bluuebunny/crossref_metadata_2025 huggingface dataset:
Computer graphics research in Japanese Universities
Authors: Herr Laurin
Published: November 2005

There is considerable research activity related to computer graphics within the Japanese academic community. However, little is known about it outside of Japan. Another problem is that some of the most interesting work being done is not called “Computer Graphics” and is therefore only reported in other fields such as “Precision Engineering” or “Image Processing.” Interpreting “Computer Graphics” broadly, this panel will survey the work of three leading Japanese researchers who will each briefly describe the history of computer graphics at their institutions, outline the level of staffing and equipment resources in their laboratories and report on their current areas of research activity. These presentations will be proceeded by the chairman's overview discussion about Japanese University research, in general. The panel will conclude with a question and answer period.

Professor Makoto Nagao, Department of Electrical Engineering, Kyoto University, Sakyo, Kyoto, Japan - The main thrust of research at Kyoto University has been in the field of digital image processing systems. Work began in 1965 on the problem of Japanese character recognition. One of the earliest digital processing systems in Japan was also designed. Working from beliefs about the human pattern recognition process, efforts were directed towards the development of a structural approach rather than mathematical theories which were popular during the early days of character recognition research. Current topics of interest include the modeling of more human-like image understanding functions, such as trial and error processes, knowledge-driven analysis processes and declaritive representation for image understanding. These can be summarized under the theme “Image Interpretation by Knowledge Presentation”.
Pyramidal parametrics
Authors: Williams Lance
Published: November 2005

The mapping of images onto surfaces may substantially increase the realism and information content of computer-generated imagery. The projection of a flat source image onto a curved surface may involve sampling difficulties, however, which are compounded as the view of the surface changes. As the projected scale of the surface increases, interpolation between the original samples of the source image is necessary; as the scale is reduced, approximation of multiple samples in the source is required. Thus a constantly changing sampling window of view-dependent shape must traverse the source image.

To reduce the computation implied by these requirements, a set of prefiltered source images may be created. This approach can be applied to particular advantage in animation, where a large number of frames using the same source image must be generated. This paper advances a “pyramidal parametric” prefiltering and sampling geometry which minimizes aliasing effects and assures continuity within and between target images.

Although the mapping of texture onto surfaces is an excellent example of the process and provided the original motivation for its development, pyramidal parametric data structures admit of wider application. The aliasing of not only surface texture, but also highlights and even the surface representations themselves, may be minimized by pyramidal parametric means.
Artificial texturing
Authors: Schweitzer Dino
Published: November 2005

Texture is an important surface characteristic which provides a great deal of information about the nature of a surface, and several computationally complex algorithms have been implemented to replicate realistic textures in computer shaded images. Perceptual psychologists have recognized the importance of surface texture as a cue to space perception, and have attempted to delineate which factors provide primary shape information. A rendering algorithm is presented which uses these factors to produce a texture specifically designed to aid visualization. Since the texture is not attempting to replicate an actual texture pattern, it is called “artificial” texturing. This algorithm avoids the computational limitations of other methods because this “artificial” approach does not require complex mappings from a defined texture space to the transformed image to be rendered. A simple filtering method is presented to avoid unacceptable aliasing.
Towards a comprehensive user interface management system
Authors: Buxton W. , Lamb M. R. , Sherman D. , Smith K. C.
Published: November 2005

A UIMS developed at the University of Toronto is presented. The system has two main components. The first is a set of tools to support the design and implementation of interactive graphics programs. The second is a run-time support package which handles interactions between the system and the user (things such as hit detection, event detection, screen updates, and procedure invocation), and provides facilities for logging user interactions for later protocol analysis.

The design/implementation tool is a preprocessor, called MENULAY, which permits the applications programmer to use interactive graphics techniques to design graphics menus and their functionality. The output of this preprocessor is high-level code which can be compiled with application-specific routines. User interactions with the resulting executable module are then handled by the run-time support package. The presentation works through an example from design to execution in a step-by-step manner.
SYNGRAPH
Authors: Olsen Dan R , Dempsey Elizabeth P.
Published: November 2005

The SYNGRAPH system automatically generates graphical user interfaces. It generates interactive Pascal programs from a description of the input language's grammar. From the grammar it deduces information about how to manage both physical and simulated devices, and how prompting and echoing are performed. Input errors are detected, and can be corrected using automatically provided rubout and cancel features. The natural integration of application specific semantics into the system is also shown including appropriate semantic recovery from input errors.
A graphics editor for benesh movement notation
Authors: Singh Baldev , Beatty John C. , Ryman Rhonda
Published: November 2005

