Abstract: Image-space simplifications have been used to accelerate the calculation of computer graphic images since the dawn of visual simulation. Texture mapping has been used to provide a means by which images may themselves be used as display primitives. The work reported by this paper endeavors to carry this concept to its logical extreme by using interpolated images to portray three-dimensional scenes. The special-effects technique of morphing, which combines interpolation of texture maps and their shape, is applied to computing arbitrary intermediate frames from an array of prestored images. If the images are a structured set of views of a 3D object or scene, intermediate frames derived by morphing can be used to approximate intermediate 3D transformations of the object or scene. Using the view interpolation approach to synthesize 3D scenes has two main advantages. First, the 3D representation of the scene may be replaced with images. Second, the image synthesis time is independent of the scene complexity. The correspondence between images, required for the morphing method, can be predetermined automatically using the range data associated with the images. The method is further accelerated by a quadtree decomposition and a view-independent visible priority. Our experiments have shown that the morphing can be performed at interactive rates on today’s high-end personal computers. Potential applications of the method include virtual holograms, a walkthrough in a virtual environment, image-based primitives and incremental rendering. The method also can be used to greatly accelerate the computation of motion blur and soft shadows cast by area light sources. CR Categories and Subject Descriptors: I.3.3 [Computer Graphics]: Picture/Image Generation; I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism. Additional Keywords: image morphing, interpolation, virtual reality, motion blur, shadow, incremental rendering, real-time display, virtual holography, motion compensation.

Abstract: We present a simple, effective, and efficient technique for approximating arbitrary polyhedra. It is based on triangulation and vertex-clustering, and produces a series of 3D approximations (also called “levels of detail”) that resemble the original object from all viewpoints, but contain an increasingly smaller number of faces and vertices. The simplification is more efficient than competing techniques because it does not require building and maintaining a topological adjacency graph. Furthermore, it is better suited for mechanical CAD models which often exhibit patterns of small features, because it automatically groups and simplifies features that are geometrically close, but need not be topologically close or even part of a single connected component Using a lower level of detail when displaying small, distant, or background objects improves graphic performance without a significant loss of perceptual information, and thus enables realtime inspection of complex scenes or a convenient environment for animation or walkthrough preview.

Abstract: The reflection of light from most materials consists of two major terms: the specular and the diffuse. Specular reflection may be modeled from first principles by considering a rough surface consisting of perfect reflectors, or micro-facets. Diffuse reflection is generally considered to result from multiple scattering either from a rough surface or from within a layer near the surface. Accounting for diffuse reflection by Lambert’s Cosine Law, as is universally done in computer graphics, is not a physical theory based on first principles. This paper presents a model for subsurface scattering in layered surfaces in terms of one-dimensional linear transport theory. We derive explicit formulas for backscattering and transmission that can be directly incorporated in most rendering systems, and a general Monte Carlo method that is easily added to a ray tracer. This model is particularly appropriate for common layered materials appearing in nature, such as biological tissues (e.g. skin, leaves, etc.) or inorganic materials (e.g. snow, sand, paint, varnished or dusty surfaces). As an application of the model, we simulate the appearance of a face and a cluster of leaves from experimental data describing their layer properties. CR Categories and Subject Descriptors: I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism.

Abstract: The RealityEngine graphics system is the first of a new generation of systems designed primarily to render texture mapped, antialiased polygons. This paper describes the architecture of the RealityEngine graphics system, then justifies some of the decisions made during its design. The implementation is near-massively parallel, employing 353 independent processors in its fullest configuration, resulting in a measured fill rate of over 240 million antialiased, texture-mapped pixels per second. Rendering performance exceeds 1 million antialiased, texture mapped triangles per second. In addition to supporting the functions required of a general purpose, high-end graphics workstation, the system enables realtime, “out-the-window” image generation and interactive image processing.

Abstract: Method and sytems are provided for rendering and displaying in a real time 3-D computer graphic system a sequence of images of a subject using a plurality of time-sequenced textures such that at least a portion of the subject appears animated. The time-sequenced textures are derived from sources such as digitized frames or fields captured from a video recording of a live actor who may be engaged in a scripted performance, or a digitally-recorded cartoon animation sequence, and can be mapped in different ways to different types of surface geometries to achieve animation.

