bluuebunny/crossref_metadata_2025 huggingface dataset:
Symbolic computer graphics and biological models
Authors: Horovitz Mark W. , Austin Donald M. , Holmes Harvard H.
Published: November 2005

In the first part of my talk I will describe the operation of a symbolic graphics computer system; next, I will show how some models can be implemented by using this system, and finally I want to discuss techniques for establishing the validity of models.
MARS -

M

issouri

A

utomated

R

adiology

S

ystem, computer graphics in an automated department
Authors: Manson D. J. , Lehr James L. , Lodwick G. S.
Published: November 2005

One begins increasingly to hear the phrase “out of control” in reference to rising health care costs. Whether or not the health care system is out of control, cost projections are beginning to approach 10% of the gross national product. A very small percent of health care costs represent the application of technology in medicine; computer automation techniques offer the promise to both increase the quality of health care and reduce costs. Our effort has been to apply these techniques to an entire department of Radiology and thus to test the cost effectiveness of automated health care in the clinical context. I am reporting today on modules of our system that involve the use of computer graphics.

I should like first to make a philosophical point. The concept of a total hospital information system is logically prior to that of any particular department. We begin by postulating that such a system will include a central file with selective access. By constructing a system that meets the needs of our department we will (1) have guaranteed the peripheral specification necessary to any system; 2) demonstrated a model for information processing applicable to other departments with similar information requirements; and 3) be ready to aid in the integration of intra-department information systems when they are ready.

This paper is concerned I ) with the medical information system being transferred to a small stand-alone computer; 2) with the system test of a 35 mm radiographic imaging system; 3) computer assisted diagnosis and 4) direct computer diagnosis from chest radiographs.
On-line modeling by curve-fitting
Authors: Knott G. , Shrager R.
Published: November 2005

Modeling, as we use the term here, means matching a set of numbers, obtained from some theory, to a set of numbers from the laboratory. We will refer to the laboratory numbers as the observed data or curve and to the theoretical numbers as the computed data or curve.

Our purpose may be to evaluate the model; or to use it to determine otherwise unobtainable values as functions of the observed curve. Thus the key problem in modeling by curve-fitting is parameter determination. The model functions contain unknown or vaguely known numbers called parameters that affect the shape of the computed curve. The problem is to find those parameter values that make the computed curve most resemble the observed curve in the least squares sense. This is why we speak of modeling by curve-fitting. Statisticians call this activity non-linear regression.
Towards device-independent graphics systems
Authors: Trambacz Ulrich
Published: November 2005

A formalism for logical input devices is presented that opens the way to input device independent graphics systems combined with a high degree of flexibility to study and utilize the psychological differences of logical equivalent physical input devices.
Simulation of natural scenes using textured quadric surfaces
Authors: Gardner Geoffrey Y.
Published: November 2005

Because of the high complexity of the real world, realistic
simulation of natural scenes is very costly in computation. The
topographical subtlety of common natural features such as trees and
clouds remains a stumbling block to cost-effective computer
modeling. A new scene model, composed of quadric surfaces bounded
with planes and overlaid with texturing, provides an efficient and
effective means of representing a wide range, of natural features.
The new model provides a compact and functional data base which
minimizes the number of scene elements. Efficient hidden surface
algorithms for quadric surfaces bounded by planes are included. A
mathematical texturing function represents natural surface detail
in a statistical manner. Techniques have been developed to simulate
natural scenes with the artistic efficiency of an impressionist
painter.
Computer-integrated manufacturing in Japan (Panel)
Authors: Kunii Tosiyasu L.
Published: November 2005

Recent progress in Japanese computer-integrated manufacturing (CIM) includes the integration of computer graphics, database management systems, local area networks, robotics and software engineering technology. This panel will discuss advanced CAD, CAM CAT (computer-aided testing) and FMS (flexible manufacturing systems) available in Japan.

After the overview by the Chair Prof. Kunii, the basic CIM related researches to support industrial applications will be explained by Prof. Nakajima of the University of Tokyo. A wide spectrum of recent industrial advances and future trends in Japanese CIM are covered by four panelists from reputed manufacturers and users of CIM facilities and equipments. As one of the features of Japanese CIM, it will be noticed throughout the panel presentations and discussions that manufacturers always send out their products into the market after extensive internal use of them. Mr. Kubo of Hitachi Omika Work will present new networked CIM workstation. A typical example of very large CIM will be shown by Mr. Nakagawa of Mitsui Engineering and Shipbuilding. Very aggressive lines of products and plans are expected from Fanuc and will be presented by Mr. Inaba of GM Fanuo Robotics. Mr. Nishioka of Sharp will conclude the session explaining how he has developed and marketed very practical CIM successfully.
A parallel processor system for three-dimensional color graphics
Authors: Niimi Haruo , Imai Yoshirou , Murakami Masayoshi , Tomita Shinji , Hagiwara Hiroshi
Published: November 2005

