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 af65
authors Akleman, E., Chen, J. and Sirinivasan, V.
year 2001
title An Interactive Shape Modeling System for Robust Design of Functional 3D Shapes
source Reinventing the Discourse - How Digital Tools Help Bridge and Transform Research, Education and Practice in Architecture [Proceedings of the Twenty First Annual Conference of the Association for Computer-Aided Design in Architecture / ISBN 1-880250-10-1] Buffalo (New York) 11-14 October 2001, pp. 248-257
summary In Architecture, it is essential to design functional and topologically complicated 3D shapes (i.e. shapes with many holes, columns and handles). In this paper, we present a robust and interactive system for the design of functional and topologically complicated 3D shapes. Users of our system can easily change topology (i.e. they can create and delete holes and handles, connect and disconnect surfaces). Our system also provide smoothing operations (subdivision schemes) to create smooth surfaces. Moreover, the system provides automatic texture mapping during topology and smoothing operations. We also present new design approaches with the new modeling system. The new design approaches include blending surfaces, construction of crusts and opening holes on these crusts.
keywords Modeling, Shape Design, Sculpting, Computer Aided Geometric Design
series ACADIA
last changed 2003/11/21 14:15

_id avocaad_2001_18
id avocaad_2001_18
authors Aleksander Asanowicz
year 2001
title The End of Methodology - Towards New Integration
source AVOCAAD - ADDED VALUE OF COMPUTER AIDED ARCHITECTURAL DESIGN, Nys Koenraad, Provoost Tom, Verbeke Johan, Verleye Johan (Eds.), (2001) Hogeschool voor Wetenschap en Kunst - Departement Architectuur Sint-Lucas, Campus Brussel, ISBN 80-76101-05-1
summary The present paper is devoted to the deliberation on the genesis and development of designing from the point of view of the potential use of computers in the process. Moreover, it also presents the great hopes which were connected with the use of the systematic designing methods in the 1960’s, as well as the great disappointment resulting from the lack of concrete results. At this time a great deal of attention was paid to the process of design as a branch of a wider process of problem-solving. Many people believed that the intuitive methods of design traditionally used by architects were incapable of dealing with the complexity of the problems to be solved. Therefore, the basic problem was the definition of a vertical structure of the designing process, which would make it possible to optimise each process of architectural design. The studies of design methodology directed at the codification of the norms of actions have not brought about any solutions which could be commonly accepted, as the efforts to present the designing process as a formally logical one and one that is not internally “uncontrary” from the mathematical point of view, were doomed to fail. Moreover, the difficulties connected with the use of the computer in designing were caused by the lack of a graphic interface, which is so very characteristic of an architect’s workshop. In result, the methodology ceased to be the main area of the architect’s interest and efforts were focused on facilitating the method of the designer’s communication with the computer. New tools were created, which enabled both the automatic generation of diversity and the creation of forms on the basis of genetic algorithms, as well as the presentation of the obtained results in the form of rendering, animation and VRML. This was the end of the general methodology of designing and the beginning of a number of methods solving the partial problems of computer-supported design. The present situation can be described with the words of Ian Stewart as a “chaotic run in all directions”. An immediate need for new integration is felt. Cyber-real space could be a solution to the problem. C-R-S is not a virtual reality understood as an unreal world. Whilst VR could be indeed treated as a sort of an illusion, C-R-S is a much more realistic being, defining the area in which the creative activities are taking place. The architect gains the possibility of having a direct contact with the form he or she is creating. Direct design enables one to creatively use the computer technology in the designing process. The intelligent system of recognising speech, integrated with the system of virtual reality, will allow to create an environment for the designer – computer communication which will be most natural to the person. The elimination of this obstacle will facilitate the integration of the new methods into one designing environment. The theoretical assumptions of such an environment are described in the present paper.
series AVOCAAD
last changed 2005/09/09 08:48

