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2D shape similarity as a complement for Voronoi-Delone methods in shape reconstruction
(PERGAMON-ELSEVIER SCIENCE LTD, 2005-02-01) Ruiz, O.E.; Cadavid, C.A.; Granados, M.; Peña, S.; Vásquez, E.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
In surface reconstruction from planar cross sections it is necessary to build surfaces between 2D contours in consecutive cross sections. This problem has been traditionally attacked by (i) direct reconstruction based on local geometric proximity between the contours, and (ii) classification of topological events between the cross sections. These approaches have been separately applied with limited success. In case (i), the resulting surfaces may have overstretched or unnatural branches. These arise from local contour proximity which does not reflect global similarity between the contours. In case (ii), the topological events are identified but are not translated into the actual construction of a surface. This article presents an integration of the approaches (i) and (ii). Similarity between the composite 2D regions bounded by the contours in consecutive cross sections is used to: (a) decide whether a surface should actually relate two composite 2D regions, (b) identify the type and location of topological transitions between cross sections and (c) drive the surface construction for the regions found to be related in step (a). The implemented method avoids overstretched or unnatural branches, rendering a surface which is both geometrically intuitive and topologically faithful to the cross sections of the original object. The presented method is a good alternative in cases in which correct reproduction of the topology of the surface (e.g. simulation of flow in conduits) is more important than its geometry (e.g. assessment of tumor mass in radiation planning). © 2004 Elsevier Ltd. All rights reserved.
Adaptative cubical grid for isosurface extraction
(2009) Congote, John; Moreno, Aitor; Barandiaran, Iñigo; Barandiaran, Javier; Ruíz, Óscar E.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
This work proposes a variation on the Marching Cubes algorithm, where the goal is to represent implicit functions with higher resolution and better graphical quality using the same grid size -- The proposed algorithm displaces the vertices of the cubes iteratively until the stop condition is achieved -- After each iteration, the difference between the implicit and the explicit representations are reduced, and when the algorithm finishes, the implicit surface representation using the modified cubical grid is more detailed, as the results shall confirm -- The proposed algorithm corrects some topological problems that may appear in the discretisation process using the original grid
Adaptative cubical grid forisosurface extraction
(2009-01-01) Congote, J.; Moreno, A.; Barandiaran, I.; Barandiaran, J.; Ruiz, O.E.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
This work proposes a variation on the Marching Cubes algorithm, where the goal is to represent implicit functions with higher resolution and better graphical qualiry using the same grid size. The proposed algorithm displaces the vertices of the cubes iteratively until the stop condition is achieved. After each iteration, the difference betvveen the implicit and the explicit representations are reduced, and when the algorithm finishes, the implicit surface representation using the modified cubical grid is more detailed, as the results shall confirm. The proposed algorithm corrects some topological problems that may appear in the discretisation process using the original grid.
Advanced HCI and 3D Web over Low performance Devices
(2012-07) Oyarzun, David; Del Pozo, Arantza; Congote, John Edgar; Olaizola, Igor G.; Sainz, Iñaki; Leturia, Igor; Arregi, Xabier; Ruíz, Óscar; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
This position paper presents the authors’ goals on advanced human computer interaction and 3D Web -- Previous work on speech, natural language processing and visual technologies has achieved the development of the BerbaTek language learning demonstrator, a 3D virtual tutor that supports Basque language students through spoken interaction -- Next steps consist on migrating all the system to multidevice web technologies -- This paper shows the architecture defined and the steps to be performed in the next months
Advanced HCI and 3D web over low performance devices
(CEUR-WS, 2012-01-01) Oyarzun, D.; Del Pozo, A.; Congote, J.E.; Olaizola, I.G.; Sainz, I.; Leturia, I.; Arregi, X.; Ruiz, O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
This position paper presents the authors' goals on advanced human computer interaction and 3D Web. Previous work on speech, natural language processing and visual technologies has achieved the development of the BerbaTek language learning demonstrator, a 3D virtual tutor that supports Basque language students through spoken interaction. Next steps consist on migrating all the system to multidevice web technologies. This paper shows the architecture defined and the steps to be performed in the next months.
