bluuebunny/crossref_metadata_2025 huggingface dataset:
BUMPS
Authors: Gurwitz Robert F. , Thorne Richard W. , Dam Andries van , Carlbom Ingrid B.
Published: November 2005

BUMPS (Brown University Multiple Projection System) is a program that illustrates the implementation of viewing transformations using animation. The program uses the viewing model defined in the Core Graphics System. BUMPS employs interactive computer graphics to demonstrate how planar geometric projections are generated, what the effects of different projections and projection parameters are on the projected object, and how the viewing functions of the Core Graphics System work. After presenting background material on projections, the features of BUMPS are described, followed by a pictorial user scenario of BUMPS in action. The paper concludes with a discussion of the merits of user controlled animation for teaching and possible improvements to the program.
Natural and efficient viewing parameters
Authors: Michener James C. , Carlbom Ingrid B.
Published: November 2005

The viewing scheme in the Core Graphics System is based on a unified approach to the specification of the viewing parameters for all types of planar geometric projections. As a result, the specification of some of the viewing parameters is inconsistent with traditional ways of specification and will often be found unnatural for use in certain application areas. Additionally, this choice of viewing parameters leads to inefficient implementations of viewing parameter modification, particularly in a high-performance graphics system which supports transformations in hardware or firmware.

The natural ways to specify the different viewing parameters are discussed and efficiency considerations for viewing implementations are described. The Core System viewing scheme is evaluated in terms of its naturalness and efficiency of implementation. An alternate viewing scheme is proposed that provides viewing parameters that are more natural for many applications and that can he modified more efficiently.
Graphics standards status report (Panel Session)
Authors: tenHagen P. , Chin Janet , Bono P. , Encarnacao J. , Michener J. , Bono Peter
Published: November 2005

Two status reports will be presented. The first report describes the activities of Working Group 2 (Computer Graphics) of the International Standards Organization Subcommittee on Programming Languages (ISO TC97/SC5/WG2). Actions taken in recent WG2 meetings in October, 1979, and June, 1980, will be covered. Significant proposals being examined by WG2 include GKS, a German-designed 2D graphics package derived from the SIGGRAPH GSPC Core System proposals, and Videotex, a Canadian-designed protocol text communication that includes geometrically coded picture images.

The second status report describes the recent activities of the American National Standards Institute (ANSI) Technical Committee X3H3, Computer Graphics. This includes the committee status, international activities, key technical issues, and future plans.
Computer-assisted chart making from the graphic designer's perspective
Authors: Marcus Aaron
Published: November 2005

It is important to improve the aesthetics and effectiveness of information graphics through greater awareness of graphic design as a visual communication discipline. Chart making is one subject area in which graphic design awareness can be enhanced. Basic design principles are reviewed which are relevant to creating better charts. Examples demonstrate improvements.
Synthetic texturing using digital filters
Authors: Feibush Eliot A. , Levoy Marc , Cook Robert L.
Published: November 2005

Aliasing artifacts are eliminated from computer generated images of textured polygons by equivalently filtering both the texture and the edges of the polygons. Different filters can be easily compared because the weighting functions that define the shape of the filters are pre-computed and stored in lookup tables. A polygon subdivision algorithm removes the hidden surfaces so that the polygons are rendered sequentially to minimize accessing the texture definition files. An implementation of the texture rendering procedure is described.
The display of characters using gray level sample arrays
Authors: Warnock John E.
Published: November 2005

Character fonts on raster scanned display devices are usually represented by arrays of bits that are displayed as a matrix of black and white dots. This paper reviews a filtering and sampling method as applied to characters for building multiple bit per pixel arrays. These arrays can be used as alternative character representations for use on devices with gray scale capability. Discussed in this paper are both the filtering algorithms that are used to generate gray scale fonts and some consequences of using gray levels for the representation of fonts including:

1. The apparent resolution of the display is increased when using gray scale fonts allowing smaller fonts to be used with higher apparent positional accuracy and readability. This is especially important when using low resolution displays.