_id f500
authors Almeida Sampaio, A.
year 1999
title Automation of Deck Bridge Representations
source AVOCAAD Second International Conference [AVOCAAD Conference Proceedings / ISBN 90-76101-02-07] Brussels (Belgium) 8-10 April 1999, pp. 69-79
summary The bridge deck has a apparent simple shape, but it is the result of an adequate combination of two longitudinal geometric components: the deck shape evolution along de longitudinal section the layout of the road, that acts in simultaneous over a cross section, defining the deck exact shape. A geometric modelling computer programme was developed for box girder decks, allowing the generation of cross sections along the deck, defined with correct shape and location. In the elaboration of the deck plan drawings, the geometric information of the real deck shape is required. This information is not managed in an integrated and automatic way. On the creation of these drawings, directly executed over a graphic system, the time consumed is considerable and it is easy to comet errors. This paper describes the drawing module included in the computer program refereed. The deck plan projections are obtained, in DXF format drawing files, using the geometric information obtained from 3D-deck model. Using the drawing module it is possible to generate the usual deck drawings required in bridge design process. Then, his module is a great support for the design process within its geometric design stage.
series AVOCAAD
last changed 2005/09/09 08:48

_id aa7c
authors Amirante, M. Isabella and Burattini, Ernesto
year 1996
title Automatic Procedures for Bio-Climatic Control
source Education for Practice [14th eCAADe Conference Proceedings / ISBN 0-9523687-2-2] Lund (Sweden) 12-14 September 1996, pp. 29-40
summary The experiences illustrated here are related to the new regulation of teaching architecture in Italy and these ones in particular have been concentrated on the technological aspects of teaching architecture. We can consider the evolution of the architect from the individual operator to the manager multi- disciplinary aspects of the building process ( building process manager) as a reality today. Information technology, specifically applied to bio-climatic architecture and environmental control, can be of great importance for this professional role, and for this reason it is very useful to include these topics at the beginning the teaching design process. This paper describes a particular approach to bio-climatic problems of the architectural project. An experimental course has been performed by the second year students of the "Laboratorio di Construzione dell' Architettura", at the School of Architecture of the Second University of Naples, in Aversa. Analysing old and new buildings, they used some flow charts for the evaluation and representation of energetic behaviour of buildings regarding their climatic and geographical environment. In the flow charts the decisions are represented by boxes that allow to determine "rightness index" related to: morphological characters of the site and environment, typology and particular organisation of the inside spaces, shape of building, technological solution of the building "skin". The navigation through the decision boxes is made with simple options like; "winds: protected or exposed site", "shape of building; free, close or cross plane", "presence of trees on the south,; yes or not",; it shows the students the bio-climatic quality of the building and, through numeric value assigned to each option, determines the "weight" of its climatic comfort.

series eCAADe
last changed 2003/11/21 14:15

_id sigradi2014_155
id sigradi2014_155
authors Andrade, Max; Cristina Matsunaga
year 2014
title Avaliação Automática de Valor no Processo de Projeto de Habitação de Interesse Social no Brasi [Alignment Automated Assessment of Value in Brazilian’s Housing Design]
source SiGraDi 2014 [Proceedings of the 18th Conference of the Iberoamerican Society of Digital Graphics - ISBN: 978-9974-99-655-7] Uruguay - Montevideo 12 - 14 November 2014, pp. 393-397
summary The method proposed in this paper addresses the management of values and the cost estimate, based on target costing approach, and integrated with Building Information Model (BIM). This design method must incorporate mechanisms of automated assessment associated with desired value at cost during the design process. The paper will try to show, in brief, that there is a real possibility of inclusion of methodological tools of design, allowing assessment of values in real time during the design actions.
keywords Building Information Modeling; Desired value; Automatic Assessment; Target Costing
series SIGRADI
last changed 2016/03/10 08:47