This paper describes an interactive computerized editor for
Benesh Movement Notation
that aids in the preparation of dance scores on a medium resolution colour display. Benesh Movement Notation is a two-dimensional system for recording human movement in three dimensions of space which has been successfully used in the preparation of scores for a wide repertoire of dances. The preparation and revision of Benesh scores is a lengthy and error-prone process which interactive editing techniques can greatly facilitate. We describe the current state and future extensions of a prototype editing system in which all user interaction is based on a menu-driven scheme using a graphics tablet. Extensive visual cues including iconic trackers and semantic information are provided at all times. Both user and system initiated dialogues are supported. This system has served as a testbed for a variety of man-machine interaction studies, allowing us to transfer the wealth of experience with interactive text editing to a related task: the preparation of dance scores. The project has given us a better understanding of the issues involved in implementing an effective user-interface.
The simulation of natural phenomena (Panel Session)
Authors: Blinn James , Gomez Julian , Max Nelson , Reeves William , Csuri Charles A.
Published: November 2005

This panel will discuss the issues and the problems associated with the simulation of natural phenomena. This is a difficult area of research since it generally involves complex data bases and in many instances time variant phenomena. The computational loads can become enormous as one considers the physics or the mathematical modeling of structures.

Most items in nature, trees, clouds, fire and comets being some examples, have not been displayed realistically in computer graphics. This lack stems from a few different problems, all of which are significant. The first is the fact that realistic portrayals require large amounts of storage and consequently large compute time. Nature is able to create diverse detail at the most minute levels within an object of grandoise scale. The second problem is that of diversity of design within a given framework. For example, if a scene requires two dozen poplar trees, how does the designer construct trees that look different but are undeniably poplars? Humans typically become tired after the first few iterations of such a design process, with a resulting degradation in the subsequent models. Clearly, this problem applies to all of the phenomena mentioned above. Finally, there is a lack of models. First, second and third order representations are commonly used in computer graphics to model various kinds of surfaces and their boolean combinations. However, their applications to objects, which do not lend themselves well to being described as surfaces has not been addressed sufficiently.

Previous attempts at realism have dealt with the appearances of the surfaces being modeled, in terms of their illumination or relief. More recently, fractal methods have introduced a new degree of realism into terrain modeling systems. However, it appears that natural phenomena will require more research into the fundamental way things occur in nature, and in terms of computer graphics, their representation will build on previous work, but will still require new modeling techniques.
A parallel scan conversion algorithm with anti-aliasing for a general-purpose ultracomputer
Authors: Fiume Eugene , Fournier Alain , Rudolph Larry
Published: November 2005

Popular approaches to speeding up scan conversion often employ parallel processing. Recently, several special-purpose parallel architectures have been suggested. We propose an alternative to these systems: the general-purpose ultracomputer, a parallel processor with many autonomous processing elements and a shared memory. The “serial semantics/parallel execution” feature of this architecture is exploited in the formulation of a scan conversion algorithm. Hidden surfaces are removed using a single scanline, z-buffer algorithm. Since exact anti-aliasing is inherently slow, a novel parallel anti-aliasing algorithm is presented in which subpixel coverage by edges is approximated using a look-up table. The ultimate intensity of a pixel is the weighted sum of the intensity contribution of the closest edge, that of the “losing” edges, and that of the background. The algorithm is fast and accurate, it is attractive even in a serial environment, and it avoids several artifacts that commonly occur in animated sequences.
Anti-aliased line drawing using brush extrusion
Authors: Whitted Turner
Published: November 2005

This algorithm draws lines on a gray-scale raster display by dragging a “brush” along the path of the line. The style of the line is determined by the properties of the brush. An anti-aliasing calculation is performed once for the brush itself and thereafter only a trivial additional operation is needed for each pixel through which the brush is dragged to yield an anti-aliased line.

There are few constraints on the size, shape, and attributes of the brush. Lines can be curved as well as straight, It is possible to produce lines with a three dimensional appearance.
A device-independent network graphics system
Authors: Cahn Deborah U. , Yen Albert C.
Published: November 2005

The design and implementation of a basic graphics system for a heterogeneous network environment is described. The design has been influenced by the SIGGRAPH Core System, GKS, and proposals being considered by the ANSI Technical Committee on Computer Graphics Programming Languages. It permits hierarchical object definition, direct and indirect attribute specification, screen window management and complex styles of interaction. Important parts of the implementation include a device-independent database for graphical objects, a workstation driver which produces device code, and a device kernel which manages the display list. Problems relating to device independence and network partitioning are discussed.
Minimal GKS
Authors: Simons Randall W.
Published: November 2005

