Cumincad : CUMINCAD Papers : Search Results

CumInCAD is a Cumulative Index about publications in Computer Aided Architectural Design
supported by the sibling associations ACADIA, CAADRIA, eCAADe, SIGraDi, ASCAAD and CAAD futures

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_id	186e
authors	Blinn, J.F. and Newell, M.E.
year	1976
title	Texture and Reflection in Computer Generated Images
source	Communications of the ACM 19 10 542-547
summary	In 1974 Catmull developed a new algorithm for rendering images of bivariate surface patches. This paper describes extensions of this algorithm in the areas of texture simulation and lighting models. The parametrization of a patch defines a coordinate system which is used as a key for mapping patterns onto the surface. The intensity of the pattern at each picture element is computed as a weighted average of regions of the pattern definition function. The shape and size of this weighting function are chosen using digital signal processing theory. The patch rendering algorithm allows accurate computation of the surface normal to the patch at each picture element, permitting the simulation of mirror reflections. The amount of light coming from a given direction is modeled in a similar manner to the texture mapping and then added to the intensity obtained from the texture mapping. Several examples of images synthesized using these new techniques are included.
series	journal paper
last changed	2003/11/21 15:16

_id	62c4
authors	Blinn, James F. and Newell, Martin E.
year	1976
title	Texture and Reflection in Computer Generated Images
source	communications of the ACM October, 1976. vol. 19: pp. 542-547 : ill. (col.). includes bibliography.
summary	In 1974 Catmull developed a new algorithm for rendering images of bivariate surface patches. This paper describes extensions of this algorithm in the areas of texture simulation and lighting models. The parametrization of a patch defines a coordinate system which is used as a key for mapping patterns onto the surface. The intensity of the pattern at each picture element is computed as a weighted average of regions of the pattern definition function. The shape and size of this weighting function are chosen using digital signal processing theory. The patch rendering algorithm allows accurate computation of the surface normal to the patch at each picture element, permitting the simulation of mirror reflections. The amount of light coming from a given direction is modeled in a similar manner to the texture mapping and then added to the intensity obtained from the texture mapping. Several examples of images synthesized using these new techniques are included
keywords	algorithms, computer graphics, shading, hidden surfaces, texture mapping, curved surfaces, rendering
series	CADline
last changed	2003/06/02 13:58

_id	ecaade2022_299
id	ecaade2022_299
authors	Bauscher, Erik, Philipp, Klaus Jan, Reisinger, Stefanie and Wortmann, Thomas
year	2022
title	Reimagining Gego: Geometrical Reconstruction of Nubes, an Undocumented and Lost Sculpture from 1974
source	Pak, B, Wurzer, G and Stouffs, R (eds.), Co-creating the Future: Inclusion in and through Design - Proceedings of the 40th Conference on Education and Research in Computer Aided Architectural Design in Europe (eCAADe 2022) - Volume 2, Ghent, 13-16 September 2022, pp. 217–226
doi	https://doi.org/10.52842/conf.ecaade.2022.2.217
summary	This paper describes a method to understand and digitally reconstruct two sculptures by Gertrud Goldschmidt, a German-born, Venezuelan artist also called Gego. Gego is best known for her series of works called “Reticuláres”. These three-dimensional and open installations, mostly hanging freely in space, are playing with the concept and perception of space as well as challenging the definition of the traditional sculpture. The paper aims to generate information about two specific structures called “Nubes” (Clouds for Spanish) to assist in a physical reconstruction for a larger exhibition about Gego and to contribute to understanding Gego’s work process. Originally, the structures were suspended from a building's ceiling as an art installation in Caracas, 1974. There are three main challenges for this reconstruction: (1) The installations exhibit a complex three-dimensional geometry. (2) Scant drawings and photographs exist. (3) Gego might not have followed her initial drawings completely when building Nubes physically, because of the mentioned complexity and due to the light and bendable material properties of the employed material. The paper describes a computational process that recreates the object’s geometry in four steps: (1) Analyse all existing media of the structure. (2) Translate found information to the digital environment of Grasshopper. (3) Use a physical simulation to derive the end state of the hanging structure. (4) Optimize and tune the simulation with an optimization algorithm for better results. This paper demonstrates the usefulness of computational tools for reconstructing lost sculptures with little documentation. In this case, these tools allow a more accurate reconstruction and contribute to a fuller understanding of the design and realization process of Gego's Nubes.
keywords	Geometry Reconstruction, Lost Art, Computational Design, Physics Simulation
series	eCAADe
email
last changed	2024/04/22 07:10

