bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation and expected performance analysis of multiple processor Z-buffer systems
Authors: Parke Frederic I.
Published: November 2005

The results of expected performance analysis and simulation of three multiple processor Z-buffer architectures are presented. These architectures have been proposed as approaches to applying many processors, working in parallel, to the task of rapidly creating shaded raster images. These architectures are attractive since they offer potentially high performance, in terms of image update rate, at modest cost. All three approaches make use of multiple instances of identical processor modules.

The analyses and simulations indicate that substantial gain is possible by applying multiple processors to the task. But, as more and more processors are added, additional gains in performance become smaller and smaller. This result suggests optimal system sizes. The performance of these architectures depends on the processors used, the number of processors, and certain characteristics of the image environments. Each architecture has its own performance characteristics and limitations.
Trends in high performance graphic systems(Panel Session)
Authors: Cohen D. , Sproull Bob , Clark Jim , Parke Fred , Fuchs Henry
Published: November 2005

Accompanying the rapid development of integrated circuit fabrication technology has been a parallel, but slower, development of IC design techniques and systems. Recent approaches to IC design enable individual designers to consider developing their own VLSI circuits. Such capability may open the door to a more varied set of system designs than could previously be considered in most design environments.

The panel members are all currently designing graphic systems oriented towards VLSI implementation. Each will give a short presentation describing one of their system designs. Following these presentations, three members of the previous session (Forest Baskett, Andreas Bechtolsheim, and Fred Parke) will discuss common issues, problems, and future prospects.
A prototype Spatial Data Management System
Authors: Herot Christopher F. , Carling Richard , Friedell Mark , Kramlich David
Published: November 2005

Spatial Data Management is a technique for organizing and retrieving information by positioning it in a spatial framework. Data is accessed in a Spatial Data Management System (SDMS) via pictorial representations which are arranged in space and viewed through a computer graphics system. These pictures can be created by an interactive graphical editor, allowing an SDMS to serve as a personal repository of diagrams, text, and photographs. Pictograms can also be generated from data in a symbolic database management system, allowing SDMS to be used as an interface to large, shared databases.

A prototype SDMS has been constructed which employs a set of color, raster scan displays driven by a large minicomputer. The user can create and examine data surfaces which are larger than the display screen, traversing a surface and zooming in and out to control the level of detail displayed. The prototype system provides a uniform mechanism for accessing a wide variety of data types in a manner which does not require the use of a formal command or query language.
Computer graphics moves into the business world (Panel Session)
Authors: Taylor Susan , Schmidt Allan , Birkhahn Paul , Hament June , Quann John , Machover Carl
Published: November 2005

Computer graphics has become an everyday tool for an engineer, scientist, and technician. Only within the last year or so has the business community demonstrated a real interest in computer graphics for their requirements. While the technically trained person had no difficulty accepting that a picture was worth a thousand words, the businessman often didn't trust pictures and felt more confident with his tabular data. Many of these attitudes are changing with the introduction of both hardware and software oriented towards business requirements. This panel will discuss a number of topics relating to computer graphics and business, hardware, software, system, and user attitudes.
QUADRIL
Authors: Levin Joshua Zev
Published: November 2005

Most man-made objects can be closely approximated by bodies whose surfaces are composed of portions of second-order (quadric) surfaces. These surfaces include elliptic, hyperbolic, and parabolic cylinders, as well as quadric cones, paraboloids, hyperboloids, ellipsoids, and pairs of planes. Simple planes (first-order surfaces) may be included as degenerate quadric surfaces.

Because these quadric-surface bodies are so useful for modelling man-made objects, it is important that any Computer-Aided Design (CAD) system be able to work with such bodies. The “QUADRIL” language described here was designed to accept descriptions of quadric-surface bodies in character-string form.

QUADRIL has a mixture of English-like and algebraic syntax. It may be used to specify quadric-surface bodies and then to display them on various media.

QUADRIL will accept descriptions of quadric-surface bodies either as “volumetric” combinations of basic bodies, or as boolean functions of bounding surfaces. English-like syntax is used for specifying what surfaces and basic bodies are used, while algebraic syntax is used to transform the canonical forms of the surfaces or bodies into the shape, position, and orientation that the user desires.

Volumetric combination of bodies involves the operations of union (+), intersection (*), and subtraction (-). Boolean specification of volumes is in terms of a boolean tree with the bounding surfaces as leaf nodes. The tree is expressed as a character string.

QUADRIL permits using user-created “STRUCTURES” as component bodies (“OBJECTS”) in greater STRUCTURES.