Algorithms for reconstruction of 3D surfaces for anthropometric modeling
(INGEGRAF, 2000) Ruíz Salguero, O.; Schrader Gil, R.; Acosta Duarte, J.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
Los protocolos de medición antropométrica se caracterizan por la profusión de medidas discretas o localizadas, en un intento para caracterizar completamente la forma corporal del sujeto -- Dichos protocolos se utilizan intensivamente en campos como medicina deportiva, forense y/o reconstructiva, diseño de prótesis, ergonomía, en la confección de prendas, accesorios, etc -- Con el avance de algoritmos de recuperación de formas a partir de muestreos (digitalizaciones) la caracterización antropométrica se ha alterado significativamente -- El articulo presente muestra el proceso de caracterización digital de forma corpórea, incluyendo los protocolos de medición sobre el sujeto, el ambiente computacional - DigitLAB- (desarrollado en el CII-CAD-CAM-CG de la Universidad EAFIT) para recuperación de superficies, hasta los modelos geométricos finales -- Se presentan comparaciones de los resultados obtenidos con DigitLAB y con paquetes comerciales de recuperación de forma 3D -- Los resultados de DigitLAB resultan superiores, debido principalmente al hecho de que este toma ventaja de los patrones de las digitalizaciones (planares de contacto, por rejilla de pixels - range images -, etc.) y provee módulos de tratamiento geométrico - estadístico de los datos para poder aplicar efectivamente los algoritmos de recuperación de forma -- Se presenta un caso de estudio dirigido a la industria de la confección, y otros efectuados sobre conjuntos de prueba comunes en el ámbito científico para la homologación de algoritmos
Aspect ratio- and size-controlled patterned triangulations of parametric surfaces
(ACTA PRESS ANAHEIM, 2007-01-01) Ruiz, Oscar E.; Pena, Sebastian; Duque, Juan; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
A method to produce patterned, controlled size triangulation of Boundary Representations is presented. Although the produced patterned triangulations are not immediately suited for fast visualization, they were used in Fixed Grid Finite Element Analysis, and do provide a control on the aspect ratio or shape factor of the triangles produced. The method presented first calculates a triangulation in the parameter space of the faces in which the B-Rep is partitioned and then maps it to 3D space. Special emphasis is set in ensuring that the triangulations of neighboring faces meet in a seamless manner, therefore ensuring that a borderless C2 2-manifold would have as triangulation a C0 borderless 2-manifold. The method works properly under the conditions (i) the parametric form of the face is a 1-1 function, (ii) the parametric pre-image of a parametric face is a connected region, and (iii) the user-requested sampling frequency ( samples per length unit ) is higher than twice the spatial frequency of the features in the B-Rep ( thus respecting the Nyquist principle ). As the conditions (i) and (ii) are possible under face reparameterization or sub-division and the condition (iii) is the minimum that a triangulation should comply with, the method is deemed as generally applicable.
