Papers by Carlo H. SEQUIN
Timing Verifier, is a program to perform static timing analysis of dependency graphs derived from... more Timing Verifier, is a program to perform static timing analysis of dependency graphs derived from logic designs, analyzing worst-case paths. Unlike other timing verifiers, A TV uses an abstract representation of time and delays that enables a user to choose the representation of time and delays most suitable to a particular analysis. Such representations include single numbers, ranges [min-max], and statistical descriptions (mean and standard deviation), or asymmetric rise/fall versions of all of these. The sophisticated user may develop new models and plug them in to the program. This technical report consists of the main body of my dissertation of the same title. It describes the background of the Abstract Timing Model that A TV uses, several different timing models, implementation of the principle algorithm for clock phase length analysis of transparent latch designs, and results of using the program. Detailed information about how to use the program is available in the companion technical report, User's Guide to ATV, an Abstract Timing Verifier, which also appeared as the appendix to my dissertation. Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.
We investigate methods to aid in the process of going from a conceptual shape of a part to its ph... more We investigate methods to aid in the process of going from a conceptual shape of a part to its physical realization. We present contributions to the "design for manufacture" problem in two major areas: surface model representation and process planning for layered manufacturing. In surface modeling, the focus is on subdivision surfaces and the analysis of their continuity behavior. We present a new algorithm for the exact evaluation of piecewise smooth Loop and Catmull-Clark surfaces near user-defined sharp features. This algorithm aids in the geometric process planning of subdivision surfaces for manufacturing. On the process planning side, we have developed an approach to layered manufacturing that produces parts with thin, dense walls filled with a loose web-like interior to reduce material usage and accelerate build times. The key algorithm in this process generates a conservative offset of a polyhedral surface by generating a stack of 2D slice contours, calculating individual offset contours, and forming appropriate Boolean combinations of these contours. We describe a numerically robust algorithm for constructing the generalized Voronoi diagram of polygonal slice contours which is then used to generate clean offset contours for each slice, which are combined between layers to create the conservative 3D offset surface.
Princeton University Press eBooks, Dec 31, 2014
Different geometric realizations of topological Klein bottles are discussed and analyzed whether ... more Different geometric realizations of topological Klein bottles are discussed and analyzed whether they can be smoothly transformed into one another and thus belong into the same regular homotopy class. Simple and distinct representatives for each of the four expected classes are introduced. In addition, novel and unusual geometries for Klein bottles are presented, some of them knotted, which may serve as proposals for large-scale sculptures.
Princeton University Press eBooks, Oct 31, 2017
We analyze the glass rhombicuboctahedron (RCO) appearing in a famous painting of Pacioli (1495), ... more We analyze the glass rhombicuboctahedron (RCO) appearing in a famous painting of Pacioli (1495), considering the extent to which it might agree with a physically correct rendering of a corresponding glass container half-filled with water. This investigation shows that it is unlikely that the painter of the RCO was looking at such a physical object. We then ask what a proper rendering of such an object might look like. Our computer renderings, which take into account multiple internal and external reflections and refractions, yield visual effects that differ strongly from their depictions in the painting. Nevertheless, the painter of the RCO has clearly succeeded in providing a rendering that appears plausible and aweinspiring to almost all observers.
Proceedings of Bridges 2015: Mathematics, Music, Art, Architecture, Culture, 2015
Maximal symmetry is used to reduce the computational complexity in the construction of the larges... more Maximal symmetry is used to reduce the computational complexity in the construction of the largest possible hyperbolic disk composed entirely of equilateral triangles meeting seven per vertex. Modeling Hyperbolic Disks Mathematicians as well as artists are fascinated by the hyperbolic plane. Hilbert proved that the infinite hyperbolic plane cannot be smoothly and isometrically embedded (without self-intersections) in 3-space. Artists have made approximate models of a finite portion of the hyperbolic plane from various materials, for instance by crocheting (Fig.1a) or by gluing together paper triangles (Fig.1b). They may start with a small hyperbolic patch (warped like a potato chip) placed at the origin, and then add consecutive annular ribbons around the perimeter. With each annulus the distance from the origin grows only linearly, but the length of the annular ribbon grows exponentially; thus the outer border becomes ever more convoluted, and needs to curl through space in ever tighter undulations. Soon the physical properties of the modeling material will reach some practical limit of packing density, and a uniform radial extension of such a hyperbolic disk is no longer possible.
Contents ii List of Figures vii List of Tables xii I gratefully appreciate Prof. Norimasa Yoshida... more Contents ii List of Figures vii List of Tables xii I gratefully appreciate Prof. Norimasa Yoshida for a careful reading and helpful comments on an earlier draft of this thesis. And of course, many thanks are due to my thesis committee for providing feedback invaluable for refining earlier drafts, and especially my advisor, Prof. Carlo Séquin.