2. Fonts of any size and orientation can be generated automatically from suitable high precision representations. This automatic generation removes the tedious process of “bit tuning” fonts for a given display.
Human vision, anti-aliasing, and the cheap 4000 line display
Authors: Leler William J
Published: November 2005

Despite its other advantages, one of the major objections to raster graphics has been the poor image quality and aliasing effects caused by discrete sampling. These effects include “jaggies” or stair-stepping, crawling, line breakup, and scintillation. Several solutions have been proposed in the literature, however, most suffer severe drawbacks and are only partially successful at eliminating aliasing effects. One solution, area anti-aliasing, is not only effective, it produces results comparable to higher resolution systems. Using widely available data on human visual response, it is shown how this technique actually increases the perceived resolution of a display beyond the hardware resolution by factors of up to 16X. The requirements of such a system are discussed, as well as some of the problems encountered.
Techniques for interactive raster graphics
Authors: Baudelaire Patrick , Stone Maureen
Published: November 2005

The visual quality of raster images makes them attractive for applications such as business graphics and document illustration. Such applications are most fully served using interactive systems to describe curves, areas and text which can be rendered at high resolution for the final copy. However, to present such imagery in an interactive environment for moderate cost is difficult. Techniques are presented that provide solutions to the problems of scan conversion, screen update, and hit testing for a class of interactive systems called
illustrators.
The design rests on the use of software display file encoding techniques. These ideas have been used in the implementation of several illustration programs on a personal minicomputer.
Simulation of wrinkled surfaces
Authors: Blinn James F.
Published: November 2005

Computer generated shaded images have reached an impressive degree of realism with the current state of the art. They are not so realistic, however, that they would fool many people into believing they are real. One problem is that the surfaces tend to look artificial due to their extreme smoothness. What is needed is a means of simulating the surface irregularities that are on real surfaces. In 1973 Ed Catmull introduced the idea of using the parameter values of parametrically defined surfaces to index into a texture definition function which scales the intensity of the reflected light. By tying the texture pattern to the parameter values, the texture is guaranteed to rotate and move with the object. This is good for showing patterns painted on the surface, but attempts to simulate rough surfaces in this way are unconvincing. This paper presents a method of using a texturing function to perform a small perturbation on the direction of the surface normal before using it in the intensity calculations. This process yields images with realistic looking surface wrinkles without the need to model each wrinkle as a separate surface element. Several samples of images made with this technique are included.
Color spaces for computer graphics
Authors: Joblove George H. , Greenberg Donald
Published: November 2005

Normal human color perception is a product of three independent sensory systems. By mirroring this mechanism, full-color display devices create colors as mixtures of three primaries. Any displayable color can be described by the corresponding values of these primaries. Frequently it is more convenient to define various other
color spaces
, or coordinate systems, for color representation or manipulation. Several such color spaces are presented which are suitable for applications involving user specification of color, along with the defining equations and illustrations. The use of special color spaces for particular kinds of color computations is discussed.
A scan line algorithm for displaying parametrically defined surfaces
Authors: Blinn James F.
Published: November 2005

This paper presents a scan line algorithm for drawing picture of parametrically defined surfaces. A scan line algorithm is characterized by the order in which it generates the picture elements of the image. These are generated left to right, top to bottom in much the same was as a picture is scanned out on a TV screen. Parametrically defined surfaces are those generated by a set of bivariate functions defining the X, Y and Z position of points on the surface. The primary driving mechanism behind such an algorithm is the inversion of the functions used to define the surface. To keep the algorithm general enough to apply to a wide variety of functional forms, this inversion is done numerically. It is only required to provide mechanism for evaluating the function and its derivatives at any parametric location.

The algorithm proceeds in two phases. First, a numerical search is made to find the local maxima of the Y definition function within the desired parameter ranges. These determine when portions of the surface first become visible as the scan plane progresses down the screen. Secondly, the actual scan conversion process is performed, maintaining a list of segments of the surface intersecting the current scan plane. As the scan plane passes local maxima of the Y function new segments are added to the list. In addition, any existing segments are updated to reflect their intersection with the updated scan plane. All intersection calculations are performed by a bivariate Newton-Raphson solution of the defining equations. If the solution does not converge, it is due to the scan plane passing a local minimum, causing segments to be deleted from the active list. Finally, within one scan line, an X scan must be performed to generate the Z information about the surface for each picture element. This is also performed by a bivariate Newton-Raphson iteration with a different set of defining functions.
A graphics-based programming-support system
Authors: Frei H. P. , Weller D. L. , Williams R.
Published: November 2005

A programming support system using extended Nassi-Shneiderman diagrams (NSD) is described. The aim of the work is to develop techniques for improving the quality and cost of specifying, documenting and producing computer programs. NSD's can be executed interpretively or compiled to produce running code. The system implementation has begun and charts can be drawn on a variety of display devices. The system is being developed using the Picture Building System developed earlier.
A microcomputer based system for automated pattern digitization and editing
Authors: Pavliscak T. J. , Stowell G. W. , Bailey M. J.
Published: November 2005

Since the first microcomputer was produced in 1969 by Intel Corporation to support the functions of an intelligent terminal, the complexion of digital computers has changed radically. Microcomputers have been successfully applied to a wide variety of dedicated tasks requiring relatively slow calculation speeds and limited numeric accuracy.