This paper describes the hardware architecture and the employed algorithm of a parallel processor system for three-dimensional color graphics. The design goal of the system is to generate realistic images of three-dimensional environments on a raster-scan video display in real-time. In order to achieve this goal, the system is constructed as a two-level hierarchical multi-processor system which is particularly suited to incorporate scan-line algorithm for hidden surface elimination. The system consists of several Scan-Line Processors (SLPs), each of which controls several slave PiXel Processors (PXPs). The SLP prepares the specific data structure relevant to each scan line, while the PXP manipulates every pixel data in its own territory. Internal hardware structures of the SLP and the PXP are quite different, being designed for their dedicated tasks.

This system architecture can easily execute scan-line algorithm in parallel by partitioning the entire image space and allotting one processor element to each partition. The specific partition scheme and some new data structures are introduced to exploit as much parallelism as possible. In addition, the scan-line algorithm is extended to include smooth-shading and anti-aliasing with the aim of rendering more realistic images. These two operations are performed on a per-scan-line basis so as to preserve scan-line and span coherence.

Performance estimation of the system shows that a typical system consisting of 8 SLPs and 8×8 PXPs can generate, in every 1/15th of a second, the shadowed image of a three-dimensional scene containing about 200 polygons.
Ray tracing with cones
Authors: Amanatides John
Published: November 2005

A new approach to ray tracing is introduced. The definition of a “ray” is extended into a cone by including information on the spread angle and the virtual origin. The advantages of this approach, which tries to model light propagation with more fidelity, include a better method of anti-aliasing, a way of calculating fuzzy shadows and dull reflections, a method of calculating the correct level of detail in a procedural model and texture map, and finally, a procedure for faster intersection calculation.
Distributed ray tracing
Authors: Cook Robert L. , Porter Thomas , Carpenter Loren
Published: November 2005

Ray tracing is one of the most elegant techniques in computer graphics. Many phenomena that are difficult or impossible with other techniques are simple with ray tracing, including shadows, reflections, and refracted light. Ray directions, however, have been determined precisely, and this has limited the capabilities of ray tracing. By distributing the directions of the rays according to the analytic function they sample, ray tracing can incorporate fuzzy phenomena. This provides correct and easy solutions to some previously unsolved or partially solved problems, including motion blur, depth of field, penumbras, translucency, and fuzzy reflections. Motion blur and depth of field calculations can be integrated with the visible surface calculations, avoiding the problems found in previous methods.
Ray tracing of Steiner patches
Authors: Sederberg Thomas W. , Anderson David C.
Published: November 2005

Steiner patches are triangular surface patches for which the Cartesian coordinates of points on the patch are defined parametrically by quadratic polynomial functions of two variables. It has recently been shown that it is possible to express a Steiner patch in an implicit equation which is a degree four polynomial in x,y,z. Furthermore, the parameters of a point known to be on the surface can be computed as rational polynomial functions of x,y,z. These findings lead to a straightforward algorithm for ray tracing Steiner patches in which the ray intersection equation is a degree four polynomial in the parameter of the ray. The algorithm presented represents a major simplification over existing techniques for ray tracing free-form surface patches.
Ray tracing volume densities
Authors: Kajiya James T. , Von Herzen Brian P
Published: November 2005

This paper presents new algorithms to trace objects represented by densities within a volume grid, e.g. clouds, fog, flames, dust, particle systems. We develop the light scattering equations, discuss previous methods of solution, and present a new approximate solution to the full three-dimensional radiative scattering problem suitable for use in computer graphics. Additionally we review dynamical models for clouds used to make an animated movie.
Shade trees
Authors: Cook Robert L.
Published: November 2005

Shading is an important part of computer imagery, but shaders have been based on fixed models to which all surfaces must conform. As computer imagery becomes more sophisticated, surfaces have more complex shading characteristics and thus require a less rigid shading model. This paper presents a flexible tree-structured shading model that can represent a wide range of shading characteristics. The model provides an easy means for specifying complex shading characteristics. It is also efficient because it can tailor the shading calculations to each type of surface
.
Compositing digital images
Authors: Porter Thomas , Duff Tom
Published: November 2005

Most computer graphics pictures have been computed all at once, so that the rendering program takes care of all computations relating to the overlap of objects. There are several applications, however, where elements must be rendered separately, relying on compositing techniques for the anti-aliased accumulation of the full image. This paper presents the case for four-channel pictures, demonstrating that a matte component can be computed similarly to the color channels. The paper discusses guidelines for the generation of elements and the arithmetic for their arbitrary compositing
.
The storage, retrieval and display of integrated graphics and text (Panel)
Authors: Earnshaw Rae A.
Published: November 2005

Methodologies, techniques and applications for the storage, retrieval and display of integrated graphics and text will be discussed. Current areas of interest include engineering drawings, CAD, publishing, graphics and databases, business graphics, office systems, cartography, typography and high quality text. This topic is at the leading edge of current developments and cost-effective applications will be examined.

