Showing papers in "IEEE Computer Graphics and Applications in 1988"
TL;DR: In this article, a volume-rendering technique for the display of surfaces from sampled scalar functions of 3D spatial dimensions is discussed, which is not necessary to fit geometric primitives to the sampled data; images are formed by directly shading each sample and projecting it onto the picture plane.
Abstract: The application of volume-rendering techniques to the display of surfaces from sampled scalar functions of three spatial dimensions is discussed. It is not necessary to fit geometric primitives to the sampled data; images are formed by directly shading each sample and projecting it onto the picture plane. Surface-shading calculations are performed at every voxel with local gradient vectors serving as surface normals. In a separate step, surface classification operators are applied to compute a partial opacity of every voxel. Operators that detect isovalue contour surfaces and region boundary surfaces are examined. The technique is simple and fast, yet displays surfaces exhibiting smooth silhouettes and few other aliasing artifacts. The use of selective blurring and supersampling to further improve image quality is described. Examples from molecular graphics and medical imaging are given. >
2,437Â citations
TL;DR: An alternative formulation of deformable models is presented in which deformations are decomposed into a reference component, which may represent an arbitrary shape, and a displacement component, allowing deformation away from this reference shape.
Abstract: A class of physically based models suitable for animating flexible objects in simulated physical environments was proposed earlier by the authors (1987). The original formulation works as well in practice for models whose shapes are moderately to highly deformable, but it tends to become numerically ill conditioned as the rigidity of the models is increased. An alternative formulation of deformable models is presented in which deformations are decomposed into a reference component, which may represent an arbitrary shape, and a displacement component, allowing deformation away from this reference shape. The application of the deformable models to a physically based computer animation project is illustrated. >
332Â citations
TL;DR: The results show that simultaneous contrast can be a major source of error when reading maps, but only partially confirm the form hypothesis, and guidelines are given for designing color sequences to be effective in both conveying form and value information.
Abstract: Pseudocoloring for presenting univariate map information on a graphic display system is investigated. The kinds of information available in maps are divided into two classes: metric information denotes the quantity stored at each point on the surface, and form information denotes the shape or structure of the surface. Theoretical principles are proposed to predict which color sequences will be effective at conveying value and form information respectively. According to this theory, a scale that approximates the physical spectrum should be good at conveying value information, because of the reduced effects of simultaneous contrast. It should be poor at conveying form information, however, because the brain prefers form information to come through the lightness-processing channel. Conversely, a gray scale should be poor at conveying value information and good at conveying form information, according to the same theory. These predictions are tested in a series of psychophysical experiments that test five color sequences. The results show that simultaneous contrast can be a major source of error when reading maps, but only partially confirm the form hypothesis. Guidelines are given for designing color sequences to be effective in both conveying form and value information. An experimental color sequence is presented to illustrate these guidelines. >
299Â citations
TL;DR: The fundamentals of hierarchical data structures are reviewed and it is shown how they are used in the implementation of some basic operations in computer graphics, focusing on quadtrees and octrees.
Abstract: The fundamentals of hierarchical data structures are reviewed and it is shown how they are used in the implementation of some basic operations in computer graphics. The properties of hierarchical structures are discussed, focusing on quadtrees and octrees. The latter are defined, some of the more common ways in which they are implemented are examined, and an explanation of the quadtree/octree complexity theorem is provided. Vector quadtrees and vector octrees are discussed. The performance of basic operations using quadtrees is considered. >
212Â citations
TL;DR: A method is presented for explicitly representing dimensions, tolerances, and geometric features in solid models in a graph structure called an object graph that provides an important foundation for higher-level application programs to automate tolerance analysis and synthesis.
Abstract: A method is presented for explicitly representing dimensions, tolerances, and geometric features in solid models. The method combines CSG and boundary representations in a graph structure called an object graph. Dimensions are represented by a relative position operator. The method can automatically translate changes in dimensional values into corresponding changes in geometry and topology. The representation provides an important foundation for higher-level application programs to automate tolerance analysis and synthesis. The implementation of a prototype interactive polyhedral modeler based on this representation is presented. >
185Â citations
TL;DR: It is shown that it is possible to ray trace large animations more quickly with space-time ray tracing using this hierarchy than with straightforward frame-by-frame rendering.