The display of the quadric-surface bodies may also be specified in QUADRIL. The user is considered fixed in space, while the body is transformed to give the desired view.
A structure from manipulation for text-graphic objects
Authors: Lakin Fred H.
Published: November 2005

The general purpose graphics systems of the future will need a simple logic for visual objects—one structure underlying both text and graphics. As an experiment, perhaps the immediate handling of visual objects by the user can provide the starting point for developing that structure. This paper describes the PAM graphics system, in which
the structure of text-graphic objects arises directly out of manual manipulation.
The needs of manual manipulation determine the
text-graphic pattern
as the simplest organizing structure for images; PAM stands for
P
Attern
M
anipulating. The PAM system is designed for the agile manipulation of text-graphic patterns—first manually, and then, later, programmatically.

Starting from this strict 'front-in' viewpoint—where immediate manipulation (hand powered animation) was to be the primary application—a 'manipulative grammar' was evolved to give the user a simple yet powerful handle on text-graphic images. This grammar turned out to be a generalization of LISP syntax from textual symbolic expressions to text-graphic forms, structuring such forms as trees and then offering:

@@@@spatial GRABBING of objects into attention

@@@@tree guided attention shifters like FIRST, REST, NEXT, and UP

spatial & tree manipulations on any object in attention.

@@@@The resulting structures also offer surprising computational power (in a manner directly analogous to the way the basic list structures and functions of LISP give rise to the flexibility and power of a full blown LISP system, McCarthy and Talcott [1]), leading finally to
computing with text-graphic forms.
Consequently, a
semantic
function is added to supplement the basic manipulative grammar:

@@@@evaluation of object in attention, result displayed at the cursor. Evaluation supports facilities like naming (and thus saving) visual objects, programming, and creation of menus (patterns of evaluatable function objects).

An experimental version of the PAM system has been implemented in MACLISP at the Stanford Artificial Intelligence Lab.
Computer rendering of fractal curves and surfaces
Authors: Carpenter Loren C.
Published: November 2005

Fractals are a class of highly irregular shapes that have myriad counterparts in the real world, such as islands, river networks, turbulence, and snowflakes. Classic fractals include Brownian paths, Cantor sets, and plane-filling curves. Nearly all fractal sets are of fractional dimension and all are nowhere differentiable.

Previously published procedures for calculating fractal curves employ shear displacement processes, modified Markov processes, and inverse Fourier transforms. They are either very expensive or very complex and do not easily generalize to surfaces. This paper presents a family of simple methods for generating and displaying a wide class of fractal curves and surfaces. In so doing, it introduces the concept of statistical subdivision in which a geometric entity is split into smaller entities while preserving certain statistical properties.
Stereographic displays of atmospheric model data
Authors: desJardins Mary , Hasler A. Frederick
Published: November 2005

A system has been developed to display color stereographic time-lapsed sequences of outputs of three-dimensional atmospheric models. Contour lines and wind vectors derived from a model can be overlaid on a geostationary satellite image or displayed with map boundaries. The colors of these graphics can be changed interactively to highlight any desired feature or aid in interpreting relationships between parameters.

The viewing portion of the system consists of a raster scan image display terminal with split screen capability and a stereoscopic viewing hood.

The user of the system can observe model outputs in color and stereo as a function of time and in a manner which permits easy visualization and comparison.

The system permits a meteorologist to visualize atmospheric parameters in a three-dimensional representation and correlate these parameters with information derived from satellite observations. This capability can significantly increase the user's ability to interact with and understand complex meteorological relationships.
Optical printing in computer animation
Authors: Max Nelson , Blunden John
Published: November 2005

The optical printer can be considered as an optical analog computer, which can perform geometric transformations and simple arithmetic operations on pictures very efficiently. The principles of operation of the printer are explained, and many of its applications to computer animation are listed and discussed briefly.

Two techniques are discussed in detail: the use of high contrast masks to suppress the bright spots where two lines of different colors cross, and the use of continuous tone masks and multiple exposures to create realistic transparency at low cost.
Real time animation playback on a frame store display system
Authors: Ackland Bryan , Weste Neil
Published: November 2005

A frame store display station capable of generating real time animation effects using filled polygonal shapes is described. The system consists of a host microcomputer, a high performance frame store display controller and a microprogrammed graphic command interpreter. Real time performance is attained using a combination of software, hardware and a systems approach. The display station can be used to interactively test and view simple animation sequences. Some proposals for further increasing performance are discussed.
Special problems in human movement simulation
Authors: Badler Norman I. , O'Rourke Joseph , Kaufman Bruce
Published: November 2005

