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Interfaz AIS para aplicaciones en CAD/CAM/CG
(1997) Ruíz S., Óscar E.; Saldarriaga, Jairo A.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
Los modeladores geométricos más comunes en el mercado ofrecen, además de sus servicios de modelado, una API (Application Programming Interface) que permite la construcción de aplicaciones o software cliente -- Estas aplicaciones aprovechan los servicios básicos del modelador para proveer tareas específicas -- Sin embargo las diferencias entre API´s de distintos modeladores imposibilita el intercambio del software cliente entre ellos -- Application Interface Specification -AIS- es una API genérica para ser usada por aplicaciones cliente de los modeladores geométricos -- Este artículo reporta la implementación de AIS sobre AutoCAD® y MicroStation® y discute aspectos importantes de dicha implementación -- Además presenta una aplicación cliente neutra que habla lenguaje AIS y por lo tanto se ejecuta transparentemente sobre los dos modeladores -- AIS se presenta como una alternativa económica para escribir aplicaciones de CAD/CAM/CG -- Futuros desarrollos incluyen la implementación de AIS para labores gráficas y/o de base de datos
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
Modelaje geométrico de estructura ósea
(1998) Ruíz Salguero, O.; Henao, C.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
En CAD/CAGC/CG la organización topológica de datos de formas geométricas presenta dificultades: (i) las características matemáticas de la superficie dependen de la consideraciones no geométricas, (ii) los datos presentan una aleatoriedad por efectos del muestreo, y, (iii) una digitalización xyz incluye en general varias direcciones e intervalos de muestreo -- En consecuencia, esta investigación presenta herramientas (portables a diferentes servidores CAD) para la organización topológica de datos de digitalizaciones y un caso de recuperación de formas óseas -- En los dos casos los resultado obtenidos rompen la combinación cerrada hardware - software propietarios tradicionales, con la consecuente reducción en costos de tecnología
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
Falcon Software tools aerophotogrametric processing
(INGEGRAF, 2000) Ruíz Salguero, Óscar; Trujillo Velásquez, Alejandro; Toro Rodríguez, Carlos Andrés; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
En el área de Aerofotogrametría Digital, el software comercial prevalente para postproceso presenta limitaciones debido a dos factores: (i) las legislaciones de cada país o región requieren diferentes convenciones, y (ii) las necesidades de las empresas son tan cambiantes que no justifican la compra de software de alto rendimiento, que puede quedar sin utilizar debido a un viraje del mercado -- El presente proyecto se ha desarrollado para atender necesidades de procesamiento automático de planos (partición, detección y corrección de errores, etc.), así como módulos de importación – exportación paquete a paquete, trazado de rutas e interacción con GPS -- Este artículo informa de los dos últimos aspectos -- Debido a necesidades de los clientes, los archivos entregados deben llevar un formato comercial (DWG, DXF), pero el procesamiento de los archivos debe ser hecho en paquetes y formatos diversos (DGN) -- Por lo tanto, fue necesario diseñar e implementar un formato acompañante que permitió llevar la información que se pierde al usar filtros comerciales (DGN a DXF/DWG) -- Asimismo se crearon módulos de importación y exportación redundantes, que hicieron efectivos dichos atributos -- En el aspecto de generación de rutas de vuelo, se reportan en este artículo la aplicación de algoritmos tradicionales de barrido (peinado) de áreas 2D, a los cuales se agregaron restricciones geométricas (puntos fijos, offsets, orden de los barridos de acuerdo a coordenadas del sitio de partida, etc.) -- Debido a los altos costos de equipos equivalentes, se decidió desarrollar software para traducción de rutas entre formatos GPS y formatos geográficos locales al país -- Ello permite la eliminación de fuentes de error y además facilita la carga del plan de vuelo, a costos mucho menores a los del hardware / software comercial
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
Topologically consistent partial surface reconstruction from range pictures
