A New Interface for Conceptual Design Based on Object Reconstruction from a Single Freehand Sketch

are troublesome for curvature-based classification, and (b) it has a short execution time that is not dependent on the length of the stroke or the number of sample points acquired (assuming coordinates have been summed while drawing the stroke). The procedure can therefore be used to provide continuous feedback of the interpreted entity during drawing, in real time. However, in spite of this ability, it is evident that geometrical-based classification is inherently limited and a more general, context-sensitive approach must be pursued. A new endpoint clustering scheme has also been presented based on adaptive tolerances at different parts of the sketch. The proposed formulation provides a framework for implementing various criteria for determining local thresholds, such as detail sensitive criteria, dynamic criteria, or other application specific criteria. Again, clustering can be improved using a contextsensitive approach. Acknowledgments This research has been supported in part by the Fund for 4 Pavlidis, T., and Van Wyk, C. J., 1985, "An Automatic Beautifler for Drawings and Illustrations," SIGGRAPH 85, Vol. 19, No. 3, pp. 225-234. 5 Bengi, F., and Ozguc, B., 1990, "Architectural Sketch Recognition," Architectural Science Review, Vol. 33, pp. 3-16. 6 Eggli, L., BrUderlin, B. P., and Elber, G. Introduction Improperly designed engineering products may fail in fatigue causing losses in revenue and personal injury or death. Currently, these failures are avoided by either using expensive design techniques involving extensive modeling and testing or by over designing the part. The expense of testing and modification of the initial design is reduced if the design criterion gives a good initial approximation. Several design approaches have been developed to address the problem of fatigue damage of ductile metals loaded with positive mean and alternating stresses. The Bagci, Gerber, Nichihara, modified Goodman, Quadratic, and Soderberg lines are a few of the techniques that have been proposed to address the problem. This paper presents the modified Findley line for designing parts which experience positive mean stress fatigue loading. The modified Findley line is based on the assumption that the critical shear decreases with an increase in the normal stress acting on the same plane, and is simple and less conservative than the modified Goodman line. The Modified Findley Line Flavenot and Skalli (1984) stated "the mechanism corresponding to the initiation of fatigue cracks is most often the shearing of crystallographic planes. It appears logical then to have a criterion relating the normal stress to alternating shear stress which might be local shear stress in most favorable oriented plane." This assumption was used before by Stanfield (1935), who suggested that both the shear and normal stresses on the fatigue plane should be considered in a fatigue failure criterion and proposed the relation (1) where TN and ON are the shear and normal stresses components on the critical plane; /and k are materials constants. Stulen and Cummings (1954), and Findley et al. (195 6) used similar forms as fatigue criteria to address the problem of absolutely reversing fatigue. Findley (1959) used the linear relationship between shear stress and normal stress on a critical plane to include the effect of mean stress on the fatigue of metals under combined loading. Journal of Mechanical Design MARCH 1997, Vol. 119/135 Copyright © 1997 by ASME where a^^" and <7" are the maximum and alternating fatigue stresses; / and k are experimental constants. Since these constants may vary with the design parameters, including materials, the actual design must be tested to determine the values of / and k. To experimentally find the values of these constants, the life of the part is determined, and at this point the values of / and k are of only academic interest. Thus, if the fatigue criterion presented in Eq. It should be noted that the negative root of Eq. Upon the application of condition (b), Eq. (4) becomes /=A:5",. Equations Substituting Eqs. 5" -[-S" + 4SI + 4(5", -5")(S", -a") ], (10) 2(5",-5") which is called the modified Findley line. Comparison With Actual Experimental Data The modified Findley, Gerber, and modified Goodman lines were compared with the experimentally developed fatigue data found in the literature. Typical data showing the fatigue points of both ferrous and non-ferrous ductile materials are shown in As shown in these figures and comparison done by Wang (1995), the modified Findley line falls between the modified Goodman line and Gerber parabola, which is supported by Conclusion The modified Findley line is based on the assumption that the critical shear decreases with an increase in the normal stress acting on the same plane, then by using ultimate strength and endurance limit as parameters to obtain a good initial approximation. Limited fatigue data is available in the open literature, and more comparison should be made before the modified Findley line is universally adopted. However, form the references found, it appears that the modified Findley line is a strong candidate for .fatigue criterion for parts made of non-ferrous ductile materials, and is conservative for ferrous parts. For a design engineer, the modified Findley line is simple and easy to use, and represents a very promising approach for leading to reasonable starting designs involving positive mean stress fatigue. Reference