Three dimensional animation of human movement may be obtained by specifying movements in a goal-directed manner and constructing a sophisticated simulator to execute those movements. We briefly describe an architecture for such a simulator and then concentrate on five special problems which arise: scheduling movements which occur concurrently, computing motion of three-link chains, processing contacts, moving the center of gravity and maintaining balance, and adjusting limb twist for a standard orientation.
Graphic analysis and planning of electrical distribution systems
Authors: Fuehring Gwendolyn L.
Published: November 2005

Techniques for computer modeling of electrical distribution systems have been available to utility engineers for years. The formation of a distribution data base can be a huge task because of the enormous number of components in a utility's distribution system. The continuous changes that occur in a distribution system make data base maintenance difficult. Application of computer graphics to distribution engineering simplifies data base formation and maintenance and aids in interpreting the results of analysis. Graphic-aided distribution analysis allows the engineer to quickly see the results of alternate modes of system operations, thus speeding the iterative process of decision-making. Future applications for graphics techniques in utilities extend to distribution SCADA, work order prepration and protective device coordination.
Interactive computer graphics at Ford Motor Company
Authors: Bliss Frank W.
Published: November 2005

Over the past fourteen years the Ford Motor Company actively pursued the development and use of interactive computer graphics in the design and manufacture of automobiles. The success of Ford's pioneering efforts in the area of minicomputer graphics led to widespread acceptance and support for graphics within the corporation. This in turn led to a rapid expansion of computer graphics equipment. The advent of numerous Federal regulations in the areas of fuel economy, emissions control, and safety has generated additional Corporate interest in the use of computer graphics to help solve these difficult problems. Use of the Ford Computer Graphics System, as well as various commercially available turnkey computer graphics systems, has contributed substantially to cost reductions, improved productivity, and better documentation and control.

This paper describes the on-going computer graphics effort at Ford Motor Company. A brief history of computer graphics is presented along with a detailed description of the Ford Computer Graphics System and the commercial systems. A few applications involving the various graphics systems are discussed. These include design activity at several design and manufacturing areas which are major users of graphics equipment.

Next, four computer graphics-related projects presently receiving considerable attention are described. They include communications between graphics systems, a graphics information system and the use of graphics in both structural analysis and numerical control.

Finally, some indication of where computer graphics is headed in the future is presented.
The workstation concept of GKS and the resulting conceptual differences to the GSPC core system
Authors: Encarnacao J. , Enderle G. , Kansy K. , Nees G. , Schlechtendahl E. G. , Weiss J. , Wißkirchen P. , Germany W.
Published: November 2005

GKS has evolved from a long process of national /1,2,3,4/ and international /5,6/ discussion on standardization of graphical systems. One of the basic principles of the Graphical Kernel System GKS is the concept of workstations that are used to address a display terminal with several input devices. This is a basic conceptual difference to the GSPC core system /6/, which will be discussed in this paper.

A workstation represents a collection of graphical devices that are operated in a coordinated fashion by an operator at a given site. The whole workstation is treated in GKS as one logical unit.

GKS features two dimensional output to and input from single or multiple workstations. Besides basic line drawing primitives raster graphics primitives are supported. The coordinates are transformed in a two-stage transformation process where the first stage can be set for each primitive and the second can be set for each workstation. Furthermore the setting of a workstation specific pen and text table allows control of the appearance of all primitives on the corresponding workstation.

A segment facility provides means for structuring a picture in subparts. Segments may be created and deleted, the segment attributes may be dynamically modified, and the segments may be transformed. They can be displayed simultaneously or alternatively on different workstations. A device independent segment storage serves for inserting segments into other segments.
Perceptual color spaces for computer graphics
Authors: Meyer Gary W. , Greenberg Donald P.
Published: November 2005

Perceptually uniform color spaces can be a useful tool for solving computer graphics color selection problems. However, before they can be used effectively some basic principles of tristimulus colorimetry must be understood and the color reproduction device on which they are to be used must be properly adjusted. The Munsell Book of Color and the Optical Society of America (OSA) Uniform Color Scale are two uniform color spaces which provide a useful way of organizing the colors of a digitally controlled color television monitor. The perceptual uniformity of these color spaces can be used to select color scales to encode the variations of parameters such as temperature or stress.
Continuous anti-aliased rotation and zoom of raster images
Authors: Weiman Carl F. R.
Published: November 2005

Raster graphics images are difficult to smoothly rotate and zoom because of geometric digitization error. A new algorithm is presented for continuous rotation and zoom, free from the disturbing aliasing artifacts introduced by traditional methods. Applications include smooth animation. No matrix multiplication of pixel coordinates is executed. Instead row and column parallel operations which resemble local digital filters are used. This suggests real time implementation with simple hardware. Anti-aliasing is inherent in the algorithm which operates solely on pixel data, not the underlying geometric structures whose images the pixels may depict. Zoom magnification is achieved without replicating pixels and is easily attained for any rational scale factor including but not restricted to the integer values which most existing commercial raster graphics systems use.