Minimal GKS is a subset of the Draft International Standard Graphical Kernel System. Minimal GKS has been implemented at Sandia in the programming language C. This implementation confirms that Minimal GKS does indeed have the anticipated advantages of easy implementation and small size. Experience in using this implementation has also demonstrated that Minimal GKS is easy to learn and use, yet is powerful enough for non-trivial, real-world applications.
Local control of bias and tension in beta-splines
Authors: Barsky Brian A. , Beatty John C.
Published: November 2005

The Beta-spline introduced recently by Barsky is a generalization of the uniform cubic B-spline: parametric discontinuities are introduced in such a way as to preserve continuity of the unit tangent and curvature vectors at joints (
geometric continuity
) while providing bias and tension parameters, independent of the position of control vertices, by which the shape of a curve or surface can be manipulated. Using a restricted form of quintic Hermite interpolation, it is possible to allow distinct bias and tension parameters at each joint without destroying geometric continuity. This provides a new means of obtaining local control of bias and tension in piecewise polynomial curves and surfaces.
Localized set operations for solid modeling
Authors: Mäntylä Martti , Tamminen Markku
Published: November 2005

Set operation algorithms form an important component of solid modeling systems. Their efficiency can be enhanced by localizing the search for geometric intersections to the region of overlap using a spatial directory. We present an algorithm that employs a three-dimensional extendible cell (EXCELL) directory to the set operation problem, and demonstrate by practical experiments the efficiency and the local nature of the algorithm.
Temporal anti-aliasing in computer generated animation
Authors: Korein Jonathan , Badler Norman
Published: November 2005

The desirability of incorporating temporal anti-aliasing, or motion blur, into computer generated animation is discussed and two algorithms for achieving this effect are described. The first approximates continuous object movement and determines intervals during which each object covers each pixel. Hidden surface removal is then performed, allowing the calculation of visible object intensity functions and subsequent filtering. The second form of algorithm detailed involves supersampling the moving image and then filtering the resulting intensity function to “multiply-expose” each output picture. The effects of filter types and the relationship of the algorithms to forms of spatial anti-aliasing are discussed.
A tutorial on compensation tables
Authors: Catmull Edwin
Published: November 2005

The generation of computer-shaded pictures requires that a program calculate intensities for each pixel. These intensities are then viewed on a monitor or transferred to film. It is desirable that the intensity values on the monitor or the reflectance values on the film have a linear relationship with the original calculated intensities both to give the user fine control over the appearance of the object and to do anti-aliasing properly. However, after the calculated intensity values are sent to the DAC'c some nonlinear distortions occur both in the CRT and on film. We can compensate for this by adjusting the intensity number just before digital-to-analog conversion. This compensation can be accomplished by a table lookup using the intensity as an index into the table and the corresponding value as the new intensity. Fortunately, most hardware manufacturers have made table lookup features part of their equipment. However, the entries in the table must still be generated. The methods for doing this are not well known in the computer graphics community. This paper presents an algorithm for generating a compensation table.
An improved illumination model for shaded display
Authors: Whitted Turner
Published: November 2005

To accurately render a scene, global illumination information that affects the intensity of each pixel of the image must be known at the time the intensity is calculated. In a simplified form, this information is stored in a tree of “rays” extending from the viewer to the first surface encountered and from there to other surfaces and to the light sources. The visible surface algorithm creates this tree for each pixel of the display and passes it to the shader. The shader then traverses the tree to determine the intensity of the light received by the viewer. Consideration of all of these factors allows the shader to accurately simulate true reflection, shadows, and refraction as well as the effects simulated by conventional shaders. Anti-aliasing is included as an integral part of the visibility calculations. Surfaces displayed include curved as well as polygonal surfaces.
Some raster graphics extensions to the Core System
Authors: Foley James D. , Templeman James N. , Dastyar Dara
Published: November 2005

The Core System is a proposed standard subroutine package for line-drawing graphics. We present some Core System extensions for use with raster graphics equipment. The extensions, which are upward-compatible with the present Core System, provide filled polygons, display of arrays of pixels, use of a color look-up table, and hidden-surface or hidden-edge removal. The extensions are being intergrated into an existing Core System implementation.
Stereoscopic computer graphics for simulation and modeling
Authors: Roese John A. , McCleary Lawrence E.
Published: November 2005