Generation of subdivision surface from network of curves

Subdivision surfaces are usually used to construct freeform surfaces from network of curves for its ability and flexibility to deal with complex wireframes. In freeform surface designing, the designers usually draw at first some curves for describing the models conceived in their mind which form a curve network representing an object of arbitrary topology. Then 3D surfaces are computed to interpolate these curves in order to create a B-Rep model. If the subdivision surface is used in the workflow, its control polyhedrons generation from curves polygons could be a time-consuming stage. In this article, we develop an approach to generate automatically a control polyhedral mesh from an arbitrary topological curve network. One of common problems in interpolating surface patch using subdivision surfaces is how to determine the connectivity of control points. Arbitrary topological curve network has no restriction in topology structure, so another problem is that it has more ambiguousness in defining surface patches. There are three steps in our approach. Firstly, we compute a 1D mesh (a unique polygonal model) from curves. Secondly, we identify on the polygon different cycles that would be the boundaries of potential surface patches. Finally, in each identified cycle we apply an algorithm of quadrangulation to construct the control mesh of subdivision

Recovering 3D geometry from single line drawings.

Xue, Tianfan.Thesis (M.Phil.)--Chinese University of Hong Kong, 2011.Includes bibliographical references (p. 52-55).Abstracts in English and Chinese.Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Previous Approaches on Face Identification --- p.3Chapter 1.1.1 --- Face Identification --- p.3Chapter 1.1.2 --- General Objects --- p.4Chapter 1.1.3 --- Manifold Objects --- p.7Chapter 1.2 --- Previous Approaches on 3D Reconstruction --- p.9Chapter 1.3 --- Our approach for Face Identification --- p.11Chapter 1.4 --- Our approach for 3D Reconstruction --- p.13Chapter 2 --- Face Detection --- p.14Chapter 2.1 --- GAFI and its Face Identification Results --- p.15Chapter 2.2 --- Our Face Identification Approach --- p.17Chapter 2.2.1 --- Real Face Detection --- p.18Chapter 2.2.2 --- The Weak Face Adjacency Theorem --- p.20Chapter 2.2.3 --- Searching for Type 1 Lost Faces --- p.22Chapter 2.2.4 --- Searching for Type 2 Lost Faces --- p.23Chapter 2.3 --- Experimental Results --- p.25Chapter 3 3 --- D Reconstruction --- p.30Chapter 3.1 --- Assumption and Terminology --- p.30Chapter 3.2 --- Finding Cuts from a Line Drawing --- p.34Chapter 3.2.1 --- Propositions for Finding Cuts --- p.34Chapter 3.2.2 --- Searching for Good Cuts --- p.35Chapter 3.3 --- Separation of a Line Drawing from Cuts --- p.38Chapter 3.4 3 --- D Reconstruction from a Line Drawing --- p.45Chapter 3.5 --- Experiments --- p.45Chapter 4 --- Conclusion --- p.5

3D object reconstruction from line drawings.