Abstract: The Fourier projection-slice theorem allos projections of volume data to be generated in O(nsquare log n) time for a volumbe of size ncube. The method operates by extracting and inverse Fourier transforming 2D slices from a 3D frequency domain representation of the volume. Unfortunately, these projections do not exhibit the occlusion that is characteristic of conventional volume renderings. We present a new frequency domain volume rendering algorithm that replaces much of the missing depth and shape cues by performing shading calculations in the frequency domain during slice extraction. In particular, we demonstrate frequency domain methods for computing linear or nonlinear depth cueing and directional diffuse reflection. The resulting images can be generated an order of magnitude faster than volume renderings and may be more useful for many applications.

Abstract: A structure model for volume rendering, called a shell, is introduced. Roughly, a shell consists of a set of voxels in the vicinity of the structure boundary together with a number of attributes associated with the voxels in this set. By carefully choosing the attributes and storing the shell in a special data structure that allows random access to the voxels and their attributes, storage and computational requirements can be reduced drastically. Only the voxels that potentially contribute to the rendition actually enter into major computation. Instead of the commonly used ray-casting paradigm, voxel projection is used. This eliminates the need for render-time interpolation and further enhances the speed. By having one of the attributes as a boundary likelihood function that determines the most likely location of voxels in the shell to be on the structure boundary, surface-based measurements can be made. The shell concept, the data structure, the rendering and measurement algorithms, and examples drawn from medical imaging that illustrate these concepts are described. >

Abstract: This paper presents a divide-and-conquer ray-traced volume rendering algorithm and a parallel image compositing method, along with their implementation and performance on the Connection Machine CM-5, and networked workstations. This algorithm distributes both the data and the computations to individual processing units to achieve fast, high-quality rendering of high-resolution data. The volume data, once distributed, is left intact. The processing nodes perform local raytracing of their subvolume concurrently. No communication between processing units is needed during this locally ray-tracing process. A subimage is generated by each processing unit and the final image is obtained by compositing subimages in the proper order, which can be determined a priori. Test results on the CM-5 and a group of networked workstations demonstrate the practicality of our rendering algorithm and compositing method.

Abstract: Flow volumes are the volumetric equivalent of stream lines. They provide more information about the vector field being visualized than do stream lines or ribbons. Presented is an efficient method for producing flow volumes, composed of transparently rendered tetrahedra, for use in an interactive system. The problems of rendering, subdivision, sorting, composing artifacts, and user interaction are dealt with. Efficiency comes from rendering only the volume of the smoke, and using hardware texturing and compositing. >

Abstract: A method and apparatus for rendering textured spheres and spherical environment maps. The method of the present invention provides for real time rotation of a textured sphere and panning of the view into a spherical environment map, along multiple axes without the need for special rendering hardware. A two-level indexing scheme for accessing pixel data in a texture map, is used to identify shading values for pixels in a display window. The two-level indexing scheme is comprised of a screen look-up table and a parametric look-up table. The screen look-up table has the dimensions of the display window, whereas the parametric look-up table has the dimensions of the parametric spherical environment map (wherein the pixel addresses are rotated 90 degrees from the origin). The method for the present invention is comprised primarily of the steps of: providing a parametric spherical environment map of the image to be viewed, generating a screen look-up table comprised of look-up addresses, generating a parametric look-up table comprised of index values into the parametric spherical environment map, and for each look-up address in the screen look-up table, mapping to an entry in the parametric look-up table, retrieving the value in the entry, and using the value to retrieve pixel values from the parametric spherical environment map. Rotation or movement of the view being seen is accomplished by adding offsets to the look-up address and/or the index values.

Abstract: A physically compact, low cost, high performance 3D graphics accelerator is presented. It supports shaded rendering of triangles and antialiased lines into a double-buffered 24-bit true color frame buffer with a 24-bit Z-buffer. Nearly the only chips used besides standard memory parts are 11 ASICs (of four types). Special geometry data reformatting hardware on one ASIC greatly speeds and simplifies the data input pipeline. Floating-point performance is enhanced by another ASIC: a custom graphics microprocessor, with specialized graphics instructions and features. Screen primitive rasterization is carried out in parallel by five drawing ASICs, employing a new partitioning of the back-end rendering task. For typical rendering cases, the only system performance bottleneck is that intrinsically imposed by VRAM.