_id	a5dc
authors	Adams, J.A.
year	1974
title	Cubic Spline Curve Fitting with Controlled End Conditions
source	Computer Aided Design. January, 1974. vol. 6: pp. 2-9 : ill. includes a short bibliography
summary	Another method for cubic spline curve fitting. It is a more flexible version of a proven technique by using a set of end conditions suggested by Nutbourne. The advantages and disadvantages of several techniques are clarified and sample graphical output is given. The result should be of interest to users of inexpensive computer graphics equipment who are interested in improving passive graphical output
keywords	computer graphics, curved surfaces, curves, splines
series	CADline
last changed	2003/06/02 13:58

_id	sigradi2008_049
id	sigradi2008_049
authors	Benamy, Turkienicz ; Beck Mateus, Mayer Rosirene
year	2008
title	Computing And Manipulation In Design - A Pedagogical Experience Using Symmetry
source	SIGraDi 2008 - [Proceedings of the 12th Iberoamerican Congress of Digital Graphics] La Habana - Cuba 1-5 December 2008
summary	The concept of symmetry has been usually restricted to bilateral symmetry, though in an extended sense it refers to any isometric transformation that maintains a certain shape invariant. Groups of operations such as translation, rotation, reflection and combinations of these originate patterns classified by modern mathematics as point groups, friezes and wallpapers (March and Steadman, 1974). This extended notion represents a tool for the recognition and reproduction of patterns, a primal aspect of the perception, comprehension and description of everything that we see. Another aspect of this process is the perception of shapes, primary and emergent. Primary shapes are the ones explicitly represented and emergent shapes are the ones implicit in the others (Gero and Yan, 1994). Some groups of shapes known as Semantic Shapes are especially meaningful in architecture, expressing visual features so as symmetry, rhythm, movement and balance. The extended understanding of the concept of symmetry might improve the development of cognitive abilities concerning the creation, recognition and meaning of forms and shapes, aspects of visual reasoning involved in the design process. This paper discusses the development of a pedagogical experience concerned with the application of the concept of symmetry in the creative generation of forms using computational tools and manipulation. The experience has been carried out since 1995 with 3rd year architectural design students. For the exploration of compositions based on symmetry operations with computational support we followed a method developed by Celani (2003) comprising the automatic generation and update of symmetry patterns using AutoCAD. The exercises with computational support were combined with other different exercises in each semester. The first approach combined the creation of two-dimensional patterns to their application and to their modeling into three-dimensions. The second approach combined the work with computational support with work with physical models and mirrors and the analysis of the created patterns. And the third approach combined the computational tasks with work with two-dimensional physical shapes and mirrors. The student’s work was analyzed under aspects such as Discretion/ Continuity –the creation of isolated groups of shapes or continuous overlapped patterns; Generation of Meta-Shapes –the emergence of new shapes from the geometrical relation between the generative shape and the structure of the symmetrical arrangement; Modes of Representation –the visual aspects of the generative shape such as color and shading; Visual Reasoning –the derivation of 3D compositions from 2D patterns by their progressive analysis and recognition; Conscious Interaction –the simultaneous creation and analysis of symmetry compositions, whether with computational support or with physical shapes and mirrors. The combined work with computational support and with physical models and mirrors enhanced the students understanding on the extended concept of symmetry. The conscious creation and analysis of the patterns also stimulated the student’s understanding over the different semantic possibilities involved in the exploration of forms and shapes in two or three dimensions. The method allowed the development of both syntactic and semantic aspects of visual reasoning, enhancing the students’ visual repertoire. This constitutes an important strategy in the building of the cognitive abilities used in the architectural design process.
keywords	Symmetry, Cognition, Computing, Visual reasoning, Design teaching
series	SIGRADI
email
last changed	2016/03/10 09:47