The algorithm is based on a digitized code for lines on rasters, generalized to an interpolation scheme capable of executing all linear geometric transformations. Samples of images which have been rotated and zoomed by a software implementation of the algorithm are presented.
The use of grayscale for improved raster display of vectors and characters
Authors: Crow Franklin C.
Published: November 2005

Decreasing memory costs will soon allow grayscale displays in low-cost raster graphic terminals. Subtle shadings can be used to provide improvements in line quality and character flexibility which could allow raster displays to compete on better terms with the more expensive calligraphic displays. Algorithms for achieving smooth vectors and rotatable dot matrix characters are outlined and scan conversion is discussed. A discussion of the relation between image quality and number and distribution of gray levels follows, with concluding remarks on costs and other practical matters.
A hidden-surface algorithm with anti-aliasing
Authors: Catmull Edwin
Published: November 2005

In recent years we have gained understanding about aliasing in computer generated pictures and about methods for reducing the symptoms of aliasing. The chief symptoms are staircasing along edges and objects that pop on and off in time. The method for reducing these symptoms is to filter the image before sampling at the display resolution. One filter that is easy to understand and that works quite effectively is equivalent to integrating the visible intensities over the area that the pixel covers. There have been several implementations of this method - mostly unpublished - however most algorithms break down when the data for the pixel is complicated. Unfortunately, as the quality of displays and the complexity of pictures increase, the small errors that can occur in a single pixel become quite noticeable. A correct solution for this filter requires a hidden-surface algorithm at each pixel! If the data at the pixel is presented as a depth-ordered list of polygons then the average visible intensity can be found using a polygon clipper in a way similar to that employed by two known hidden-surface algorithms. All of the polygons in a pixel are clipped against some front unclipped edge into two lists of polygons. The algorithm is recursively entered with each new list and halts when the front polygon is clipped on all sides, thereby obscuring the polygons behind. The area weighted colors are then returned as the value to be added to the other pieces in the pixel.
Color gamut transform pairs
Authors: Smith Alvy Ray
Published: November 2005

Digital control of color television monitors—in particular, via frame buffers—has added precise control of a large subset of human colorspace to the capabilities of computer graphics. This subset is the gamut of colors spanned by the red, green, and blue (RGB) electron guns exciting their respective phosphors. It is called the
RGB monitor gamut
. Full-blown color theory is a quite complex subject involving physics, psychology, and physiology, but restriction to the RGB monitor gamut simplifies matters substantially. It is linear, for example, and admits to familiar spatial representations. This paper presents a set of alternative models of the RGB monitor gamut based on the perceptual variables hue (H), saturation (S), and value (V) or brightness (L). Algorithms for transforming between these models are derived. Particular emphasis is placed on an RGB to HSV non-trigonometric pair of transforms which have been used successfully for about four years in frame buffer painting programs. These are fast, accurate, and adequate in many applications. Computationally more difficult transform pairs are sometimes necessary, however. Guidelines for choosing among the models are provided. Psychophysical corrections are described within the context of the definitions established by the NTSC (National Television Standards Committee).
Towards the design of an intrinsically graphical language
Authors: Futrelle R. P. , Barta G.
Published: November 2005

Coding a large and diversified graphics application system is a difficult task. We suggest an approach to this problem in which programs are built up using
Objects
(e.g., Classes, Modules) newly generated or drawn from a library. Each Object has an
Aid
which supports an interactive dialogue with the programmer resulting in the insertion of the appropriate references to the Object into the developing code. An Aid can display graphical Objects and accept sketching and picture editing. An
Association
capability allows the programmer to generate code corresponding to the displayed graphical material. The Association can be literal, with numerical values being inserted, or symbolic, with variable arguments inserted. A
Programming System
that is so structured implements an
Intrinsically Graphical Language
because the code can be “written” using both textual and graphical dialogues.
BASIC Zgrass—a sophisticated graphics language for the Bally Home Library Computer
Authors: DeFanti Tom , Fenton Jay , Donato Nola
Published: November 2005

Home computer users are just now discovering computer graphics. Modest extensions to BASIC allow plotting but not much more. The Bally Home Library Computer, however, has hardware to aid implementation of video games. Custom integrated circuits working on a 160×102 pixel (2 bits per pixel) color television screen allow certain forms of animation in real time. To give this power to the user, BASIC Zgrass has been designed and implemented. It is an extension of BASIC that allows parallel processes, picture objects that move, scale and group together as well as several drawing modes. There are also software controls of a three-voice music synthesizer, interactive input devices, a film camera and an IEEE bus interface. We will concentrate mainly on the language design for making it all easy to learn and use.
Definition and use of higher-level graphics input tools
Authors: Bos Jan Van den
Published: November 2005

A proposal is made for the definition of 'tools', high-level graphics input functions based on the six primitive input classes Clock, Pick, Button, Key, Valuator and Locator.

