Visuelle Analyse großer Partikeldaten

Partikelsimulationen sind eine bewährte und weit verbreitete numerische Methode in der Forschung und Technik. Beispielsweise werden Partikelsimulationen zur Erforschung der Kraftstoffzerstäubung in Flugzeugturbinen eingesetzt. Auch die Entstehung des Universums wird durch die Simulation von dunkler Materiepartikeln untersucht. Die hierbei produzierten Datenmengen sind immens. So enthalten aktuelle Simulationen Billionen von Partikeln, die sich über die Zeit bewegen und miteinander interagieren. Die Visualisierung bietet ein großes Potenzial zur Exploration, Validation und Analyse wissenschaftlicher Datensätze sowie der zugrundeliegenden Modelle. Allerdings liegt der Fokus meist auf strukturierten Daten mit einer regulären Topologie. Im Gegensatz hierzu bewegen sich Partikel frei durch Raum und Zeit. Diese Betrachtungsweise ist aus der Physik als das lagrange Bezugssystem bekannt. Zwar können Partikel aus dem lagrangen in ein reguläres eulersches Bezugssystem, wie beispielsweise in ein uniformes Gitter, konvertiert werden. Dies ist bei einer großen Menge an Partikeln jedoch mit einem erheblichen Aufwand verbunden. Darüber hinaus führt diese Konversion meist zu einem Verlust der Präzision bei gleichzeitig erhöhtem Speicherverbrauch. Im Rahmen dieser Dissertation werde ich neue Visualisierungstechniken erforschen, welche speziell auf der lagrangen Sichtweise basieren. Diese ermöglichen eine effiziente und effektive visuelle Analyse großer Partikeldaten

GPU Based Real-time Welding Simulation with Smoothed-Particle Hydrodynamics

Welding training is essential in the development of industrialization. A good welder will build robust workpieces that ensure the safety and stability of the product. However, training a welder requires lots of time and access professional welding equipment. Therefore, it is desirable to have a training system that is economical and easy to use. After decades development of computer graphics, sophisticated methodologies are developed in simulation fields, along the advanced hardware, enables the possibility of simulation welding with software. In this thesis, a novel prototype of welding training system is proposed. We use smoothed-particle hydrodynamics (SPH) method to simulate fluid as well as heat transfer and phase changing. In order to accelerate the processing to reach the level of real-time, we adopt CUDA to implement the SPH solver on GPU. Plus, Leap Motion is utilized as the input device to control the welding gun. As the result, the simulation reaches decent frame rate that allows the user control the simulation system interactively. The input device permits the user to adapt to the system in less than 5 minutes. This prototype shows a new direction in the training system that combines VR, graphics, and physics simulation. The further development of VR output device like Oculus Rift will enable the training system to a more immersive level