Cao Liangliang.Thesis (M.Phil.)--Chinese University of Hong Kong, 2005.Includes bibliographical references (leaves 64-69).Abstracts in English and Chinese.Chapter 1 --- Introduction and Related Work --- p.1Chapter 1.1 --- Reconstruction from Single Line Drawings and the Applications --- p.1Chapter 1.2 --- Optimization-based Reconstruction --- p.2Chapter 1.3 --- Other Reconstruction Methods --- p.2Chapter 1.3.1 --- Line Labeling and Algebraic Methods --- p.2Chapter 1.3.2 --- CAD Reconstruction --- p.3Chapter 1.3.3 --- Modelling from Images --- p.3Chapter 1.4 --- Finding Faces of Line Drawings --- p.4Chapter 1.5 --- Generalized Cylinder --- p.4Chapter 1.6 --- Research Problems and Our Contribution --- p.5Chapter 1.6.1 --- A New Criteria --- p.5Chapter 1.6.2 --- Recover Objects from Line Drawings without Hidden Lines --- p.6Chapter 1.6.3 --- Reconstruction of Curved Objects --- p.6Chapter 1.6.4 --- Planar Limbs Assumption and the Derived Models --- p.6Chapter 2 --- A New Criteria for Reconstruction --- p.8Chapter 2.1 --- Introduction --- p.8Chapter 2.2 --- Human Visual Perception and the Symmetry Measure --- p.10Chapter 2.3 --- Reconstruction Based on Symmetry and Planarity --- p.11Chapter 2.3.1 --- Finding Faces --- p.11Chapter 2.3.2 --- Constraint of Planarity --- p.11Chapter 2.3.3 --- Objective Function --- p.12Chapter 2.3.4 --- Reconstruction Algorithm --- p.13Chapter 2.4 --- Experimental Results --- p.13Chapter 2.5 --- Summary --- p.18Chapter 3 --- Line Drawings without Hidden Lines: Inference and Reconstruction --- p.19Chapter 3.1 --- Introduction --- p.19Chapter 3.2 --- Terminology --- p.20Chapter 3.3 --- Theoretical Inference of the Hidden Topological Structure --- p.21Chapter 3.3.1 --- Assumptions --- p.21Chapter 3.3.2 --- Finding the Degrees and Ranks --- p.22Chapter 3.3.3 --- Constraints for the Inference --- p.23Chapter 3.4 --- An Algorithm to Recover the Hidden Topological Structure --- p.25Chapter 3.4.1 --- Outline of the Algorithm --- p.26Chapter 3.4.2 --- Constructing the Initial Hidden Structure --- p.26Chapter 3.4.3 --- Reducing Initial Hidden Structure --- p.27Chapter 3.4.4 --- Selecting the Most Plausible Structure --- p.28Chapter 3.5 --- Reconstruction of 3D Objects --- p.29Chapter 3.6 --- Experimental Results --- p.32Chapter 3.7 --- Summary --- p.32Chapter 4 --- Curved Objects Reconstruction from 2D Line Drawings --- p.35Chapter 4.1 --- Introduction --- p.35Chapter 4.2 --- Related Work --- p.36Chapter 4.2.1 --- Face Identification --- p.36Chapter 4.2.2 --- 3D Reconstruction of planar objects --- p.37Chapter 4.3 --- Reconstruction of Curved Objects --- p.37Chapter 4.3.1 --- Transformation of Line Drawings --- p.37Chapter 4.3.2 --- Finding 3D Bezier Curves --- p.39Chapter 4.3.3 --- Bezier Surface Patches and Boundaries --- p.40Chapter 4.3.4 --- Generating Bezier Surface Patches --- p.41Chapter 4.4 --- Results --- p.43Chapter 4.5 --- Summary --- p.45Chapter 5 --- Planar Limbs and Degen Generalized Cylinders --- p.47Chapter 5.1 --- Introduction --- p.47Chapter 5.2 --- Planar Limbs and View Directions --- p.49Chapter 5.3 --- DGCs in Homogeneous Coordinates --- p.53Chapter 5.3.1 --- Homogeneous Coordinates --- p.53Chapter 5.3.2 --- Degen Surfaces --- p.54Chapter 5.3.3 --- DGCs --- p.54Chapter 5.4 --- Properties of DGCs --- p.56Chapter 5.5 --- Potential Applications --- p.59Chapter 5.5.1 --- Recovery of DGC Descriptions --- p.59Chapter 5.5.2 --- Deformable DGCs --- p.60Chapter 5.6 --- Summary --- p.61Chapter 6 --- Conclusion and Future Work --- p.62Bibliography --- p.6

Reconstrucción geométrica de sólidos utilizando técnicas de optimización

Este trabajo tiene por objetivo la reconstrucción automática de modelos geométricos, a partir de la información contenida en una única imagen vectorial y geométricamente consistente de un objeto poliédrico. Los procesos de optimización son a nuestro entender el camino más prometedor para la reconstrucción, en tanto que pueden simular la manera en que percibe el ser humano. Sin embargo la Reconstrucción Geométrica planteada como proceso de optimización presenta como problema fundamental una función objetivo compleja: con muchos mínimos locales. Los mínimos locales son modelos no válidos, porque no son acordes con la percepción visual humana (no son psicológicamente plausibles). Además, el punto de partida del algoritmo (la imagen), constituye un mínimo local. Nuestro trabajo se orientó inicialmente a implementar un algoritmo de optimización de los que se proclaman capaces de obtener mínimos globales. Sin embargo, llegamos a la conclusión de que ni siquiera dichos algoritmos garantizan el óptimo en el caso de la Reconstrucción Geométrica, porque su comportamiento depende mucho de sus propios parámetros de ajuste y de la naturaleza del modelo a reconstruir. Es por ello que creemos necesario que los algoritmos de optimización vengan asistidos de estrategias de inflado tentativo, para generar modelos iniciales tan próximos como sea posible al optimo global, es decir, que sean lo más parecidos posible al modelo psicológicamente plausible. En ese camino hemos desarrollado tres estrategias que permiten generar modelos iniciales. Hemos comprobado que cada una de estas estrategias funcionan bien cuando se aplican a modelos de ciertas tipologías, por lo que hemos desarrollado una clasificación específica de poliedros acorde con nuestros fines. Dado que la clasificación está orientada a seleccionar la estrategia de inflado tentantivo más conveniente, también hemos desarrollado un algoritmo para detectar el tipo de poliedro automáticamente a partir de la imagen de entrada.Universidad Politécnica de CartagenaPrograma de Doctorado en Análisis y Diseño Avanzado de Estructura