Revisión de literatura de jerarquía volúmenes acotantes enfocados en detección de colisiones

(Eng) A bounding volume is a common method to simplify object representation by using the composition of geometrical shapes that enclose the object; it encapsulates complex objects by means of simple volumes and it is widely useful in collision detection applications and ray tracing for rendering algorithms. They are popular in computer graphics and computational geometry. Most popular bounding volumes are spheres, Oriented-Bounding Boxe s (OBB’ s), Axis-Align ed Bound ing Boxes (AABB’ s); moreover , the literature review includes ellipsoids, cylinders, sphere packing, sphere shells , k-DOP’ s, convex hulls, cloud of points, and minimal bounding boxe s, among others. A Bounding Volume Hierarchy is ussualy a tree in which the complete object is represented thigter fitting every level of the hierarchy. Additionally, each bounding volume has a cost associated to construction, update, and interference te ts. For instance, spheres are invariant to rotation and translations, then they do not require being updated ; their constructions and interference tests are more straightforward then OBB’ s; however, their tightness is lower than other bounding volumes. Finally , three comparisons between two polyhedra; seven different algorithms were used, of which five are public libraries for collision detection.(Spa) Un volumen acotante es un método común para simplificar la representación de los objetos por medio de composición de formas geométricas que encierran el objeto; estos encapsulan objetos complejos por medio de volúmenes simples y son ampliamente usados en aplicaciones de detección de colisiones y trazador de rayos para algoritmos de renderización. Los volúmenes acotantes son populares en computación gráfica y en geometría computacional; los más populares son las esferas, las cajas acotantes orientadas (OBB’s) y las cajas acotantes alineadas a los ejes (AABB’s); no obstante, la literatura incluye elipses, cilindros empaquetamiento de esferas, conchas de esferas, k-DOP’s, convex hulls, nubes de puntos y cajas acotantes mínimas, entre otras. Una jerarquía de volúmenes acotantes es usualmente un árbol, en el cual la representación de los objetos es más ajustada en cada uno de los niveles de la jerarquía. Adicionalmente, cada volumen acotante tiene asociado costos de construcción, actualización, pruebas de interferencia. Por ejemplo, las esferas so invariantes a rotación y translación, por lo tanto no requieren ser actualizadas en comparación con los AABB no son invariantes a la rotación. Por otro lado la construcción y las pruebas de solapamiento de las esferas son más simples que los OBB’s; sin embargo, el ajuste de las esferas es menor que otros volúmenes acotantes. Finalmente, se comparan dos poliedros con siete algoritmos diferentes de los cuales cinco son librerías públicas para detección de colisiones

WebGL-Based Simulation of Bone Removal in Surgical Orthopeadic Procedures

The effective role of virtual reality simulators in surgical operations has been demonstrated during the last decades. The proposed work has been done to give a perspective of the actual orthopeadic surgeries such as a total shoulder arthroplasty with low incidence and visibility of the operation to the surgeon. The research in this thesis is focused on the design and implementation of a web-based graphical feedback for a total shoulder arthroplasty (TSA) surgery. For portability of the simulation and powerful 3D programming features, WebGL is being applied. To simulate the reaming process of the shoulder bone, multiple steps has been passed to be able to remove the volumetric amount of bone which was touched by the reamer tool. A fast and accurate collision detection algorithm utilizing Möller –Trumbore ray-triangle method was implemented to detect the first collision of the bone and the tool in order to accelerate the computations for the bone removal process. Once the collision detected, a mesh Boolean operation using CSG method is being invoked to calculate the volumetric amount of bone which is intersected with the tool and should be removed. This work involves the user interaction to transform the tool in a Three.js scene for the simulated operation

Implementation of a Discrete Element Method (DEM) particle simulator for GPU cluster