Abstract: Techniques for the efficient ray tracing of animated scenes are presented. They are based on two central concepts: spacetime ray tracing, and a hybrid adaptive space subdivision/boundary volume technique for generating efficient, nonoverlapping hierarchies of bounding volumes. In spacetime ray tracing, static objects are rendered in 4-D space-time using 4-D analogs to 3-D techniques. The bounding volume hierarchy combines elements of adaptive space subdivision and bounding volume techniques. The quality of hierarchy and its nonoverlapping character make it an improvement over previous algorithms, because both attributes reduce the number of ray/object intersections that must be computed. These savings are amplified in animation because of the much higher cost of computing ray/object intersections for motion-blurred animation. It is shown that it is possible to ray trace large animations more quickly with space-time ray tracing using this hierarchy than with straightforward frame-by-frame rendering. >
151Â citations
TL;DR: The Cube architecture as mentioned in this paper is centered around a 3D cubic frame buffer of voxels, and it entertains three processors that access the frame buffer to input sampled and synthetic data, to manipulate the 3D images, and to project and render them.
Abstract: A versatile voxel-based architecture for 3-D volume visualization, called the Cube architecture, is introduced. A small-scale prototype of the architecture has been realized in hardware and has been operating in true real-time, faster than the alternative voxel systems. The Cube architecture is centered around a 3-D cubic frame buffer, of voxels, and it entertains three processors that access the frame buffer to input sampled and synthetic data, to manipulate the 3-D images, and to project and render them. To cope with the huge quantity of voxels and still perform in real-time, two special features were incorporated within the architecture: a unique skewed memory organization, which permits the retrieval and storage of voxels in parallel, and a multiple-write bus, which speeds up the viewing process. These features allow Cube, for example, to project an image of n/sup 3/ voxels in O(n/sup 2/ log n) time rather than the conventional O(n/sup 3/) time. >
142Â citations
TL;DR: In this article, a 6D variant on the conventional mouse, called the "bat", is used for 6D object placement in a hierarchically constructed scene, and two distinct parts of the placement operation are examined and the hardware and software environment designed as a test for the study are described.
Abstract: Existing strategies for 6-D placement (i.e positioning and orienting) are briefly reviewed. An approach is presented that uses a 6-D variant on the conventional mouse, called the 'bat', because it is like a mouse that flies. This device encodes relative position, like the mouse, but delivers data in all six dimensions needed for object placement. The goal is to evaluate the bat to determine how well it is suited to placement operations, which are studied in the context of a hierarchically constructed scene. Two distinct parts of the placement operation, visualization and manipulation, are examined and the hardware and software environment designed as a test for the study are described. Manipulation with the bat, which is discussed in some detail, is judged to be successful. >
135Â citations
TL;DR: The author considers the problem, in making space movies, of figuring out where to place the camera and in what direction to point it to get an interesting picture and develops an approach whereby the program is told what is to appear on the screen and determinesWhere to place and point the camera.
Abstract: The author considers the problem, in making space movies, of figuring out where to place the camera and in what direction to point it to get an interesting picture. He develops an approach whereby the program is told what is to appear on the screen and determines where to place and point the camera. He bases the approach on the standard 'look at' transformation. >
122Â citations
TL;DR: A color space defined by the fundamental spectral sensitivity functions of the human visual system is used and specific guidelines are offered for the design of computer graphics displays that will accommodate almost all color-deficient users.
Abstract: A color space defined by the fundamental spectral sensitivity functions of the human visual system is used to assist in the design of computer graphics displays for color-deficient users. The functions are derived in terms of the CIE standard observer color-matching functions. The Farnsworth-Munsell 100-hue test, a widely used color vision test administered using physical color samples, is then implemented on a digitally controlled color television monitor. The flexibility of this computer graphics medium is then used to extend the Farnsworth-Munsell test in a way that improves the specificity of the diagnoses rendered by the test. The issue of how the world appears to color-deficient observers is addressed, and a full-color image is modified to represent a color-defective view of the scene. Specific guidelines are offered for the design of computer graphics displays that will accommodate almost all color-deficient users. >
121Â citations
TL;DR: A taxonomy for the user-visible parts of window managers is presented, and it is noted that there are actually very few significant differences, and the differences can be classified in a taxonomy with fairly limited branching.
