bluuebunny/crossref_metadata_2025 huggingface dataset:
PIKS and BIIF explored
Authors: Carson George S. , Pratt William K.
Published: November 2005

This issue's column is an introduction to the Image Processing and Interchange standards (ISO/IEC 12087) developed by ISO/IEC JTC I/ SC 24 (Computer Graphics and Image Processing.). First, Bill Pratt of PixelSoft, the Editor of the Programmer's Imaging Kernel System (PIKS) International Standard (ISO/IEC 12087-1:1995), describes PIKS and how it can be applied. Next, I describe the Basic Image Interchange Format (BIIF), ISO/IEC 12087-1:1998, and its applications.
CGW founder shares his experiences
Authors: Stickrod Randall , Machover Carl
Published: November 2005

One of the intentions of this column is to let you share the experiences of some of the computer graphics Pioneers. This month, we are most fortunate to present the following column from a friend --- and one of our industry's "movers and shakers" --- Randy Stickrod, whom many of you will recognize from his days at
Computer Graphics World
magazine
(CGW).
Enjoy!
SIGGRAPH 98 activities and ACM/Policy 98 wrap-up
Authors: Ellis Bob
Published: November 2005

This column provides a summary of our public policy activities at the SIGGRAPH 98 conference as well as a wrap-up of the ACM/Policy 98 Conference. See also
http://www.siggraph.org/othercom/pubpolicy.html.
Anisotropic reflection models
Authors: Kajiya James T.
Published: November 2005

We present a new set of lighting models derived from the questions of electromagnetism. These models describe the reflection and refraction of light from surfaces which exhibit anisotropy---surfaces with preferred directions. The model allows a new mapping technique, which we call
frame mapping
. We also discuss the general relationship between geometric models, surface mapping of all types, and lighting models in the context of rendering images with extreme complexity.
Efficient alias-free rendering using bit-masks and look-up tables
Authors: Abram Greg , Westover Lee
Published: November 2005

We demonstrate an efficient method of rendering alias-free synthetic images using precomputed convolution integrals. The method is based on the observation that a
visible polygon fragment's contribution
to an
image is
solely a function of its position and shape, and that within a reasonable level of accuracy, a limited number of shapes represent the majority of cases encountered in
images commonly rendered
.The convolution integral is precomputed for all pixels affected by the polygon fragment and is stored in a table. Completely visible fragments which are either triangular or trapezoidal produce two indices into the table. Most other fragments which are represented as differences of simple fragments. The remaining cases are characterized by a bit-mask for which each bit has a corresponding set of look up tables.The basic technique has been applied to several fundamentally different rendering algorithms. In addition, we illustrate a version of the newly introduced nonuniform sampling technique implemented in the same program, but with different table values.
Integrated analytic spatial and temporal anti-aliasing for polyhedra in 4-space
Authors: Grant Charles W.
Published: November 2005

A visible surface algorithm with integrated analytic spatial and temporal anti-aliasing is presented. This algorithm models moving polygons as four dimensional (X,Y,Z,T) image space polyhedra, where time (T) is treated as an additional spatial dimension. The linearity of these primitives allows simplification of the analytic algorithms. The algorithm is exact for non-intersecting primitives, and exact for the class of intersecting primitives generated by translation and scaling of 3-d (X,Y,Z) polygons in image space. This algorithm is an extension of Catmull's analytic visible surface algorithm for independent pixel processing, based on the outline of integrated spatial and temporal anti-aliasing given by Korien and Badler. An analytic solution requires that the visible surface calculations produce a continuous representation of visible primitives in the time and space dimensions. Visible surface algorithm, graphical primitives, and filtering algorithm, (by Feibush, Levoy and Cook) are extended to include continuous representation of the additional dimension of time. A performance analysis of the algorithm contrasted with a non-temporally anti-aliased version is given.
There's more to menu systems than meets the screen
Authors: Lieberman Henry
Published: November 2005

Love playing with those fancy menu-based graphical user interfaces, but afraid to program one yourself for your own application? Do windows seem opaque to you? Are you scared of mice? Like what-you-see-is-what-you-get but don't know how to get what you want to see on the screen?Everyone agrees using systems like graphical document illustrators, circuit designers, and iconic file systems is fun, but programming user interfaces for these systems isn't as much fun as it should be. Systems like the Lisp Machines, Xerox D-Machines, and Apple Macintosh provide powerful graphics primitives, but the casual applications designer is often stymied by the difficulty of mastering the details of window specification, multiple processes, interpreting mouse input, etc.This paper presents a kit called
EZWin
, which provides many services common to implementing a wide variety of interfaces, described as generalized
editors for sets of graphical objects
. An individual application is programmed simply by creating objects to represent the interface itself, each kind of graphical object, and each command. A unique interaction style is established which is insensitive to whether commands are chosen before or after their arguments. The system
anticipates
the types of arguments needed by commands, preventing selection mistakes which are a common source of frustrating errors. Displayed objects are made "mouse-sensitive" only if selection of the object is appropriate in the current context. The implementation of a graphical interface for a computer network simulation is described to illustrate how EZWin works.
Modeling the mighty maple
Authors: Bloomenthal Jules
Published: November 2005

