Abstract: A method of and system for rendering a halftone image of a gray scale image by utilizing a pixel-by-pixel comparison of the gray scale image against a blue noise mask is disclosed in which the gray scale image is scanned on a pixel-by-pixel basis and compared on a pixel-by-pixel basis to an array of corresponding data points contained in a blue noise mask stored in a PROM or computer memory in order to produce the desired halftoned image. Both digital and optically implemented halftone methods are disclosed. Application specific modifications of the blue noise mask as well as its use for producing halftoned color images are also disclosed.

Abstract: We describe a recently completed implementation of a virtual environment for exploring numerically-generated three-dimensional unsteady flowfields. A boom-mounted six degree of freedom head-position-sensitive stereo CRT system is used for viewing. A hand position sensitive glove controller is used for injecting various tracers (e.g., "smoke") into the virtual flowfield. A mutiprocessor graphics workstation is used for computation and rendering. We describe our techniques for visualizing unsteady flows and discuss the computer requirements for a variety of visualization techniques. These techniques generalize to visualization of other three-dimensional vector fields.

Abstract: A method and apparatus for providing a texture mapped perspective view for digital map systems. The system includes apparatus for storing elevation data, apparatus for storing texture data, apparatus for scanning a projected view volume from the elevation data storing apparatus, apparatus for processing, apparatus for generating a plurality of planar polygons and apparatus for rendering images. The processing apparatus further includes apparatus for receiving the scanned projected view volume from the scanning apparatus, transforming the scanned projected view volume from object space to screen space, and computing surface normals at each vertex of each polygon so as to modulate texture space pixel intensity. The generating apparatus generates the plurality of planar polygons from the transformed vertices and supplies them to the rendering apparatus which then shades each of the planar polygons. In one alternate embodiment of the invention, the polygons are shaded by apparatus of the rendering apparatus assigning one color across the surface of each polygon. In yet another alternate embodiment of the invention, the rendering apparatus interpolates the intensities between the vertices of each polygon in a linear fashion as in Gouraud shading.

Abstract: A computer graphics system for modeling chemical molecules includes simultaneous two-dimensional and three-dimensional display of models of molecules from a single data set, and allows a user to edit in either two dimensions or three dimensions. A two-dimensional model may be stylized while a three-dimensional model of the same molecule remains chemically (geometrically) correct. The system has editing tools for use in both two dimensions and three dimensions, and changes made in one mode are immediately reflected in the other, and the editing tools include manipulation components for the user to display on elements of a model, and to use to move parts of a model of a molecule relative to other parts. The system includes techniques for structure determination and display that significantly reduce the computer power required to perform system functions, rendering techniques formally reserved to supercomputers usable on smaller computer platforms. Physically based modeling is included, allowing the user to perturb the geometry of a model and to investigate interactively the effects of perturbation according to a dynamic force equation. The system also includes a procedure for displaying multiple models of molecules and performing docking studies between the models.

Abstract: Imaging system whereby color image data intended for reproduction on an image reproduction means may be provided to a functional engine for modification according to one or more functional transforms. Color management may be applied to the data before output to the selected image reproduction device, so as to achieve WYSIWYG color matching of the image data with respect to the color fidelity limitations or other characteristics of the intended image reproduction device.

Abstract: The invention concerns a method for rendering scene information in images having a large dynamic range, i.e. sunny and shady areas. The method takes particular advantage of image segmentation and computations employed in compression of images for electronic still photography. In distinguishing large areas, the method selectively adjusts the brightness of all portions of the area without necessarily preserving contrast which avoids halo artifacts. Those portions in areas of intermediate size are subjected to a smoothing feature which avoids the production of artifacts in the form of a line at the boundary.