Abstract: A taxonomy for the user-visible parts of window managers is presented. It is noted that there are actually very few significant differences, and the differences can be classified in a taxonomy with fairly limited branching. This taxonomy should be useful in evaluating various window managers, and it will also serve as a guide for the issues that need to be addressed by designers if future window-manager user interfaces. The advantages and disadvantages of the various options are presented. >
TL;DR: In this article, the advantages of using perceptually uniform color spaces in data displays are described, and it is shown how one-, two-, and three-dimensional representations of color gamuts can provide an understanding, at various visualization levels, of the colors that can be produced on display devices, of how they restrict color displays in practice, and how they form an essential part of a user interface in the design of color displays.
Abstract: The advantages of using perceptually uniform color spaces in data displays are described. It is shown how one-, two-, and three-dimensional representations of color gamuts can provide an understanding, at various visualization levels, of the colors that can be produced on display devices, of how they restrict color displays in practice, and of how they form an essential part of a user interface in the design of color displays. >
TL;DR: The use of the quadtree as a basis for hidden-surface algorithms, parallel and perspective projection methods to display a collection of objects represented by an octree, and the use of octrees to facilitate such image-rendering techniques as ray tracing and radiosity are discussed in this article.
Abstract: For pt.I see ibid., vol.8, no.3, p.48-68, May (1988). Advanced applications for preliminary display methods are focused on, with emphasis on the octree. Topics include use of the quadtree as a basis for hidden-surface algorithms, parallel and perspective projection methods to display a collection of objects represented by an octree, and the use of octrees to facilitate such image-rendering techniques as ray tracing and radiosity. >
TL;DR: Starlike surfaces can be defined in spherical coordinates by a function r( theta, phi ) on the unit sphere, which can be expanded in spherical harmonics to give a consequence of smooth approximations to the surface.
Abstract: Starlike surfaces can be defined in spherical coordinates by a function r( theta , phi ) on the unit sphere, which can be expanded in spherical harmonics to give a consequence of smooth approximations to the surface. This method has been used to approximate the solvent-accessible surface of a molecule. The coefficients in the expansion provide a small collection of numbers that characterize the molecular shape. The resulting smooth surfaces can be rendered with random dots or smooth shading. These spherical harmonic surfaces have advantages for modeling overall molecular shape, particularly time-averaged shapes relevant to electrostatic and other intermolecular interactions. >
TL;DR: MacSpin uses rotation to display 3-D scatterplots, and offers such dynamic graphics primitives as animation, identification, and highlighting, which allow the user to transform, edit, and categorize data as patterns in the display indicate.
Abstract: The authors describe how MacSpin, a program for dynamic display of multivariate data, and its user interface facilitate a high level of interaction between analyst and data. MacSpin uses rotation to display 3-D scatterplots, and offers such dynamic graphics primitives as animation, identification, and highlighting. With these features the user can visually find trends, clusters, and other patterns in multivariate data as well as highly unusual observations (outliers). The program offers a broad range of data manipulation and calculation features that allow the user to transform, edit, and categorize data as patterns in the display indicate. MacSpin also provides display options and a number of statistical summaries. The authors describe how the program is used on real data. They discuss some history of dynamic graphics, the program's environment and user interface, and experiences and conclusions. >
TL;DR: The author discusses data representations and analytical tools commonly used in solid modelers for three analysis operations: boundary evaluation, image generation, and mechanical property calculation.
Abstract: The author discusses data representations and analytical tools commonly used in solid modelers for three analysis operations: boundary evaluation, image generation, and mechanical property calculation. The methods described are generally applicable to solid models bounded by quadric surfaces (e.g. planes, cylinders, spheres, and cones). Only methods applicable to constructive solid geometry or boundary representation modelers are considered. The author concludes with a review of ongoing research into other analysis operations appropriate for solid modeling representations. >
IBM1
TL;DR: The authors demonstrate the utility of examining seismic data with a volumetric scheme, whereby a synoptic view of the interior of the data volume is possible before conventional interpretation, and the resulting 3-D images reveal the structure of the geological layers.