A method is presented for representing botanical trees, given three-dimensional points and connections. Limbs are modeled as generalized cylinders whose axes are space curves that interpolate the points. A free-form surface connects branching limbs. "Blobby" techniques are used to model the tree trunk as a series of non-circular cross sections. Bark is simulated with a bump map digitized from real world bark; leaves are textures mapped onto simple surfaces.
How real-time technology can improve the quality of life
Authors: Wiederhold Brenda K. , Wiederhold Mark D. , Fraser Glen , Fisher Scott S. , Oyama Hiroshi , Katsumata Noriyuki , Ohsuga Meiko , Tatsuno Yoko
Published: November 2005

In the February issue, we looked at an application of interactive real-time graphics systems for entertainment. Previous columns have dealt with interactive gaming, simulation and other areas. In this column, we present two articles about ways in which the same kind of real-time technology can be applied with the goal of improving quality of life."How's your health?"There is no doubt that physical and mental health help from a foundation on which to build a happy, satisfying life. People who suffer from phobias or other "anxiety disorders" are often painfully aware of the impact these can have on their happiness and their lives. For some, activities which most of us don't think twice about --- like driving a car to work or being flown to a favorite vacation spot --- can be seemingly insurmountable obstacles to personal fulfillment. Could it be that computer technology can help people surmount some of these fears? In our first article, Mark and Brenda Wiederhold --- both medical professionals from southern California --- give us a look at some of the work being done in this area.Sometimes, mental stress, fatigue and depression are caused by physical pain. Cancer patients frequently suffer excessive pain and this only adds to the psychological trauma of the whole experience. In Japan, Dr. Hiroshi Oyama and others at the National Cancer Center Hospital and the Mitsubishi Electric Corporation are working to help relieve some of this stress. They are developing a "wellness system" to try to ease some of the anxiety and stress that cancer patients experience, by allowing them to virtually experience a natural environment, from the convenience of their bedside. Our second article describes this ongoing effort, and some of their initial findings.A reminder --- we are very interested in hearing from our readers. In particular, if you are involved in a new (real-time, interactive) application, or have a related topic that you think might be interesting to share with the SIGGRAPH membership through our column, please let us know. Also, if you have feedback to offer on current or past columns, we would be more than glad to hear it!
Smashing images—a review
Authors: West Thomas G.
Published: November 2005

"In the eighth century, a sect arose from within the ranks of its highly literate clergy that so despised images that its members declared an all-out war against statues and paintings…. At first, they sought out only religious images to smash. Church mosaics, painted icons, and stained-glass artistry fell to their savage assaults. Later their targets also included painters, sculptors and craftsmen. They even murdered those whose crime it was to love art. Monks who resisted were blinded and had their tongues torn out. The iconoclasts beheaded the Patriach of the Eastern Chruch in 767 for refusing to support their cause."The iconoclast movement never spread to illiterate Western Europe; its madness consumed only the segment of Christendom that boasted the highest literacy rate. Artists fled for their lives from Byzantium, heading for the western court of Charlemagne whose largely illiterate courtiers welcomed them with open arms" (pp. 275-276) [1].
Annual report shows high activity
Authors: Lang Scott
Published: November 2005

Every year, each Director on the SIGGRAPH Executive Committee compiles an annual report for the annual SIGGRAPH organization report. To keep the overall report from becoming a book, the SIGGRAPH Chair must pick highlights from each area. This issue's
Computer Graphics
column contains my full annual report as presented to the SIGGRAPH Executive Committee I hope that it helps to give you a better understanding of the structure of the Professional Chapters, the events we sponsor at the annual conference and what it is we do over the course of a typical year. Please keep in mind that this report is for the 1998-99 year so some information dates back to SIGGRAPH 98. As always, if you have any questions or comments, feel free to email me at
lang@siggraph.org.
Visual modeling for computer animation
Authors: Terzopoulos Demetri
Published: November 2005

