation of data at multiple levels and arbitrary resolution. Efficient search strategies can be implemented for the selection of data to be rendered or analyzed by a specific technique. Furthermore, sphere quadtrees offer significant potential for improving the accuracy and efficiency of spherical surface rendering algorithms as well as for spatial data management and geographic information systems. Most importantly, geometric and topological consistency with the data is maintained.

Abstract: Traditional radiosity methods can compute the illumination for a scene independent of the view position. However, if any part of the scene geometry is changed, the radiosity process will need to be repeated from scratch. Since the radiosity methods are generally expensive computationally, the traditional methods do not lend themselves to interactive uses where the geometry is constantly changing. This paper presents a new radiosity algorithm to incrementally render scenes with changing geometry and surface attributes. In other words, the question to be asked is "What is the minimum recomputation I need to do if I turn off a light source, change the color of a surface, add or move an object?" Because a modeling change generally exhibits some coherence and affects only parts of an image, the proposed method may drastically reduce the rendering time and therefore allow interactive manipulation. In addition, since the method is conducted incrementally and view-independently, the rendering process can start before the modeling process is completed. The traditional paradigm of modeling-then-rendering is changed to rendering-while-modeling. This approach not only gives the user better visual feedback but also effectively utilizes CPU time otherwise wasted in the modeling process.

Abstract: A technique for efficiently converting an original sampled image into a bitmap suitable for a specific output device. The method includes explicit printer and perception effects, and employs local permutations of bits, to find optimal bit settings. A continuous-tone image is first sampled to form a sampled image (12), through which a series of swaths are defined. For each swath (14i) in turn, an iterative procedure examines a column of bits (16) at a time, determining which configuration of the column of bits yields a minimal local difference value between the trial bitmap and the sampled image. While holding the rest of the trail bitmap constant, the column of bits is permuted and the difference value calculated, for each configuration of the column's look-ahead bits (22). To determine the difference values, local printer (17a) and perception (17b) models calculate effects between bits, while a local comparison model calculates the difference between the trial bitmap and the sampled image. The printable bitmap resulting from the methods of the present invention can be displayed by the output device to provide a faithful duplication of the original image.

Abstract: Direct volume rendering can visualize sampled 3D scalar data as a continuous medium or extract features. However, it is generally slow. Furthermore, most algorithms for direct volume rendering have assumed rectilinear gridded data. This paper discusses methods for using direct volume rendering when the original volume is curvilinear, i.e., is divided into six-sided cells which are not necessarily equilateral hexahedra. One approach is to ray-cast such volumes directly. An alternative approach is to ray-cast such volumes directly. An alternative approach is to interpolate the sample volumes to a rectilinear grid, and use this regular volume for rendering. Advantages and disadvantages of the two approaches in terms of speed and image quality are explored.

Abstract: There are many imaging modalities (e.g., medical imaging scanners) that capture information about internal structures and generate three-dimensional (3D) digital images of the distribution of some physical property of the material of the structure. Such images have been found to be very useful in analyzing the form and function of the structure and in detecting and correcting deformities in the structure. Visualization of 3D structures is an essential component of such analyses. One commonly used approach to visualization consists of identifying the structure of interest, forming its surfaces, and then rendering the surfaces on a two-dimensional screen. This paper addresses the surface formation problem assuming that object identification has already been done and a 3D binary image is available that represents the structure. For the existing 3D boundary tracking algorithms, the user has to somehow specify each surface that is to be tracked. Often, the 3D image consists of many surfaces of interest. Their manual specification is very tedious and may be impossible if the structure is of complex shape. This paper describes a methodology for automatically tracking all boundary surfaces—i.e., labelling boundary surfaces—in the given 3D image. The algorithms also generate additional information from which the 3D connected components in the image are trivially obtained. Examples from medical imaging are included to illustrate the usefulness of the new methodology.

Abstract: We have developed a rendering technique to generate realistic images meeting designers' requirements by strictly analyzing various physical phenomena relevant to the appearance of actual objects.We have numerically compared the results of the calculations using this technique with colorimetry values. As a result, both values were virtually equal, so we have been able to confirm the effectiveness of the established technique.Application of this technique to car design, which has not been realized to a large extent because of severe requests for realism, will make it possible to evaluate styles and colors on a graphics display before making a clay model.