Tools are defined in terms of input expressions, the operands of which are themselves tools, the definition of which may be nested inside this tool. Input expressions are written much like production rules in phrase structure grammars. Determining whether a tool is 'satisfied' can therefore be done most advantageously by an input expression parser.

Tool definitions may occur in-line or stored in a library. They are activated by a 'create' primitive, which creates an instance of the tool and causes the input expression to be made active. The parser then determines whether a tool is actually used. Following a 'read' issued to the tool, the tool body generates the returned information as specified by the tool definition. Tools may be explicitly freed by a 'free' primitive; in the case of nesting, tools are freed implicitly when the surrounding tool is freed.

Using this approach to higher-level input primitives, a programmer does not have to think about graphics input in terms of awaiting events, interrupts and the like. The creation of a defined tool implies a function awaiting action from the tool.
GAIN
Authors: Towle Tom , DeFanti Tom
Published: November 2005

Recent trends in the manufacturing and sales of home computers indicate that a new form of instruction must be developed for teaching programming in the home. Students learn programming from interacting with computers and other students in a classroom setting. The home user may not have this option. Manuals do not teach; they are good for looking up information you have forgotten. Workbooks and textbooks do not have a structure conducive to teaching—you have to understand everything before you can figure out “undiagnosible syntax error” or “OC4.” An approach has been developed at UICC which uses sophisticated error handling and modest program verification to supervise the beginning user while he/she is constructing and executing computer graphics programs. New, inexperienced computer users are now doing interesting (to them) programs within a half hour. This “interactive workbook” concept will be expanded and is currently a working prototype of a teaching package to be available on a home computer graphics/color TV system next year.
A high performance graphics system for the CRAY-1
Authors: Ewald Robert H. , Maas Lynn D.
Published: November 2005

This paper describes the design and implementation of a state-of-the-art interactive vector graphics system connected to the CRAY-1 supercomputer. The primary design goal for this graphics system is that it support large hydrodynamic computer programs used in weapons design calculations. The interactive use of these programs requires displays consisting of up to 20,000 vectors, extensive interaction tools, and high-bandwidth communication rates. The major system components selected for this project were an Evans and Sutherland Picture System 2 and a Digital Equipment Corporation (DEC) PDP-11/70 and PDP-11/34 running the UNIX operating system.

This paper presents the system design goals and performance criteria. The hardware/software systems chosen for this project are reviewed, and the integration of this system into the Los Alamos Scientific Laboratory's (LASL) Integrated Computer Network (ICN) is described. This implementation involved most areas of applied computing, including computer graphics, communications, distributed processing, and computer security. The level of effort required for this implementation is described, and the results and benefits are presented. Future plans for this system are also briefly described.
Computer graphics in support of Space Shuttle simulation
Authors: Weinberg Richard
Published: November 2005

Electronic scene generation plays an important role in simulation of the Space Shuttle at the Johnson Space Center in Houston, Texas. Simulators for astronaut training, system integration and engineering development utilize both a moving camera/map board system as well as computer generated images. Launch, on-orbit, payload handling and landing tasks are simulated with shaded computer graphics to provide realtime visual feedback. An overview of these simulators is presented.
System design and implementation of BGRAF2
Authors: Kaufman Arie A.
Published: November 2005

BGRAF2 is a real-time interactive 2D graphics language. Its supporting system contends with an unusual combination of features: timing, events, parallelism, image manipulation, user interaction and procedural structures. This combination creates within the system many unpredictable interrelated tasks competing for execution.

A BGRAF2 program is compiled into an object module consisting of a sequence of pure code blocks, tasks, and a set of data blocks. The real-time environment is a hierarchical structure, where the highest level is a Scheduler, and the next level is composed of the object module and five additional processors: Graphics Processor, Control Processor, Input-Output Processor, Real-Time Processor and Memory Manager. The Scheduler is an abstract monitor responsible for scheduling tasks in accordance with a multi-level priority from a multi-queue scheme.
The effect of System Response Time on interactive computer aided problem solving
Authors: Goodman T. , Spence R.
Published: November 2005

The effects of System Response Time, SRT, on interactive graphical problem solving were investigated for fixed SRT's of 0.16, 0.72 and 1.49 seconds. The object was to demonstrate the importance or otherwise of even small SRT values for interactive graphical problem solving of a type which often occurs in Computer Aided Design. A SRT of 1.49 sec was found to degrade performance by about 50%, measured by problem solution time, compared with that found for 0.16 and 0.72 seconds.
How to color in a coloring book
Authors: Lieberman Henry
Published: November 2005