Dr. Rae Earnshaw, Chairman of the BCS Displays Group, will outline current needs and objectives for integrating graphics and text in the context of information processing and display, and indicate progress towards the long term goal of “what you see is what you print”.
Near real-time shaded display of rigid objects
Authors: Fuchs Henry , Abram Gregory D. , Grant Eric D.
Published: November 2005

Described is a visible surface algorithm and an implementation that generates shaded display of objects with hundreds of polygons rapidly enough for interactive use — several images per second. The basic algorithm, introduced in [Fuchs, Kedem and Naylor, 1980], is designed to handle rigid objects and scenes by preprocessing the object data base to minimize visibility computation cost. The speed of the algorithm is further enhanced by its simplicity, which allows it to be implemented within the internal graphics processor of a general purpose raster system.
A scan-line hidden surface removal procedure for constructive solid geometry
Authors: Atherton Peter R
Published: November 2005

This paper presents a new methodology for resolving visible surface images of solid models derived from Boolean combinations of volumetric building blocks. The algorithm introduced here is an extension of well-established scan-line hidden surface removal procedures, and it integrates knowledge of a Boolean construction tree in the surface resolution process. Several hidden surface coherence properties are discussed in terms of their possible exploitation in the intricate solid model visualization process. While many of the earlier coherence techniques depend on a polygon environment in which surfaces and volumes do not intersect, the Boolean process can not afford that luxury because it is inherently required to handle intersecting volumes and surfaces. Initial tests indicate that substantial performance improvements over previous methods can be achieved with the algorithm described in this paper, and that these improvements increase as model complexity increases.

An underlying philosophy of a dual solid modeling system is proposed in this paper. It suggests that two solid modelers are necessary to successfully satisfy both analytical precision requirements and user interface visualization requirements. The visual solid modeling task addressed in this paper provides greatly improved response capabilities, as compared to other systems, by striving to optimize the constructive solid model (CSG) solid model computations specifically for display purposes.
New techniques for ray tracing procedurally defined objects
Authors: Kajiya James T.
Published: November 2005

We present new algorithms for efficient ray tracing of three procedurally defined objects: fractal surfaces, prisms, and surfaces of revolution. The fractal surface algorithm performs recursive subdivision adaptively. Subsurfaces which cannot intersect a given ray are culled from further consideration. The prism algorithm transforms the three dimensional ray-surface intersection problem into a two dimensional ray-curve intersection problem, which is solved by the method of strip trees. The surface of revolution algorithm transforms the three dimensional ray-surface intersection problem into a two dimensional curve-curve intersection problem, which again is solved by strip trees.
Edge Inference with Applications to Antialiasing
Authors: Bloomenthal Jules
Published: November 2005

An edge, when point-sampled for display by a raster device and not aligned with a display axis, appears as a stair-case.This common aliasing artifact often occurs in computer images generated by two- and three-dimensional algorithms. The precise edge information often is no longer available but, from the set of vertical and horizontal segments which form the staircase, an approximation to the original edge with a precision beyond that of the raster may be inferred. This constitutes a smoothing of the staircase edge.

Among other applications, the inferred edges may be used to reshade the pixels they intersect, thereby antialiasing the inferred edges. The antialiased inferred edges prove a more attractive approximation to the real edges than their aliased counterparts.

Presented here are algorithms for the detection and smoothing of edges and the filtering of an image in accordance with the inferred edges.
Geometric modelling and display primitives towards specialised hardware
Authors: Thomas A. L.
Published: November 2005

Work over the last ten years developing a simple geometric modelling scheme has led to the design of a high speed display processor capable of generating real time moving displays directly from a three dimensional model. The geometric model consists of a graph-matrix boundary representation linked to a boolean expression volume overlap representation. The architecture of the display processor is particularly suitable for implementation as a pipeline of VLSI components, and current work is exploring this possibility. A divide and conquer, quad tree algorithm applied to the boolean expression model allows the system to make use of scene coherence, and used with the hardware will make it possible to handle scenes of high complexity.
Graphics in overlapping bitmap layers
Authors: Pike Rob
Published: November 2005

One of the common uses of bitmap terminals is storing multiple programming contexts in multiple, possibly overlapping, areas of the screen called windows. Windows traditionally store the visible state of a programming environment, such as an editor or debugger, while the user works with some other program. This model of interaction is attractive for one-process systems, but to make full use of a multiprogramming environment, windows must be asynchronously updated, even when partially or wholly obscured by other windows. For example, a long compilation may run in one window, displaying messages as appropriate, while the user edits a file in another window.