Aspect ratio-and size-controlled patterned triangulations of parametric surfaces
(2007-02) Ruíz, Óscar E.; Peña, Sebastián; Duque, Juan; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
A method to produce patterned, controlled size triangulation of Boundary Representations is presented -- Although the produced patterned triangulations are not immediately suited for fast visualization, they were used in Fixed Grid Finite Element Analysis, and do provide a control on the aspect ratio or shape factor of the triangles produced -- The method presented first calculates a triangulation in the parameter space of the faces in which the B-Rep is partitioned and then maps it to 3D space -- Special emphasis is set in ensuring that the triangulations of neighboring faces meet in a seamless manner, therefore ensuring that a borderless C2 2-manifold would have as triangulation a C0 borderless 2-manifold -- The method works properly under the conditions(i) the parametric form of the face is a 1-1 function, (ii) the parametric pre-image of a parametric face is a connected region, and (iii) the user-requested sampling frequency (samples per length unit ) is higher than twice the spatial frequency of the features in the B-Rep ( thus respecting the Nyquist principle ) -- As the conditions (i) and (ii) are possible under face reparameterization or sub-division and the condition (iii) is the minimum that a triangulation should comply with, the method is deemed as generally applicable
Automatic Tools for Data Diagnostic and Correction in Aerophotogrametry
(INGEGRAF, 1999) Ruíz Salguero, Óscar E.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
En Aerofotogrametría, el proceso de restitución (paso de imagen a formato electrónico vectorizado) es realizado por un operador humano, con asistencia de hardware y Software especializado -- Dicho proceso implica la traducción de accidentes geográficos, detalles topográficos, etc., la cual conlleva errores tanto geométricos (precisión) como topológicos (conectividad) de los datos digitales vectorizados -- Adicionalmente, aun si la vectorizacion es perfecta, los editores en etapas subsecuentes deben realizar tareas repetitivas: formateo, marcado, ajuste de convenciones, etc., que por el tamaño de los archivos de datos se hacen prolongadas y propensas al error -- Tanto los procesos de corrección como de formateo y marcado requieren además la ejecución de entradas / salidas con el usuario en el computador, proceso que es particularmente lento -- Esta investigación presenta el desarrollo de herramientas automáticas de (i) detección y corrección de errores comunes en los planos restituidos, (ii) partición y re-agrupación inteligentes de planos grandes, y (iii) formateo y marcado automático -- El desarrollo de software se hace usando el standard AIS (Application Interface Specification), lo que lo hace portable a los modeladores cuya interface AIS haya sido implementada -- El proyecto se desarrolla para la firma AeroEstudios LTDA de Colombia, la cual lo ha incorporado a sus herramientas de procesamiento de información digital
Boolean 2D Shape Similarity For Surface Reconstruction
(2001) Ruíz, Óscar E.; Cadavid, Carlos A.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
Surface reconstruction problem (SRP) from planar samples has been traditionally approached by either (i) using local proximity between data points in adjacent layers, or by(ii) classifying the topological transitions that may explain the evolution of the cross sections -- Strategy (i) is robust in the sense that it has answers for every possible case, although in some scenarios renders counterintuitive surfaces, commented below -- Approach (ii) has mainly remained in the theoretical terrain -- The present work follows on aspect (ii), by using a Morse-based topological classification of the transitions, and complementing it with reasoning based on the geometry of the evolving cross sections to determine a high level description of the transitions from m to n contours (m:n transitions) -- This reasoning of shape similarity is performed by boolean operators -- Finally, the surface is synthesized using the m:n transitions -- This conjunction of topological and geometrical reasoning renders highly intuitive results, and allows for the incorporation of methods derived from the area of machine vision
Comparison of FEM software for 2D heat transfer analysis in sheet metal laser cutting
(2015) Mejía, Daniel; Moreno, Aitor; Barandiaran, Iñigo; Ruíz, Óscar; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
Finite Element Methods (FEM) have been used to simulate a variety of physical phenomena in the industrial manufacturing sector -- This paper addresses the simulation of the thermal properties in the metal sheet laser cutting -- A comparison of very well known FEM software is presented -- The results present small differences between the temperature distributions computed by the different software
Computational geometry in the preprocessing of point clouds for surface modeling
(1998) Ruíz, O.E.; Posada, J.L.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
In Computer Aided Geometric Design ( CAGD ) the automated fitting of surfaces to massive series of data points presents several difficulties: (i) even the formal definition of the problem is ambiguous because the mathematical characteristics (continuity, for example) of the surface fit are dependent on non-geometric considerations, (ii) the data has an stochastic sampling component that cannot be taken as literal, and, (iii) digitization characteristics, such as sampling interval and directions are not constant, etc -- In response, this investigation presents a set of computational tools to reduce, organize and re-sample the data set to fit the surface -- The routines have been implemented to be portable across modeling or CAD servers -- A case study is presented from the footwear industry, successfully allowing the preparation of a foreign, neutral laser digitization of a last for fitting a B-spline surface to it -- Such a result was in the past attainable only by using proprietary software, produced by the same maker of the digitizing hardware