Abstract: A hierarchical Z-buffer scan-conversion algorithm that does well on both (a) quickly rejecting most of the hidden geometry in a model, and (b) exploiting the spatial and temporal coherence of the images being generated. The method uses two hierarchical data structures, an object-space octree and an image-space Z-pyramid, in order to accelerate scan conversion. The two hierarchical data structures make it possible to reject hidden geometry very rapidly while rendering visible geometry with the speed of scan conversion. For animation purposes, the algorithm is also able to exploit temporal coherence. The resulting method is well suited to models with high depth complexity, achieving significant speedup in some cases compared to ordinary scan conversion.

Abstract: We present a general linear transform method for handling full spectral information in computer graphics rendering. In this framework, any spectral power distribution in a scene is described with respect to a set of fixed orthonormal basis functions. The lighting computations follow simply from this decision, and they can be viewed as a generalization of point sampling. Because any basis functions can be chosen, they can be tailored to the scenes that are to be rendered. We discuss efficient point sampling for scenes with smoothly varying spectra, and we present the use of characteristic vector analysis to select sets of basis functions that deal efficiently with irregular spectral power distributions. As an example of this latter method, we render a scene illuminated with fluorescent light.

Abstract: A computer graphics display system and method are described for rendering a scene formed of at least one geometric primitive as a pixel image having shadows produced by at least one defined light source. Multiple passes are made through the primitive data structure for each light source capable of producing shadows in the scene to be rendered. In a first pass, the scene is rendered to a frame buffer in the usual way, but using only the ambient component of the light specification, and a first Z-buffer is updated with the viewpoint Z value. For each defined light source (i), two additional passes (PASS 2i and 2i+1) through the data structure are required. In the first of these, a transformation matrix is set up in such a way that the viewpoint is moved to the position of the light source. The scene is then rendered in the usual way except that the frame buffer is not updated, and a second Z-buffer (light source view Z-buffer) is used instead of the first Z-buffer. In the next pass, the shaded image and shadows are generated in parallel using the content of the first and second Z-buffers. When the frame buffer is updated, it is accomplished in a cumulative manner with each computed intensity value due to a specific light source being added to any value already stored there. In this way, intensities resultant from each of multiple light sources are accumulated on the image.

Abstract: A method and apparatus convert font outlines to rasterized bitmaps. The method accesses stored outline data representing an object in a first coordinate space and transforms the outline data to corresponding data representing the object in a second corrdinate space. Regional relationship information is maintained in both corrdinate spaces through a non-linear transformation expressed as a plurality of linear transformation matrices, and a bit map, suitable for displaying the object, is generated as a result of the transformation. The apparatus of the invention analyzes Bezier curves and subdivides them as necessary until each portion is sufficiently flat to be approximated as a straight line, and calculates where line segments cross pixel midlines in order to fill the outline, and then generates the bit map.

Abstract: : We present a new algorithm for simulating the effect of light travelling through volume objects. Such objects (haze, fog, clouds…) are usually modelized by voxel grids which define their density distribution in a discrete tridimensional space. The method we propose is a two-pass Monte-Carlo ray-tracing algorithm that does not make any restrictive assumptions neither about the characteristics of the objects (both arbitrary density distributions and phase functions are allowed) nor about the physical phenomena included in the rendering process (multiple scattering is accounted for). The driving idea of the algorithm is to use the phase function for Monte-Carlo sampling, in order to modify the direction of the ray during scattering.

Abstract: A method and device for describing a complex color raster image as a collection of objects in a hierarchical and device independent format. The purpose of structured imaging (SI) is to expand the scope of a raster image to a collection of individually manipulable component objects. An SI is a hierarchical description of a single output image raster which may be used as one component of a page in a structured document. Objects contributing to the output raster may originate from text, graphics, other rasters or a combination thereof, and all maintain their heritage for selectability and modification. The SI describes not only the source data but also the image processing operations required for rendering the output raster. SI technology supports re-editability, customization and enhancement, automatic image assembly and high performance imaging. Thus, such a model has implications not only in an image editing and processing arena, but also in the filing and printing services used for image handling.