Children's coloring books contain line drawings which a child can fill in with a crayon to produce colored pictures. Two dimensional colored areas can be produced on a raster display by an analogous method. After drawing a closed curve with line drawing commands, the graphics system can fill the area bordered by the curve. This paper presents an algorithm for filling in areas of any size or shape. The area may be filled with any color, texture, or “wallpaper” pattern. The algorithm is simple, flexible and efficient, optimized to take advantage of the the memory organization of most current raster graphics systems.
A microprocessor display controller for combining refresh and storage tube graphics
Authors: Satterfield Steven G. , Rodriguez Francisco , Rogers David F.
Published: November 2005

This paper describes a stand alone graphics system utilizing a microprocessor based display controller with the capability of combining refresh with storage tube graphics. This combination is accomplished by utilizing the Write-Thru feature of a Tektronix 4014 display terminal. The display controller is a typical Z-80 microprocessor system interfaced to the 4014 by a standard Tektronix parallel interface. A portion of the Z-80 memory is used as the display buffer, allowing it to be divided into store and non-store (refreshed) segments. The microprocessor performs the conversion from the simple integer X, Y coordinates in the display buffer to actual Tektronix drawing commands. A second Z-80 microprocessor is used to perform graphical transformations and transfer the data from the PDP-11 host to the Z-80 display controller. The operations performed by the second microprocessor include translation, rotation and scaling. These operations are implemented by matrix multiplication of the user data by a user specified transformation matrix. The stand alone capabilities of the graphics system is made complete with interactive devices such as a tablet, analog dials, and function switches interfaced directly to the host computer.
Texture tile considerations for raster graphics
Authors: Dungan William , Stenger Anthony , Sutty George
Published: November 2005

As a technique for rendering texture in images, texture tiles meet the subjective criterion of visual acceptability. A texture tile is a digital array of stored texture information that is replicated on a surface within an image. The purpose is to give the surface a textured appearance. The repetitive pattern inherent in the tiling approach can be suppressed. A texture tile must not exhibit macropatterns to avoid this problem. Properties that the mapping algorithm must include are oriented toward controlling aliasing. The tile is stored and accessed at several different levels-of-detail. The accessing technique is based on the size of the footprint the sample projects onto the surface to be textured. Aliasing is further controlled by a combination of increased sampling per pixel and filtering. Several textured images are presented, produced by the texture tile technique. These images show the realistic effect that is added by texture tiles.
A chip for low-cost raster-scan graphic display
Authors: Matherat Philippe
Published: November 2005

Lowering the cost of graphic display units for use in personnal computers and as time-sharing consoles suggests the use of TV sets. Display electronics for such a raster-scan unit will include a screen memory containing the state of all displayable points, that is up to 256 Kbits for 512 × 512 B&W display and more for colour applications. Technological advances in NMOS memories make such memory sizes cheaper and cheaper. The control part ensuring screen refresh, memory management, vector and character generation, and computer coupling remains very complex. A microprocessor-oriented Large-Scale-Integrated circuit including all these functions has been designed at the Ecole Normale Supérieure.

Versatility has guided the design, as well for screen memory organization as for microprocessor interface. Display resolution from 64 × 64 to 512 × 512 are possible, with any number of colours or grey levels, depending only upon the memory size. Microprocessor interface is standard: an eight bits bidirectionnal data bus, a four bits address bus, a read-write signal and an interrupt request. These signals control the vector and character generators which execute microprocessor's commands during the idle phasis of the display controller. This permits an always clean diplay and yet a decent average speed of one point every 1.3 μs.

In addition, a light-pen or crosshair circuitry allows interactive graphic use.
Conversion of complex contour line definitions into polygonal element mosaics
Authors: Christiansen H. N. , Sederberg T. W.
Published: November 2005

A simple algorithm is presented for processing complex contour arrangements to produce polygonal element mosaics which are suitable for line drawing and continuous tone display. The program proceeds by mapping adjacent contours onto the same unit square and, subject to ordering limitations, connecting nodes of one contour to their nearest neighbors in the other contour. While the mapping procedure provides a basis for branching decisions, highly ambiguous situations are resolved by user interaction. The program was designed to interface a contour definition of the components of a human brain. These brain data are a most complex definition and, as such, serve to illustrate both the capabilities and limitations of the procedures.
Spatial management of information
Authors: Donelson William C.
Published: November 2005

Methods of spatially managing data are currently under study at the Architecture Machine Group. Management concepts are drawn from everyday examples of paper and document handling. However, the work elaborates data types to include: animation, movies, and sound-sync computer graphics.