Orientador: Luiz Otávio Saraiva FerreiraDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia MecânicaResumo: Os avanços na tecnologia das GPUs, tanto em hardware quanto em ferramentas de programação, tornaram-nas uma opção viável como processadores de uso geral, sendo adequadas para a realização de processamento paralelo com alta demanda de cálculos. Dentre os problemas que podem fazer uso das GPUs são as simulações que envolvem o fluxo de partículas como o Método dos Elementos Discretos (DEM). Assim, a proposta deste trabalho foi implementar em cluster de GPUs um simulador utilizando o Método dos Elementos Discretos. O simulador foi inicialmente validado para uma única GPU utilizando resultados experimentais disponíveis na literatura, onde foram possíveis obter resultados com erros menores do que 10%. Além disso, os tempos de processamento para uma única GPU foram comparados com outro simulador, também implementado em GPU, resultando em tempos de execução semelhantes aos reportados. Finalmente, o método foi expandido para o cluster de GPUs, utilizando uma abordagem híbrida (MPI + CUDA), e apresentou um ganho de desempenho adequado à medida que o número de GPUs foi aumentadoAbstract: Advances in GPU technology, both in hardware and programming tools, have made them a viable option as general-purpose processors, suitable for performing parallel processing tasks with high computational demand. The Discrete Element Method (DEM) studies a class of problems that can make use of GPUs high computational power. Thus, the proposal of this work was to implement a simulator using the Discrete Element Method in a GPU cluster. The simulator was initially validated for a single GPU using experimental results available in the literature, where it was possible to obtain results with errors less than 10%. Also, processing times for a single GPU were compared with another simulator, also implemented in GPU, resulting in run times similar to those reported. Finally, the method was ported to the GPU cluster, using a hybrid approach (MPI + CUDA), and presented a suitable gain of performance as the number of GPUs was increasedMestradoMecanica dos Sólidos e Projeto MecanicoMestre em Engenharia Mecânic

New geometric algorithms and data structures for collision detection of dynamically deforming objects