Abstract: A technique for rendering particles in general, and surface particles in particular, is presented. This technique incorporates an improved shading model, the use of Gaussian filters to prevent spatial and temporal artifacts, and an efficient scan-conversion algorithm. The steps of the rendering are described: shading, filtering, scan conversion, and occlusion. Ways in which the process may be varied to further improve the results and widen the range of applications are discussed. >

Abstract: An experimental 3D interface is described, including rendering acceleration hardware, a 3D mouse, and 3D interaction techniques. A 3D cursor, controlled by the augmented mouse, allows direct manipulation of 3D objects. Objects are selected by placing the tip of the cursor inside. Objects can be moved in 3D, or simultaneously moved and rotated using a technique called “tail-dragging.” A method called “snap-to” helps users align objects. The interface is designed without using explicit modes or commands. Sounds accentuate the interaction. Details of the implementation and informal user observations are described, as well as topics for future work.

Abstract: A technique for producing a second image for display in the context of an original image uses a model data structure, in contrast to an image-based data structure, and a model-based operation, called a viewing operation, in contrast to an image-based operation, to produce the second image. The second image is displayed in the spatial context of the original image, as that context is defined by a viewing operation region, or VOR, at the same time as the original image is being displayed, giving the perception to a machine user of providing information related to the original image in the spatial context of the original image. The VOR functions as a type of "visual filter", binding the second view of the original image to the display area defined by the VOR. In one illustrated embodiment, the method operates within the environment of a rendering application executing in a graphical user interface environment. A machine user moves the VOR over a portion of a rendered image, and in response to the user's movement action, a viewing operation associated with the VOR invokes the renderer that produced the original rendered image to produce a second modified view of the original image using a new value for a global parameter in the scene description. The second image is then clipped to the size and shape of the VOR, and is then presented in the VOR, showing the second modified view.

Abstract: Volume Visualization is becoming an important tool for understanding large 3D datasets. A popular technique for volume rendering is known as splatting. With new hardware architectures offering substantial improvements in the performance of rendering texture mapped objects, we present textured splats. An ideal reconstruction function for 3D signals is developed which can be used as a texture map for a splat. Extensions to the basic splatting technique are then developed to additionally represent vector fields.

Abstract: A three-dimensional edge operator for detecting anatomical structures in medical imaging is presented. It uses the spatial moments of the gray-level surface, and operates in three dimensions with any window size. It allows the location and the contrast surface, as well as the surface orientation, to be estimated. The computation of the discrete version is reported. Bias and errors due to the spatial sampling and noise are analyzed at both a theoretical and experimental level. The moment-based operator is compared with other well-known edge operators using simple shaped primitives for which the analytical solution is known. The 3-D rendering of real data is then provided by merging the operator in a ray-tracing framework. >

Abstract: This is an integrated book/CD-ROM package which allows users to explore the techniques used in scientific visualization. It is designed for a broad range of computer professionals, scientists, researchers, teachers, students and other interested readers. Employing the image as the fundamental concept, the book covers a range of subjects under the broad heading of scientific visualization, including: image display and processing; image animation; video; visualization of multiparameter data; terrain rendering; 3-D solid modelling, rendering and animation; and visualization in film and TV. Practical hints on the use of commercial and public domain software in producing scientific visualization are also provided, as are discussions of the computation and production of the images used in the text.

Abstract: A method for rendering a graphics image of a three-dimensional graphics model is described. The method consists of the steps of projecting a parametric surface representation of the three-dimensional graphics model into a two-dimensional parametric space; mapping an array of grid points onto the parametric space; evaluating a shading function at each grid point to form an array shading values; applying a contouring function to the array of shading values to determine boundary curves for regions of constant shading; applying a silhouette function to the parametric surface representation of the three-dimensional graphics model to determine the boundaries for regions of consistent-facing; clipping the regions of constant shading by the regions of consistent-facing to determine consistent-facing regions of constant color; mapping the regions of constant shading back to the surface of the three-dimensional model; occluding hidden surfaces; mapping the clipped regions of constant shading to display space; and filling the regions of constant shading in display space. The regions of constant shading are available for editing by a two-dimensional drawing package.

