Dissertations / Theses on the topic '3D mesh generation'

Massive graph visualization in an immersive environment, such as virtual reality (VR) or Augmented Reality (AR), has the possibility to improve users’ understanding when exploring data in new ways. To make the most of a visualization, such as this, requires interactive components that are fast enough to accommodate interactivity. By rendering the edges of the graph as shaded lines that imitate three‑dimensional (3D) lines or tubes, one can circumvent technical limitations. This method works well enough when using traditional two‑dimensional (2D) monitors, but representing tubes as flat lines in a virtual environment (VE) makes for a less immersive user experience as opposed to visualizing true 3D geometry. In order to accommodate for these requirements i.e., speed and visual fidelity, we need a time efficient way of producing tubular meshes. This thesis project explores how one can generate tubular geometry utilizing compute shaders in the modern game engine, Unreal Engine (UE). Exploiting the parallel computing power of the graphical processing unit (GPU) we use compute shaders to generate a tubular mesh following a predetermined path. The result from the project is an open source plugin for UE, able to generate tubular geometry at rapid rates. While not giving any major advantages when generating smaller models, comparing it to a sequential implementation, the compute shader implementation create and render models &gt; 40× faster when generating 106 tube segments. A secondary effect of generating most of the data on the GPU, is that we avoid bottlenecks that can occur when surpassing the bandwidth of the central processing unit (CPU) to GPU data transfer. Using this tool researches can more easily explore information visualization in a VE. Furthermore, this thesis promotes extended development of mesh generation, using compute shaders in UE.<br>Att visualisera stora grafer i en immersiv miljö, såsom VR eller AR, kan förbättra en användares förståelse när de utforskar data på nya sätt. För att få ut det mesta av denna typen av visualiseringar krävs interaktiva komponenter som är tillräckligt snabba för att tillgodose interaktivitet. Genom att visa de linjer, som binder samman en grafs noder, som plana linjer som imiterar 3Dlinjer eller rör, kan man undvika att slå i det tak som tekniska begränsningar medför. Denna metoden är acceptabel vid användning av traditionella 2Dskärmar, men att representera rör som plana linjer i VE ger en mindre immersiv användarupplevelse, i kontrast till att visualisera sann 3D -geometri. För att tillgodose dessa krav dvs, tidseffektivitet och visuella kvaliteter, behöver vi ett effektivt sätt att producera 3D-linjer. Denna uppsats undersöker hur man kan generera rörformad geometri med hjälp av compute shaders i den moderna spelmotorn Unreal Engine (UE). Genom att använda compute shaders kan vi utnyttja den parallella beräkningskraften hos en GPU, kan vi generera ett rörformat mesh som följer en förutbestämd bana. Resultatet från projektet är ett open source-plugin för UE, som kan generera rörformad geometri i höga hastigheter. Även om det inte kan visas ge några större fördelar när man genererar mindre modeller, jämfört med en sekventiell implementering, skapar och renderar implementeringen av compute Shaders modeller &gt; 40× snabbare, när de genererar 106 rörsegment. I och med att den större delen av datan skapas på GPU kan vi också undvika den flaskhals som kan uppstå när vi överskrider bandbredden mellan CPU och GPU. Med hjälp av verktyget som skapats i samband med denna uppsats kan människor lättare utforska informationsvisualisering i VE. Dessutom främjar denna uppsats utökad utveckling av mesh-generering med hjälp av compute shaders i UE.

<p>Digitizing objects and environments from real world has become an important part of creating realistic computer graphics. Through the use of structured lighting and laser time-of-flight measurements the capturing of geometric models is now a common process. The result are visualizations where viewers gain new possibilities for both visual and intellectual experiences. </p><p>This thesis presents the reconstruction of the Parthenon temple and its environment in Athens, Greece by using a 3D laser-scanning technique. </p><p>In order to reconstruct a realistic model using 3D scanning techniques there are various phases in which the acquired datasets have to be processed. The data has to be organized, registered and integrated in addition to pre and post processing. This thesis describes the development of a suitable and efficient data processing pipeline for the given data. </p><p>The approach differs from previous scanning projects considering digitizing this large scale object at very high resolution. In particular the issue managing and processing huge datasets is described. </p><p>Finally, the processing of the datasets in the different phases and the resulting 3D model of the Parthenon is presented and evaluated.</p>