Abstract: A technique is described for adding natural-looking hair to standard rendering algorithms Using an explicit hair model, in which each individual hair is represented by a three-dimensional curve, the technique uses pixel blending combined with Z-buffer and shadow buffer information from the scene to yield a final anti-aliased image with soft shadows Although developed for rendering human hair, this technique can also be used to render any model consisting of long filaments of sub-pixel width The technique can be adapted to any rendering method that outputs Z-buffer and shadow buffer information and is amenable to hardware implementation

Abstract: rendering techniques. Methods in surface mapping, surface rendering, and volume rendering are presented, with discussion of specific clinical applications in nuclear medicine, computed tomography, and magnetic resonance imaging. J Nucl Med 1991; 32:534-546

Abstract: Pixel arithmetic and logical units for rendering pixels in graphics systems. Circuits for performing arithmetic operations on raster scan data are provided. The circuits comprise opcode registers for selecting an arithmetic function which transforms pixel value data corresponding to graphics primitives, multiplication circuits interfaced with the opcode registers for multiplying graphics operators with graphics data to obtain transform pixel value data, combining circuits interfaced with the multiplication circuits for adding transform pixel value data to existing pixel value data and processing circuitry interfaced with the combining circuitry for storing overflow data from the combining circuitry when adding transform pixel data overflows the combining circuitry.