However, little has been done to bring the LSI microprocessor into stand alone interactive graphics systems. This has been so probably because of the large data files and rapid computation speeds demanded by most interactive graphics applications. This paper outlines a hardware and software configuration for a microcomputer based graphics system developed in response to a need in the sewing industry for a low cost pattern digitizer.

A basic graphics package was written which renders both text and vectors on the storage terminal. Around this core, an application program was organized which permits an operator to log piercing point coordinate data from a scaled drawing. Output is then committed to paper tape for permanent storage and PROM for control of the sewing machine. Additional features allow for graphical editing of patterns, display of stored pattern “programs” from PROM or paper tape, and merging of new and/or old patterns.

Some proof of the success of this project was documented during final checkout, where the time to reduce a drawing to formatted binary on a control PROM was improved from about one man day to a matter of minutes.
The interactive digitizing of polygons and the processing of polygons in a relational database
Authors: McIntosh John F.
Published: November 2005

A system is described for the interactive digitizing of polygons for such two-dimensional spatial modeling applications as growth studies and thematic map production. A digitizer connected online to a mini-computer with a refresh display is used for capturing polygon data from source documents. An area boundary network is developed by digitizing nodes, pointing to node pairs, and then digitizing edges only once. A CRT display monitors, and bell-rings confirm input operations. Facilities to erase nodes or edges are available. From the nodes and edges, software produces polygons which the user may name or discard. Slivering and overlap are eliminated because contiguous polygons have identical edge descriptions. Named polygons are then transferred to a large university time-sharing computer where spatial editing operations may be carried out, such as unioning pieces of a large map. The named polygons may he given additional non-spatial attributes and entered into a relational type of data base.
A fixed grid curve representation for efficient processing
Authors: Burton Warren
Published: November 2005

A compact form of representation for curves and regional boundaries is described.

A curve is approximated by a polygonal line where each side joins a grid point to one of its eight nearest neighbors (as is done in the commonly used chain-encoded representation). Vertex number (2k + 1)2
m
is defined relative to vertex number k2
m+l
. The resulting representation requires about 5 bits of storage per vertex, irrespective of the total length of the curve.

Sections of a curve may be collectively examined. Typically, that part of the curve between vertices number k2
m
and (k + 1)2
m
, for some k and m, is considered. Given the locations of the endpoints of a section and the number of sides in the section, it is easy to compute a bounding rectangle which must completely contain the section. Often, this is all the information we need to know about a section. For example, two sections cannot intersect if their bounding rectangles do not overlap. When necessary, a section can be easily divided into two smaller sections, each of which can be examined in turn. This process may be continued down to single sided sections if necessary.

Under favorable circumstances, for an n sided approximation to a closed curve, the time required to determine if a point is inside the curve is independent of n. The intersection of n sided approximations to two curves can usually be found in 0(1n n) time.
Application of shape-preserving spline interpolation to interactive editing of photogrammetric data
Authors: Deimel L. E. , Doss C. L. , Fornaro R. J. , McAllister D. F. , Roulier J. A.
Published: November 2005

The Integrated Photogrammetric Instrument Network (IPIN) is being designed and developed by the Defense Mapping Agency Aerospace Center in St. Louis, Mo. to meet database demands for terrain elevation information. IPIN is a network of computers and instrumentation dedicated to digitizing and editing photo-source terrain data [1]. Editing procedures are required because of digitizing errors inherent in the data-collection process. Some of these errors are random; others are systematic and predictable.

The techniques of one of the editing procedures being developed may find application elsewhere. The procedure of interest here involves smoothing raw data that have been collected by the operator of an analytical stereoplotter. When digitizing geomorphic features from aerial stereophotographs, the double-line drain (DLD) presents special problems. The digitizing of a DLD (a relatively broad river or stream) requires specifying trlples (x,y,z) (latitude, longitude, elevation) at points spaced along the length of each shoreline. The drain boundaries thus collected usually have acceptable latitude and longitude values. The elevation values, however, require smoothing.
A sensor simulation and animation system
Authors: Zimmerlin Timothy , Stanley John , Stone Warren
Published: November 2005

A shaded computer graphics system for sensor simulation and animation must possess extensive capabilities. Sensor simulation involves scenes that are viewed, environments that produce tones in the scenes, and sensors that image the scenes. Animation centers on image generation, but data input, motion specification, and tone specification routines are very important for an effective system.