This paper describes a set of low-level graphics primitives to manipulate overlapping asynchronous windows, called
layers,
on a bitmap display terminal. Unlike previous window software, these primitives extend the domain of the general bitmap operator
bitblt
to include bitmaps that are partially or wholly obscured.
Modeling motion blur in computer-generated images
Authors: Potmesil Michael , Chakravarty Indranil
Published: November 2005

This paper describes a procedure for modeling motion blur in computer-generated images. Motion blur in photography or cinematography is caused by the motion of objects during the finite exposure time the camera shutter remains open to record the image on film. In computer graphics, the simulation of motion blur is useful both in animated sequences where the blurring tends to remove temporal aliasing effects and in static images where it portrays the illusion of speed or movement among the objects in the scene.

The camera model developed for simulating motion blur is described in terms of a generalized image-formation equation. This equation describes the relationship between the object and corresponding image points in terms of the optical system-transfer function. The use of the optical system-transfer function simplifies the description of time-dependent variations of object motion that may occur during the exposure time of a camera. This approach allows us to characterize the motion of objects by a set of system-transfer functions which are derived from the path and velocity of objects in the scene and the exposure time of a camera.
A general purpose graphic system for computer aided design
Authors: Uno Sakae , Matsuka Hideo
Published: November 2005

The experimental Advanced Integrated Designer's Activity Support (A-IDAS) system is intended to be a base for a total engineering system rather than a pure graphic system. The system provides a database in which graphic data, geometric data and engineering data are stored in a relational data model. It also provides a graphic management facility which can manipulate not only pictures drawn with lines, but those drawn as areas. Areas are represented by crosshatched lines or colors. In more complicated ways, they can be represented as texture or scenery. The system controls two kinds of graphic display devices: a vector display and a raster display. These devices are supported through a device independent user interface when pictures are drawn with lines. With this experimental system, it has been found out that one can develop an engineering system having fairly general purpose capabilities.
Some principles for the effective display of data
Authors: Morse Alan
Published: November 2005

Since computers can produce output at a high rate, it is often useful for it to put that output in a form that facilitates human analysis. There has been much research on the human factors of displays; from this research, we can evolve principles to guide the effective display of computer output. The two main principles described here are the principle of proportional effect, which guides the encoding of a datum's identity and value, and the principle of least effort, which minimizes the effort needs to scan, and perceive and interpret the display. Some of these ideas are illustrated using data generated by a neural simulation.
The Number Wheel
Authors: Thornton Robert W.
Published: November 2005

A logical valuator device which provides interactive graphical input of numeric values is presented. This device, called the
Number Wheel,
was developed for interactive control of highly dynamic three-dimensional displays but is not limited to this use: It is a general purpose valuator device. The implementation of the Number Wheel described here is based upon a digitizer tablet as the physical input device.

The character of the Number Wheel is best explained by developing an analogy with a hypothetical physical device. The Number Wheel can be thought of as a wheel which has a portion of its circumference, or tread, protruding through a slot on the surface of the tablet, somewhat like a giant thumb wheel. Each value in the desired range of the valuator is represented by a point on the circumference of the wheel with the value of the device at any given time being the point at the top of the wheel. The valuator is changed by putting the pen on the wheel where it protrudes through the tablet and moving it back or forth in the direction of rotation. Whenever the pen leaves the rim of the wheel while still moving, the Number Wheel maintains the same speed of rotation until the pen returns to the wheel in order to change or stop its movement.
An algorithm for shading of regions on vector display devices
Authors: Brassel Kurt E. , Fegeas Robin
Published: November 2005

The display of shaded polygons by line, cross-hatch, and dot patterns on vector devices is a task frequently used in computer graphics and computer cartography. In applications such as the production of shaded maps polygon shading turns out to be critical with respect to time requirements, and the development of efficient algorithms is of importance.