Solid freeform fabrication (SFF) refers to a class of technologies used for making rapid prototyp... more Solid freeform fabrication (SFF) refers to a class of technologies used for making rapid prototypes of 3-D parts. With these processes, a triangulated boundary representation of the CAD model of the part is "sliced" into horizontal 2.5-D layers of uniform thickness that are successively deposited, hardened, fused, or cut, depending on the particular process, and attached to the layer beneath. The stacked layers form the final part. The current de facto standard interface to these machines, STL, has many shortcomings. We have developed a new "Solid Interchange Format" (SIF) for use as a digital interface to SFF machines. SIF includes constructs for specifying surface and volume properties, precision information, and transmitting unevaluated Boolean trees. We have also developed a 2-D variant, LSIF (Layered SIF), for describing the sliced layers. Many solid modeling applications require information not only about the geometry of an object but also about its "topology"-the connectivity of its faces, edges, and vertices. We have designed a new topological data structure, the loop edge data structure (LEDS), specifically targeted at supporting SFF software. For very large data sets, the topological data structure itself can be bigger than core memory, and a naive algorithm for building it becomes prohibitively slow due to memory thrashing. We have developed an algorithm for building the LEDS efficiently from a boundary representation, even when it doesn't fit in List of Tables 3.1 The context-free grammar for SIF :
Proceedings of Bridges 2013: Mathematics, Music, Art, Architecture, Culture, 2013
Boy's surface is the simplest and most symmetrical way of making a compact model of the projectiv... more Boy's surface is the simplest and most symmetrical way of making a compact model of the projective plane in R 3 without any singular points. This surface has 3-fold rotational symmetry and a single triple point from which three loops of intersection lines emerge. It turns out that there is a second, homeomorphically different way to model the projective plane with the same set of intersection lines, though it is less symmetrical. There seems to be only one such other structure beside Boy's surface, and it thus has been named Girl's surface. This alternative, finite, smooth model of the projective plane seems to be virtually unknown, and the purpose of this paper is to introduce it and make it understandable to a much wider audience. To do so, we will focus on the construction of the most symmetrical Möbius band with a circular boundary and with an internal surface patch with the intersection line structure specified above. This geometry defines a Girl's cap with C 2 front-to-back symmetry.
The operating principles of charge-coupled devices are described in terms of the basic properties... more The operating principles of charge-coupled devices are described in terms of the basic properties of semiconductors. The overall aim is for those unfamiliar with CCD's to understand how they work and thus to appreciate their capabilities as well as their limitations. The topics discussed include charge storage and transfer, electrical and optical inputting of charge and charge sensing, factors governing maximum and minimum operating frequencies, transfer efficiency, and basic CCD fabrication techniques. i.
ACADIA proceedings, 1995
He joined Berkeley in 1992 after spending 10 years at the State University of New York at Buffalo... more He joined Berkeley in 1992 after spending 10 years at the State University of New York at Buffalo. His current research focuses on developing software that can assist architects to predicts and evaluate their design decisions. CARLO SÉQUIN has been a professor of Computer Science at the University of California, Berkeley since 1977. He first worked in digital systems design and on CAD tool for VLSI. Now he works in computer graphics, solid modeling and on CAD tools for mechanical engineers and architects. An upper-level undergraduate architectural design studio and a graduate computer science CAD course were paired to study client-designer interactions. The dual nature of these courses led to two sets of products: building designs compatible with the specifications of the clients, and prototype CAD tool to assist architects in the conceptual design phases. First, the computer scientists acted as clients to the architects, who designed a 383 building for the computer science department. Once the computer science students had become familiar, through observation, with the architectural design process, they began developing tools for the architects' use. In that reversed-role, the architects became the clients of the computer scientists. For both parties this interaction provided an opportunity to experience the social aspects of the design process, in particular, the designer-client relationships, which most often are absent in traditional educational settings. This paper describes the objectives of this integrated pair of courses, the methods and processes used, and some of the results.
Princeton University Press eBooks, Dec 31, 2011
's monumental sculpture Solstice is analyzed and its generative geometrical logic based on a twis... more 's monumental sculpture Solstice is analyzed and its generative geometrical logic based on a twisted toroidal sweep is captured in a computer program with interactively adjustable control parameters. This program is then used to generate other models of ribbed sculptures based on one or more interlinked torus knots. From this family of sculptures related to Perry's Solstice we derive a broader paradigm for the generation of "ribbed" sculptures. It is based on one or two simple, mathematically defined "guide rails," which are then populated with a dense set of thinner "ribs" to create lightweight, transparent surfaces. With this broadened concept and a few suitably modified and parameterized programs we can emulate many other ribbed sculptures by Charles Perry and also create new sculpture designs and mathematical visualization models that profit from the semi-transparent look of these structures.
Interactive 3D Graphics and Games, Mar 1, 2001
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The consmaction and refinement of a computer graphics scene is unacceptably slow when using ray t... more The consmaction and refinement of a computer graphics scene is unacceptably slow when using ray tracing. We in~oduce a new technique to speed up the generation of successive ray traced images when the geometry of the scene remains constant and only the light source intensities and the surface properties need to be adjusted. When the scene is first ray traced, an expression parameterized in the color of all lights and the surface property coefficients of all objects is calculated and stored for each pixel. Redisplaying a scene with a new set of lights and colors then consists of substituting values for the corresponding parameters and re-evaluating the expressions for the pixels. This parameter updating and redisplay takes only a few seconds, as compared to the many rnirtutes or hours required to ray trace the entire scene again, but it uses much more memory and disk space. With suitable expression sharing, however, these storage needs can be reduced to an acceptable level.
The paper starts with a review of three hierarchical approaches for making tubular 3D sculptures ... more The paper starts with a review of three hierarchical approaches for making tubular 3D sculptures that capture the characteristics of the 2D Gosper curve: Gosper-Balls , Gosper-Pole , and Gosper-Lattice , and it discusses some of their shortcomings. It then analyzes three non-hierarchical approaches: Gosper-Stars with some internal branching, Gosper-Onions that use a small number of layered shells, and Gosper-Shells that map a Gosper-like path onto the surface of a regular polyhedron. The focus is on creating a modular polyline that connects nearest neighbor vertices on a regular lattice, while favoring the characteristic turning angles of 60 and 120 degrees of the 2D Gosper curve.
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Papers by Carlo H. SEQUIN