A unique system has been developed that models a variety of scenes, environments, and sensors. It possesses a balance of data input, motion and tone specification, and frame generation routines. The system possesses several user languages for data input. User defined sections of the scene can move. Visible, infrared, laser radar, and radar sensors have been modeled. The frame generator possesses advanced aliasing controls, textured shading, and a very fast list priority hidden surface algorithm. The system is used as a test bed for training simulators and sensor-based system simulation.
Three-dimensional representations for computer graphics and computer vision
Authors: Badler Norman , Bajcsy Ruzena
Published: November 2005

Representing complex three-dimensional objects in a computer involves more than just evaluating its display capabilities. Other factors are the uses and costs of the representation, what operations can be performed on it and, ultimately, how useful it is for computer recognition or description or three-dimensional objects. Many of the questions which are posed arise from the joint consideration of computer graphics and computer vision, and a specific representation hierarchy is proposed for complex objects which makes them amenable to display, manipulation, measurement, and analysis.
On display of space filling atomic models in real-time
Authors: Staudhammer John
Published: November 2005

Earlier work on real-time display of planar polygonal three-dimensional object scenes is extended to the inclusion of repetitive curved surfaces. In earlier work the visible scene components were calculated and reduced to scan line encoded image segments to generate real-time cartoons. That work was limited to visible planar surface elements because of the display algorithms employed. Display time is limited to 33 ms so that scan-interlaced TV may be used. Curved surfaces would normally be approximated by a large number of facets; however, Mach effect's faceting of the surface will occur for all but the simplest cases. Point by point curved surface shading is examined in detail so that special hardware may be defined for displaying the visible surface parts in 33 ms. The hardware concepts employed can be extended to other simple curvatures that appear repeatedly in a visible scene. CONTENT INDICATORS: 3.13, 6.22, 6.35, 6.4, 3.89.
One-point touch input of vector information for computer displays
Authors: Herot Christopher F. , Weinzapfel Guy
Published: November 2005

The finger as a graphical stylus enjoys a coefficient of friction with glass sufficient to provide input of direction and torque as well as position from a single point. This report describes a pressure-sensitive digitizer (PSD) capable of accepting these force inputs, and discusses a set of five simple input applications used to assess the capabilities of this device. These applications include techniques for specifying vectors, and pushing, pulling, dispersing and reorienting objects with a single touch. Experience gained from these applications demonstrates that touch and pressure sensing open a rich channel for immediate and multi-dimensional interaction.
On storing and changing shape information
Authors: Braid I. C.
Published: November 2005

A data structure for modelling engineering components and assemblies is described. It is shown how the same structure, slightly extended, can also be used to represent a single component defined as boolean combinations of more primitive shapes. This leads to a unified method of handling both the concise boolean description and the longer explicit description in terms of faces, edges and vertices. The technique permits close control of evaluation from boolean to explicit description, and facilitates saving of partly evaluated results and back tracking.

The data structure is built up and evaluation is controlled through a geometrical language embedded in Algol 68. The language is intended for the construction of computer-aided design systems, for simulating engineering production processes, or for any application in which shapes and changes to shapes must be recorded and manipulated.
The PADL-1.0/2 system for defining and displaying solid objects
Authors: Voelcker H. , Requicha A. , Hartquist E. , Fisher W. , Metzger J. , Tilove R. , Birrell N. , Hunt W. , Armstrong G. , Check T. , Moote R. , McSweeney J.
Published: November 2005

PADL (Part and Assembly Description Language) is a language for defining solid objects via constructive solid geometry, i.e. as (regularized) set-theoretical compositions of primitive solid “building blocks”. The current processor for Version 1.0 of the language accepts PADL statements either in batch or in keyboard-interactive mode and produces line drawings of objects on CRT's and plotting devices. A variety of drawing styles is available: dimensioned orthographics, perspectives, section views, interference drawings, etc.

Novel characteristics of the PADL-1.0/2 system include 1) general combinational operators that may be applied to any part defined in PADL, 2) correct handling of “pathologies” that occur when (for example) two objects have partially coincident boundaries, 3) maintenance of consistent multiple representations of the same object, and 4) automatic posting on drawings of dimensions to reflect user-defined geometric relations between features of objects.