Given an arbitrary polygon in the plane without self-crossing edges (simply-connected polygon), the task at hand is to shade this polygon with one or two sets of parallel lines where for each set a shading angle and a line distance are given. The basic concept of this new algorithm is to decompose the polygon into a set of mutually exclusive trapezoids (in special cases triangles) where the parallel edges of the trapezoids are parallel to the desired shading lines. These trapezoids and triangles are then shaded in a fast procedure. In its present form the algorithm handles regions with up to 300 islands. Possible extensions include the construction of dash and cross patterns.
A fast scan-line algorithm for rendering parametric surfaces
Authors: Clark James H.
Published: November 2005

An algorithm for rendering shaded pictures of parametric curved surfaces is presented. The algorithm recursively subdivides each surface element on the basis of its screen-space parametric curvature until it is sufficiently close to bilinear to be scan-converted by conventional polygon rendering techniques. The mathematical basis chosen to carry out the subdivision process yields the curvature criterion as a coefficient so that the tests for termination of the subdivision process are extremely simple. In addition, a surface is subdivided only in the parametric direction in which its curvature deviates from the tolerance. The algorithm incorporates a very simple solution to the problem of separations between sibling subpatches.
Movies from music
Authors: Mitroo J. B. , Herman Nancy , Badler Norman I.
Published: November 2005

A theory of music visualization proposed by Nancy Herman postulates an association between colors and pitches of musical scales. A color raster graphics display is used to generate images of notes, chords, and chord progressions based on this theory. Temporal adjacency of notes or chords is mapped to spatial adjacency of colors, usually in a concentric pattern of squares or circles. By varying certain image parameters, different “brush stroke” effects may be obtained. Illustrations of several computer generated “musical paintings” are included, along with some original paintings for comparison.
Special session on effective information presentation techniques
Authors: Kurlansky Mervyn , Marcus Susan , Reineck Jack , Reineck Gay , Marcus Aaron
Published: November 2005

Are computer graphics displays as effective as they should be? Are they as appealing as they could be? How can displays of information acquire more impact? How can they be made more memorable. Questions like these are being asked frequently in the computer graphics community.

Because of advanced display equipment, lower costs, effective communication networks, and increasingly sophisticated user groups, computer graphics is entering a new stage in its development. Visualized information will reach more people in this decade than ever before. Computer graphics displays will become centrally involved with concept formation and decision making on a mass scale. For this reason computer graphics systems should incorporate more successfully the knowledge of visual communication professionals who have developed valid, effective principles for conveying facts and concepts through typography, color, symbols, motion, photography, etc.
Atlas supplement to the 1972 County and City Data Book
Authors: Tedrow Lucky M. , Hoerauf Eugene A.
Published: November 2005

A series of maps presenting the spatial distribution of the tabular data from the
1972 County and City Data Book
is discussed. Using an automated mapping procedure developed on a minicomputer by two non-computer scientists, 196 choropleth maps of county-level data for the State of Washington were prepared. The maps provide governmental decision-makers and planners a means to quickly comprehend patterns in the data that are not readily noticeable in the tabular presentation of the data.
Integrating solid image capability into a general purpose calligraphic graphics package
Authors: Laib G. , Puk R. , Stowell G.
Published: November 2005

Raster scanned graphics terminals provide several features not found in standard line drawing displays. Among them are area fill and an extensive color palette. Hardware support for such functions is becoming cost effective and available in a variety of forms. What is now needed is high level, device independent software that assists in the generation of and interaction with these terminals. To accomplish this, a project has been undertaken jointly by Sandia Laboratories, Purdue University, and MEGATEK Corporation to integrate solid image capabilities into the Graphics Compatibility System, GCS. GCS is a widely used, general purpose calligraphic graphics package. Due to the similarity of the GCS model to that of the GSPC Core System, GCS provides a timely test bed for solid image extensions to a line drawing package. This paper will summarize the capabilities being implemented, the method and motivation behind each function, and suggestions for further work.

The heart of the extensions is a hidden surface algorithm similar to Myers' approach which combines the simplicity of a Z buffer with the efficiency of a Watkin's algorithm. Facilities will be provided for hidden line removal as well as hidden surface processing in order to satisfy the basic GCS design goal of device independence. In this way, random vector terminals as well as raster devices will benefit.

If a user does not require hidden object processing then very little additional overhead will remain in those routines which have been called. Hidden surface processing may also be intermixed with wire frame drawings and text.

Two remaining issues are the user interface for 3D object definition and the specification of lighting models. Since the Myers algorithm requires N sided polygons as input, a basic call has been provided for such definitions. Higher level constructs, called “shells” and “faces”, which facilitate creation of complex 3D bodies, have been implemented.