Over the past decade, the Visual Modeling Research Program at the University of Toronto has consistently championed the concerted exploration of computer graphics and computer vision. Our premise has been this: graphics, the forward/synthesis/models-to-images problem, and vision, the inverse/analysis/images-to-models problem, pose mutually converse challenges, which may best be tackled synergistically through the development of advanced modeling techniques catering to the needs of both fields. With illustrated case studies of three projects spanning a twelve-year period, this brief article presents a personal retrospective on image-based modeling for computer animation. As we shall see, one of the projects has also created opportunities for computer animation to contribute to the study of visual perception in living systems.I shall begin by reviewing an early computer animation project that pioneered the use of image-based modeling to combine natural and synthetic imagery. The animation
Cooking with Kurt,
produced in 1987 at the Schlumberger Palo Alto Research center, introduced a paradigm in which computer vision was applied to acquire 3D models of objects from their images. The acquired models were then dynamically animated in a simulated physical scene reconstructed from the image of a real scene. The approach demonstrated a promising alternative to the established convention of keyframe animating manually constructed geometric models.The human face is a natural objective for the image-based modeling approach. I will next describe a facial animation project that uses specialized imaging devices to capture models of human heads with functional, biomechanically simulated faces conforming closely to human subjects. Facial animation is by no means the sole benefactor of an exciting area of advanced graphics modeling that lies at the intersection of virtual reality and artificial life [6]. Accordingly, I will also describe a virtual "seaquarium" populated by artificial marine animals whose 3D shapes and appearances were captured from images of real fishes. As I discuss in the final section, lifelike, self-animating creatures now serve as biomimetic autonomous agents in the study of animal perception.
Generating antialiased images at low sampling densities
Authors: Mitchell Don P.
Published: November 2005

Ray tracing produces point samples of an image from a 3-D model. Constructing an antialiased digital picture from point samples is difficult without resorting to extremely high sampling densities. This paper describes a program that focuses on that problem. While it is impossible to eliminate aliasing totally, it has been shown that nonuniform sampling yields aliasing that is less conspicuous to the observer. An algorithm is presented for fast generation of nonuniform sampling patterns that are optimal in some sense. Some regions of an image may require extra sampling to avoid strong aliasing. Deciding where to do extra sampling can be guided by knowledge of how the eye perceives noise as a function of contrast and color. Finally, to generate the digital picture, the image must be reconstructed from the samples and resampled at the display pixel rate. The nonuniformity of the samples complicates this process, and a new nonuniform reconstruction filter is presented which solves this problem efficiently.
Discrete Beta-splines
Authors: Joe Barry
Published: November 2005

Goodman (1985) and Joe (1986) have given explicit formulas for (cubic) Beta-splines on uniform knot sequences with varying ß1 and ß2 values at the knots, and nonuniform knot sequences with varying ß2 values at the knots, respectively. The advantage of the latter formula is that it can also be used for knot sequences with multiple knots. Discrete Beta-splines arise when a Beta-spline curve is subdivided, i.e. the knot sequence is refined so that the curve is expressed in terms of a larger number of control vertices and Beta-splines. We prove that discrete Beta-splines satisfy the same properties as discrete B-splines, and present an algorithm for computing discrete Beta-splines and the new control vertices using the explicit formula of Joe (1986).
Controlling dynamic simulation with kinematic constraints
Authors: Isaacs Paul M. , Cohen Michael F.
Published: November 2005

Theoretical and numerical aspects of the implementation of a DYNAmic MOtion system, dubbed DYNAMO, for the dynamic simulation of linked figures is presented. The system introduces three means for achieving, control of the resulting motion which have not been present in previous dynamic simulation systems for computer animation. (1) "Kinematic constraints" permit traditional keyframe animation systems to be embedded within a dynamic analysis. Joint limit constraints are also handled correctly through kinematic constraints. (2) "Behavior functions" relate the momentary state of the dynamic system to desired forces and accelerations within the figure. (3) "Inverse dynamics" provides a means of determining the forces required to perform a specified motion.The combination of kinematic and dynamic specifications allows the animator to think about each part of the animation in the way that is most suitable for the task. Successful experimental results are presented which demonstate the ability to provide control without disrupting the dynamic integrity of the resulting motion.
An efficient new algorithm for 2-D line clipping: Its development and analysis
Authors: Nicholl Tina M. , Lee D. T. , Nicholl Robin A.
Published: November 2005

This paper describes a new alorithm for clipping a line in two dimensions against a rectangular window. This algorithm avoids computation of intersection points which are not endpoints of the output line segment. The performance of this algorithm is shown to be consistently better than existing algorithms, including the Cohen-Sutherland and Liang-Barsky algorithms. This performance comparison is machine-independent, based on an analysis of the number of arithmetic operations and comparisons required by the different algorithms. We first present the algorithm using procedures which perform geometric transformations to exploit symmetry properties and then show how program transformation techniques may be used to eliminate the extra statements involved in performing geometric transformations.
A two-pass solution to the rendering equation: A synthesis of ray tracing and radiosity methods
Authors: Wallace John R. , Cohen Michael F. , Greenberg Donald P.
Published: November 2005