<p>Throughout the development of this report there will be a brief explanation of what the actual Aircraft Design Process is and in which stages the methodology that the authors are proposing will be implemented as well as the tools that will interact to produce this methodology.</p><p>The proposed tool will be the first part of a methodology that, according to the authors, by integrating separate tools that are currently used in different stages of the aeronautical design, will promote a decrease in the time frame for the initial stages of the design process.</p><p>The first part of the methodology above, that is proposed in this project, starts by creating a computer generated aircraft model and analyzing its basic aerodynamic characteristics “Lift Coefficient” and “Induced Drag Coefficient”, this step will be an alternative to statistical and empirical methods used in the industry, which require vast amount of data.</p><p>This task will be done in several steps, which will transfer the parametric aircraft model to an input file for the aerodynamic analysis program. To transfer the data a “translation” program has been developed that arranges the geometry and prepares the input file for analysis.</p><p>During the course of this report the reader will find references to existing aircrafts, such as the MD-11 or Airbus 310. However, these references are not intended to be an exact computer model of the mentioned airplanes. The authors are using this as reference so the reader can relate what he/she is seeing in this paper to existing aircrafts. By doing such comparison, the author intends to demonstrate that the Parametric Model that has been created possesses the capability to simulate to some extend the shape of existing aircrafts.</p><p>Finally from the results of this project it is concluded that the methodology in question is promising. Linking the two programs is possible and the aerodynamic characteristics of the models tested fall in the appropriate range. None the less the research must continue following the line that has been discussed in this report.</p>