Tools for fluid simulation control in computer graphics

L’animation basée sur la physique peut générer des systèmes aux comportements complexes et réalistes. Malheureusement, contrôler de tels systèmes est une tâche ardue. Dans le cas de la simulation de fluide, le processus de contrôle est particulièrement complexe. Bien que de nombreuses méthodes et outils ont été mis au point pour simuler et faire le rendu de fluides, trop peu de méthodes offrent un contrôle efficace et intuitif sur une simulation de fluide. Étant donné que le coût associé au contrôle vient souvent s’additionner au coût de la simulation, appliquer un contrôle sur une simulation à plus haute résolution rallonge chaque itération du processus de création. Afin d’accélérer ce processus, l’édition peut se faire sur une simulation basse résolution moins coûteuse. Nous pouvons donc considérer que la création d’un fluide contrôlé peut se diviser en deux phases: une phase de contrôle durant laquelle un artiste modifie le comportement d’une simulation basse résolution, et une phase d’augmentation de détail durant laquelle une version haute résolution de cette simulation est générée. Cette thèse présente deux projets, chacun contribuant à l’état de l’art relié à chacune de ces deux phases. Dans un premier temps, on introduit un nouveau système de contrôle de liquide représenté par un modèle particulaire. À l’aide de ce système, un artiste peut sélectionner dans une base de données une parcelle de liquide animé précalculée. Cette parcelle peut ensuite être placée dans une simulation afin d’en modifier son comportement. À chaque pas de simulation, notre système utilise la liste de parcelles actives afin de reproduire localement la vision de l’artiste. Une interface graphique intuitive a été développée, inspirée par les logiciels de montage vidéo, et permettant à un utilisateur non expert de simplement éditer une simulation de liquide. Dans un second temps, une méthode d’augmentation de détail est décrite. Nous proposons d’ajouter une étape supplémentaire de suivi après l’étape de projection du champ de vitesse d’une simulation de fumée eulérienne classique. Durant cette étape, un champ de perturbations de vitesse non-divergent est calculé, résultant en une meilleure correspondance des densités à haute et à basse résolution. L’animation de fumée résultante reproduit fidèlement l’aspect grossier de la simulation d’entrée, tout en étant augmentée à l’aide de détails simulés.Physics-based animation can generate dynamic systems of very complex and realistic behaviors. Unfortunately, controlling them is a daunting task. In particular, fluid simulation brings up particularly difficult problems to the control process. Although many methods and tools have been developed to convincingly simulate and render fluids, too few methods provide efficient and intuitive control over a simulation. Since control often comes with extra computations on top of the simulation cost, art-directing a high-resolution simulation leads to long iterations of the creative process. In order to shorten this process, editing could be performed on a faster, low-resolution model. Therefore, we can consider that the process of generating an art-directed fluid could be split into two stages: a control stage during which an artist modifies the behavior of a low-resolution simulation, and an upresolution stage during which a final high-resolution version of this simulation is driven. This thesis presents two projects, each one improving on the state of the art related to each of these two stages. First, we introduce a new particle-based liquid control system. Using this system, an artist selects patches of precomputed liquid animations from a database, and places them in a simulation to modify its behavior. At each simulation time step, our system uses these entities to control the simulation in order to reproduce the artist’s vision. An intuitive graphical user interface inspired by video editing tools has been developed, allowing a nontechnical user to simply edit a liquid animation. Second, a tracking solution for smoke upresolution is described. We propose to add an extra tracking step after the projection of a classical Eulerian smoke simulation. During this step, we solve for a divergence-free velocity perturbation field resulting in a better matching of the low-frequency density distribution between the low-resolution guide and the high-resolution simulation. The resulting smoke animation faithfully reproduces the coarse aspect of the low-resolution input, while being enhanced with simulated small-scale details