(2000) Ruíz S., Óscar E.; Neugebauer, Peter; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
Surface or shape reconstruction from 3D digitizations, range pictures play an important role as the sizes and accessibility of the sampled object become intractable -- Range pictures, however, present challenges regarding: (i) recovery of topological structure from geometrical information of a partial view: (ii) inclusion of several or self obstructing objects on the same picture, and (iii) conciliation of partial topological and geometrical information from the individual views into a main model -- Issue (i) and (ii) require introduction of data structures and algorithms able to consistently represent incompleteness and discontinuities in the surface -- Aspect (iii) demands the application of statistical methods to sort redundant e inconsistent information in the overlaps between the individual views -- In this investigation, tasks (i) and (ii) have been undertaken by designing and populating an extended Boundary Representation (B-rep), using equivalence relations that induce partitions on the data sets -- Task (iii) has been carried out by using data processing tools (DigitLAB) that filter, resample, and recover shape from planar digitizations, by applying formalisms of differential topology
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
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
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
PL-Geodesics on PL-continuous partial meshes
(2001) Ruíz, Óscar E.; Cadavid M., Carlos A.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
Geometric characteristics of 2-manifolds embedded in R3 space have been analyzed from the point of view of differential geometry and topology -- In the past, results relevant to these areas have been found for C∞ curves and surfaces -- However, current scientific, industrial, entertainment and medical applications, and availability of more powerful point sampling systems, press for characterization of discrete counterparts for the continuous properties and characteristics evaluated previously in C∞ curves and surfaces -- Recent works have presented estimation methods for properties such as the principal and rotated quadrics of point sampled surfaces -- The present article uses the findings of previous investigations to propose and implement a method for evaluation of planarity of surfaces -- It is based on:(i) Estimation of a C0 partial mesh fitting sets of planar or grid sample points -- (ii) Evaluation of the piecewise - linear (PL) version of families of geodesic curves on the mesh -- (iii) Diagnostic of the property of planarity based on the behavior of the families of geodesic curves -- The present work can be applied in the area of design and manufacturing of products based on sheet materials, such as apparel, metal stamping, thin structures, etc
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
PL-geodesics on PL-continuous partial meshes
(VYDAVATELSTVI ZAPADOCESKE UNIVERZITY, 2001-01-01) Ruiz, OE; Carlos, A; Cadavid, M; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
Geometric characteristics of 2-manifolds embedded in R-3 space have been analyzed from the point of view of differential geometry and topology. In the past, results relevant to these areas have been Pound for C-infinity curves and surfaces. However, current scientific, industrial, entertainment and medical applications, and availability of more powerful point sampling systems, press for characterization of discrete counterparts for the continuous properties and characteristics evaluated previously in C-infinity curves and surfaces. Recent works have presented estimation methods for properties such as the principal and rotated quadrics of point sampled surfaces. The present article uses the findings of previous investigations to propose and implement a method for evaluation of planarity of surfaces. It is based on: (i) Estimation of a CO partial mesh fitting sets of planar or grid sample points. (ii) Evaluation of the piecewise – linear (PL) version of families of geodesic curves on the mesh. (iii) Diagnostic of the property of planarity based on the behavior of the families of geodesic curves. The present work can be applied in the area of design and manufacturing of products based on sheet materials, such as apparel, metal stamping, thin structures, etc.