Coupling Terrain and Building Database Information for Ray-Tracing Applications
(2003) Fontán, F.P.; Ruíz S., O.E.; Peña, S.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
In this paper a methodology for the combination and integration into a single data base of terrain and building data is presented -- This study is justified if ray-tracing techniques are to be used in propagation and channel modeling studies -- Usually terrain is available in grid or elevation form while building information is normally facet-oriented -- Ray-tracing (RT) techniques deal with flat facets and straight edges, if possible in triangular format -- To allow the use of RT on urban areas over irregular terrain a common format made up of facets and edges is therefore needed -- In this article, the procedure to accomplish this data homogeneity is presented -- It is assumed that terrain data is available in two formats: a) grid elevation and b) contour or iso-altitude lines -- Building data is assumed available in plant, polygonal planar contour form, a primitive and yet widely used format which is yet to be transformed into 3D entities -- The geometric modeling of joint terrain and building data is further difficuledt because union of surface objects (even after achieving a unified format) is undefined from the point of view of 3D boolean operations
A curvature-sensitive parameterization-independent triangulation algorithm
(2008-09) Ruíz, Óscar; Congote, John; Cadavid, Carlos; Lalinde, Juan G.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
Triangulations of a connected subset F of parametric surfaces S(u,v) (with continuity C2 or higher) are required because a C0 approximation of such F(called a FACE) is widely required for finite element analysis, rendering, manufacturing, design, reverse engineering, etc -- The triangulation T is such an approximation, when its piecewise linear subsets are triangles (which, on the other hand, is not a compulsory condition for being C0) -- A serious obstacle for algorithms which triangulate in the parametric space u−v is that such a space may be extremely warped, and the distances in parametric space be dramatically different of the distances in R3 -- Recent publications have reported parameter -independent triangulations, which triangulate in R3 space -- However, such triangulations are not sensitive to the curvature of the S(u,v) -- The present article presents an algorithm to obtain parameter-independent, curvature-sensitive triangulations -- The invariant of the algorithm is that a vertex v of the triangulation if identified, and a quasiequilateral triangulation around v is performed on the plane P tangent to S(u,v) at v -- The size of the triangles incident to v is a function of K(v), the curvature of S(u,v) at v -- The algorithm was extensively and successfully tested, rendering short running times, with very demanding boundary representations
Design of computer experiments applied to modeling compliant mechanisms
(DELFT UNIV TECHNOLOGY, FAC INDUST DESIGN ENG, 2010-01-01) Arango, D.R.; Acosta, D.A.; Durango, S.; Ruiz, O.E.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
This article discusses a procedure for force-displacement modeling compliant mechanisms by using a design of computer experiments methodology. This approach produces a force-displacement metamodel that is suited for real-time control of compliant mechanisms. The term metamodel is used to represent a simplified and efficient mathematical model of unknown phenomenon or computer codes. The metamodeling of compliant mechanisms is performed from virtual experiments based on factorial and space filling design of experiments. The procedure is used to modeling the quasi-static behavior of the HexFlex compliant mechanism. The HexFlex is a parallel compliant mechanism for nanomanipulating that allows six degrees of freedom of its moving stage. The metamodel of the HexFlex is performed from virtual experiments by the Finite Element Method (FEM). The obtained metamodel for the HexFlex is linear for the movement range of the mechanism. Simulations of the metamodel were conducted, finding good accuracy with respect to the virtual experiments. © Organizing Committee of TMCE 2010 Symposium.
DigitLAB, an Environment and Language for Manipulation of 3D Digitizations
(Presses internationales Polytechnique, 2000) Ruíz, Óscar E.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
In Computer Aided Geometric Design the fitting of surfaces to massive series of data points has many applications, ranging from medicine to aerophotogrametry -- However, even the mathematical meaning of fitting a surface to a set of points is dependent on functional considerations, and not only on the geometric properties of the point set -- Also, characteristics of some parts of the data set must be interpreted as stochastic in nature, while others must be taken as literal and therefore they become constraints of the surface -- For these reasons, among others, automated surface fitting alone does not produce results usable at industrial level -- At the same time, it does not take advantage of sampling patterns, particular shapes of the cross sections, functionally different regions within the object, etc -- The latest literature reviews show the need for utilities to process point data sets that must be asynchronous, (applicable at any time and upon any region of the point set) -- Addressing this need, this article reports new tools developed within DigitLAB, a language that allows topological traversal, retrieval and statistical modifications to the data, and surface fitting -- They can handle arbitrary topology, as case studies in medicine, mathematics, landscaping, etc discussed here demonstrate
Direct Scalar Field - to - Truss Representation and Stress Simulation of Open Pore Domains
(2018-10-18) M, J; Ruiz-Salguero O.; Montoya, D; Cortes, C; Cadavid, C; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
In the domain of lattice and porous material geometric modeling, the problem of data size is central.