This paper provides an overview of both the language and the current processor's capabilities and organization. Detailed discussions of the underlying mathematics, algorithms, and implementation are presented elsewhere.
A flexible, high performance interactive graphics system
Authors: Hubbold R. J. , Bramhall P. J.
Published: November 2005

A computer graphics system with refresh and storage displays, flat-bed plotter, digitizer and film recorder is described. The software structure comprises a device-independent, front-end graphics package and a driver program for each device. Two and three-dimensional vectors, hardware and software characters, transformations and windowing, picture segmentation, element and segment attributes, and input from interactive tools, such as a light-pen, are supported. The extent to which the system is used by different research groups shows that this is a very cost-effective way to provide computer graphics facilities.
A system for interactive modeling of physical curved surface objects
Authors: England J. N.
Published: November 2005

It is often important to obtain descriptions of existing objects for computer graphics data bases. A system to aid interactive modeling (in three dimensions) of a physical object is described. The system allows a user to fit a bi-cubic parametric spline surface to an object by superimposing stereoscopic views of the computer surface with stereoscopic television views of the object. A 3-D joystick is used to manipulate surface control points while the user views the computed surface as isoparametric contours.

A raster scan display polarization stereoscope is used.

The left eye and right eye surface views are computed using a unique display processor designed and constructed for the evaluation of raster scan graphics techniques. The display processor consists of multiple non-pipelined concurrently operating microprogrammed modules. The computation of the two reasonably complex images (>500 vectors each) takes less than 33 msec allowing real time display at standard television rates.
Association of graphic images and dynamic attributes
Authors: Bergman S. , Kaufman A.
Published: November 2005

Various approaches to explicit and implicit control of time and motion in procedural real-time graphic
packages
and languages are discussed and illustrated. The particular approach of independentty defining static objects and dynamic attribute is introduced and developed. The procedures which alter and manipulate basic objects at interactive run time, teamed "dynamic attributes," may be defined independently of objects as a function of time, input, and other variables. Attributes, once defined,
may be
associated with and dissociated from objects dynamically. Several objects may simultaneously have
the
identical attribute. A particular & association exists within its own zero-origin local time frame. Basic objects are static two-or three-dimensional
entities
in some
space.
Dynamic objects termed "images" may
be
recursively defined in teams oa basic objects and attributes. Objects and attributes are the basic building blocks enabling modular program construction.
The
notions presented here can
be
used as the basis for design of interactive graphic languages or oda the implementation of graphics packages.
An
experimental FORTRAN-callable package has
been
developed to test
these
notions.
Interactive graphics an aid to health planning and decision making
Authors: Willard Christopher , Hamann Jay R.
Published: November 2005

One of the major functions of State and Federal Public Health agencies is the collection and maintenance of large amounts of data. The utilization of this data for research and planning may be impaired by such factors as: lack of organization and accessibility of the data, users lack of knowledge of statistical and operations research techniques, inability to determine important variables from a large selection, and the need to present results in a form which is understandable and useful to the general public.This paper presents interactive graphics approaches which are designed to aid the public health planner and administrator through presentation of data in map and table form. Interactive graphics is a form of real time computing in which all or part of the input and output operations are handled through a graphics terminal. The systems described below present statistics for different civil divisions and allow the user to display and compare data from a large set of variables. These variables include locational data such as the position of emergency medical services, hospitals, cities and towns; quantities such as travel distance, travel time, service area, and service population; and summary statistics. The display is controlled either through light pen activated commands or the use of a "button board". The systems have been applied to problems in administrative area designation and emergency service placement.The use of interactive graphics allows the public health planner and administrator to handle large data bases with minimal expertise. Data may be reviewed quickly and useful variable selected. These systems also allow for the maximum use of the administrators experience and knowledge of the areas particular needs and qualitative factors by allowing direct interface to the data. These systems require a minimal amount of training to use, thus allowing interested public groups to use them to develop and compare different solutions to health planning and administrative problems.
Computer graphics for facilities management
Authors: Renfrow Nancy V.
Published: November 2005

By combining the gaming aspects of interactive, refreshed screen graphics with accurate cost data and realistic schedules, solid front end planning as well as control and monitoring through the life of the building can be achieved. This process enables the user to examine more alternatives in less time, to evaluate solutions against established criteria, to increase production and to design to cost. The development and manipulation of the graphic data and hardware will be explained through examples from housing, hospitals, industrial and commercial buildings.
Anima II
Authors: Hackathorn Ronald J.
Published: November 2005