Geometric modeling in design of naval elements
(2003) Ruíz S., Óscar E.; Leiceaga Baltar, Xoán; Rodrígez Pérez, Manuel; Prieto Villar, José; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
Boundary Representations (B-Reps) of actual solid parts are correct from the geometrical and topological points of view -- However, when the solid to model has extreme slender ratios, the rigid rules of the B-Rep force a large number of finite elements required to model the solid interior of a closed shell (also called a 2-manifold without border) -- In the practice, modelling is then pursued by using only a partial shell (2-manifold with border), excluding the “interior” of it -- For the same reasons, other slender elements (trusses or beams) must be modelled as 1-dimensional wires (1-manifolds with border) -- Assumptions are made in both cases to replace the solid model information left aside -- The scenarios in which both 2-manifolds and 1-manifolds must coexist are undesirable from the mathematical point of view, since they render flawed topologies and geometries -- However, in the engineering domain, they are required, and enabled, by replacing the information lost in the modelling with additional kinematic and structural constraints -- These constraints force the 1-manifolds and 2-manifolds to intervene together in the numerical solution, therefore rendering realistic results, without actually coexisting in the geometric model -- These techniques are discussed here and applied to examples of shipbuilding industry, where slender forms and extremely large models are ubiquitous
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
Usage of 2D Region Similarity For Surface Reconstruction From Planar Samples
(2003) Ruíz S., Óscar E.; Cadavid, Carlos A.; Granados, Miguel; Peña, Sebastián; Vásquez, Eliana; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
In surface reconstruction from planar slices it is necessary to build surfaces between corresponding 2D regions in consecutive levels -- The problem has been traditionally attacked with (i) direct reconstruction based on local geometric proximity between the regions, and (ii) classification of topological events between the slices, which control the evolution of the cross cuts -- These approaches have been separately applied with mixed success -- In the case (i), the results may be surfaces with over-stretched or unnatural branches, resulting from a local contour proximity which does not correspond to global similarity between regions -- In (ii), the consequences from topological events upon the actual surface realization have not been drawn -- In this paper an integration of (i) and (ii) is presented, which uses a criteria of similarity between composed 2D regions in consecutive slices to: (a) decide if a surface should actually relate those regions, (b) identify the topological transitions between levels and (c) construct the local surface for the related regions -- The method implemented hinders over-stretched and unnatural branches, therefore rendering a surface which adjusts to geometrically-sound topological events -- This is a good alternative when the surface reconstructed needs to be topologically faithful (for example in flow simulation) in addition to represent the a rough geometrical space (for example in radiation planning)
Principal component analysis -PCA- and delone triangulations for PL approximation C-1-continuous 1-manifolds in R-N
(ACTA PRESS, 2004-01-01) Ruiz, OE; Cadavid, CA; Garcia, MJ; Martinod, R; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
A Method is presented which combines statistical (Principal Component Analysis) and deterministic (Voronoi-Delone) methods to find Piecewise Linear approximations of curves C-i(u) in R-3 sampled with statistical noise. If the curves are self-intersecting, there are a finite number of points in which they are not 1-manifolds. Otherwise, they are 1-manifolds in all extents. The combination presented, of PCA and V-D methods, allows the recovery of 1-manifold approximations for C-i(u) for self-intersecting quasi-planar and non self-intersecting curves. In the later case the PCA alone succeeds in finding 1-manifold PL approximations for them. The algorithm implemented finds applications in contour and shape reconstruction from noisy data, subject to sampling errors or blockage.
Principal component analisis-PCA-and Delone Triangulations for PL approximation C1-continuous 1-manifolds in Rn
(ACTA Press, 2004-08) Ruíz, Óscar; Cadavid, Carlos; García, Manuel J.; Martinod, Ronald; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
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.
Spring–particle model for hyperelastic cloth
(2005-05) García, Manuel; Gómez, Mario; Ruíz, Óscar; Boulanger, Pierre; Universidad EAFIT. Departamento de Ingeniería Mecánica; Laboratorio CAD/CAM/CAE
This article presents a computational model to simulate the deformation of hyperelastic fabrics -- The model is based on a spring−particle approach and it simulates the interaction of a textile tissue with a forming body -- The fabric is represented by rectangular meshes of springs -- This fact enables the model to behave orthotropically and therefore it is possible to simulate the warp and weft properties -- The constitutive relations preserve the natural hyperelastic capabilities of the cloth -- In the model developed herein, initially the cloth lies in its relaxed un−deformed state -- Then it is given an initial deformation that guarantees no contact nor intersection with the forming rigid body -- Finally, the deformed cloth is realised, and moves iteratively towards an equilibrium location -- The final equilibrium location is reached when the internal forces are balanced by the external contact forces caused by the rigid object -- This is achieved when the stop criterion has been satisfied

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