View-independent and view-dependent image synthesis techniques, represented by radiosity and ray tracing, respectively, are discussed. View-dependent techniques are found to have advantages for calculating the specular component of illumination and view-independent techniques for the diffuse component. Based on these observations a methodology is presented for simulating global illumination within complex environments using a two-pass approach. The first pass is view-independent and is based on the hemi-cube radiosity algorithm, with extensions to include the effects of diffuse transmission, and specular to diffuse reflection and transmission. The second pass is view-dependent and is based on an alternative to distributed ray tracing in which a z-buffer algorithm is used to sample the intensities contributing to the specularly reflected or transmitted intensity.
SIGGRAPH public policy committee activity detailed
Authors: Nelson David , Ellis Bob , Reinhart Laurie
Published: November 2005

We start this column with the results of our third on-line opinion survey on public policy issues affecting computer graphics. Next we provide an introduction to and a copy of the definition paper for a prospective study of computer graphics research to be conducted by the National Research Council with partial funding from SIGGRAPH. This is followed by an update on our activities in proposing a course on public policy and a panel on digital rights management of intellectual property for SIGGRAPH 2001. Myles Losch provides an update on the issues related to the slow pace of adoption of Digital TV. Finally, we close with another set of comments from a reader.
A rendering algorithm for visualizing 3D scalar fields
Authors: Sabella Paolo
Published: November 2005

This paper presents a ray tracing algorithm for rendering 3D scalar fields. An illumination model is developed in which the field is characterized as a varying density emittter with a single level of scattering. This model is equivalent to a particle system in which the particles are sufficiently small. Along each ray cast from the eye, the field is expressed as a function of the ray parameter. The algorithm computes properties of the field along the ray such as the attenuated intensity, the peak density, and the center of gravity, etc., These are mapped into HSV color space to produce an image for visualization.Images produced in this manner are perceived as a varying density 'cloud' where color highlights the computed attributes. The application of this technique is demonstrated for visualizing a three dimensional seismic data set.
A ray tracing solution for diffuse interreflection
Authors: Ward Gregory J. , Rubinstein Francis M. , Clear Robert D.
Published: November 2005

An efficient ray tracing method is presented for calculating interreflections between surfaces with both diffuse and specular components. A Monte Carlo technique computes the indirect contributions to illuminance at locations chosen by the rendering process. The indirect illuminance values are averaged over surfaces and used in place of a constant "ambient" term. Illuminance calculations are made only for those areas participating in the selected view, and the results are stored so that subsequent views can reuse common values. The density of the calculation is adjusted to maintain a constant accuracy, permitting less populated portions of the scene to be computed quickly. Successive reflections use proportionally fewer samples, which speeds the process and provides a natural limit to recursion. The technique can also model diffuse transmission and illumination from large area sources, such as the sky.
Graphical search and replace
Authors: Kurlander David , Bier Eric A.
Published: November 2005

Graphical search
is a technique for finding all instances of a graphical pattern in a synthetic picture in which objects are regions bounded by lines and curves. The pattern may descirbe shape, color and other properties. Matched objects may be allowed to differ from the pattern in rotation and scale or may differ in shape by a specified tolerance.
Graphical replace
is a technique for replacing the shape, color, or other properties of matched objects with new properties described in a replacement pattern. Combined, the two techniques are similar to textual search and replace in text editors. Graphical search and replace can be used to make global changes to illustrations with repetitive patterns, independent of the means used to make those patterns. It can also be used to create a class of iterative or recursive shapes that can be specified by replacement rules.
Modeling inelastic deformation
Authors: Terzopoulos Demetri , Fleischer Kurt
Published: November 2005

We continue our development of physically-based models for animating nonrigid objects in simulated physical environments. Our prior work treats the special case of objects that undergo perfectly elastic deformations. Real materials, however, exhibit a rich variety of inelastic phenomena. For instance, objects may restore themselves to their natural shapes slowly, or perhaps only partially upon removal of forces that cause deformation. Moreover, the deformation may depend on the history of applied forces. The present paper proposes inelastically deformable models for use in computer graphics animation. These dynamic models tractably simulate three canonical inelastic behaviors---viscoelasticity, plasticity, and fracture. Viscous and plastic processes within the models evolve a reference component, which describes the natural shape, according to yield and creep relationships that depend on applied force and/or instantaneous deformation. Simple fracture mechanics result from internal processes that introduce local discontinuities as a function of the instantaneous deformations measured through the model. We apply our inelastically deformable models to achieve novel computer graphics effects.
Constraints methods for flexible models
Authors: Platt John C. , Barr Alan H.
Published: November 2005