Abstract: The authors demonstrate the utility of examining seismic data with a volumetric scheme, whereby a synoptic view of the interior of the data volume is possible before conventional interpretation. High-amplitude seismic events, representing reflections from subterranean surfaces, are transformed to color pixels, and the resulting 3-D images reveal the structure of the geological layers. Such morphological features as hills, valleys, and faults are apparent indicating that the approach could prove useful for identifying potential oil reservoirs. The authors implement the technique on a personal computer to produce displays of similar quality, but they find that the construction of the 3-D images is too slow for reasonable interactivity. However, with the addition of a parallel-processing accelerator, a personal-computer-based workstation would be feasible for this kind of 3-D visualization and interpretation. >
TL;DR: An algorithm is described for partitioning intersecting polyhedrons into disjoint pieces and removing intersections from sets of planar polygons embedded in three space and includes provisions to detect and in some cases overcome, the effects of numerical inaccuracy on the topological decisions that the algorithm must make.
Abstract: An algorithm is described for partitioning intersecting polyhedrons into disjoint pieces and, more generally, removing intersections from sets of planar polygons embedded in three space. Polygons, or faces, need not be convex and may contain multiple holes. Intersections are removed by considering pairs of faces and slicing the faces apart along their regions of intersection. To reduce the number of face pairs examined, bounding boxes around groups of faces are checked for overlap. The intersection algorithm also computes set-theoretic operations on polyhedrons. Information gathered during face cutting is used to determine which portions of the original boundaries may be present in the result of an intersection, a union, or a difference of solids. The method includes provisions to detect and in some cases overcome, the effects of numerical inaccuracy on the topological decisions that the algorithm must make. The regions in which ambiguous results are possible are flagged so that the user can take appropriate action. >
TL;DR: Simulations of natural images as they are mapped in the brain by these architectures are shown, including the simulation of a stereo image at the level of primary visual cortex.
Abstract: A description is given of a series of studies in computational neuroscience that illustrate the application of computer graphics and image processing to the reconstruction and representation of the complex architectures that make up primate visual cortex Techniques are demonstrated for reconstructing brains in three dimensions, 'peeling' them apart, and flattening the brain with minimal metric error Simulations of natural images as they are mapped in the brain by these architectures are shown, including the simulation of a stereo image at the level of primary visual cortex >
TL;DR: In this article, a tracking algorithm is given for curves that have equations of the form f(x,y) = 0, which produces the next approximating pixel by looking for a sign difference in function evaluations at midpoints between the eight nearest neighboring pixels.
Abstract: A tracking algorithm is given for curves that have equations of the form f(x,y)=0. It produces the next approximating pixel by looking for a sign difference in function evaluations at midpoints between the eight nearest neighboring pixels. The search proceeds in order of decreasing likelihood, examining the most probable candidates first. >
TL;DR: Two methods are presented for generating Koch curves, analogous to the commonly used iterative methods for producing images of Julia sets, based on a characterization of Koch curves as the smallest nonempty sets closed with respect to a union of similarities on the plane.
Abstract: Two methods are presented for generating Koch curves, analogous to the commonly used iterative methods for producing images of Julia sets. The attractive method is based on a characterization of Koch curves as the smallest nonempty sets closed with respect to a union of similarities on the plane. The repelling method is in principle dual to the attractive one but involves a nontrivial problem of selecting the appropriate transformation to be applied at each iteration step. Both methods are illustrated with a number of computer-generated images. The mathematical presentation emphasizes the relationship between Koch construction and formal languages theory. >
TL;DR: A macro facility that allows end users to extend interactive graphical applications is presented as part of a user-interface management system (UIMS), and the unique facilities of the MIKE (menu interaction kontrol environment) semantics-based model are presented.
Abstract: A macro facility that allows end users to extend interactive graphical applications is presented as part of a user-interface management system (UIMS). Such macros are expressed by example; that is, the end user programs the macro in the application's generated user interface. Problems with macros-by-example in graphical applications are explored, and requirements to accommodate such a facility are defined for the UIMS dialogue model. Existing UIMS models are reviewed relative to these requirements, and the unique facilities of the MIKE (menu interaction kontrol environment) semantics-based model are presented. The implementation of the macro-by-example system is discussed, as well as the particular implementation of a multicommand UNDO facility, which is necessary when editing micros by example. >
IBM1
TL;DR: A method for calculating accurate boundary representations of solid models is introduced that uses a pair of bounding polyhedral approximations to enclose the boundary of each object.