Abstract: The present invention provides a method for producing auditory renderings of digitized works and, in particular, digitized documents containing complex mathematical expressions. Documents are first entered into a computer system and formatted with a markup language, such as one of the TeX® or LaTeX® family of languages. The formatted documents are parsed to provide a tree-structured, high-level representation. Mathematical expressions are in quasi-prefix form. Lexical analysis and recognition processes are then undertaken. The resulting analyzed documents are provided to an audio output device (such as a voice synthesizer) operating under control of a set of predetermined rendering rules. The resultant audio signal contains not only textual content but also the analogical markings produced by the reading rules. Multichannel audio outputs may be used to allow for spatial placement capability, in addition to the other analogical markings. An audio formatting language (AFL) is provided to allow for manipulation of rendering rules. A browsing capability is also provided to allow a listener to easily locate his or her place in a document.

Abstract: There are five fundamental concerns in the synthesis of realistic imagery of fractal landscapes: (1) convincing geometric models of terrain; (2) efficient algorithms for rendering those potentially-large terrain models; (3) atmospheric effects, or aerial perspective, to provide a sense of scale; (4) surface textures as models of natural phenomena such as clouds, water, rock strata, and so forth, to enhance visual detail in the image beyond what can be modelled geometrically; and (5) a global context in which to situate the scenes. Results in these five areas are presented, and some aspects of the development of computer graphics as a new process and medium for the fine arts are discussed. Heterogeneous terrain models are introduced, and preliminary experiments in simulating fluvial erosion are presented to provide fractal drainage network features. For imaging detailed terrain models we describe grid tracing, a time- and memory-efficient algorithm for ray tracing height fields. To obtain aerial perspective we develop geometric models of aerosol density distributions with efficient integration schemes for determining scattering and extinction, and an efficient Rayleigh scattering approximation. We also describe physically-based models of the rainbow and mirage. Proceduralism is an underlying theme of this work; this is the practice of abstracting models of complex form and behaviors into relatively terse algorithms, which are evaluated in a lazy fashion. Procedural textures are developed as models of natural phenomena such as mountains and clouds, culminating a procedural model of an Earth-like planet which in the future may be explored interactively in a virtual reality setting.

Abstract: An image synthesizing system improves perspective transformation of images by giving a far and near sense to the spatial change in the surface data of an object. A texture data storage unit stores texture data at positions represented by texture coordinates. An image supply unit outputs texture coordinates, brightness data, attribute data and the other data which correspond to the vertex coordinates arid vertices of polygons. A processor unit determines rendering data for each dot by subjecting the texture coordinates and brightness data to the perspective transformation, linear interpolation and inversely perspective transformation. The resulting rendering data is then mapped to representing coordinates determined by a main processor in a field buffer unit. Thereafter, the rendering data is transformed into RGB data by a palette/mixer circuit using color data which are read out from a texture data storage unit by the texture coordinates, attribute data and brightness data. Thus, an image data can be formed.

Abstract: An overview of 3-D rendering techniques of medical data is presented. It is pointed out that volume rendering, and especially ray tracing, can be considered to be the most sophisticated and general method to display 3-D medical data. However, surface rendering still remains the most relevant technique for displaying noncommensurate information such as anatomical atlases. Hence, one of the main practical issues is to select the most appropriate image rendering method, based on the data acquisition modes and the medical relevance. The future of 3-D medical imaging is also discussed. >

Abstract: of EP0568357In order to produce high quality colour presentation graphics such as posters, advertisements, notices, greeting cards etc., efficiently and at a low cost, there is provided a graphics system (1) for a colour copier(24). The system (1) includes a memory card (15) input (7) for object image data, a host processor (2) connected to a user controllable keyboard (20) for selecting and editing the object image data to create edited image data, a real-time object processor (12) for rendering the edited image data to output an image signal (17) to the copier (24) for printing an image represented by the image signal. The system (1) is characterised by the absence of an image frame store.