A visually effective stereoscopic CRT display technique has been developed which uses continuous tone computer graphics in combination with electro-optic shutter viewing devices. The technique involves the generation of left and right perspective views of an object model using continuous tone computer graphics. The perspective views constitute stereo pairs and are displayed in an alternating manner on the even and odd field scans of a conventional 2:1 interlace raster scan CRT display. When viewed with electro-optic shutters operated synchronously with the CRT field scan rate, the alternating perspective views are perceived as stereoscopic images with strong binocular depth-of-field sensations. Lightweight stereoscopic viewing glasses have been developed which use lead lanthanum zirconate titanate (PLZT) ceramics as electronically controlled shutter elements. Representative applications of the stereoscopic display technique to dynamic flight simulation and complex molecular modeling are presented. The flight simulation illustrates a landing sequence on an aircraft carrier while the modeling application shows complex three-dimensional structures of double helix DNA and bacterial ferredoxin molecules. The stereoscopic display technique has been shown to be highly effective for adding binocular depth-of-field to computer graphics displays with a resulting enhancement of object model realism.
Digital video display systems and dynamic graphics
Authors: Baecker Ronald
Published: November 2005

Most digital video display systems have been capable of producing only text or static imagery. This paper shows that these limitations are not intrinsic to the technology, but are rather a direct consequence of the display system architecture. The paper begins by summarizing some of the background required to understand digital video display systems. The state-of-the-art is then surveyed, supported by an extensive bibliography. Existing systems are described in terms of a methodology which clarifies the effect of system architecture on capabilities and performance. It is shown how dynamic graphics capabilities can be provided if systems adhere to one or the other of two possible architectures. Examples of such systems are presented.
A response to the 1977 GSPC Core Graphics System
Authors: Cahn Deborah U. , Johnston Nancy E. , Johnston William E.
Published: November 2005

This paper responds to the 1977 Core Graphics System of SIGGRAPH's Graphic Standards Planning Committee (GSPC). The authors are interested in low-level device-independent graphics for applications doing data representation and annotation. The level structure and bias in the Core System toward display list processor graphics are criticized. Specific issues discussed include display contexts, attributes, current position, 3-dimensional graphics, area filling, and graphics input.
Aspects of quality in the design and production of text
Authors: Pringle Alison , Robinson Peter , Wiseman Neil
Published: November 2005

The problem of quality in printed text produced by computer has received little attention. Three pieces of recent work at Cambridge which relate to different aspects of the problem are presented in this paper. The first is a letter design system, which enables the typographer to exploit not only the power of the computer but also the freedom which modern printing technology has made available. The second is an attack on the problem of high quality text for television transmission, especially where the text is itself computer generated. Third, is a system which enables the user to set and correct tabular text easily and flexibly.
An interactive documentation system
Authors: Beatty John C. , Chin Janet S. , Moll Henry F.
Published: November 2005

Most chronic users of time sharing computer systems are familiar with programs that allow the creation and manipulation of text files. Less often they have at their disposal programs that will format the document described by a text file, generating output such as a typist might produce. Rarely is there any mechanism by which graphics can be integrated with text. Lawrence Livermore Laboratory has a powerful, flexible and interactive computer-based documentation system that will format a source document description according to user specifications and incorporate illustrations to produce online documents, offset reproduction masters, 35mm color slides, movie titles, or viewgraphs. The flexibility of the system is greatly enhanced by the use of a device independent graphics library. Text may be plotted using the hardware characters specific to a device (when possible), or may be drawn as Hershey characters or polygonally outlined symbols. Illustrations may be defined in a simple 2d graphics language, and graphical output from application programs may also be incorporated directly into a document.
Raster graphics for interactive programming environments
Authors: Sproull Robert F.
Published: November 2005

Raster-scan display terminals can significantly improve the quality of interaction with conventional computer systems. The design of a graphics package to provide a “window” into the extensive programming environment of interlisp is presented. Two aspects of the package are described: first, the functional view of display output and interactive input facilities as seen by the programmer, and second, the methods used to link the display terminal to the main computer via a packet-switched computer network. Recommendations are presented for designing operating systems and programming languages so as to simplify attaching display terminals.
Graphical human interface to a neutral beam system
Authors: Fiddler Jerry , Elischer Victor
Published: November 2005

A color graphics system has been designed and implemented as the human interface to a 120KV, 60 amp neutral beam source being built at Lawrence Berkeley Laboratory for Tokamak Fusion Test Reactors. The system is based upon a 64 × 64 touch panel and allows a number of control and high level analysis displays to be brought up on any of three monitors. Included among the displays are a “Super-oscilloscope” package, a data acquisition timing package, numerical control displays and pictograms. The system succeeds in being very friendly and easy to learn for the operator. All control is via the touch panel and a set of six knobs and two keypads.
The semantics of graphical input
Authors: Anson Ed
Published: November 2005

Any graphical input device may be represented by a data structure, modified from time to time by actions in response to certain events, and the ability to cause certain events as part of its repertoire of actions. Portions of a device's state may be made visible to other devices in a controlled way, and the remainder hidden. Conversely, a device may make use of the visible portions of another device's state. Typically, the pattern of device interaction forms a hierarchy, but no device is part of any other. This provides for the interchangeability of a single device with a group of devices, and allows a single device to support the function of several others. Device independence is thus enhanced without the usual sacrifice of human factors considerations.