_id	585a
authors	Gips, James Elliot
year	1974
title	Shape grammars and their uses : artificial perception, shape generation and computer aesthetics
source	Stanford University
summary	Shape grammars are defined and their uses investigated. Shape grammars provide a means for the recursive specification of shapes. The formalism for shape grammars is designed to be easily usable and understandable by people and at the same time to be adaptable for use in computer programs. Shape grammars are similar to phrase structure grammars, which were developed by Chomsky. Where a phrase structure grammar is defined over an alphabet of symbols and generates a language of sequences of symbols, a shape grammar is defined over an alphabet of shapes and generates a language of shapes. The dissertation is divided into three sections and an Appendix.In the first section: Shape grammars are defined. Some simple examples are given for instructive purposes. Shape grammars are used to generate a new class of reversible figures. Shape grammars are given for some well-known mathematical curves (the Snowflake curve, a variation of Peano's curve, and Hubert's curve). To show the general computational power of shape grammars, a procedure that given any Turing machine constructs a shape grammar that simulates the operation of that Turing machine is presented. Related work on various formalisms for picture grammars is described. A symbolic characterization of shape grammars is given that is useful for implementing shape grammars in computer programs. In the second section, a program that uses a shape grammar to solve a perceptual task is described. The task involves analyzing and comparing line drawings that portray three -dimensional objects of a restricted type. The third section is divided into two parts. First, a formalism for generating paintings is defined. The primary component of this formalism is a shape grammar. The paintings generated are material representations of shapes specified by shape grammars. The computer implementation of this formalism is described. The second part is concerned with aesthetics. A formalism is defined for specifying an aesthetic viewpoint. The formalism is used to specify a particular aesthetic viewpoint for interpreting and evaluating paintings generated using shape grammars. This viewpoint has been implemented on the computer. The net result is that the program described in Section 3 can be used to interactively define the rules for producing a painting, can use the rules to generate and display the resulting painting, and can then evaluate the painting relative to the specific aesthetic viewpoint. Relationships between the formalism for aesthetic viewpoints and information theory and science are touched upon. Finally, the possibility of using this approach to aesthetics to write programs that automatically analyze presented art objects or design new art objects is explored. In the Appendix, a method for constructing the inverse of a Turing machine is presented. This construction was created in response to a problem that is described in the aestheticssection.
keywords	Formal Languages; Computer Art; Aesthetics; Data Processing
series	thesis:PhD
email
more	http://jenson.stanford.edu
last changed	2003/02/12 22:37

_id	a9c2
authors	Gordon, William J. and Riesenfeld, Richard F.
year	1974
title	Bernstein- Bezier Methods for the Computer-Aided Design of Free-Form Curves and Surfaces
source	Journal of the ACM. April, 1974. vol. 21: pp. 293-310 : ill. includes bibliography
summary	The mth degree Bernstein polynomial approximation to a function f defined over [0,1] is Em-o f(u/m) Ou(s), where the weights Ou(s) are binomial density functions. The Bernstein approximations inherit many of the global characteristics of f, like monotonicity and convexity, and they always are at least as 'smooth' as f, where 'smooth' refers to the number of undulations, the total variation, and the differentiability class of f. Historically, their relatively slow convergence in the Loo-norm has tended to discourage their use in practical applications. However, in a large class of problems the smoothness of an approximating function is of greater importance than closeness of fit. This is especially true in connection with problems of computer-aided geometric design of curves and surfaces where aesthetic criteria and the intrinsic properties of shape are major considerations. For this latter class of problems, P. Bezier of Renault has successfully exploited the properties of parametric Bernstein polynomials. The purpose of this paper is to analyze the Bezier techniques and to explore various extensions and generalizations. In a sequel, the authors consider the extension of the results contained herein to free-form curve and surface design using polynomial splines. These B-spline methods have several advantages over the techniques described in the present paper
keywords	CAD, computer graphics, Bezier, curves, curved surfaces, representation, design, Bernstein, representation, B- splines, user interface, approximation, interpolation
series	CADline
last changed	2003/06/02 13:58

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