Any virtual environment that supports interactions between virtual objects and/or a user and objects, needs a collision detection system to handle all interactions in a physically correct or plausible way. A collision detection system is needed to determine if objects are in contact or interpenetrates. These interpenetrations are resolved by a collision handling system. Because of the fact, that in nearly all simulations objects can interact with each other, collision detection is a fundamental technology, that is needed in all these simulations, like physically based simulation, robotic path and motion planning, virtual prototyping, and many more. Most virtual environments aim to represent the real-world as realistic as possible and therefore, virtual environments getting more and more complex. Furthermore, all models in a virtual environment should interact like real objects do, if forces are applied to the objects. Nearly all real-world objects will deform or break down in its individual parts if forces are acted upon the objects. Thus deformable objects are becoming more and more common in virtual environments, which want to be as realistic as possible and thus, will present new challenges to the collision detection system. The necessary collision detection computations can be very complex and this has the effect, that the collision detection process is the performance bottleneck in most simulations. Most rigid body collision detection approaches use a BVH as acceleration data structure. This technique is perfectly suitable if the object does not change its shape. For a soft body an update step is necessary to ensure that the underlying acceleration data structure is still valid after performing a simulation step. This update step can be very time consuming, is often hard to implement and in most cases will produce a degenerated BVH after some simulation steps, if the objects generally deform. Therefore, the here presented collision detection approach works entirely without an acceleration data structure and supports rigid and soft bodies. Furthermore, we can compute inter-object and intraobject collisions of rigid and deformable objects consisting of many tens of thousands of triangles in a few milliseconds. To realize this, a subdivision of the scene into parts using a fuzzy clustering approach is applied. Based on that all further steps for each cluster can be performed in parallel and if desired, distributed to different GPUs. Tests have been performed to judge the performance of our approach against other state-of-the-art collision detection algorithms. Additionally, we integrated our approach into Bullet, a commonly used physics engine, to evaluate our algorithm. In order to make a fair comparison of different rigid body collision detection algorithms, we propose a new collision detection Benchmarking Suite. Our Benchmarking Suite can evaluate both the performance as well as the quality of the collision response. Therefore, the Benchmarking Suite is subdivided into a Performance Benchmark and a Quality Benchmark. This approach needs to be extended to support soft body collision detection algorithms in the future.Jede virtuelle Umgebung, welche eine Interaktion zwischen den virtuellen Objekten in der Szene zulässt und/oder zwischen einem Benutzer und den Objekten, benötigt für eine korrekte Behandlung der Interaktionen eine Kollisionsdetektion. Nur dank der Kollisionsdetektion können Berührungen zwischen Objekten erkannt und mittels der Kollisionsbehandlung aufgelöst werden. Dies ist der Grund für die weite Verbreitung der Kollisionsdetektion in die verschiedensten Fachbereiche, wie der physikalisch basierten Simulation, der Pfadplanung in der Robotik, dem virtuellen Prototyping und vielen weiteren. Auf Grund des Bestrebens, die reale Umgebung in der virtuellen Welt so realistisch wie möglich nachzubilden, steigt die Komplexität der Szenen stetig. Fortwährend steigen die Anforderungen an die Objekte, sich realistisch zu verhalten, sollten Kräfte auf die einzelnen Objekte ausgeübt werden. Die meisten Objekte, die uns in unserer realen Welt umgeben, ändern ihre Form oder zerbrechen in ihre Einzelteile, wenn Kräfte auf sie einwirken. Daher kommen in realitätsnahen, virtuellen Umgebungen immer häufiger deformierbare Objekte zum Einsatz, was neue Herausforderungen an die Kollisionsdetektion stellt. Die hierfür Notwendigen, teils komplexen Berechnungen, führen dazu, dass die Kollisionsdetektion häufig der Performance-Bottleneck in der jeweiligen Simulation darstellt. Die meisten Kollisionsdetektionen für starre Körper benutzen eine Hüllkörperhierarchie als Beschleunigungsdatenstruktur. Diese Technik ist hervorragend geeignet, solange sich die Form des Objektes nicht verändert. Im Fall von deformierbaren Objekten ist eine Aktualisierung der Datenstruktur nach jedem Schritt der Simulation notwendig, damit diese weiterhin gültig ist. Dieser Aktualisierungsschritt kann, je nach Hierarchie, sehr zeitaufwendig sein, ist in den meisten Fällen schwer zu implementieren und generiert nach vielen Schritten der Simulation häufig eine entartete Hüllkörperhierarchie, sollte sich das Objekt sehr stark verformen. Um dies zu vermeiden, verzichtet unsere Kollisionsdetektion vollständig auf eine Beschleunigungsdatenstruktur und unterstützt sowohl rigide, wie auch deformierbare Körper. Zugleich können wir Selbstkollisionen und Kollisionen zwischen starren und/oder deformierbaren Objekten, bestehend aus vielen Zehntausenden Dreiecken, innerhalb von wenigen Millisekunden berechnen. Um dies zu realisieren, unterteilen wir die gesamte Szene in einzelne Bereiche mittels eines Fuzzy Clustering-Verfahrens. Dies ermöglicht es, dass alle Cluster unabhängig bearbeitet werden und falls gewünscht, die Berechnungen für die einzelnen Cluster auf verschiedene Grafikkarten verteilt werden können. Um die Leistungsfähigkeit unseres Ansatzes vergleichen zu können, haben wir diesen gegen aktuelle Verfahren für die Kollisionsdetektion antreten lassen. Weiterhin haben wir unser Verfahren in die Physik-Engine Bullet integriert, um das Verhalten in dynamischen Situationen zu evaluieren. Um unterschiedliche Kollisionsdetektionsalgorithmen für starre Körper korrekt und objektiv miteinander vergleichen zu können, haben wir eine Benchmarking-Suite entwickelt. Unsere Benchmarking- Suite kann sowohl die Geschwindigkeit, für die Bestimmung, ob zwei Objekte sich durchdringen, wie auch die Qualität der berechneten Kräfte miteinander vergleichen. Hierfür ist die Benchmarking-Suite in den Performance Benchmark und den Quality Benchmark unterteilt worden. In der Zukunft wird diese Benchmarking-Suite dahingehend erweitert, dass auch Kollisionsdetektionsalgorithmen für deformierbare Objekte unterstützt werden