Made available in DSpace on 2014-12-17T14:58:00Z (GMT). No. of bitstreams: 1 RairamFCA_DISSERT2.pdf: 4758176 bytes, checksum: bfb1653549a50848b4721bda9a78bd6e (MD5) Previous issue date: 2010-03-26<br>The pumping through progressing cavities system has been more and more employed in the petroleum industry. This occurs because of its capacity of elevation of highly viscous oils or fluids with great concentration of sand or other solid particles. A Progressing Cavity Pump (PCP) consists, basically, of a rotor - a metallic device similar to an eccentric screw, and a stator - a steel tube internally covered by a double helix, which may be rigid or deformable/elastomeric. In general, it is submitted to a combination of well pressure with the pressure generated by the pumping process itself. In elastomeric PCPs, this combined effort compresses the stator and generates, or enlarges, the clearance existing between the rotor and the stator, thus reducing the closing effect between their cavities. Such opening of the sealing region produces what is known as fluid slip or slippage, reducing the efficiency of the PCP pumping system. Therefore, this research aims to develop a transient three-dimensional computational model that, based on single-lobe PCP kinematics, is able to simulate the fluid-structure interaction that occurs in the interior of metallic and elastomeric PCPs. The main goal is to evaluate the dynamic characteristics of PCP s efficiency based on detailed and instantaneous information of velocity, pressure and deformation fields in their interior. To reach these goals (development and use of the model), it was also necessary the development of a methodology for generation of dynamic, mobile and deformable, computational meshes representing fluid and structural regions of a PCP. This additional intermediary step has been characterized as the biggest challenge for the elaboration and running of the computational model due to the complex kinematic and critical geometry of this type of pump (different helix angles between rotor and stator as well as large length scale aspect ratios). The processes of dynamic generation of meshes and of simultaneous evaluation of the deformations suffered by the elastomer are fulfilled through subroutines written in Fortan 90 language that dynamically interact with the CFX/ANSYS fluid dynamic software. Since a structural elastic linear model is employed to evaluate elastomer deformations, it is not necessary to use any CAE package for structural analysis. However, an initial proposal for dynamic simulation using hyperelastic models through ANSYS software is also presented in this research. Validation of the results produced with the present methodology (mesh generation, flow simulation in metallic PCPs and simulation of fluid-structure interaction in elastomeric PCPs) is obtained through comparison with experimental results reported by the literature. It is expected that the development and application of such a computational model may provide better details of the dynamics of the flow within metallic and elastomeric PCPs, so that better control systems may be implemented in the artificial elevation area by PCP<br>O sistema de bombeamento por cavidades progressivas est? sendo cada vez mais empregado na ind?stria do petr?leo, devido ? sua capacidade de eleva??o de ?leos altamente viscosos ou de fluidos com grandes concentra??es de areia ou outras part?culas s?lidas. Uma Bomba de Cavidades Progressivas (BCP) ? composta, basicamente, por um rotor - uma pe?a met?lica de forma semelhante a um parafuso exc?ntrico, e um estator - um tubo de a?o revestido internamente por uma h?lice dupla, a qual pode ser r?gida ou deform?vel/elastom?rica. Em geral, uma BCP ? submetida a uma combina??o de press?o do po?o com press?o gerada pelo pr?prio processo de bombeio. Em BCPs elastom?ricas, essa combina??o de esfor?os comprime o estator, gerando ou aumentando a folga existente entre o rotor e o estator, reduzindo, portanto, o efeito de veda??o entre suas cavidades. Tal abertura da regi?o de selagem produz o que ? conhecido como escorregamento do fluido, diminuindo, com isso, a efici?ncia de sistema de bombeio por BCP. Dessa maneira, este trabalho se prop?e a desenvolver um modelo computacional tridimensional transiente do processo din?mico da intera??o fluido-estrutural (FSI) que ocorre no interior de BCPs met?licas e elastom?ricas. O objetivo principal ? avaliar, a partir do uso do modelo desenvolvido, as caracter?sticas din?micas de efici?ncia de bombeio por BCPs, em fun??o de informa??es locais e instant?neas detalhadas dos campos de velocidade, press?o e deforma??o no seu interior. Para o alcance de tais metas (desenvolvimento e uso do modelo), fez-se necess?rio o desenvolvimento de uma metodologia pr?pria para gera??o de malhas computacionais din?micas, m?veis e deform?veis, representando as regi?es fluida e estrutural de uma BCP. Tal procedimento caracterizou-se como o maior desafio para a elabora??o do modelo computacional, devido ? cinem?tica complexa e ? geometria cr?tica desse tipo de bomba (?ngulos de h?lice diferentes entre rotor e estator e grandes diferen?as de escala de comprimento). Os processos de gera??o din?mica das malhas e de avalia??o simult?nea das deforma??es sofridas pelo elast?mero s?o realizados atrav?s de sub-rotinas em linguagem Fortran 90, as quais interagem dinamicamente com o software de din?mica dos fluidos computacional CFX/ANSYS. Desde que o modelo linear el?stico ? empregado para avaliar as deforma??es elastom?ricas, n?o ? necess?rio usar nenhum software para an?lise estrutural. Entretanto, uma proposta inicial para simula??o din?mica no ANSYS empregando-se modelos constitutivos hiper-el?sticos para o elast?mero ? tamb?m apresentada no presente trabalho. A valida??o dos resultados produzidos com a presente metodologia (gera??o de malha, simula??o do escoamento em BCPs met?licas e simula??o da intera??o fluido-estrutural em BCPs elastom?ricas) ? obtida atrav?s da compara??o com resultados experimentais reportados pela literatura. Vislumbra-se que o desenvolvimento e aplica??o de tal ferramenta computacional poder?o fornecer maiores detalhes da din?mica do escoamento no interior de BCPs met?licas e elastom?ricas, de maneira que melhores sistemas de controle possam ser implementados na ?rea de eleva??o artificial por BCPs