The specification of lighting models is an area of considerable debate. It has been concluded that a choice of a few common models will be made available to the user. These include interpolated and noninterpolated shading (smooth and flat). Objects may be color-shaded or black-and-white. A hook is provided for user definition of more exotic lighting models.
On visible surface generation by a priori tree structures
Authors: Fuchs Henry , Kedem Zvi M. , Naylor Bruce F.
Published: November 2005

This paper describes a new algorithm for solving the hidden surface (or line) problem, to more rapidly generate realistic images of 3-D scenes composed of polygons, and presents the development of theoretical foundations in the area as well as additional related algorithms. As in many applications the environment to be displayed consists of polygons many of whose relative geometric relations are static, we attempt to capitalize on this by preprocessing the environment's database so as to decrease the run-time computations required to generate a scene. This preprocessing is based on generating a “binary space partitioning” tree whose in order traversal of visibility priority at run-time will produce a linear order, dependent upon the viewing position, on (parts of) the polygons, which can then be used to easily solve the hidden surface problem. In the application where the entire environment is static with only the viewing-position changing, as is common in simulation, the results presented will be sufficient to solve completely the hidden surface problem.
Color graphics for remote teaching
Authors: Hankley William , Wallentine Virgil
Published: November 2005

A system for preparation and manipulation of color graphics video frames is described. The system commands are designed for use by a class instructor (who is not a computer science person) in preparation and delivery of lectures to a remote site. The system can provide the types of images, overlays, and coloring that could be drawn using transparency sheets and color pens, or that could prepared as 35 mm technical slides (not photographs, but text and diagrams). The hardware consists of standardly available input, display, and output components. Several hardware alternatives are noted so that cost and capability tradeoffs can be compared. Communication between the instructor's site and the remote class site uses standard telephone lines for transmission of participants' voices and for digital graphics commands and compressed image data. The system software is yet in experimental form. It is in BASIC, but in modular form. While none of the individual components or graphics concepts in this system is in itself dramatically new, the integrated system demonstrates an important advancement in state-of-the-art for remote instruction.
Computer graphics in television (Panel Session)
Authors: Klimek Tom , Evans Larry , Black Peter , Bley H. , Weise D. , Shoup Richard
Published: November 2005

Our society is increasingly relying on symbolic and imaginal communication to augment written and spoken language (advertising graphics, logos and corporate I.D.s, satellite weather maps, international traffic, dashboard symbols, etc.). Nowhere are graphics and sophisticated imagery being more widely and innovatively used than in television production. Greater availability of computer graphics and a strong trend in television technology towards digital electronics makes this an application of high synergy and potential.

The purpose of this panel is to bring together several top system designers and leading graphic designers in television to exchange points of view about this exciting application area. Panelists will show and discuss recent on-air uses of electronic graphics and will exchange ideas about what is needed, possible, important, and useful for the future.
The user's view of CAD/CAM (Panel Session)
Authors: Thompson Myrl , Harris D. H. W. , Wilson R. , Crowley B. , Boyd C. , Wozny M. , Anderson Ken
Published: November 2005

“The User's View of CAD/CAM” will share the experience gained in over 50 man-years of day-to-day use of CAD/CAM systems. Six industry segments are represented in this presentation. In addition, a wide range of systems costing under $50,000 to over $1,000,000 will be discussed.

There is good news and bad news. All panelists admit to improved productivity and/or reduced design cycle time, but all is not free. You will hear about what it takes to operate and support CAD/CAM systems. Subjects include facilities planning, cost effectiveness, training, internal support requirements, and more. Here is your chance to hear practical and common sense comments about what CAD/CAM can and cannot do for you.
“Put-that-there”
Authors: Bolt Richard A.
Published: November 2005

Recent technological advances in connected-speech recognition and position sensing in space have encouraged the notion that voice and gesture inputs at the graphics interface can converge to provide a concerted, natural user modality.

The work described herein involves the user commanding simple shapes about a large-screen graphics display surface. Because voice can be augmented with simultaneous pointing, the free usage of pronouns becomes possible, with a corresponding gain in naturalness and economy of expression. Conversely, gesture aided by voice gains precision in its power to reference.
Prototyping and simulation tools for user/computer dialogue design
Authors: Hanau Paul R. , Lenorovitz David R.
Published: November 2005

The design and development of user interfaces to interactive computer systems is enhanced by permitting designers to easily express their design concepts in concrete, comprehensive, and comprehensible working models.