Abstract: Fluid Flow Visualization.- 1 Introduction.- 1.1 Purposes and Problems of Flow Visualization.- 1.2 Overview.- 2 Experimental Flow Visualization.- 2.1 Addition of Foreign Material.- 2.2 Optical Techniques.- 2.3 Addition of Heat and Energy.- 3 Computer Graphics Flow Visualization.- 3.1 The Flow Visualization Process.- 3.2 Flow Visualization Mappings.- 3.3 Data Preparation.- 3.3.1 Filtering.- 3.3.2 Data Selection.- 3.3.3 Domain Transformations.- 3.3.4 Interpolation.- 3.3.5 Point Location.- 3.3.6 Computing Derived Scalar Quantities.- 3.3.7 Computing Particle Path Lines.- 3.3.8 Contour Lines and Surfaces.- 3.4 Flow Field Topology.- 3.4.1 Critical points.- 3.4.2 Integral Curves and Surfaces.- 4 Presentation Techniques.- 4.1 Human Perception and Depth Cues.- 4.2 Basic Rendering Techniques.- 4.2.1 Arrows.- 4.2.2 Curves.- 4.2.3 Surfaces.- 4.2.4 Particles.- 4.2.5 Environment Geometry.- 4.2.6 Volume Rendering.- 4.3 Special Rendering Techniques.- 4.3.1 Animation.- 4.3.2 Aliasing and Anti-Aliasing.- 4.3.3 Texture Synthesis and Texture Mapping.- 4.3.4 Hybrid Rendering.- 4.3.5 Advanced Particle Rendering.- 5 Conclusions and Research Directions.- References.- Volume Visualization in Medicine: Techniques and Applications.- 1 Introduction.- 1.1 Objectives.- 1.2 Related Fields.- 2 Imaging Modalities.- 3 Methods.- 3.1 Overview.- 3.2 Preprocessing.- 3.2.1 Data Conversion.- 3.2.2 Filtering.- 3.2.3 Interpolation.- 3.2.4 Data Structures.- 3.3 Object Definition.- 3.3.1 Segmentation.- 3.3.2 Interpretation.- 3.4 Surface-Based Rendering.- 3.4.1 Surface Reconstruction from Contours.- 3.4.2 Surface Reconstruction from Volumes.- 3.4.3 Shading.- 3.5 Voxel-Based Rendering.- 3.5.1 Projection Techniques.- 3.5.2 Surfaces.- 3.5.3 Cut Planes.- 3.5.4 Integral and Maximum Intensity Projection.- 3.5.5 Volume Rendering.- 3.6 Advanced Segmentation Methods.- 3.6.1 Point-Based Segmentation.- 3.6.2 Edge-Based Segmentation.- 3.6.3 Region-Based Segmentation.- 3.7 Multimodality Matching.- 3.8 Manipulation.- 3.9 Image Fidelity.- 3.10 Implementation Aspects.- 4 Applications.- 5 Conclusions.- References.- Application of Visualization in Environmental Protection.- 1 Introduction.- 2 Applications of Software Systems in Environmental Protection.- 2.1 Monitoring and Control Systems.- 2.2 Information Systems.- 2.3 Evaluation and Interpretation Systems.- 2.4 Decision Support Systems.- 2.5 Environmental Information Systems.- 3 Requirements of Visualization Systems.- 4 Methods and Applications.- 4.1 Data Analysis and Control in Monitoring Systems.- 4.2 Information Systems.- 4.3 Scattered Data Methods.- 4.4 Particle Flow Visualization and Animation.- 4.5 Groundwater Protection and Finite Element Methods.- 4.6 Intelligent User Interfaces in Process Control.- 5 Conclusions.- References.- Data Structures in Scientific Visualization.- 1 Introduction.- 2 Computer Based Problem Handling.- 2.1 The Modeling Phase.- 2.2 The Simulation Phase.- 2.3 The Evaluation Phase.- 3 Data Types of Dependent Variables.- 3.1 Basic Data Types.- 3.2 Dimensionality of Dependent Variables.- 3.2.1 Scalar Fields.- 3.2.2 Vector Fields.- 3.2.3 Tensor Fields.- 4 Coordinate Systems.- 5 Connectivity.- 5.1 Cartesian Grids.- 5.2 Uniform Grids.- 5.3 Rectilinear Grids.- 5.4 Regular Grids.- 5.5 Block-Structured Grids.- 5.6 Irregular Grids.- 5.7 Hybrid Grids.- 5.8 Scattered Locations.- 6 Zone Data.- 7 Auxiliary Information.- 8 Relationship between Data Sets.- 9 Consideration of Time.- 9.1 Handling of Time Information.- 9.1.1 Fixed Time Step Size.- 9.1.2 Variable Time Step Size.- 9.2 Time Dependence of Data.- 9.3 Time Dependence of Grids.- 9.4 Time Dependence of Connectivity.- 9.5 Different Time Steps in Separate Parts.- 10 Data Structures in Different Software Packages.- 10.1 The Irregular Grid Approach.- 10.2 Differentiated Data Structure Approach.- 11 Application Package Independent Data Access Software.- 12 Conclusions.- References.- A Visualization-Based Model for a Scientific Database System.- 1 Introduction.- 2 A Paradigm for Interdisciplinary Scientific Research.- 3 Nature of Scientific Data.- 3.1 Lattice-Oriented Data.- 3.2 Relationships Among Data.- 3.3 Data and Models of Data.- 3.4 Meaning of Updates.- 3.5 Related Database Developments.- 4 Nature of Scientific Data Visualization.- 4.1 Traditional Visualization Techniques.- 4.2 Multi-Dimensional Data Visualization.- 4.3 Systems for Scientific Data Visualization.- 5 Toward a Target Scientific Database System.- 5.1 Terminology.- 5.2 Metadata.- 5.3 Schema Model.- 5.4 Schema Evolution.- 5.5 Bridge to Knowledge Based Systems Technology.- 5.6 Project Overview.- 6 Conclusion.- References.- Volume Synthesis Principles.- 1 Background.- 2 Motivation.- 3 Voxelization Algorithms.- 4 Discrete Ray Tracing.- 5 Concluding Note.- References.- Surface Interpolation from Cross Sections.- 1 Introduction.- 2 Topological Reconstruction.- 2.1 Assignment Graphs and Nesting Trees.