Les matériaux composites à renforts tissés 3D connaissent une utilisation grandissante dans de nombreux domaines de par entre autres leurs excellentes propriétés mécaniques. Cependant, le manque de compréhension de leur comportement est un facteur limitant. Ces limites sont liées à la complexité des phénomènes intervenant à différentes échelles qui jouent un rôle essentiel sur la prédiction de la réponse du matériau. Pour comprendre et résoudre ce problème, ce travail a pour objectifs d’étudier les matériaux composites 3D à l’aide de simulations numériques et d’observations expérimentales réalisées aux échelles micro, méso et macro. L’étude expérimentale a été réalisée afin d’obtenir : les propriétés macroscopiques du matériau et les paramètres nécessaires à la reconstruction géométrique. Ces caractéristiques ont été évaluées à l’aide de diverses techniques : microscopies optique et électronique et tomographie par rayons X sur des éprouvettes avant et après essais mécaniques afin de détecter les éventuels endommagements. Ces observations ont permis de définir les stratégies numériques à mettre en place aux différentes échelles. Ainsi, à l’échelle microscopique, un algorithme de dynamique moléculaire a été développé et testé sur des volumes représentatifs élémentaires et sur des sections de fils. Les résultats obtenus montrent une grande capacité à générer la variabilité microstructurale. A l’échelle mésoscopique, une stratégie de reconstruction à partir d’images tomographiques a permis de prendre en compte l’architecture réelle du composite 3D. Cette technique de modélisation a montré son grand intérêt dans la prédiction de la réponse non linéaire du matériau<br>3D textile reinforced composites have gained extensive application in many industrial domains by taking their excellent mechanical properties and neat-shape manufacturing. However, lack of understanding in material behaviour might be limiting factors at the design stage. One of these limits is the complexity of the multi-scale phenomena which play a critical role in predicting the material response. In order to tackle this problem, the systematic and detailed investigations are required at different material scales. Therefore, this work addresses to study 3D composites alternating and combining numerical simulations and experimental observations at different material scales. Experiments were carried out to provide twofold parameters: material properties and required geometrical reconstruction parameters. X-ray tomography was employed to inspect the intact samples. Electronic and optical microscopy techniques have been used in order to investigate in details the yarn cross-sections at initial states and eventual damages mechanisms accumulated during mechanical tests. All those observations allowed choosing numerical strategies at different material scales. Thus, at the micro-scale, the modified molecular dynamics algorithm has been developed and tested on RVE and irregular cross-section yarns. The results show great capacity and originality in the generation of the microstructural variability. Consequently, at the meso-scale, the reconstruction strategy was chosen which allowed representing real mesostructure of the composites. This modelling technique has great importance in the prediction of the material response, especially at the non-linear stage

碩士<br>國立交通大學<br>機械工程系<br>90<br>The purpose of this thesis is to use the method of modified Delaunay triangulation to generate adaptive finite-element-meshes for machine components. First of all, we introduce the method of modified Delaunay triangulation. Then, we discuss the process of 3D Mesh Generation, and some solutions for this task will be elaborated at this part. Finally, by some computing results of 2D and 3D cases, we verify this modified method and make a conclusion.

3D scanning has grown to become an important tool in a wide variety of applications. Still, acquiring high-quality 3D models using scanning technology is a challenging task. In this thesis, we present various ways that reduce the hurdles of existing 3D scanning pipelines with the ultimate goal of bringing this technology closer to the end user. To achieve this goal, we focus on three sub problems of traditional scanning pipelines: First, we present a novel algorithm that can be used to consistently orient the normals of huge point clouds. We achieve this by formulating the orientation problem as a graph-based energy minimization problem and applying out-of core methods. Second, we introduce interactivity into the scanning pipeline by presenting an online surface reconstruction method that produces high-quality semi-regular meshes. The resulting interactive pipeline is highly efficient because it reduces the turn-around between presentation of the final result and possible corrections by the user. Third, we develop a robust method to texture-map semi-regular meshes. This approach is based on a generalization of motorcycle graphs, which partitions arbitrary meshes into quadrilateral patches. These patches then serve as the parametrization domains of the texture atlas. Finally, we present an application from the area of cave science. The application is targeted at quantitatively and objectively assessing a cave's size. To achieve this goal, we present methods to analyze the structure of caves, especially to distinguish chambers from passages.