Simulating flexible models can create aesthetic motion for computer animation. Animators can control these motions through the use of
constraints
on the physical behavior of the models. This paper shows how to use mathematical constraint methods based on physics and on optimization theory to create controlled, realistic animation of physically-based flexible models. Two types of constraints are presented in this
paper: reaction constraints (RCs)
and
augrmented Lagrangian constraints
(ALCs). RCs allow the fast computation of collisions of flexible models with polygonal models. In addition, RCs allow flexible models to be pushed and pulled under the control of an animator. ALCs create animation effects such as volume-preserving squashing and the molding of taffy-like substances. ALCs are compatible with RCs. In this paper, we describe how to apply these constraint methods to a flexible model that uses finite elements.
Computer graphics curricula: a survey of PhD granting departments
Authors: Anderson Bennett W. , Burton Robert P.
Published: November 2005

Computer graphics is not a required course of study in the ACM computer science curriculum. Advances in computer graphics technology along with recommendations from SIGGRAPH encourage computer graphics to be required in the computer science curriculum to keep education in step. Ohlson outlines core and advanced elective computer graphics courses and suggests both be offered.A February 1987 survey of computer science PhD granting institutions shows: 1) 97 percent of the institutions already teach one or more computer graphics courses: 59 percent teach two or more courses, 2) courses cover basic and advanced material, 3) a few common textbooks determine course contents and 4) average enrollment is 29. The survey illustrates the prevalence of computer graphics courses and suggests that academic interest warrants its inclusion in future curriculum recommendations. Data from the university survey provides suggested outlines for typical computer graphics courses. Eleven of thirteen publishers answering a February 1987 survey publish or are interested in publishing computer graphics related texts.
Visfiles
Authors: Elvins T. Todd
Published: November 2005

In this issue of
Computer Graphics,
Allen McPherson, Jamie Painter, and their cohorts, report on several techniques used to visualize simulation data. The resulting animations will be part of a multimedia exhibit at the American Museum of Natural History.
Contour rendering
Authors: Christensen Per H.
Published: November 2005

A contour image represents the essence of a scene, a "simplified reality." Contours are used in non-photorealistic images for comics and cartoons to illustrate geometric shape, spatial relationships, color, texture and illumination. This article describes traditional and computer-generated contour rendering, gives examples of contour placement and styles, discusses some practical issues, and describes the contour shader interface of the rendering program mental ray.
Computer graphics pioneers
Authors: Machover Carl
Published: November 2005

In the early 1970s, I first encountered Dr. Encarnação at the University of Saarbruchen where he was an associate of Professor Wolfgang Giloi in the computer graphics department. I met Dr. W. Straβer sometime later.At that time, I worked for Information Displays Inc. (IDI). Dr. Giloi and Dr. Encarnação were interested in acquiring a graphics system for their department and after much discussion, they agreed to purchase our unit, the IDIIOM (IDI Input Output Machine). See Figure 9.Shortly after we delivered the unit to Saarbruchen, Dr. Encarnação told us that he had accepted a new position at the University of Daarmstadt, and would go there as a full professor to head up their computer graphics efforts. We were delighted to learn that he intended to bring the IDIIOM with him, Dr. Encarnação and I developed a warm personal, as well as professional, relationship and although I left IDI in 1976 to form my consultancy, we continued to find ways to work together.
Standards pipeline
Authors: Carson George S.
Published: November 2005

This edition of the Standards Pipeline reports on new work in JTC I/ SC 24 (Computer Graphics and Image Processing) in the area of synthetic environments. The last Standards Pipeline described how at SC 24's Synthetic Environments Study Group met in the Republic of Korea in June 1999 and recommended that work should proceed to prepare for development of an international standard in cooperation with the SEDRIS Organization. As a result, SC 24 called an organizational meeting for October 1-4, 1999 in Alexandria, VA, to form a new working group and begin the development of this standard. In addition, a series of other meetings have been held to discuss coordination of spatial standardization among the many interested parties, including JTC I, ISO TC 211, the SEDRIS Organization and the Open GIS Consortium.
The role of visualization in understanding a complex forest simulation model
Authors: Deutschman Douglas H. , Devine Catherine , Buttel Linda A.
Published: November 2005

Ecological research is changing as scientists confront the complexities of natural and human-influenced ecosystems. Early ecological research was dominated by the concepts of equilibrium and determinism [30]. Ecosystems were thought to be stable "super-organisms," fine-tuned by thousands of years of mutual adaptation. In such a world, ecosystems can be completely described with static measures of equilibrium population densities. Although this view has been challenged since its inception, it is only in the past 25 years that it has been displaced as the dominant paradigm in ecology. Today, ecologists describe ecosystems as a dynamic collection of individuals responding in different ways to local interactions, broad-scale environmental change and frequent accidents of history [18, 23, 30]. Although the behavior of the ecosystem is partially understandable from population densities, ecosystem dynamics are variable and complex.Ecologists use an increasingly sophisticated toolbox of techniques to characterize these complex dynamics. Field surveys and laboratory experiments measure the responses of individuals under varied conditions. Thus the mean response as well as the variance in response can be estimated. Improved statistical analyses allow ecologists to describe spatial structure, temporal dynamics and complex spatio-temporal patterns. Finally, mathematical models are being developed that can simulate the complex local interactions of thousands of individuals in a dynamic, heterogeneous environment [9, 17, 34].Improvements in computer hardware and software have facilitated this shift toward increasing complexity. Today, ecologists are seldom limited by hardware, and software to acquire, store and analyze data has improved dramatically in the past decade. In addition, computational models of ecological systems are becoming common [14]. Models are tools to express our understanding of mechanisms governing the structure and function of ecological communities [20]. Models can also be used to make predictions, determine the robustness of these predictions, reveal system properties and highlight weaknesses in our knowledge [8, 25]. Complex ecological models have several important drawbacks including the need for huge amounts of input data, propagation of errors and difficulty interpreting the often voluminous model output [10, 11, 13]. As a result, increased model complexity and detail may not lead to increased understanding [10, 16, 22].
Simulation of object and human skin formations in a grasping task
Authors: Gourret J.-P. , Thalmann N. M. , Thalmann D.
Published: November 2005