- 2.2 Enumeration of Assignment Graphs.- 2.3 Similarity of Contours.- 2.4 Mutual Location of Contours.- 3 Geometrie Reconstruction.- 4 Triangulated Surfaces.- 4.1 Point Reduction.- 4.2 Cylindric Triangulation.- 4.3 Saddle Point Triangulation.- 4.4 Extremal Points.- 4.5 Penetrations.- 4.6 Quality of Triangulations.- 4.6.1 Measure Criteria.- 4.6.2 Shape Criteria and Deformation.- 4.7 Intermediate Layers.- 5 Pyramidal Extrapolation.- 6 Smooth Surface Interpolation.- 7 Volume Oriented Reconstruction.- 8 Interpolation by Spatial Delaunay Triangulations.- 9 Reconstruction with Spatial Grids.- 10 Acquisition of Data.- 11 Interaction.- 11.1 Segmentation.- 11.2 Topological Assignment.- 11.3 Deformation.- 11.4 Triangulation.- 12 Concluding Remarks.- References.- Modeling and Visualizing Volumetrie and Surface-on-Surface Data.- 1 Introduction.- 2 Data.- 2.1 Pressure on a Wing Example.- 2.2 CAT Scan Data Example.- 2.3 Precipitation on Earth Data Example.- 2.4 Temperature Analysis Data Example.- 2.5 Flame Data Example.- 2.6 Well Log Data Example.- 2.7 Brain Data Example.- 2.8 Spatial Sound Data Example.- 2.9 Summary of Data Examples.- 3 Visualization Methods.- 3.1 Techniques for Visualizing Volumetrie Models.- 3.1.1 Domain Decomposition Methods.- 3.1.2 Slice Methods.- 3.1.3 Contour Methods.- 3.1.4 Volume Rendering (Ray Casting) Methods.- 3.1.5 Volume Interrogation Techniques.- 3.2 Techniques for Visualizing Surface-on-Surface Models.- 4 Modeling Methods.- 4.1 Distance Function Approach.- 4.1.1 Volumetrie Data.- 4.1.2 Surface-on-Surface Data.- 4.2 Piecewise Hermite Approach.- 4.2.1 Surface-on-Surface Data.- 4.2.2 Volumetric Data.- References.- Curve and Surface Interrogation.- 1 Introduction.- 2 Reflection Line Method.- 3 Isophotes.- 4 Orthotomics.- 5 Polarity Method.- 6 Focal Surfaces.- References.- Sorting for Polyhedron Compositing.- 1 Polyhedron Compositing.- 2 A General Sorting Algorithm.- 3 Adaptive Mesh Refinement.- 4 Sorting for the AMR Method.- 5 Interpolation and Contour Surfaces.- 6 Sorting for Cloud Visualization.- 7 Results.- References.- Joining Volume with Surface Rendering.- 1 Introduction.- 2 Converting Data.- 2.1 Converting Volume Data into Polygonal Data.- 2.2 Converting Polygonal Data into Volumetrie Data.- 3 Combining Rendering Methods.- 3.1 Hybrid Ray Tracer.- 3.2 Rendering Volumetric Data in Molecular Systems.- 3.3 Hybrid Rendering of Volume Data and Polygons.- 3.4 Combining Volume with Line and Surface Rendering.- 3.4.1 Architecture of the System.- 3.4.2 Common Parameters.- 3.4.3 Transformations and Coordinate Systems.- 3.4.4 Requirements on Volume Rendering.- 3.4.5 The Volume Rendering Algorithm.- 3.4.6 Rendering of Geometrically Defined Objects.- 3.4.7 Geometry Rendering in Hardware.- 3.4.8 Merging Image Space Elements.- 3.5 Z-Buffer Merging.- 4 Applications - Two Examples.- References.- The Volume Priority Z-Buffer.- 1 Introduction.- 2 Overview of the Algorithm.- 3 Projection Strategy.- 4 Block Processing.- 4.1 Determination of the Convex Hull.- 4.2 Scan-Conversion of the Convex Hull.- 4.3 Visualizing the Volumetrie Data.- 4.3.1 Color Intensity Determination.- 4.3.2 The z-Buffer.- 5 Conclusion.- References.- A Fourier Technique for Volume Rendering.- 1 Introduction.- 2 Fourier Projection-Slice Theorem.- 3 Fourier Volume Rendering.- 4 Data Shifting.- 5 Resampling Implementation Details.- 6 Zero Padding and Premultiplication.- 7 Resampling Rate.- 8 Conclusion.- References.- An Improved Shading Algorithm for Radiosity Based Renderers.- 1 Introduction.- 2 Rendering.- 2.1 Linear Interpolation.- 2.1.1 Mach bands.- 2.1.2 Loss of Diffuse Highlights.- 2.2 The "Perfect" Solution.- 2.3 Vector Form Factors.- 2.4 An Improved Interpolation Technique.- 3 Comparisons.- 4 Results.- 5 Implementation.- References.- Some Annotations on X-ray Tracing.- 1 Introduction.- 2 Underlying Principle.- 2.1 Vera Geometry.- 2.2 Color of an Object at the Target Point.- 3 X-ray Tracing Stills.- 3.1 Enhanced Edges.- 3.2 Texture.- 3.3 Miscellaneous Effects.- 3.4 Animated X-ray Traced Images.- References.- Auditory Representation of Scientific Data.- 1 Introduction.- 2 Technical Considerations.- 3 Sensory and Perceptual considerations.- 4 Experiments in Auditory Data Representation.- 5 Systems for Research in Auditory Data Representation.- 6 Evaluation of Auditory Data Representations.- 7 Summary and Conclusions.- References.- Color Illustrations.- 1 Fluid Flow Visualization.- 2 Volume Visualization in Medicine: Techniques and Applications.- 3 Application of Visualization in Environmental Protection.- 4 Data Structures in Scientific Visualization.- 5 A Visualization-Based Model for a Scientific Database System.- 6 Visualizing Volumetrie and Surface-on-Surface Data.- 7 Curve and Surface Interrogation.- 8 Sorting for Polyhedron Compositing.- 9 Joining Volume with Surface Rendering.- 10 An Improved Shading Algorithm for Radiosity Based Renderers.