A group of devices defined in this manner can simulate any group of devices defined in the usual manner. Conversely, useful groups of devices may be defined, which cannot conveniently be simulated by the usual input semantics. The proposed semantic is thus more complete, and provides the additional benefit of a uniform language for describing both physical and virtual devices.
Human vision and computer graphics
Authors: Montalvo Fanya S.
Published: November 2005

Is one picture really worth a thousand words? Why do cleverly designed graphic displays make visual information stand out more clearly with strikingly greater impact than numbers buried in pages of computer printout?

Graphic output devices shift the burden of integrating information generated by computers onto the human vision system: the sensory channel with the highest capacity for distributed parallel processing. The system consists of hundreds of successive two-dimensional arrays of millions of interconnected parallel computers. Perception seems instantaneous because we are not conscious of the massive amounts of computation that occur. What we consciously “see at a glance” is already a highly structured, synthesized, and summarized version of the actual light intensity mosaic that enters the retina.

We will demonstrate some results of the visual structuring that occurs in the human visual system, show why some features stand out instantaneously and others do not, and explain why knowledge of the human input device is crucial to the design of effective computer output devices and displays.
An algorithmic approach to controlling search in three-dimensional image data
Authors: Rhodes Mìchael L.
Published: November 2005

In many three-dimensional imaging applications random shaped objects, reconstructed from serial sections, are isolated to display their overall structure in a single view. This paper presents an algorithm to control an ordered search strategy for locating all contours of random shaped objects intersected by a series of cross-section image planes. Classic search techniques in AI problem solving and software for image processing and computer graphics are combined here to aid program initialization and automate the search process thereafter. Using three-dimensional region growing, this method isolates all spatially connected pixels forming a structure's volume and enters image planes the least number of times to do so. An algorithmic description is given to generalize the process for controlling search in 3-D image data where little core memory is available. Phantom and medical computer tomographic data are used to illustrate the algorithm's performance.
A terrain and cloud computer image generation model
Authors: Dungan William
Published: November 2005

A method is presented that produces a realistic simulation of terrain using source data from the Defense Mapping Agency (DMA). Spatially compact objects are presently modeled with some success at realism. Because terrain is large in extent it exhibits special problems. These problems include: data base size and generation, masking priority, and shading.

An array of height values can be created from the DMA terrain file. Height is a single valued function of the array coordinate pair. The pair has implicit positional information. A masking priority algorithm is used which has no restriction on observer geometry. The algorithm searches the height array along the line of sight for the first visible position in the array. This approach requires no clipping or depth sorting of surface representations. The height array indices are used to access the pixel shade from a registered, orthonormal texture array. The use of texture provides a simple way to add nonlinear shading for a realistic representation with flexible data base generation.

Atmospheric attenuation is a method used to increase realism. Methods are in use which produce haze or fog with constant attenuation. The line-of-sight search is used to produce realistic clouds with spatially variable attenuation.

Terrain and clouds are adequately simulated using this method of modeling. The data structures of height and texture arrays are simple, easily generated, and make good use of storage resources. Resolving masking priority along the line of sight is a visible surface algorithm which has advantages over hidden surface algorithms. Realistic representations such as texture and atmospheric attenuation are used with some success.
The haloed line effect for hidden line elimination.
Authors: Appel Arthur , Rohlf F. James , Stein Arthur J.
Published: November 2005

The haloed line effect is a technique where when a line in three-dimensional space passes in front of another line, a gap is produced in the projection of the more distant line. The gap is produced as if an opaque halo surrounded the closer line. This method for approximate hidden-line-elimination is advantageous because explicit surface equations are not necessary. The relative depth of lines, axes, curves and lettering is easily perceived. This technique is especially suitable for the display of finite element grids, three-dimensional contour maps and ruled surfaces. When the lines or curves on a surface are closer than the gap size, the gaps produced close up to produce a complete hidden-line-elimination. A simple but efficient implementation is described which can be used in the rendering of a variety of three-dimensional situations.
Predetermining visibility priority in 3-D scenes (Preliminary Report)
Authors: Fuchs Henry , Kedem Zvi M. , Naylor Bruce
Published: November 2005