Abstract: A large variety of different algorithms for rendering radiological volume data has been described in the past. It has turned out that not every method is equally well suited for all kinds of modalities and organs. We therefore compare algorithms for different applications. The algorithms include Z-buffer gradient shading, gray level gradient shading, transparent gray level gradient shading, and two mutations of the marching cubes algorithm. The object classes are bone (CT), head (MRI), heart (MRI), vessels (MRI), ultrasound, and isodoses in radiotherapy. Properties of the algorithms, such as the achieved realism, the flexibility, and the computational cost are discussed. As a general result we found that the best visualization is achieved when different algorithms appropriate to the objects can be applied within one image.

Abstract: Five hardware architectures for volume rendering, which requires efficiently handling a huge amount of volumetric data, are surveyed, categorized, and compared. They are Cube, Insight, PARCUM, Voxel Processor, and 3DP. General-purpose graphics systems that exploit their surface-based geometry engine to reduce the computational burden of the rendering process are briefly reviewed. >

Abstract: Numerical data values are analyzed, organized, and stored for retrieval and rendering on a graphics display system. Numerical data arrays are organized for rapid access and display using graphical transforms. Scientific data is transformed into concurrently displayed translucent three dimensional contour surfaces allowing analysis of multi-dimensional data. Display management functions are provided for viewing transformed data in three dimensional form, as cut by specified plane or as viewed over time by using short time delays between related displays to provide a movie-like presentation. Input data may be accepted from an operator by the visualization manager for redirecting or steering an underlying numerical simulation.

Abstract: In virtually all rendering systems, linear light sources are modeled with a series of point light sources that require considerable computing resources to produce realistic looking results. A general solution for shading surfaces illuminated by a linear light source is proposed. A formulation allowing for faster computation of the diffuse component of light reflection is derived. By assuming Phong's specular component, simple, inexpensive and convincing results are produced with the use of a Chebyshev approximation. A shadowing algorithm is also presented. As shadowing from linear light sources is expensive, two acceleration schemes, extended from ray tracing, are evaluated.

Abstract: This is a methodology which reduces the time required to render a volume with extracted isocontours and inserted cutting plane and perform an arbitrary rotation within a three-dimensional volume. The volume is first partitioned among the processors of a multiple-instruction, multiple-data (MIMD) multiprocessor computer. As the user indicates the isocontour to be extracted, rotation, and cutting plane to be inserted into the image space volume, each processor independently selects the optimum algorithm for rendering the volume using the indicated display parameters on its local data set. If the processor is fully behind the cutting plane, a front-to-back (FTB) volume rendering algorithm is used. If the cutting plane lies behind the cutover point, then a back-to-front (BTF) volume rendering algorithm is used, otherwise the FTB volume rendering algorithm is used.

Abstract: A new two pass approach is presented based on a variation of backward ray tracing backward beam tracing. Advantages include its capability of rendering complex, hitherto unattainable, specular to d...

Abstract: We describe the main algorithms used in an interactive lighting simulation program based on a two-pass extension of the radiosity method. The system allows interactive walk-through as other systems based on radiosity calculations. Moreover, it offers increased realism in the lighting effects by use of extended form factors which accounts for "specular reflection of diffuse light", fast production and display of progressively refined images by distribution of the calculations, good quality of the images in the early stages of the refinement by the use of "hardware light sources", "cheap" rendering of some of the specular highlights at any time by use of the built-in specular shading model, lighting modification (color, intensity of the light sources) by use of "negative light", fast simulation of mirror effects and interactive tools for controling the quality of the final image.

Abstract: A hardware bit block transfer operator for transferring blocks of data from a source address to a destination address in a display memory, a bit mapped memory, or a host processor, or between the two source and destination addresses in a graphics rendering cogenerator. Functionally, blocks to be transferred are addressable to the bit level thus requiring shifting and reformatting from the source word to the destination word alignment. The cogenerator automatically identifies all required boundary exceptions and applies the appropriate sequencing at the proper time during the block transfer operation. All that the programmer is required to provide are definitions of color depth, source transparency address, source start address, destination transparency address and destination window. The proper transfer is then performed by the cogenerator with a single command to the transfer operator.

Abstract: A method for employing hierarchical display list in global rendering comprises the steps of traversing the display list and extracting selected primitives and attributes. A bounding volume is defined for selected primitives, and data indicative of the selected primitives, attributes, and bounding volumes are stored in a global database. Global rendering may be performed by either ray tracing or radiosity based upon the data in the global database. In the event that global rendering is performed by radiosity, then a plurality of surface elements for each selected primitive is defined and also stored in the global data base. Shading attribute data for each of the surface elements is defined upon application of a radiosity rendering algorithm to the global database. An alternative display list may be defined from the global database, if desired.