_id 0bab
authors Araya, Hirokazu and Kagoshima, Masayuki
year 2001
title Semi-automatic control system for hydraulic shovel
source Automation in Construction 10 (4) (2001) pp. 477-486
summary A semi-automatic control system for a hydraulic shovel has been developed. Using this system, unskilled operators can operate a hydraulic shovel easily and accurately. A mathematical control model of a hydraulic shovel with a controller was constructed and a control algorithm was developed by simulation. This algorithm was applied to a hydraulic shovel and its effectiveness was evaluated. High control accuracy and high-stability performance were achieved by feedback plus feedforward control, nonlinear compensation, state feedback and gain scheduling according to the attitude.
series journal paper
last changed 2003/05/15 19:22

_id 623e
authors Arumi-Noe, Francisco
year 1995
title Algorithm For The Automatic Design Of A Shading Device
source Computing in Design - Enabling, Capturing and Sharing Ideas [ACADIA Conference Proceedings / ISBN 1-880250-04-7] University of Washington (Seattle, Washington / USA) October 19-22, 1995, pp. 233-242
summary Given that there is a need to shade a window from the summer sun and also a need to expose it to the winter sun, this article describes an algorithm to design automatically a geometric construct that satisfies both requirements. The construct obtained represents the minimum solution to the simultaneous requirements. The window may be described by an arbitrary convex polygon and it may be oriented in any direction and it may be placed at any chosen latitude. The algorithm consists of two sequential steps: first to find a winter solar funnel surface; and the second to clip the surface subject to the summer shading conditions. The article introduces the design problem, illustrates the results through two examples, outlines the logic of the algorithm and includes the derivation of the mathematical relations required to implement the algorithm. This work is part of the MUSES project, which is a long term research effort to integrate Energy Consciousness with Computer Graphics in Architectural Design.
keywords Energy Conscious Design, Green Architecture, Sustainable Architecture, Solar Design, Computer Aided Design
series ACADIA
last changed 1999/03/29 15:15

_id ecaade2008_160
id ecaade2008_160
authors Aschwanden, Gideon; Halatsch, Jan; Schmitt , Gerhard
year 2008
title Crowd Simulation for Urban Planning
source Architecture in Computro [26th eCAADe Conference Proceedings / ISBN 978-0-9541183-7-2] Antwerpen (Belgium) 17-20 September 2008, pp. 493-500
summary This paper presents a semi-automatic visualization method for the evaluation of urban environments that is based on artificial intelligence. It proposes the use of agent-based crowd simulation software on a mid-scale urban planning level for design evaluation. The information on agents’ movements is noted in standard raster images. The results are maps that are easy to understand. These maps show movement paths of the agents and density and give further conclusion on bottlenecks in planning contexts. Key measures, like the occupant movement in a given district, until now relied greatly on empirical knowledge or data that could be only gathered after an urban design had become built reality. Our method focuses on the adaptation of common software technology that is originally situated in film and TV productions. A practical workflow shows how our method can be easily integrated in daily design tasks.
keywords Artificial intelligence, agent-based, crowd simulation, urban planning, design evaluation, occupant movement
series eCAADe
last changed 2008/09/09 13:55

_id 843d
authors Avron, Barr and Feigenbaum, Edward A. (editors)
year 1982
title The Handbook of Artificial Intelligence
source xiii, 428 p. Stanford, California: Heuristech Press, 1982. vol. 2 of 3: Includes bibliography p.383-402 and indexes
summary Part 2 of a three vol. work. This vol covers: AI programming languages, the kinds of programming languages suitable for AI, features and environments developed that were developed for its purpose. Expert systems in science, medicine and education. The last chapters reviews automatic programming
keywords AI, programming, languages, expert systems, automation
series CADline
last changed 2003/06/02 11:58