The principal calculation performed by all visible surface algorithms is the determination of the visible polygon at each pixel in the image. Of the many possible speedups and efficiencies found for this problem, only one published algorithm (developed almost a decade ago by a group at General Electric) took advantage of an observation that many visibility calculations could be performed without knowledge of the eventual viewing position and orientation—
once for all possible images
. The method is based on a “potential obscuration” relation between polygons in the simulated environment. Unfortunately, the method worked only for certain objects; unmanagable objects had to be manually (and expertly!) subdivided into managable pieces.

Described in this paper is a solution to this problem which allows substantial a priori visibility determination for all possible objects without any manual intervention. The method also identifies the ( hopefully, few) visibility calculations which remain to be performed after the viewing position is specified. Also diescussed is the development of still stronger solutions which could further reduce the number of these visibility calculations remaining at image generation time.

The reduction in overall processing and memory requirements enabled by this approach may be quite significant, especially for those applications (e.g., 3-D simulation, animation, interactive design) in which numerous visible surface images are generated from a relatively stable data base.
ISOSRF—an algorithm for plotting Iso-valued surfaces of a function of three variables
Authors: Wright Thomas , Humbrecht John
Published: November 2005

Given a three-dimensional array containing values of a function of three variables, the algorithm presented here draws an approximation of the surface or surfaces where the function attains a specified value. This is done by contouring two-dimensional subsets of the three-dimensional array and suppressing the invisible parts of the contours. The union of all the contour line parts approximates the desired surface. The suppression of the invisible lines is the most complicated part of the algorithm and is done by forming a silhouette of the processed subset of the array and testing lines against this structure.
Automatic extraction of Irregular Network digital terrain models
Authors: Fowler Robert J. , Little James J.
Published: November 2005

For representation of terrain, an efficient alternative to dense grids is the Triangulated Irregular Network (TIN), which represents a surface as a set of non-overlapping contiguous triangular facets, of irregular size and shape. The source of digital terrain data is increasingly dense raster models produced by automated orthophoto machines or by direct sensors such as synthetic aperture radar. A method is described for automatically extracting a TIN model from dense raster data. An initial approximation is constructed by automatically triangulating a set of feature points derived from the raster model. The method works by local incremental refinement of this model by the addition of new points until a uniform approximation of specified tolerance is obtained. Empirical results show that substantial savings in storage can be obtained.
A colour display unit for a 21-channel EEG-monitor
Authors: Paternoster R. H. , Bousse L. J. , Steenhaut O. L.
Published: November 2005

A system for the simultaneous display of several functions of one or two variables has been developed. One-variable functions are represented by their graphs, while two-variable functions are displayed by means of contour maps, with a light intensity proportional to the displayed value. By assigning a fixed colour to each contour map, it is possible to superimpose different maps without losing charity. The display unit is connected with a microprocessor system, which allows the real-time calculation and display of time-changing functions.

The primary application of the system is the representation of the distribution of the spectral contents of EEG (electro-encephalographic) signals on the surface of the head.
The shaded surface display of large molecules
Authors: Porter Thomas K
Published: November 2005

The complexity of computer generated images is often restricted by the storage requirements of the data and the processing time in keeping it sorted. A method is presented which alleviates the burden of storing and sorting for one previously published hidden surface algorithm.
A network graphical conferencing system
Authors: O'Brien Michael T.
Published: November 2005

A network-oriented color graphical conferencing system is being built by the Information Sciences Dept. of the Rand Corporation. This system is designed to allow several people to confer simultaneously over a network. Users share a common display, which is divided into sections: an individual section (or “window”) for each user, and a common graphical “blackboard” window where the users may take turns sketching out and modifying a graphical display in full color. The display uses bit-map color raster-scan technology.

Each user's private window is identified with that user's name and location. Text typed by a user appears in his window as he types it. Several users may be typing text simultaneously. A special symbol appears in the window of a user who is sketching to indicate who is drawing the picture.

Several conferences may be going on at the same time; users may request a menu page showing who is participating in which conferences. Conferences may be “locked” to prevent others from joining.