A set of prototyping and simulation tools has been developed to be used as an integral part of the specification and design process. These include an interactive display building utility and a syntax-driven interactive dialogue controller. The display builder is used to develop initial conceptual snapshots of system display appearance at selected points in the user/system dialogue. The dialogue controller interprets a grammatical description of input tools and system logic, using predrawn and dynamically constructed displays to simulate the external appearance of the desired end system.
3-D transformations of images in scanline order
Authors: Catmull Ed , Smith Alvy Ray
Published: November 2005

Currerntly texture mapping onto projections of 3-D surfaces is time consuming and subject to considerable aliasing errors. Usually the procedure is to perform some inverse mapping from the area of the pixel onto the surface texture. It is difficult to do this correctly. There is an alternate approach where the texture surface is transformed as a 2-D image until it conforms to a projection of a polygon placed arbitrarily in 3-space. The great advantage of this approach is that the 2-D transformation can be decomposed into two simple transforms, one in horizontal and the other in vertical scanline order. horizontal scanline order, Sophisticated light calculation is also time consuming and difficult to calculate correctly on projected polygons. Instead of calculating the lighting based on the position of the polygon, lights, and eye, the lights and eye can be transformed to a corresponding position for a unit square which we can consider to be a canonical polygon. After this canonical polygon is correctly textured and shaded it can be easily conformed to the projection of the 3-D surface.
Filling regions in binary raster images
Authors: Shani Uri
Published: November 2005

Filling regions in raster images is the term given to the problem of extracting a connected region (that contains some preselected
seed
pixel) and filling it with some
color
. A connected region is formally defined as the collection of all pixels that are in the transitive closure of a pixel-connectivity operator that is applied to the seed. For example, the 4-pixel-connectivity operator selects all pixels that are (spatially) 4-connected to the pixel operand, and have the same color. This problem can be solved relatively easily if the fill color is distinguishable so that every pixel, once colored (i.e. flagged OLD) will not be considered again. In binary images, the fill “color” is usually a binary pattern and therefore, a “colored” pixel may still have its previous (e.g., black or white) color. This fact makes the problem non-trivial.

In this paper, a region to be filled is represented as a connected directed a-cyclic planar graph in which nodes are
regular regions
(defined below) that are easy to handle. An arc connects a regular region to its neighbor below which shares a common horizontal sub-boundary. Based on this abstract representation of a region, a formulation of the filling problem is developed as a variant of graph traversing. The difficulties imposed by filling with a binary pattern, and the avoidance of an explicit description of the graph are explored and a solution is presented. This solution utilizes the frame buffer (that is used to display the image) for improved efficiency of a graph traversal algorithm.

This method turns out to be similar to [Lieberman-78], that is shown here to be incorrect. The complexity of the new algorithm is 0(N*L+ N*Log N), compared to 0(N*L*Log N) there, where N is the number of nodes in the graph and L is the average composite degree of each node. A proof of correctness for the new algorithm is given too.
A scan line algorithm for computer display of curved surfaces
Authors: Whitted Turner
Published: November 2005

The conventional procedure for generating shaded images of curved surfaces is to approximate each surface element by a mosaic of polygons and to then apply one of several established polygon display algorithms. The method described here extends these polygon based techniques to produce an excellent approximation of bi-cubic parametric surfaces in scan line order.

Each surface patch is described in terms of cubic edge curves, including parametric curves on the interior of the patch as well as the patch boundaries. Specifying interior edges has the effect of subdividing the patch and generally results in a more accurate image. The silhouette, approximated by a piecewise cubic interpolant, further divides the patch into front facing and rear facing portions.

The edge curves are intersected by successive scanning planes to form the endpoints of scan line segments. Depth and surface normal are linearly interpolated between the endpoint values. Visibility is calculated for each segment by a hybrid priority/z-buffer scheme. Shading is computed using Phong's illumination model with the interpolated surface normal.

The algorithm is currently used for display of B-spline surfaces as part of an experimental display processor.
3-D graphic display of discrete spatial data by prism maps
Authors: Franklin Randolph , Lewis Harry R.
Published: November 2005

An efficient algorithm for displaying 3-D scenes showing a discrete spatially varying surface is described. Given a 2-D map or planar graph composed of polygons where each polygon has a positive real number attribute, a prism is erected on each polygon with height proportional to that attribute. The resulting 3-D scene is plotted with shading and hidden lines removed. Thus the spatial variation of the attribute may be quickly and intuitively grasped by the nontechnical observer. This has applications to areas such as geography if the map is a cartographic map, or to physics if the map diagrams the periodic table. The algorithm takes time O(N*log(N)) where N is the number of edges in the map. Most of the calculations can be done without knowing the prism heights so extra plots with different attributes for the prisms can be produced quickly. This algorithm has been implemented and tested on maps of up to 12000 edges.
A fast and economic scan-to-line-conversion algorithm
Authors: Woetzel Gerd
Published: November 2005

In order to generate cartographic data bases, it is necessary to digitize a large number of existing base maps. One way of replacing the error-prone and very time-consuming manual digitization by an automatic method is scanning the map and extracting the linework from the resulting binary matrix. A sufficiently fast and economic scan-to-line-conversion algorithm has to be developed for the line extraction.