An animation software system has been developed at The Computer Graphics Research Group which allows a person with no computer background to develop an animation idea into a finished color video product which may be seen and recorded in real time. The animation may include complex polyhedra forming words, sentences, plants, animals and other creatures. The animation system, called Anima II, has as its three basic parts: a data generation routine used to make colored, three-dimensional objects, an animation language with a simple script-like syntax used to describe parallel motion and display transformations in a flexible, scheduled environment, the Myers algorithm used in the visible surface and raster scan calculations for the color display. This paper discusses the requirements, the problems, and the trade-offs of such a system. An overview of research in the area is given as well as the design and implementation highlights of the Anima II system.
Real-time playback in animation systems
Authors: Potel M. J.
Published: November 2005

A technique often employed in animated vector graphics involves the use of a real-time playback mechanism. This technique is an alternative when it is not possible to generate animation frames in real-time. Instead frames are compiled in advance at non-real-time rates, saved in secondary storage, and then played back at desired real-time rates. The basic design of such a playback mechanism will be considered, including discussions of synchronization, buffering, and blocking. Two special properties will be established for these systems: the conditions required to achieve real-time reversal in the direction of the playback sequence, and the existence of upstream/downstream effects, performance differences between directions in systems that are run "too fast."
An interdisciplinary laboratory for graphics research and applications
Authors: Greenberg Donald P.
Published: November 2005

This paper describes the facilities and operation of the Program of Computer Graphics at Cornell University. A variety of graphic procedures are used for both input and output. The laboratory has the capability for producing dynamic vector displays and for generating full color images. Numerous research projects in a variety of disciplines which are actively using this multi-user graphics environment are presented.
A practical approach to implementing line printer graphics
Authors: Rumsey John R. , Walker Roger S.
Published: November 2005

The capability of generating graphical images on a line printer is very desirable. Many ad hoc special purpose implementations exist that satisfy the needs of particular users. A single general purpose line printer graphics capability, however, compatible with widely distributed Calcomp pen plotter software, could eliminate the need for many special purpose implementations. An implementation approach is described for a set of subroutines which are designed to minimize storage requirements to maintain a complete graphical image. The software has been widely accepted in university, government, and industry environments to augment and occasionally replace pen plotting facilities.
An extensible approach to imagery of gridded data
Authors: Dutton Geoffrey
Published: November 2005

A program offering a variety of cartographic techniques for mapping gridded data is described. Dot-distribution maps, several forms of contour maps and screen-toned maps are currently implemented for plotter and vector CRT. The structure and logic of the program is discussed and illustrated. The approach requires only local access to a data grid in a paging environment, allowing large data sets to be manipulated. Maps output may be plotted at any scale, irrespective of the size of the plotting device. Additional graphic techniques and output devices are readily accommodated, and will become even more so when full virtual memory is implemented. Possibilities for image overlay are discussed and illustrated, and plans for data overlay are outlined.
Automated contour mapping using triangular element data structures and an interpolant over each irregular triangular domain
Authors: Gold C. M. , Charters T. D. , Ramsden J.
Published: November 2005

Surface display techniques, including contour mapping, usually use an interpolant when data values are on a rectangular grid; but when values are irregularly located some form of assumed or estimated distance-weighting function is often used to estimate the "influence" of data points at other locations. If moving average (or some other) techniques are then applied, slopes may be zero at data points; extrema may fall at data points exclusively; or surfaces may not pass through data points.An alternative method is proposed whereby a map area is automatically divided into suitable triangular domains with a data point at each vertex. Surface estimation and contour plotting are then performed independently for each triangle using a measured or best-fit plane associated with each data point. The approach requires the utilization of three non-original aspects: 1) the derivation of a local homogeneous "area" coordinate system for any arbitrary triangle; 2) the construction of a data-structure linking each triangular domain with its three neighbouring triangles and three associated data points, and 3) the use of a "conforming" triangular finite-element interpolating function.Use of the first two of these concepts permits the economic generation and optimization of a triangular mesh from a set of data points. Optimization criteria used to define the "best" triangular partition are described in some detail, along with computer timing for this step. Use of the first and third concepts permits the interpolation of a smooth surface over the whole map area even though each triangular element is estimated and plotted independently. The requirements for a suitable interpolating function are discussed, and an interpolant is suggested that preserves elevation and slope at each data point as well as elevation and slope continuity between domains. Extrema need not be located at data points but are constrained by their associated planes. Contour line segments are produced by division of each triangle into N
2
sub-triangles, elevation estimation at each resulting node, and linear interpolation and plotting withing each sub-triangle. Resolution is then a function of N and local data point density. Extension of the method to higher dimensions is briefly discussed.
A query language for a network data base with graphical entities
Authors: Phillips Richard L.
Published: November 2005