Engineering design using evolutionary structural optimisation based on iso-stress-driven smooth geometry removal
(2001) García, M.J.; Ruíz, O.E.; Steven, G.P.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
The main goal of Evolutionary Structural Optimisation (ESO) research has been to provide an easily applicable optimisation method for the engineering industry which assists the design process for product improvement -- Originally O was based on the concept of fully stressed structures and it is obtained by slowly removing, from a Finite Element mesh these elements that present the lowest stress value -- Following this heuristically-driven removal criteria, the initial topology evolves towards the optimum one -- Since its introduction in 1992, ESO has been developed and extended to several types of structural problems -- Initial weaknesses of ESO were (i) typically long solution times and (ii) topologies with jagged surfaces as a result of removing whole elements in the optimisation process -- These characteristics hindered its application to computer aided design and analysis -- In this investigation, these weaknesses have been addressed for 2D situations by (i) basing the stress computation on the Fixed Grid (FG) finite element method and (ii) removing material with the lowest values along iso-stress contours instead of removing whole elements -- A boundary representation (B-rep) of the structure is maintained at each iteration of the optimisation process -- Modification to the workpiece is made by identifying the stress contour lines and incorporating them into the evolving geometry -- The topological consistency of the B-rep is maintained via normalized 2D boolean operations
Evaluation of 2D shape likeness for surface reconstruction
(2001) Ruíz, Óscar Eduardo; Cadavid, Carlos Alberto; Granados, Miguel; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
Surface or shape reconstruction from 3D digitizations performed in planar samplings are frequent in product design, reverse engineering, rapid prototyping, medical and artistic applications, etc -- The planar slicing of the object offers an opportunity to recover part of the neighborhood information essential to reconstruct the topological 2-manifold embedded in R3 that approximates the object surface -- Next stages of the algorithms find formidable obstacles that are classified in this investigation by the following taxonomy: (i) Although real objects have manifold boundaries, in objects with thin sections or walls, the manifold property remains in the data sample only at the price of very small sampling intervals and large data sets -- For relaxed sampling rates nonmanifold situations are likely. (ii) The position of the planar slices may produce an associated level function which is non – Morse -- This means, the set of critical points of the associated level function is isomorphic to compact subsets of R1 or R2 -- The fact that the Hessian matrix at critical points is non-singular is the Morse condition(as a consequence critical points are isolated), and allows for the algorithms presented here(iii) For Morse condition, the slicing interval may be such that several critical points occur between immediate slices (non- simple condition) -- This article presents the degenerate cases arising from points (i)-(iii) and discusses a shape reconstruction algorithm for digitizations holding the Morse – Simple condition -- It presents the results of applying the prescribed algorithms to data sets, and discusses future actions that enlarge the mentioned scope
Extending marching cubes with adaptative methods to obtain more accurate iso-surfaces
(Springer Verlag, 2010-01-01) Congote, J.; Moreno, A.; Barandiaran, I.; Barandiaran, J.; Ruiz, O.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
This work proposes an extension of the Marching Cubes algorithm, where the goal is to represent implicit functions with higher accuracy using the same grid size. The proposed algorithm displaces the vertices of the cubes iteratively until the stop condition is achieved. After each iteration, the difference between the implicit and the explicit representations is reduced, and when the algorithm finishes, the implicit surface representation using the modified cubical grid is more accurate, as the results shall confirm. The proposed algorithm corrects some topological problems that may appear in the discretization process using the original grid. © 2010 Springer-Verlag Berlin Heidelberg.

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