_id c777
authors Bach, Fr.-W., Rachkov, M., Seevers, J. and Hahn, M.
year 1995
title High tractive power wall-climbing robot
source Automation in Construction 4 (3) (1995) pp. 213-224
summary There are a lot of tasks in building construction and maintenance which demand either the carriage of heavy technological equipment along vertical and sloping surfaces and/or provision for force technological operations on such surfaces For example, surface cleaning or grinding by automatic equipment, the mounting of expansion bolts and anchors by drilling or by driving in. Additionally surface inspection by heavy measuring devices and the painting of big construction areas are difficult and expensive to perform manually. It is therefore expedient to apply climbing robots to automate these tractive power operations. The climbing robot was developed for such purposes. The design of the robot with increased load capacity and improved gripper system was carefully considered. The robot has a video camera for orientation and for the monitoring of processes. A sensor-based computer control system is used. This paper contains a brief overview of the technical parameters and experimental characteristics of the robot's transport module, control system with video camera unit, and the different schemes of the robot's application.
keywords Climbing robot; Two-staged gripper system Monitoring Sensor-based computer control system; Automatic Technological equipment
series journal paper
last changed 2003/06/02 07:36

_id acadia10_313
id acadia10_313
authors Banda, Pablo
year 2010
title Parametric Propagation of Acoustical Absorbers
source ACADIA 10: LIFE in:formation, On Responsive Information and Variations in Architecture [Proceedings of the 30th Annual Conference of the Association for Computer Aided Design in Architecture (ACADIA) ISBN 978-1-4507-3471-4] New York 21-24 October, 2010), pp. 313-319
summary The following paper deals with a performance-driven morphogenetic design task to improve the conditions of room acoustics, using as a case study the material laboratory of the School of Architecture at Federico Santa Maria University of Technology. Combining contemporary Parametric Modeling techniques and a Performance- Based approach, an automatic generative system was produced. This system generated a modular acoustic ceiling based on Helmholtz Resonators. To satisfy sound absorption requirements, acoustic knowledge was embedded within the system. It iterates through a series of design sub-tasks from Acoustic Simulation to Digital Fabrication, searching for a suitable design solution. The internal algorithmic complexity of the design process has been explored through this case study. Although it is focused on an acoustic component, the proposed design methodology can influence other experiences in Parametric Design.
keywords Parametric Modeling, Sound Absorption & Acoustic Knowledge, Performance-Based Design, Design Task, Scripting, Digital Fabrication, Custom Tools, Honeycomb.
series ACADIA
type normal paper
last changed 2010/12/07 13:27

_id 2832
authors Baraniak, David W.
year 1987
title Automatic Data Capture: Scanners Offer a Cost-effective Solution
source computer Graphics World November, 1987. vol. 10: pp. 93-94, 97 : ill.
summary table. In order to decide whether today's scanner deliver the price and performance a particular CAAD application demand, the author lists vendors, scanner type, raster to vector conversion editing raster vector, data exchange format and compares them
keywords hardware, CAD, scanning, business
series CADline
last changed 2003/06/02 11:58

_id 6002
authors Barduzzi, Ondina and Pascolo, Carlo
year 1986
title CAD System (Computer Aided Design) for the Planning of the Territory, with Reference to the Automatical Estimate of Works of Urbanization
source Teaching and Research Experience with CAAD [4th eCAADe Conference Proceedings] Rome (Italy) 11-13 September 1986, pp. 167-179
summary Any applied research, no matter what discipline is concerned, needs affined and suitable tools; as regards the studies in the field of architecture and planning, the use of automatic systems of analysis, data ordering and comparison is of particular interest. The quickness of operations by means of computers and the corresponding graphical representation gives new possibilities for scientific work, once impossible, not certainly because of conceptual limits, but practically, for the limits of available tools. It is the wideness of applications of computers to be pointed out, for although studied for scientific reasons, their practical usefulness is often enormous. This has been generally verified. It guilts in particular for the CAD System, proposed and explained in this paper. The practical utility this and other systems from the same field have for the public administration, contractors and consultants is well known and therefore not necessary to be described further. The use of such systems is particularly convenient in those sectors where the graphical representation is the basic part of the production process.