A generalized high level query language has been developed for use with a network data base, as defined by the CODASYL DBTG report. Of particular interest is the capability of manipulating graphical entities with this language. The system was developed to supportan offshore oil lease information project where one must formulate queries pertaining to proximity of graphical entities. To facilitate such requests new relational operators were defined and implemented. Thus compound Boolean expressions can be formed which involve graphical as well as non-graphical criteria. Since one goal of the information system is to produce selectively colored maps via an FR80 microfilm recorder, the query language syntax provides the user with a comprehensive thematic cartography capability. The query language is designed to isolate the user from the underlying network structure of the data base. In order to accomplish this generalized pathfinding and accessing algorithms had to be developed. Pathfinding is facilitated through an adjacency matrix involving all record types in the data base, while accession is controlled by examining the local owner-member relation for current record types. Besides querying, the system provides the usual complement of data base management system functions, i.e. deletion, updating, reporting, etc.
Models of light reflection for computer synthesized pictures
Authors: Blinn James F.
Published: November 2005

In the production of computer generated pictures of three dimensional objects, one stage of the calculation is the determination of the intensity of a given object once its visibility has been established. This is typically done by modelling the surface as a perfect diffuser, sometimes with a specular component added for the simulation of hilights. This paper presents a more accurate function for the generation of hilights which is based on some experimental measurements of how light reflects from real surfaces. It differs from previous models in that the intensity of the hilight changes with the direction of the light source. Also the position and shape of the hilights is somewhat different from that generated by simpler models. Finally, the hilight function generates different results when simulating metallic vs. nonmetallic surfaces. Many of the effects so generated are somewhat subtle and are apparent only during movie sequences. Some representative still frames from such movies are included.
Raster-scan hidden surface algorithm techniques
Authors: Hamlin Griffith , Gear C. William
Published: November 2005

Two new techniques are presented for reducing the number of depth calculations in hidden surface elimination. Two new algorithms using the techniques are compared with three existing algorithms and it is shown by examples that the new techniques reduce the number of multiplications involved in the depth calculations. A technique for increasing the parallelism of operations is also presented. This allows the calculation to be done more rapidly in hardware and is particularly useful for generating line drawings rather than the usual TV raster scan images in the common raster-scan hidden surface algorithms.
Shadow algorithms for computer graphics
Authors: Crow Franklin C.
Published: November 2005

Shadows are advocated for improved comprehension and enhanced realism in computer-synthesized images. A classification of shadow algorithms delineates three approaches: shadow computation during scanout; division of object surfaces into shadowed and unshadowed areas prior to removal of hidden surfaces; and inclusion of shadow volumes in the object data. The classes are related to existing shadow algorithms and implementations within each class are sketched. A brief comparison of the three approaches suggests that the last approach has the most appealing characteristics.
An interactive computer graphics approach for dissecting a mixture of normal (or lognormal) distributions
Authors: McCammon Richard B.
Published: November 2005

An interactive computer graphics program has been developed to dissect mixtures of normal (or lognormal) distributions. The program incorporates both graphical and analytical techniques to obtain a more satisfactory solution to the problem of dissection. Within a matter of minutes, a mixed frequency curve can be decomposed into its normal (or lognormal) components. A statistical summary following dissection makes it possible to evaluate the goodness-of-fit and the separability of the inferred subpopulations. Individual components can be added or subtracted and adjustments can be made to individual parameters of components. An example of dissection is given in geology and in sports.
A user-oriented computer graphics system
Authors: Pooch Udo W.
Published: November 2005

A user-oriented Computer Graphics System (CGS) is described, which primarily has been designed to aid the application programmer, and not just the sophisticated computer graphics user. The system has been designed to provide a very simple interaction capability, where the interaction is based on a variety of input devices and a simple input/output graphics command language. The result of this system has been an increase in programming efficiency, reduction in span time from creations of design to actual implementation. Typical application developments have included such system as flowcharting systems, Computer Aided Architectural Space Planning, Animation, Vehicle-Pedestrian Interactions, Computer-aided designs, and the simulation of the NASA Space Shuttle.
A digital video information storage and retrieval system
Authors: Myers Allan J.
Published: November 2005

A concept of general purpose systems which generate, store, retrieve, process and display raster-scan format images is developed. The general purpose nature of such systems allows the handling of static and dynamic images from multiple sources as well as system synthesized images while precluding the use of special function hardware. A particular system implementation is described. The implementationwas accomplished with standard digital computer and video hardware with the exception of one special hybrid subsystem. Most of the equipment belongs to the digital computer class with the only video hardware being a standard broadcast television receiver. The system has application to many areas including computer animation, medicine, computerized picture libraries and the study of the mechanisms of visual perception. Problems and future developments are discussed.This research was supported in part by the National Science Foundation Division of Mathematical and Computer Sciences under grant DCR 74-00768A01.
A graphics editor for labanotation
Authors: Brown Maxine D. , Smoliar Stephen W.
Published: November 2005