Beyond the application of management information systems, the paper portrays a sophisticated surround of keyboardless, interactive, and large scale graphics. Computer graphics, image processing, and broadcast are viewed as one. The system includes three frame buffers, four minicomputers, two touch sensitive displays, an octophonic sound system, and an MCA Optical Videodisc.
Making nested rotations convenient for the user
Authors: Britton Edward G. , Lipscomb James S. , Pique Michael E.
Published: November 2005

Subimage motion in a three-dimensional computer graphic system is much easier for the user to control if the subimage moves the same direction as his hand while he manipulates the control device. The implementation of such coordinated motion of hand and subimage implies modification of the normal procedure for calculating transformations. The convenience of such manipulation also depends on appropriate selection or design of the input device.

This paper reviews the relevant attributes of locator devices and presents an approach to selection. It presents the mathematics of transformation nesting and “compensation” to preserve motionsynchrony. Finally, it offers a case history of an interactive graphic system whose human factors were improved by these techniques.
User performance under several automated approaches to changing displayed maps
Authors: Moses Franklin L. , Maisano Richard E.
Published: November 2005

State-of-the-art computer displays seldom have sufficient resolution and size to show usable detail for a large map. One solution is to satisfy user needs by designing map display systems that present sequential map segments. The utility of two types of presentation conditions was evaluated: (a) continuous map scanning, and (b) discrete map segments using three different amounts of border overlap (0%, 25% and 50%). The task was to determine the fastest road routes between cities. A 19 in. color television monitor displayed 6×8 km map segments (1:50,000 scale) within a 60×80 km map region; participants viewed the larger map area by changing the displayed segments. Solution time, number of map segments viewed, and quality of route solutions were recorded by 24 participants on each of 12 problems divided among presentation conditions. Results showed that different presentation conditions did not significantly affect the quality of routes chosen. Problems took the least time when map segments with 50% overlap were used although 25% overlap produced similar data. Overall, the participants who changed map segments more often took less time working problems. Discrete map segments with around 25% overlap would contribute to an efficient design for a sequential map display system.
Object models for computer aided design
Authors: Athay Russell J.
Published: November 2005

A computer aided design system must deal with large amounts of both spatial and non-spatial data. It must also provide quick graphic response to user interaction. If the CAD system is to support real time graphic interaction, it must be able to respond within at most a few refresh cycles. If the data base is structured and accessed at a record level, it becomes very difficult to guarantee this real time response. For this efficiency reason, and for clarity reasons, we will introduce a new level of data structure called an “object” which is a linked structure of record level structures called “attributes”. The data structures for a CAD support system which provides support both for large data bases and real time graphic response will be described.
Clipping using homogeneous coordinates
Authors: Blinn James F. , Newell Martin E.
Published: November 2005

Clipping is the process of determining how much of a given line segment lies within the boundaries of the display screen. Homogeneous coordinates are a convenient mathematical device for representing and transforming objects. The space represented by homogeneous coordinates is not, however, a simple Euclidean 3-space. It is, in fact, analagous to a topological shape called a “projective plane”. The clipping problem is usually solved without consideration for the differences between Euclidean space and the space represented by homogeneous coordinates. For some constructions, this leads to errors in picture generation which show up as lines marked invisible when they should be visible. This paper will examine these cases and present techniques for correctly clipping the line segments.
A unified approach to geometric modelling
Authors: Forrest A. R.
Published: November 2005

Whereas, historically, much of the effort on computer-aided geometric design has concentrated on the problems of representing so-called sculptured surfaces, there has recently been much interest in systems which can handle typical mechanical components by a volume modelling approach. The paper is concerned with the possibility of combining the two approaches and discusses the issues raised. A solution in terms of applying smoothing operators to a geometric coarse structure is proposed, with the added benefits of detecting and successfully handling anomalous regions in surfaces and leading to potential benefits in the analysis of geometric properties.
Casting curved shadows on curved surfaces
Authors: Williams Lance
Published: November 2005

Shadowing has historically been used to increase the intelligibility of scenes in electron microscopy and aerial survey. Various methods have been published for the determination of shadows in computer synthesized scenes. The display of shadows may make the shape and relative position of objects in such scenes more comprehensible; it is a technique lending vividness and realism to computer animation.

To date, algorithms for the determination of shadows have been restricted to scenes constructed of planar polygons. A simple algorithm is described which utilizes Z-buffer visible surface computation to display shadows cast by objects modelled of smooth surface patches. The method can be applied to all environments, in fact, for which visible surfaces can be computed. The cost of determining the shadows associated with each light source is roughly twice the cost of rendering the scene without shadows, plus a fixed transformation overhead which depends on the image resolution. No extra entities are added to the scene description in the shadowing process. This comprehensive algorithm, which permits curved shadows to be cast on curved surfaces, is contrasted with a less costly method for casting the shadows of the environment on a single ground plane.