The algorithm presented operates with a skeletonization technique which is further developed from known line thinning methods, so that the scan lines are now skeletonized in a single pass and that only a small number of scan lines has to be held in core storage. The result of this process is equivalent to a multi-pass skeletonization which utilizes a quasi-parallel line thinning in four partitions of the binary matrix for each pass.

The data produced by the extraction algorithm following the skeletonization have two important advantages over data produced by manual digitization: First, the nodes corresponding to the line end points are exactly determined and, second, the correction phase is shortened since the automatic process is less error-prone.

Time and storage requirements of the implemented algorithm applied to some typical scan data show that the conversion for even a complex line structure can be carried out within the time of scanning and the economic use of core storage makes it possible to implement the algorithm on a minicomputer with an on-line scanner.
Hidden line removal for vector graphics
Authors: Wein M. , Tanner P. , Bechthold G. , Burtnyk N.
Published: November 2005

A system for removing hidden edges in line displays of three dimensional scenes is described. The hardware system is relatively low cost, and operates on several hundred vectors in real-time. The system consists of a graphics peripheral connected to a PDP 11/55 computer and a software package to drive the peripheral.

As each convex object is displayed, the occlusion hardware extracts the silhouette and retains it in a one-plane “matte memory”. As subsequent objects, taken from a priority ordered list, are displayed, the vector generator tests the contents of the frame buffer at the coordinates along the vector. The contents of the matte memory determine which portions of the vector should be intensified.

To produce the priority ordered list of objects, the software algorithm uses three ordering techniques applied selectively to different potions of the scene. One technique, used for ordering unconstrained pairs of objects is described in detail.
Comparing figures by regression
Authors: Tobler W. R.
Published: November 2005

A procedure is described to obtain an empirical transformation regressing an independent plane configuration against a similar dependent configuration. As implemented the procedure constructs the mapping by estimating two bivariate tables, with arguments on a square lattice interpolated from the irregularly arranged original observations. The tables are constructed so that the transformation has smooth derivatives and so as to agree, as nearly as possible, with the empirical data. The curvilinear regression coefficients are represented a spatially varying, but coordinate invariant, second order tensor field. Bidimensional regression can automatically be illustrated by a warped coordinate grid, by comparison of the original configuration and the regression estimate, by a field of displacement vectors, by a diagram of the principal strains, and by a contour map. Intermediate configurations and extrapolations are also available.
Computer generated images for medical applications
Authors: Sunguroff Alexander , Greenberg Donald
Published: November 2005

Two computer graphics systems for the presentation of biomedical information for diagnosis and treatment planning are described. Both systems presented utilize computer tomographic (CT) data as input. One of the systems produces three-dimensional surface representations of organs and anatomical features found within the body. The other system is a radiation treatment planning aid which uses tomographic data in its computations.
Interaction with a color computer graphics system for archaeological sites
Authors: Badler Norman I. , Badler Virginia R.
Published: November 2005

Our goal was to design and implement an interactive system using a color video display to assist an archaeologist in the task of analyzing the spatial distribution of various objects from an excavated site. The existing system configuration required controlling the display over a slow communications line from the mainframe CPU, and there was little local intelligence in the minicomputer display driver. The user of the system was expected to be computer-naive. Certain design principals evolved which should be applicable to graphical database query systems in other domains.
Characterizing non-ideal shapes in terms of dimensions and tolerances
Authors: Hillyard R. C. , Braid I. C.
Published: November 2005

A geometric model of a shape is extended so as to represent not only its nominal dimensions but also tolerance information and surface specifications. The data structure defining an object is visualised as a pin-jointed, infinitely elastic wire frame covered by elastic membranes. Constraints corresponding to the dimensions of technical drawings are applied to the structure, either by the designer or by an automatic dimensioning algorithm. The validity of the resultant scheme can be checked and then drawn using drawing office conventions. The data structure can handle dimensions fixing various types of curved surface; other types can easily be added by following the same rules. A method of changing the nominal shape of an object is demonstrated. These results provide a systematic account of the ill-defined art of dimensioning and tolerancing, and should make the draughting process more amenable to computation.
A microprocessor-assisted graphics system
Authors: Hamlin Griffith , Crockett Thomas
Published: November 2005

GRAF80 is a small scale graphics system designed to demonstrate some of the capabilities offered by microprocessor-assisted graphics. As such, it employs both hardware and software techniques. The system implements in a microprocessor a subset of the features of the SIGGRAPH-ACM CORE (1) graphics package, including picture segmentation and a subset of the output primitives and primitive attributes.