The system makes use of other Rand-developed utilities for the design and display of arbitrary characters, as well as Rand's Virtual Terminal UNIX (TM) operating system.
A building block approach to color graphics
Authors: Flexer J. Robert , Wiederhold Gio
Published: November 2005

Graphics and imaging are important in scientific, academic and industrial environments. In the past graphics systems have been used with large computers and were only available to a minority of users. The relatively small and specialized use of graphics has inhibited sharing of software and prevented standardization necessary for widespread use. Dense semiconductor memory has recently become easily available in large quantities and makes high resolution graphics and imaging systems feasible. The concepts leading to the design of the present system come from the need to provide a large number of graphic and imaging functions, in a compact form, to a commonly used microprocessor bus. Three fundamental functions are implemented: a video frame digitizer, an image memory, and an output video generator. Video images can be digitized in one frame time with a precision of 1, 2 or 4 bits per pixel. The video generator can display the images in gray levels or in color. The software selectable system parameters include a variety of image formats, video output controls, digitization commands, addressing modes, vertical image offset, and lightpen controls. A novel contouring digitization mode is useful to reduce images obtained in gray scale to outline form. Such real-time preprocessing reduces memory and bandwidth requirements. Photographic illustrations demonstrate various operating modes.
Implementation of an interactive computer graphics environment at NASA/JSC
Authors: Lang M. S. , Cohen R. L. , Eschenberg K. E. , Ochs J. B. , Stocker F. R. , Raney J. L. , Stuckey B. F.
Published: November 2005

The implementation of visually-oriented software for graphics support on the high-performance computer graphics hardware at NASA's Johnson Space Center is the latest step in the evolution of an interactive computer applications technology being developed by the Computer Graphics Group at The Applied Research Laboratory of Penn State University. This technology is designed to aid the typical scientist or engineer in learning and using computer graphics productively, including writing his own programs and interfacing to software specialists who will write and maintain his programs. Key aspects of the current development include the creation and incorporation of a visually-oriented learning package for graphics geometric perception and graphics programming, as well as a sophisticated control environment which aids the user in obtaining a quick understanding of and access to the system. Preliminary results indicate that this software support can substantially reduce the startup time for a novice graphics user with some background in Fortran.
Generating smooth 2-D monocolor line drawings on video displays
Authors: Barros Jose , Fuchs Henry
Published: November 2005

One of the major drawbacks of video display systems for line drawing applications has been the poor image quality they usually produce—“jaggy”, “staircased” line edges, moire patterns in regions of closely spaced lines, even, with some systems, lines disappearing (“falling in”) between pixels. Correcting these effects, with appropriate area-sampling techniques, has generally been too computationally expensive to adopt.

A new algorithm is presented which generates precise, smooth images of line drawings and solid polygonal-shaped objects on multi-grey-level pixel-mapped video systems. The method is based on an analysis of boundary conditions at each pixel affected by one or more lines. With this method a number of previously needed steps can be quickly eliminated. The commonality of boundary conditions between adjacent pixels and the coherence of such conditions in a raster-scan ordering of such pixels allows efficient generation of these boundary conditions. A recursive subdivision approach allows handling of arbitrarily complex cases by a simple boundary-analyzing technique. Compared with current line-drawing systems, a video system with this algorithm would also display an improved image with respect to certain common visual effects—e.g., distance modulation of line intensity (which may be desirable), artificial small bright clusters of detail (which is undesirable).

Since the software interface to the algorithm may be handled through already-standard graphical subroutines, adoption of the algorithm may be accomplished without burdening graphic system users or graphic system-utilizing software.
Smoothly shaded renderings of polyhedral objects on raster displays
Authors: Duff Tom
Published: November 2005

The appearance of raster-scan renderings of polyhedral approximations to curved surfaces can be enhanced greatly by shading them in a manner that varies smoothly across each polygon and which matches the correct shade at each vertex. Henri Gouraud and Bui Tuong-Phong have previously described two methods of computing such shading functions. While the computations in Gouraud's method are quite quick to perform, the renderings produced often exhibit pronounced Mach bands, and animated sequences tend to have annoying fluctuations in intensity. Phong's method tries to cure these problems, but is much more expensive computationally. We will show a new, faster method of computing Phong shading, and discuss the relationship of this method to Gouraud shading. We will also exhibit representatives of a class of surfaces for which Phong shading surprisingly produces worse Mach bands than Gouraud shading.
The theory, design, implementation and evaluation of a three-dimensional surface detection algorithm
Authors: Artzy Ehud , Frieder Gideon , Herman Gabor T.
Published: November 2005

In many three-dimensional imaging applications the three-dimensional scene is represented by a three-dimensional array of volume elements, or voxels for short. A subset Q of the voxels is specified by some property. The objects in the scene are then defined as subsets of Q formed by voxels which are “connected” in some appropriate sense. It is often of interest to detect and display the surface of an object in the scene, specified say by one of the voxels in it.