This paper addresses the problem of simulating deformations between objects and the hand of a synthetic character during a grasping process. A numerical method based on finite element theory allows us to take into account the active forces of the fingers on the object and the reactive forces of the object on the fingers. The method improves control of synthetic human behavior in a task level animation system because it provides information about the environment of a synthetic human and so can be compared to the sense of touch. Finite element theory currently used in engineering seems one of the best approaches for modeling both elastic and plastic deformation of objects, as well as shocks with or without penetration between deformable objects. We show that intrinsic properties of the method based on composition/decomposition of elements have an impact in computer animation. We also state that the use of the same method for modeling both objects and human bodies improves the modeling both objects and human bodies improves the modeling of the contacts between them. Moreover, it allows a realistic envelope deformation of the human fingers comparable to existing methods. To show what we can expect from the method, we apply it to the grasping and pressing of a ball. Our solution to the grasping problem is based on displacement commands instead of force commands used in robotics and human behavior.
Pixel-planes 5: a heterogeneous multiprocessor graphics system using processor-enhanced memories
Authors: Fuchs Henry , Poulton John , Eyles John , Greer Trey , Goldfeather Jack , Ellsworth David , Molnar Steve , Turk Greg , Tebbs Brice , Israel Laura
Published: November 2005

This paper introduces the architecture and initial algorithms for Pixel-Planes 5, a heterogeneous multi-computer designed both for high-speed polygon and sphere rendering (1M Phong-shaded triangles/second) and for supporting algorithm and application research in interactive 3D graphics. Techniques are described for volume rendering at multiple frames per second, font generation directly from conic spline descriptions, and rapid calculation of radiosity form-factors. The hardware consists of up to 32 math-oriented processors, up to 16 rendering units, and a conventional 1280 × 1024-pixel frame buffer, interconnected by a 5 gigabit ring network. Each rendering unit consists of a 128 × 128-pixel array of processors-with-memory with parallel quadratic expression evaluation for every pixel. Implemented on 1.6 micron CMOS chips designed to run at 40MHz, this array has 208 bits/pixel on-chip and is connected to a video RAM memory system that provides 4,096 bits of off-chip memory. Rendering units can be independently reasigned to any part of the screen or to non-screen-oriented computation. As of April 1989, both hardware and software are still under construction, with initial system operation scheduled for fall 1989.
Scan line display of algebraic surfaces
Authors: Sederberg Thomas W. , Zundel Alan K.
Published: November 2005

A robust algorithm is presented for scan line display of algebraic surfaces of arbitrary degree and topology. The algorithm correctly displays singularities of any complexity, even those missed by ray tracing or polygonization, and (for surfaces of degree less than eight) offers a significant speed improvement over ray tracing. Antialiasing can generally be accomplished very quickly. In addition to its typical function of shaded raster display, the algorithm is particularly adept at quickly plotting silhouette and intersection curves. A practical use for the algorithm is to display boolean combinations of algebraic half spaces, including blend surfaces.A new polynomial basis is introduced, referred to as the Bernstein pyramid polynomial basis, which enhances numerical stability and which simplifies several computations such as scan planesurface intersection and silhouette detection.
Rendering cubic curves and surfaces with integer adaptive forward differencing
Authors: Chang S.-L. , Rocchetti M. S. R.
Published: November 2005

For most compute environments, adaptive forward differencing is much more efficient when performed using integer arithmetic than when using floating point. Previously low precision integer methods suffered from serious precision problems due to the error accumulation inherent to forward differencing techniques. This paper proposes several different techniques for implementing adaptive forward differencing using integer arithmetic, and provides an error analysis of forward differencing which is useful as a guide for integer AFD implementation. The proposed technique using 32 bit integer values is capable of rendering curves having more than 4K forward steps with an accumulated error of less than one pixel and no overflow problems. A hybrid algorithm employing integer AFD is proposed for rendering antialiased, texture-mapped bicubic surfaces.
Goal-directed, dynamic animation of human walking
Authors: Bruderlin A. , Calvert T. W.
Published: November 2005