series eCAADe
last changed 2003/11/21 14:16

_id 58f4
authors Barequet, G. and Kumar, S.
year 1997
title Repairing CAD models
source Proceedings of IEEE Visualizationí97, pp. 363-370
summary We describe an algorithm for repairing polyhedral CAD models that have errors in their B-REP. Errors like cracks, degeneracies, duplication, holes and overlaps are usually introduced in solid models due to imprecise arithmetic, model transformations, designer's fault, programming bugs, etc. Such errors often hamper further processing like finite element analysis, radiosity computation and rapid prototyping. Our fault-repair algorithm converts an unordered collection of polygons to a shared-vertex representation to help eliminate errors. This is done by choosing, for each polygon edge, the most appropriate edge to unify it with. The two edges are then geometrically merged into one, by moving vertices. At the end of this process, each polygon edge is either coincident with another or is a boundary edge for a polygonal hole or a dangling wall and may be appropriately repaired. Finally, in order to allow user- inspection of the automatic corrections, we produce a visualization of the repair and let the user mark the corrections that conflict with the original design intent. A second iteration of the correction algorithm then produces a repair that is commensurate with the intent. Thus, by involving the users in a feedback loop, we are able to refine the correction to their satisfaction.
series other
last changed 2003/04/23 13:14

_id 6559
authors Barrionuevo, Luis F. and Borsetti, Ricardo
year 2001
title LA POTENCIALIDAD ESPACIAL DE LOS "SPIROLATERALS" EN LA ARQUITECTURA (The Spacial Potential of the "Spirolaterals" in Architecture)
source SIGraDi biobio2001 - [Proceedings of the 5th Iberoamerican Congress of Digital Graphics / ISBN 956-7813-12-4] Concepcion (Chile) 21-23 november 2001, pp. 74-76
summary “Spirolaterals” (Odds, 1973) are mathematical entities created by drawing a set of lines, the first at a unit length, then each additional line increasing by a value of certain longitude while turning a constant or variable direction. (Krawczyk, 2000) The objective of this work is to propose the use of spirolaterals as a geometric support to produce preliminary alternatives for architectural layouts. A computation program is implemented to demonstrate the automatic production of spatial spirolaterals: spirospace, and images of results are exposed.
series SIGRADI
last changed 2016/03/10 08:47

_id caadria2003_c4-3
id caadria2003_c4-3
authors Belblidia, S. and Alby, E.
year 2003
title Implicit Handling of Geometric Relations in an Existing Modeler
source CAADRIA 2003 [Proceedings of the 8th International Conference on Computer Aided Architectural Design Research in Asia / ISBN 974-9584-13-9] Bangkok Thailand 18-20 October 2003, pp. 613-622
summary This paper presents a constraint-based modeling system, integrated into a widely used CAD modeler. Using a notification mechanism, the system records the precision functions called by the user in order to maintain geometric relations between points locations and source objects. These relations are stored in a directed graph which allows an automatic update of the model.
series CAADRIA
last changed 2003/12/02 06:47

_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
last changed 2016/03/10 08:47

_id 48a2
authors Bergstrom, Axel Lennart
year 1982
title Computer Graphics in Community Planning
source June, 1982. 3 p
summary The digitized map of Sweden uses a technique for graphical presentation in color based on an automatic drawing machine called the 'color ink jet plotter.' A short description of this project is given
keywords mapping, computer graphics
series CADline
last changed 1999/02/12 14:07