Abstract: Although curved-surface solid modeling systems achieve a higher level of accuracy than faceted systems, they also introduce a host of topological, geometric, and numerical complications. A method for calculating accurate boundary representations of solid models is introduced that reduces the impact of these complications. The method uses a pair of bounding polyhedral approximations to enclose the boundary of each object. A structural analysis automatically determines where to make adaptive refinements to the polyhedrons to assure the topological validity of the results. Potential singularities are localized. The implementation is an experimental extension to the Geometric Design Processor (GDP) solid modeling system. >
TL;DR: The MML language can be used to produce both interactive and batch animation programs and has the advantages of being independent of the detailed structure of the object and lending itself to the construction of good user interfaces for animation systems.
Abstract: A description is given of MML, a special-purpose programming language developed for procedural models. The language is used to specify both the generation of the model and the motion of the objects in the model. A motion specification technique that works well with natural phenomena is presented. It has the advantages of being independent of the detailed structure of the object and lending itself to the construction of good user interfaces for animation systems. The MML language can be used to produce both interactive and batch animation programs. The user interface for the interactive animation programs is automatically constructed by the MML system. Several examples of the use of MML are given. >
TL;DR: To demonstrate the feasibility and practicability of designing and building low-cost flight simulators, a prototype system was developed to model the performance of a new US Army remotely piloted missile system.
Abstract: To demonstrate the feasibility and practicability of designing and building low-cost flight simulators, a prototype system was developed to model the performance of a new US Army remotely piloted missile system. The flight simulator displays a dynamic, three-dimensional, out-the-window view of the terrain in real time while responding to operator input from the command and control system. A description is given of the hardware, software, and database implementations. The system capabilities and limitations are examined. The total development cost is an order of magnitude less than that of the sophisticated systems currently in use. >
IBM1
TL;DR: A technique that allows alternative eliminations to be examined is proposed and a potentially efficient, but geometrically approximate, method of implementation is outlined.
Abstract: Set-theoretic solid models often contain redundant primitives, which slow down rendering and other processes. They are not simple to remove, especially as there can be alternative eliminations that may not be equally desirable. Existing techniques for eliminating such redundant primitives do not fully consider the possibilities and rely on repeated evaluation of parts of the object's boundary, a process that is likely to be very slow. A technique that allows alternative eliminations to be examined is proposed and a potentially efficient, but geometrically approximate, method of implementation is outlined. >
TL;DR: In designing imagery systems, simply increasing the spatial and temporal addressability and resolution beyond limits set by the human visual system will have a negligible impact on image quality, but that effective use of antialiasing techniques could allow visual information about object features to be presented with great fidelity.
Abstract: The assumption that antialiasing destroys useful visual information about object features is challenged in three experiments that examine the effects of antialiasing on the visual information for object location and motion. The results show that proper antialiasing eliminates the spurious visual information produced by sampling processes in image synthesis and allows the viewer's visual system to produce a precise representation of object location and a continuous representation of object motion. This suggests that in designing imagery systems, simply increasing the spatial and temporal addressability and resolution beyond limits set by the human visual system will have a negligible impact on image quality, but that effective use of antialiasing techniques could allow visual information about object features to be presented with great fidelity. >
TL;DR: The design of a prototype flat-panel interactive display system (FIDS) based on state-of-the-art human-computer-interaction techniques is described and an example application, namely, a text editor using the standard proof correction marks drawn directly on the display, is presented.
Abstract: The design of a prototype flat-panel interactive display system (FIDS) based on state-of-the-art human-computer-interaction techniques is described. An example application, namely, a text editor using the standard proof correction marks drawn directly on the display, is presented. Software design and implementation are discussed. The use of the keystroke-level mode to evaluate the prototype is considered. >
TL;DR: The design of HutWindows, a user interface management system intended for applications in mechanical CAD, is discussed, which features a three-layered internal architecture, where the presentation, dialogue-control, and application-processing layers are clearly separated from each other.
Abstract: The design of HutWindows, a user interface management system intended for applications in mechanical CAD, is discussed,. HutWindows features a three-layered internal architecture, where the presentation, dialogue-control, and application-processing layers are clearly separated from each other. This leads to increased simplicity and flexibility in user interface design over the more traditional situation where all of these layers are closely coupled. >