Abstract: A system and method to accurately digitally simulate a rendering of a printed articulation, stroke or mark by a donor medium used in graphic arts, such as paints, pencils, erasers or other implements. Using a computer (1) or other hardware the system and method provides a digital representation of dye-concentration color mixing, receptor grain and variable grain penetration, and a smooth continuous brush stroke without visible artifacts on a color monitor (6). Other objects of the invention include methods for varying the shape of a tip of an implement (5) across a stroke over a tablet (4) to accurately simulate brushes and other donor-receptor articulation common to natural media, and for rendering a brush stroke in multiple strokes to accurately simulate brush bristles.

Abstract: An algorithm that automatically produces polygonal representations of 3-D structures within a volume from a set of cross-sectional images is presented. The method incorporates the requirements necessary for structure analysis to go beyond plain rendering. The algorithm is fully automatic, using local voxel values to determine the connectivity of the surface. The resulting polygons are coherently ordered and connected, and no polygon occurs more than once. Each surface is complete, that is, no holes occur (except as an option, on the boundaries of the volume). The algorithm can be used to describe and visualize normal as well as pathological anatomy. >

Abstract: Object instancing is the efficient method of representing an hierarchical object with a directed graph instead of a tree. If this graph contains a cycle then the object it represents is a linear fractal. Linear fractals are difficult to render for three specific reasons: (1) ray-fractal intersection is not trivial, (2) surface normals are undefined and (3) the object aliases at all sampling resolutions.Ray-fractal intersections are efficiently approximated to sub-pixel accuracy using procedural bounding volumes and a careful determination of the size of a pixel, giving the perception that the surface is infinitely detailed. Furthermore, a surface normal for these non-differentiable surfaces is defined and analyzed. Finally, the concept of antialiasing "covers" is adapted and used to solve the problem of sampling fractal surfaces.An initial bounding volume estimation method is also described, allowing a linear fractal to be rendered given only its iterated, function system. A parallel implementation of these methods is described and applications of these results to the rendering of other fractal models are given.

Abstract: Data parallel computer architectures hold great promises for high performance computing. Volume visualization (raytracing) is an application that can greatly benefit from these architectures. We describe an algorithm for rendering of orthographic views of volume data on such architectures. In particular the problem of rotating the volume in regard to the communication overhead associated with finely distributed memory is analyzed. We extend an earlier technique (shear decomposition) to 3D and show how this can be mapped onto a data parallel architecture using only grid communication during the resampling associated with the rotation. The rendering uses efficient parallel computation constructs that allow us to use sophisticated shading models and still maintain high speed throughout. This algorithm has been implemented on the Connection MachineR parallel supercomputer and is used in an interactive volume rendering application, with multiple frames per second performance.

Abstract: Techniques for displaying 3D isovalues of scalar fields such as stress within a solid finite-element model generally involve examining each element for values of interest. An inexpensive, straightforward method is discussed for reducing the number of elements searched for such isovalues. It takes advantage of one traversal of the element data to yield a compact classification of the model by result values and ranges, with no sorting required. This data structure can then relate any scalar isovalue to a set of element groups which are closely inclusive of the isovalue. This method is intended for applications requiring repeated access to the analysis data, such as animation and interactive rendering of isosurfaces and scalar fields. While applicable to general volume visualization problems, it is particularly well suited to optimizing real-valued continuum field results such as those found in finite-element data. >

Abstract: A raster image processor for an all points addressable printer includes at least three digital computer controlled processing units (40, 42, 44) arranged in a parallel processing pipeline. The first unit (40) is a master processing unit that receives printing instructions and generates rendering commands. The record unit (42) is connected to the first unit by a dedicated bus (48) and receives the rendering commands over the bus and generates bit maps corresponding to the rendering commands. The third unit (44) is a memory unit connected to the second unit by a second dedicated bus (54), and receives the bit maps from the second unit and stores them in a page memory. All three units are connected by a communications and control bus (46) for overall coordination of the units.