This paper presents a hybrid approach to the animation of human locomotion which combines goal-directed and dynamic motion control. Knowledge about a locomotion cycle is incorporated into a hierarchical control process. The desired locomotion is conveniently specified at the top level as a task (e.g. walk at speed
v
), which is then decomposed by application of the concepts of
step symmetry
and
state-phase-timings
. As a result of this decomposition, the forces and torques that drive the dynamic model of the legs are determined by numerical approximation techniques. Rather than relying on a general dynamic model, the equations of motion of the legs are tailored to locomotion and analytically constrained to allow for only a specific range of movements. The dynamics of the legs produce a generic, natural locomotion pattern which is visually upgraded by some kinematic "cosmetics" derived from such principles as
virtual leg
and
determinants of gait
. A system has been implemented based on these principles and has shown that when a few parameters, such as velocity, step length and step frequency are specified, a wide variety of human walks can be generated in almost real-time.
Guaranteed ray intersections with implicit surfaces
Authors: Kalra D. , Barr A. H.
Published: November 2005

In this paper, we present a robust and mathematically sound ray-intersection algorithm for implicit surfaces. The algorithm is guaranteed to numerically find the nearest intersection of the surface with a ray, and is guaranteed not to miss fine features of the surface. It does not require fine tuning or human choice of interactive parameters. Instead, it requires two upper bounds: "L" that limits the net rate of change of the implicit surface function
f(x,y,z)
and "G" that limits the rate of change of the gradient. We refer to an implicit surface with these rate limits as an "LG-implicit surface."Existing schemes to intersect a ray with an implicit surface have typically been guaranteed to work only for a limited set of implicit functions, such as quadric surfaces or polynomials, or else have been ad-hoc and have not been guaranteed to work. Our technique significantly extends the ability to intersect rays with implicit surfaces in a guaranteed fashion.
Preparing for the future
Authors: Plazzi M. , Carlson W. , Lucas R. , Schweppe M. , Yanilmaz M.
Published: November 2005

Welcome to Preparing for the Future, a panel on educational issues in computer graphics. The field of computer graphics education, as no other, combines the disciplines of science and art, and in this sense presents computer graphics instructors in both art and science with some unique problems not faced by their counterparts in other fields.As computer graphics courses become a standard addition in art and science curricula, the way in which we prepare students for this evolutionary field is changing.This panel explores the methods of establishing computer graphics curriculum and maintaining these programs. Panel members will share curricula developments and goals, its integration with existing courses, plan growth, raising monetary resources, hardware and software selection, and various educational issues.This session's panelists come from varied backgrounds -- private and public institutions with limited and unlimited resources to share their experiences with you.The first panelist will be Wayne Carlson, an assistant professor in the department of computer and information science at the Ohio State University.
Interactive dynamics
Authors: Witkin Andrew , Gleicher Michael , Welch William
Published: November 2005

Our goal is to use physical simulation as an interactive medium for building and manipulating a wide range of models. A key to achieving this goal is the ability to create complex physical models dynamically by snapping simple pieces together, integrating the process of model creation into the ongoing simulation. We present a mathematical and computational formulation for constrained dynamics that makes this possible, allowing encapsulated objects, constraints, and forces to be combined dynamically and simulated efficiently. The formulation handles arbitrary objects, including nonrigid bodies. We describe an implementation for interactive dynamics, and discuss applications to mechanism construction, geometric modeling, interactive optimization data fitting, and animation.
Improving interaction with radiosity-based lighting simulation programs
Authors: Puech Claude , Sillion Francois , Vedel Christophe
Published: November 2005

We describe the main algorithms used in an interactive lighting simulation program based on a two-pass extension of the radiosity method. The system allows interactive walk-through as other systems based on radiosity calculations. Moreover, it offers increased realism in the lighting effects by use of extended form factors which accounts for "specular reflection of diffuse light", fast production and display of progressively refined images by distribution of the calculations, good quality of the images in the early stages of the refinement by the use of "hardware light sources", "cheap" rendering of some of the specular highlights at any time by use of the built-in specular shading model, lighting modification (color, intensity of the light sources) by use of "negative light", fast simulation of mirror effects and interactive tools for controling the quality of the final image.
Real-time digital of virtual acoustic environments
Authors: Wenzel Elizabeth M. , Foster Scott H.
Published: November 2005