In this paper, the problem of surface detection is translated into a problem of traversal of a directed graph, G. The nodes of G correspond to faces separating voxels in Q from voxels not in Q. It has been proven that connected subgraphs of G correspond to surfaces of connected components of Q (i.e., of objects in the scene). Further properties of the directed graph have been proven, which allow us to keep the number of marked nodes (needed to avoid loops in the graph traversal) to a small fraction of the total number of visited nodes.

This boundary detection algorithm has been implemented. We discuss the interaction between the underlying mathematical theory and the design of the working software. We illustrate the software on some clinical studies in which the input is computed tomographic (CT) data and the output is dynamically rotating three-dimensional displays of isolated organs. Even though the medical application leads to very large scale problems, our theory and design allows us to use our method routinely on the minicomputer of a CT scanner.
Polygon comparison using a graph representation
Authors: Weiler Kevin
Published: November 2005

All of the information necessary to perform the polygon set operations (union, intersection, and difference) and therefore polygon clipping can be generated by a single application of a process called
polygon comparison.
This process accepts two or more input polygons and generates one or more polygons as output. These output polygons contain unique homogenous areas, each falling within the domain of one or more input polygons. Each output polygon is classified by the list of input polygons in which its area may be found. The union contour of all input is also generated, completing all of the information necessary to perform the polygon set operations.

This paper introduces a polygon comparison algorithm which features reduced complexity due to its use of a graph data representation. The paper briefly introduces some of the possible approaches to the general problem of polygon comparison including the polygon set and clipping problems. The new algorithm is then introduced and explained in detail.

The algorithm is sufficiently general to compare sets of concave polygons with holes. More than two polygons can be compared at one time; all information for future comparisons of subsets of the original input polygon sets is available from the results of the initial application of the process.

The algorithm represents polygons using a graph of the boundaries of the polygons. These graphs are imbedded in a two dimensional geometric space. The use of the graph representation simplifies the comparison process considerably by eliminating many special cases from explicit consideration.

Polygon operations like the ones described above are useful in a variety of application areas, especially those which deal with problems involving two dimensional or projected two dimensional geometric areas. Examples include VLSI circuit design, cartographic and demographic applications, and polygon clipping for graphic applications such as viewport clipping, hidden surface and line removal, detailing, and shadowing.
Acoustic radar graphic input device
Authors: de Bruyne P.
Published: November 2005

Accurate X,Y position determining digitizers presently require a precision array of wires embedded in the tablet. In rear-projection tablets these wires tend to limit the optical quality of images projected on the screen. Principles of acoustic radar are applied in a device which achieves better resolution, at a lower cost and without the use of wires, either in a tablet or a cursor. The function of acoustic reflectors for automatic calibration is described, achieving an accuracy of + mn; 0.01% of the distance to the sensors. In the case of small tablets, a hand-held stylus may be tracked at the rate of 900 locations a second.
Movie-maps
Authors: Lippman Andrew
Published: November 2005

An interactive, dynamic map has been built using videodisc technology to engage the user in a simulated “drive” through an unfamiliar space. The driver, or map reader, is presented with either sparsely sampled sequences of images taken by single frame cameras that replicate actual imagery from a space, or with computer synthesized replicas of those images. The reader may control the speed, route, angle of view and mode of presentation of this information and may thus tour the area. In addition, he may access spatially stored ancillary data stored in the buildings or in locales in the environment. This basic map is being enhanced to provide topographic views, and to incorporate optical and electronic image processing to provide a more responsive, visually complete representation of an environment.
High-performance raster graphics for microcomputer systems
Authors: Bechtolsheim Andreas , Baskett Forest
Published: November 2005

A frame buffer architecture is presented that reduces the overhead of frame buffer updating by three means. First, the bit-map memory is (x,y) addressable, whereby a string of pixels can be accessed in parallel. Second, the pixel-change operation is performed by hardware in a single read-modify-write cycle. Third, multiple objects in the frame buffer are addressable simultaneously by a set of address registers. The remaining task of generating (x,y) addresses and providing new data can be managed rapidly by current microprocessors or DMA-devices.

With a modest expenditure of hardware, this architecture eliminates all the bit-shifting, bit-masking, and bit-manipulation conventionally associated with frame buffer graphics, while retaining the full generality of user-programmable control. The particular implementation described allows raster manipulation at full bit-map memory bandwidth. It can paint a 16×16 pixel character into the frame buffer in 16 microseconds and can modify a 1024×1024 pixel raster in 64 milliseconds.