碩士<br>國立成功大學<br>醫學工程研究所碩博士班<br>90<br>It is important to have a good 3D human face model in plastic surgery simulation. The surgery simulation can be applied on cranial-facial disease or malocclusion. Real-time and accuracy are important goals in developing surgery simulation system. To reduce data set and to build a finite element model can achieve these goals. Shape from shading is cheaper and safer above the methods of reconstruct 3D human face data. At the beginning shape from shading acquire the image of the object from several light source positions. Next we reconstruct the object’s 3D image from the 2D pictures according the illumination gradient of the pictures. The method of shape from shading proposed by Lee and Kuo has the characteristic of high accuracy but high computation time and huge storage data set. To improve the triangular mesh model in their method can solve the problem. Our research firstly acquires the face image from four different light source positions. After applying the Otsu’s thresholding method, we continuum the four images to find out the region of interest. Next we average the images of the four pictures; we can get the image that is approximately light source in the central. After smoothing the image, we can set the image into 3 areas based on illumination gradient initially. Then we apply morphological operator to deal with these 3 areas. After this, we determine the nodes distribution density and distribute grid nodes based on the illumination gradient of each area. Next we use Delaunay triangulation to get the mesh of human face.

Mit 3D-Netzmodellen werden Objekte der materiellen Welt oder unserer Vorstellung computergestützt abgebildet. In digitalen Produktentwicklungsprozessen werden mit ihnen sowohl die Objektgestalt als auch anwendungsspezifische Informationen von Objekten und von Prozessen definiert. Mit flächenhaften Netzen (z. B. Dreiecksnetze) wird die Oberfläche von Objekten in diskreter Form repräsentiert, mit volumenhaften Netzen (z. B. Tetraedernetze) zusätzlich das Objektinnere. 3D-Netzmodelle werden bei der Erzeugung und der Manipulation, der Analyse und der Validierung, in fertigungsvorbereitenden Prozessen sowie zur Präsentation digitaler 3D-Objekte angewandt.

碩士<br>逢甲大學<br>航太與系統工程學系<br>102<br>This paper is mainly used the boundary element method to analysis and calculate for three-dimensional objects and the cracks, then, compared with the results of ANSYS to verify the accuracy and the error values. But currently, used the boundary element method to establish the analysis model is done by artificial judgment, dividing the required node coordinates to complete cutting the grid, so, often takes a great time to establish the model. And, compared with the time it takes to use the finite element method to establish the model, the boundary element method becomes less efficient. Therefore, in order to look after both accuracy and speed in the process, in this paper the part of program development , is using the Compaq Visual Fortran to calculate, and, based on the boundary element method to write programs, to develop to automatically generate the 3D mesh graphics for reducing the difficulty and the time when cutting the mesh. After that, will combinate the different analysis models with the boundary conditions to verify its reliability. In this paper, to discuss with the basic 3D graphics, and analyze the problems of three-dimensional cracks by boundary element method.

碩士<br>國立成功大學<br>機械工程學系<br>89<br>Abstract In recently years, the technology in computer domain has a highly progress and the CAE software has become a powerful tool to help engineers to predict the quality of the products. However, the model built in CAD software can’t be directly used in CAE software. It costs a lots time to rebuild model in CAE software. This paper has developed a 3D mesh generator to reduce analyze time and save manpower. By using Borland C++Builder 5.0 and OpenGL graphic library, the system has a friendly user interface. A DXF file can be directly used in this system and you don’t need to build the 3D model. By using toolbar and dialog, engineers can use the system easily without any experiences in CAE analyses. Keywords : IC Package，Mesh Generation，Preprocessor

碩士<br>國立成功大學<br>機械工程學系碩博士班<br>96<br>With the progress of the technologies in computer,engineers have more and more chance to use the CAE software to predict the quality of the products and solve the processing problems. However, the model construction and mesh generation capability of CAE tools is often not powerful and convenient enough for practical applications. For IC packaging analysis, different meshes of the same model need to be built for different analyses. It will be the best to have one model and generate all the different meshes automatically.This thesis has developed a 3D mesh generator for IC package to reduce time and human resource via Visual Studio 2005 and OpenGL graphic library. The system has simple and friendly user interface and a DXF file from AutoCAD can be directly used. With the high quality tetrahedral or hexahedral solid mesh, the difficulty of mesh generation in IC packaging analysis could be reduced and the efficiency and accuracy of simulation could be improved.