There is a need for a simple mechanized way to design, update and produce final copies of scores of Labanotation, a symbolic, graphical language for the recording of body movement used by choreographers, anthropologists, psychologists and therapists. This paper discusses the design and implementation of a machine-independent data structure for Labanotation and its application in an interactive storage, retrieval and editing system.
A film on schemes for interactive curve design
Authors: Riesenfeld Richard F.
Published: November 2005

The accompanying film shows some general sessions of working with an interactive graphics system to design free-form curves and surfaces. In particular, it demonstrates the use of a very general B-spline curve package that allows the user to specify desired attributes like degree, shape, type of parametrization, and periodicity. Other schemes that show the use of "tension" as a parameter in design will ge presented.
Architecture-by-yourself
Authors: Weinzapfel Guy , Negroponte Nicholas
Published: November 2005

Architecture-by-Yourself is an experiment in computer aided design that applies the medium of computer graphics, used by a general populace. The research program confronts the delicate balance between insightfulness and paternalism toward a user who ultimately bares the risk. The paper reports on a case study, on the underlying philosophy's of the French architect Yona Friedman, and on a computer implementation called YONA. As part of a larger research effort,
Machine Recognition and Inference Making in Computer Aids to Design,
we postulate further developments that will exercise input and visualization techniques in a relentless setting, relentless in the sense that the user is demanding, the problem is hard, and the product is a personal, one-of-a-kind design.
Automatic drafting systems
Authors: Machover Carl
Published: November 2005

A primary advantage of computer graphics is that a comfortable environment can be created for an individual to communicate with a computer. A properly people-designed automatic drafting system is an excellent example of such an environment.
Interactive simulation of network pumping policies on a computer-based graphics system
Authors: Perry P. F. , Keenan J. D.
Published: November 2005

This paper is concerned with the development of a computer-based graphics system for interactive simulation of pumping policies on water supply networks. The method evaluates various strategies which are input to the computer via a light-pen graphics facility, and displays to the operator the cost of the input strategy based on a mathematical model of the pumping tariff which is developed. The method has been used for policy analysis on a pressure zone of a network in the United Kingdom, and the calculations implemented on a Fortran-based minicomputer graphics system.
Graphical input through machine recognition of sketches
Authors: Herot Christopher F.
Published: November 2005

A family of programs has been developed to allow graphical input through continuous digitizing. Drawing data, sampled at a high and constant rate, is compressed and mapped into lines and splines, in two and three dimensions. This is achieved by inferring a particular user's intentions from measures of speed and pressure.Recent experiments have shown that even the most basic inference making cannot rely solely upon knowledge of the user's drawing style, but needs additional knowledge of the subject being drawn, the protocols of its domain, and the stage of development of the user's design. This requirement implies a higher level of machine intelligence than currently exists. An alternate approach is to increase the user's involvement in the recognition process.Contrary to previous efforts to move from sketch to mechanical drawing without human intervention, this paper reports on an interactive system for graphical input in which the user overtly partakes in training the machine and massaging the data at all levels of interpretation. The initial routines for data compression employ parallel functions for extracting such features as bentness, straightness, and endness. These are planned for implementation in microprocessors.Results offer a system for rapid (and enjoyable) graphical input with real-time interpretation, the beginnings of an intelligent tablet.
A computer-terminal, hardware/software system with enhanced user input capabilities
Authors: Kaplow Roy , Molnar Michael
Published: November 2005

The Enhanced-Input Terminal project is directed at providing major new degrees of freedom for touch-type computer input, especially for on-line use of interactive computer systems. The terminal comprises an integrated of hardware and software. While various choices are available for the actual input and output devices, the present prototype utilizes video display for both devices and a "cross-wire", touch-sensitive input panel. The EITS allows an "author" to define an essentially infinite set of symbols, and an infinite variety of "keyboard" formats. Chord inputs (i.e., simultaneous, multiple-"key" combinations) are also supported. Symbols can be defined in terms of dot matrices, generalized graphics, symbol strings, and functional operations. In spite of the complete generality afforded, the integrated system develops a standard-type of binary-bit-coded input stream, in which the individual symbols are uniquely and canonically represented, and which is amenable to all of the usual "text-file" operations, such as character manipulation, editing, transmission and re-display.