In order to attain good results, the discrete nature of the visible-surface computations must be treated with care. The effects of dither, interpolation, and geometric quantization at different stages of the shadowing algorithm are examined. The special problems posed by self-shadowing surfaces are described.
Polygon shadow generation
Authors: Atherton Peter , Weiler Kevin , Greenberg Donald
Published: November 2005

A general purpose method for generating shadows using a polygonal coordinate data base is presented. The method is based on an object space polygon clipping hidden surface removal algorithm. Output from the program is in the same three-dimensional polygon format as the input. Thus, a shadowed data environment may be easily created and viewed from any observer position with no additional depth sorting time required for the hidden surface removal process. Shadows can also be cast by more than one light source. Since the shadows are generated in object space, the results can be used for both visual display and numerical analysis.
TIGS
Authors: Heilman Robert L. , Marchant Jean M.
Published: November 2005

TIGS is a general purpose subroutine package providing display generation and interaction capability for a general class of graphics terminals. The package is computer, operating system, and display device independent. Primary design objectives were transportability, maintainability, and ease of use.

Features supported by TIGS include line, arc, multi-line plot, test and dot primitives with resettable attributes such as line style, character size, intensity, font, color, transformation matrix, etc. The package uses virtual devices such as locators, keyboards, picking devices and function keys which can represent a wide range of physical devices. TIGS supports modelling transformations, 2D and 3D viewing transformations for clipping and window to viewport mapping.

Unlike the GSPC Core System, TIGS uses the interpretive approach which uses a device independent neutral display file. This neutral display file contains information describing all segments, pictures, windows, and viewports in a device independent manner. The file may be saved and used in a later job with a different display device. Additionally, all attributes such as line style, font, character size, etc., can be re-specified without re-defining the contents of a segment.

In planning for expansion for distributed graphics applications, multiple independent user coordinate spaces are used. Each coordinate space is called a picture. This allows for re-specification of a window without re-defining the contents of it. A picture and all the segments contained therein can be manipulated as a group.

Device independence was implemented by dividing TIGS into a device-independent pre-processor invoked by the applications programmer, and internal device drivers, one per display device. Part of the device driver may reside on a separate processor.
Core standard graphic package for the VGI 3400
Authors: Levine Ken
Published: November 2005

Implementing the 1977 Core System standard proposal of ACM/Siggraph for a state-of-the-art microprogrammable refresh display system presents a number of design tradeoffs. Thus, there are areas of contention between a strict interpretation of the standards and the advanced capabilities of the display that led the user to purchase such a system in the first place. These methodological differences lead to a “loosely defined” Core system, which adheres to the spirit of the standards without sacrificing display performance.
DIGRAF—a FORTRAN implementation of the proposed GSPC standard
Authors: Warner James R. , Polisher Margaret A. , Kopolow Robert N.
Published: November 2005

A machine-independent FORTRAN implementation of the GSPC proposed standard is presented. DIGRAF (
D
evice
I
ndependent
GRA
phics from
F
ORTRAN) has been designed to closely parallel level-3 of the 'CORE' system. The present implementation allows portability to any computer with a FORTRAN compiler and a word length of at least 16-bits.

Several CORE system design issues are discussed from the implementor's viewpoint. A breakdown of the functional modules reinforces the portability aspects. Special features of the user interface are presented. A storage structure for retained segments is presented with a review of the memory management alternatives. The device-dependent interface for two common classes of devices is discussed. Finally, the design and data structure techniques used to implement several CORE functions is presented.
An implementation of the ACM/SIGGRAPH proposed graphics standard in a multisystem environment
Authors: Kellner Richard G. , Reed Theodore N. , Solem Ann V.
Published: November 2005

Los Alamos Scientific Laboratory (LASL) has implemented a graphics system designed to support one user interface for all graphics devices in all operating environments at LASL. The Common Graphics System (CGS) will support Level One of the graphics standard proposed by the ACM/SIGGRAPH Graphic Standards Planning Committee.

CGS is available in six operating environments of two different word lengths and supports four types of graphics devices. It can generate a pseudodevice file that may be postprocessed and edited for a particular graphics device, or it can generate device-specific graphics output directly. Program overlaying and dynamic buffer sharing are also supported.

CGS is structured to isolate operating system dependencies and graphics device dependencies. It is written in the RATFOR (RATional FORtran) language, which supports control flow statements and macro expansion. CGS is maintained as a single source program from which each version can be extracted automatically.