As with most research in information displays, virtual displays have generally emphasized visual information. Many investigators, however, have pointed out the importance of the auditory system as an information channel. We believe that a three-dimensional auditory display can substantially enhance situational awareness by combining spatial and semantic information to form dynamic, multidimensional patterns of acoustic events which convey meaning about objects in the spatial world of the user. Such a display can be realized with an array of real sound sources or loudspeakers (Doll et. al., 1986). The signal-processing device being developed at NASA-Ames maximizes flexibility and portability by synthetically generating three-dimensional sound in realtime for delivery through headphones. Unlike conventional stereo, sources can be perceived outside the head at discrete distances and directions from the listener. The 3-D auditory display is currently being integrated with Ames' Virtual Interactive Environment Workstation (VIEW) which allows the user to explore and interact with a 360-degree synthesized or remotely-sensed world using a head-mounted, wide-angle, stereoscopic display controlled by operator position, voice, and gesture.Applications of a three-dimensional auditory display involve any context in which the user's spatial awareness is important, particularly when visual cues are limited or absent. Examples include advanced teleconferencing environments, monitoring telerobotic activities in hazardous situations, and scientific "visualization" of multi-dimensional data. (e.g., Doll, et. al., 1986; Foley, 1987; Fisher, et. al., 1988; Brooks, 1988).
Computational complexity versus virtual worlds
Authors: Pentland Alex
Published: November 2005

The ability to simulate complex physical situations in real-time is a critical element of any "virtual world" scenario, as well as being key for many engineering and robotics applications. Unfortunately the computation cost of standard physical simulation methods increases rapidly as the situation becomes more complex. The result is that even when using the fastest supercomputers we are still able to interactively simulate only small, toy worlds. To solve this problem I propose changing the way we represent and simulate physics in order to reduce the computational complexity of physical simulation, thus making possible interactive simulation of complex situations.
Design, implementation and experiences with a higher-level graphics language for interactive computer-aided design purposes
Authors: Schrack Guenther
Published: November 2005

The higher-level graphics language LIG has now been operational for over two years. The language has proven to be easy to learn and easy to use, as attested by a number of programmers. Through its use, many improvement possibilities of the syntax and the supporting subprogram system have shown up.

The experimental design of a higher-level special purpose programming language in terms of the linguistic characteristics of a language extension and its implementation with the aid of a compiler generator is discussed. A consideration of the data type GRAPHICAL, its properties and its manipulation as well as a description of the major parts of the language LIG follows, stressing its graphic capabilities and its features for handling interactive application programs. The paper concludes with remarks regarding an evaluation of the approach taken for the design and the language itself, together with a number of suggestions for improvements.
An extended Algol-60 for Shaded Computer Graphics
Authors: Jones Ben
Published: November 2005

This report describes a high level programming language implemented for the Shaded Graphic System at Case Western Reserve University. It consists of a complete implementation, for the PDP-11, of Algol-60 with the addition of string variables, I/O facilities, and extensions for handling shaded graphic images. The primary purpose of this work was to facilitate the use of a custom-built system which can produce shaded perspective images in real-time.
SUGAR
Authors: Kriger Mark P.
Published: November 2005

This paper presents the recently designed interactive computer language for cartography called SUGAR. It is intended for use by non-computer specialists, especially geographers, city planners and landscape architects to make maps by computer. The syntax given is based on English key words with a grammar easily understood by specialists with a non-mathematical background. Different keyword dialects for SUGAR are being designed for different cartographic applications within the basic syntax. A version of SUGAR being implemented is a prototype interpreter for an interactive choropleth mapping program called INPOM. Examples of the graphics capabilities of INPOM are included together with examples of the INPOM dialect of SUGAR. The useability of the language in the batch program environment is discussed as well as directions of further research and implementation.
Automatic generation of computer graphics languages
Authors: Suski Gregory J.
Published: November 2005

This paper describes a system currently under development at Northwestern University which allows a user of a computer graphics system to generate specialized graphics programming languages which are particularly suited to a user's own needs and expertise. Termed a Language Generation System (LGS), it differs from the more traditional compiler-compiler and extensible language systems in the ease and speed of language specification and generation and also in the actual method of language specification employed.

We will discuss here the motivation behind the development of LGS, some representative examples of user generated languages, and several principal areas of interest in the design and implementation of language generation systems. The paper concludes with a summary of the major topics presented and the current status of LGS.
A computer graphics approach for understanding of prosthetic heart valve characteristics
Authors: Au Anthony D. , Greenfield Harvey S.
Published: November 2005

The present investigation applies fluid dynamics principles and numerical analysis techniques in an attempt to study stress distributions in blood caused by the motion of the occluder in a prosthetic heart valve. An interactive computer graphics program is developed for control of the computer simulation of the flow process and the pictoral presentation of the solution for analysis. A simplified model of a disc-type heart valve is used in the analysis to demonstrate the capability of the interactive graphics program. Resulting displays show the stress distribution and other useful information describing the movement of a disc occluder from almost full-closed position to almost full-open position. The possible contribution of this study to the understanding of hemolysis and thrombosis is discussed.