Abstract: A method and apparatus for simultaneously rendering multiple scanlines. Using a scanline approach to rendering, multiple scanlines may be rendered simultaneously through the use of parallel rendering means. The rendering of multiple scanlines in parallel is enabled by creating scanline independence. Scanline independence is achieved by interpolation through direct evaluation of object information. During the rendering process each of the rendering means vertically interpolates to identify a span corresponding to the scanline being rendered. A span is identified by it's X, Y coordinates on a scanline. The scanline being rendered provides the Y-coordinate. Vertical interpolation generally involves the step of deriving the X-coordinates for the endpoints of the span and comprises the steps of: identifying active edges of the object, calculating a relative interpolation weight for each active edge and solving a linear interpolation function using the relative interpolation weight and the leftmost X-coordinate of the active edges and the rightmost X-coordinate of the active edges.

Abstract: Contents: Keynote and Invited Papers.- Animation.- Parallel Processing.- Volume Rendering.- Visualization Methods.- Ray Tracing/Rendering.- Picture Generation.- Computational Geometry.- Visualization in Engineering.- Fluid Flow Visualization.- Applications.

Abstract: An improved graphics processor has rapid response to higher priority tasks. It is implemented with multiple channels of FIFO input circuits and with task interrupt and context switching capability. The graphics processor servicing a first channel task is interrupted when a higher priority task is available in a second channel. Context switching facilitates interrupting of the lower priority first channel task, then saving of the context of the first channel task, then performing higher priority second channel task, then restoring the interrupted first channel task, and then continuing with the processing of the restored first channel task. It is also implemented with concurrent downloading from a host computer and processing by the graphics processor and implemented with general purpose graphics processing capability, including multi-level nested interrupts and nested subroutines.

Abstract: A three dimensional computer graphics method employs ray tracing to compute form factors. The form factors are utilized in a radiosity technique to determine global illumination for a scene.

Abstract: Described is a hardware architecture for combining the outputs of a number of z-buffer rendering engines to achieve higher performance than is possible with a single renderer. It allows a combination of renderers to achieve the same price/ performance ratio as the individual renderers that compose it, and can be extended to create systems with arbitrarily high performance. The described architecture is based on a fusion of scan-line rendering and the conventional z-buffer algorithm. The frame buffers of several z-buffer engines are modified to scan out z-values as well as color values. Multiplexing devices combine the z/color streams from each pair of frame-buffers. These z/color streams are then combined by further multiplexers, creating a binary tree that funnels the z/color information from the many conventional frame buffers into a single z/color stream. The color stream is then used to dnve a standard display device. The proposed architecture allows rendering rates of millions and even tens of millions of polygons per second. The basic architecture can be extended with additional hardware to perform antialiasing and texture-mapping.

Abstract: An apparatus and method for optical recognition of chemical graphics allows documents containing chemical structures to be optically scanned so that both the text and the chemical structures are recognized. The structures are converted directly into molecular structure files suitable for direct input into chemical databases, molecular modeling programs, image rendering programs and programs that perform real time manipulation of structures.

Abstract: Techniques for visualizing mathematical objects in four-dimensional (4D) space that exploit four-dimensional lighting effects are explored. The geometry of image production, stereography, and shadows in 4D is analyzed. Alternatives for smooth and specular shaded rendering of curves, surfaces, and solids in 4D are examined and a new approach that systematically converts curves or surfaces into uniquely renderable solids in 4D space by attaching spheres or circles to each point is proposed. Analogs of 3D shading methods are used to produce volume renderings that distinguish objects whose 3D projections from 4D are identical. Analyzing the procedures needed to justify and evaluate a system as this for teaching humans to 'see' in four dimensions leads to the proposal of a generally applicable four-step visualization paradigm. >

Abstract: A graphics processor including an interface for providing triangle primitives and line primitives representing a graphical image, a line drawer for receiving line primitives and for rendering the line primitives, and a triangle interpolator for receiving the triangle primitives from the interface and for providing line primitives therefrom to the line drawer, wherein the interface includes a register for storing graphics image line primitives and for selectively providing the stored line primitives to the line drawer.