_id cf2011_p098
id cf2011_p098
authors Bernal, Marcelo; Eastman Charles
year 2011
title Top-down Approach for Interaction of Knowledge-Based Parametric Objects and Preliminary Massing Studies for Decision Making in Early Design Stages
source Computer Aided Architectural Design Futures 2011 [Proceedings of the 14th International Conference on Computer Aided Architectural Design Futures / ISBN 9782874561429] Liege (Belgium) 4-8 July 2011, pp. 149-164.
summary Design activities vary from high-degree of freedom in early concept design stages to highly constrained solution spaces in late ones. Such late developments entail large amount of expertise from technical domains. Multiple parallel models handle different aspects of a project, from geometric master models to specific building components. This variety of models must keep consistency with the design intent while they are dealing with specific domains of knowledge such as architectural design, structure, HVAC, MEP, or plumbing systems. Most of the expertise embedded within the above domains can be translated into parametric objects by capturing design and engineering knowledge through parameters, constraints, or conditionals. The aim of this research is capturing such expertise into knowledge-based parametric objects (KPO) for re-usability along the design process. The proposed case study ‚Äì provided by SOM New York‚ is the interaction between a massing study of a high-rise and its building service core, which at the same time handles elevators, restrooms, emergency stairs, and space for technical systems. This project is focused on capturing design expertise, involved in the definition of a building service core, from a high-rise senior designer, and re-using this object for interaction in real-time with a preliminary massing study model of a building, which will drive the adaption process of the service core. This interaction attempts to provide an integrated design environment for feedback from technical domains to early design stages for decision-making, and generate a well-defined first building draft. The challenges addressed to drive the instantiation of the service core according to the shifting characteristics of the high-rise are automatic instantiation and adaptation of objects based on decision rules, and updating in real-time shared parameters and information derived from the high-rise massing study. The interaction between both models facilitates the process from the designer‚Äôs perspective of reusing previous design solutions in new projects. The massing study model is the component that handles information from the perspective of the outer shape design intent. Variations at this massing study model level drive the behavior of the service core model, which must adapt its configuration to the shifting geometry of the building during design exploration in early concept design stages. These variations depend on a list of inputs derived from multiple sources such as variable lot sizes, building type, variable square footage of the building, considerations about modularity, number of stories, floor-to-floor height, total building height, or total building square footage. The shifting combination of this set of parameters determines the final aspect of the building and, consequently, the final configuration of the service core. The service core is the second component involved in the automatic generation of a building draft. In the context of BIM, it is an assembly of objects, which contains other objects representing elevators, restrooms, emergency stairs, and space for several technical systems. This assembly is driven by different layouts depending on the building type, a drop-off sequence, which is the process of continuous reduction of elevators along the building, and how this reduction affects the re-arrangement of the service core layout. Results from this research involves a methodology for capturing design knowledge, a methodology for defining the architecture of smart parametric objects, and a method for real-time-feedback for decision making in early design stages. The project also wants to demonstrate the feasibility of continuous growth on top of existing parametric objects allowing the creation of libraries of smart re-usable objects for automation in design.
keywords design automation, parametric modeling, design rules, knowledge-based design
series CAAD Futures
last changed 2012/02/11 18:21

_id c57b
authors Bier, Eric A.
year 1988
title Snap-Dragging. Interactive Geometric design in Two and Three Dimensions
source University of California, Berkeley
summary Graphic artists, mechanical designers, architects, animators, authors of technical papers and others create geometric designs (illustrations and solid models) as a major part of their daily efforts. Some part of this shape construction must be done with precision. For instance, certain line segments should be horizontal, parallel or congruent. In recent years, interactive computer programs have been used to speed up the production of precise geometric designs. These programs take advantage of high-speed graphics, equation solving, and computer input peripherals to reduce the time needed to describe point positions to the machine. Previous techniques include rounding the cursor to points on a rectangular grid, solving networks of constraints, and supporting step-by-step drafting-style constructions. Snap-dragging is a modification of the drafting approach that takes advantage of powerful workstations to reduce the time needed to make precise illustrations. Using a single gravity mapping, a cursor can be snapped to either points, lines or surface. The gravity algorithm achieves good performance by computing intersection points on the fly. To aid precise construction, a set of lines, circles, planes, and spheres, called alignment objects, are constructed by the system at a set of slopes, angles, and distances specified by the user. These alignments objects are constructed at each vertex or edge that the user has declared to be hot (of interest). Vertices and edges can also be made hot by the system through the action of an automatic hotness rule. When snap-dragging is used, shapes can often be constructed using a few more keystrokes than would be needed to sketch them freehand. Objects can be edited at arbitrary orientations and sizes. The number of primitive operations is small, making it possible to provide keyboard combinations for quickly activating most of these operations. The user interface works nearly identically in two or three dimensions. In three dimensions, snap-dragging works with a two-dimensional pointing device in a single perspective view.  
series thesis:PhD
last changed 2003/02/12 21:37

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