Numerical modeling of microfluidic through the smoothed particle hydrodynamics mesh-free lagrangian method

Orientador: Luiz Otávio Saraiva FerreiraTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia MecânicaResumo: O transporte controlado de pequenas quantidades de fluidos é fundamental para desenvolver os laboratórios químicos em um chip (Lab-On-a-Chip, ou LOC, em inglês), ou seja, sistemas miniaturizados de crescente utilização na análise em áreas como Química, Bioquímica, Farmácia e Biologia, que tendem a substituir os atuais equipamentos analíticos. Os microdispositivos são essenciais para o transporte controlado e preciso de fluidos. Porém, ainda não foi desenvolvida uma metodologia para o cálculo do comportamento de fluidos em micro-dispositivos, existindo assim uma demanda por modelos numéricos capazes de realizá-lo. Esse trabalho apresenta a implementação do método sem malha Smoothed Particle Hydrodynamics (SPH) no desenvolvimento de um simulador 2D para problemas de escoamento de fluidos em micro-dispositivos. O simulador foi programado na linguagem C/C++ para processamento em CPU e na linguagem CUDA-C para processamento em GPU. O estudo da formulação SPH incluiu fenômenos como tensão superficial, multi-fase, capilaridade e molhabilidade para problemas com interação fluido-fluido e fluido-estrutura. As etapas de desenvolvimento do simulador computacional foram: Revisão de métodos de partículas Lagrangianos sem malha elegíveis para a modelagem da interação fluido-estrutura em micro-sistemas; Metologia e formulação das equações constitutivas para a descrição do comportamento do fluido, da estrutura e da interação fluido-estrutura usando SPH; Implementação de fenômenos caraterísticos para micro-fluídica como multi-fase (líquido-líquido) e tensão superficial e capilaridade; E modelagem numérica de microdispositivos para caso de estudo em micro-válvulas e micro-bomba peristáltica. Todas as implementações das formulações no simulador foram validadas através da comparação com resultados da literatura e da experimentação. Assim, o principal objetivo desse trabalho é apresentar o método SPH como uma alternativa na modelagem numérica de fluidos com interação líquido-líquido e líquido-estrutura em problemas de micro-fluídicaAbstract: Controlled transport of small amounts of fluids is critical for Lab-On-a-Chip, miniaturized systems of increasing use of chemical, biochemical, pharmaceutical and biological analyzes that tend to replace current analytical equipment. Micro-Devices are essential for controlled and accurate transport of fluids. However, a methodology for the calculation of fluid behavior in micro-devices has not yet been developed, and there is a demand for capable numerical models. This work presents the implementation of the Smoothed Particle Hydrodynamics (SPH) meshless method in the development of a 2D simulator for fluid flow problems in micro-devices. The simulator was programmed in the C/C++ language for CPU processing and CUDA-C language for GPU processing. The study of SPH formulation included phenomena such as surface tension, multi-phase, capillarity and wettability between fluid-fluid and fluid-structure. The steps of development of the computational simulator were: Review of non-mesh lagrangean particle methods eligible for modeling of fluid-structure interaction in micro-systems; Metology and formulation of constitutive equations for the description of fluid, structure and fluid-structure behavior using SPH; Implementation of micro-fluidic phenomena such as multi-phase (liquid-liquid) and surface tension and capillarity. All implementations of formulations and simulator validated by comparing results in literature and experimentation. Thus, the main objective of this work was to demonstrate SPH as a tool in the numerical modeling of fluids in liquid-liquid interaction and liquid-structure for the problems involved in microfluidic and micro-devicesDoutoradoMecanica dos Sólidos e Projeto MecanicoDoutor em Engenharia Mecânica2012/21090-5FAPES