Virtual Reality Applied to Welder Training

Welding is a challenging, risky, and time-consuming profession. Recently, there has been a documented shortage of trained welders, and as a result, the market is pushing for an increase in the rate at which new professionals are trained. To address this growing demand, training institutions are exploring alternative methods to train future professionals with the goals of improving learner retention of information, shortening training periods, and lowering associated expenses. The emergence of virtual reality technologies has led to initiatives to explore their potential for welding training. Multiple studies have suggested that virtual reality training delivers comparable, or even superior, results when compared to more conventional approaches, with shorter training times and reduced costs in consumables. Additionally, virtual reality allows trainees to try out different approaches to their work. The primary goal of this dissertation is to develop a virtual reality welding simulator. To achieve this objective effectively, the creation of a classification system capable of identifying the simulator’s key characteristics becomes imperative. Therefore, the secondary objective of this thesis is to develop a classification system for the accurate evaluation and comparison of virtual reality welding simulators. Regarding the virtual reality welding simulation, the HTC VIVE Pro 2 virtual reality equipment was employed, to transfer the user’s action from the physical to the virtual world. Within this virtual environment, it was introduced a suite of welding tools and integrated a Smoothed Particle Hydrodynamics simulator to mimic the weld creation. After conducting comprehensive testing that revealed certain limitations in welding quality and in the simulator performance, the project opted to incorporate a Computational Fluid Dynamics (CFD) simulator. The development of the CFD simulator proved to be a formidable challenge, and regrettably, its complete implementation was unattainable. Nevertheless, the project delved into three distinct grid architectures, from these, the dynamic grid was ultimately implemented. It also proficiently integrated two crucial solvers for the Navier-Stokes equations. These functions were implemented in the Graphics Processing Unit (GPU), to improve their efficiency. Upon comparing GPU and Central Processing Unit (CPU) performance, the project highlighted the substantial computational advantages of GPUs and the advantages it brings to fluid simulations.A soldadura é uma profissão exigente, perigosa e que requer um grande investimento de tempo para alcançar resultados satisfatórios. Recentemente, tem sido registada uma falta de profissionais qualificados na área da soldadura. Como resultado, o mer cado está a pressionar para um aumento do ritmo a que os novos trabalhadores são formados. Para responder a esta crescente procura, as instituições de formação estão a explorar métodos alternativos para formar futuros profissionais, com o objetivo de melhorar a retenção de informação, encurtar os períodos de treino e reduzir as despe sas associadas. Com o desenvolvimento de tecnologias nas áreas de realidade virtual e realidade aumentada, têm surgido iniciativas para explorar o potencial destas na formação de soldadura. Vários estudos sugeriram que a formação em realidade virtual proporciona resultados comparáveis, ou mesmo superiores, aos de abordagens mais convencionais, com tempos de formação mais curtos e reduções nos custos de consumíveis. Além disso, a realidade virtual permite aos formandos experimentar diferentes abordagens ao seu trabalho. O objetivo principal desta dissertação é o desenvolvimento de um simulador de soldadura em realidade virtual. Para atingir este objetivo de forma eficaz, torna-se imperativa a criação de um sistema de classificação capaz de identificar as características chave do simulador. Assim, o objetivo secundário desta dissertação é desenvolver um sistema de classificação para a avaliação e comparação precisas de simuladores de soldadura em realidade virtual. Relativamente ao simulador de soldadura em realidade virtual, foi utilizado o kit de realidade virtual HTC VIVE Pro 2, para transferir as ações do utilizador no mundo físico para o mundo virtual. No ambiente virtual, foi introduzido um con junto de ferramentas de soldadura e integrado um simulador de Hidrodinâmica de Partículas Suavizadas para simular a criação da solda. Após a realização de testes exaustivos que revelaram algumas limitações na qualidade da solda e no desempenho do simulador, o projeto optou por incorporar um simulador de Dinâmica de Fluidos Computacional (CFD). O desenvolvimento do simulador CFD revelou-se um desa fio formidável e, infelizmente, não foi possível completar a sua implementação. No entanto, o projeto aprofundou três arquiteturas de grelha distintas, das quais foi implementada a grelha dinâmica. O projeto também implementou duas funções cru ciais para resolver as equações de Navier-Stokes. As funções relativas ao simulador de fluidos foram implementadas na Unidade de Processamento Gráfico (GPU), a fim de melhorar a sua eficiência. Ao comparar o desempenho da GPU com o da Unidade Central de Processamento (CPU), o projeto evidenciou os beneficios computacionais das GPUs e as vantagens que trazem para as simulações de fluidos

Real-time fluid simulations under smoothed particle hydrodynamics for coupled kinematic modelling in robotic applications

Although solids and fluids can be conceived as continuum media, applications of solid and fluid dynamics differ greatly from each other in their theoretical models and their physical behavior. That is why the computer simulators of each turn to be very disparate and case-oriented. The aim of this research work, captured in this thesis book, is to find a fluid dynamics model that can be implemented in near real-time with GPU processing and that can be adapted to typically large scales found in robotic devices in action with fluid media. More specifically, the objective is to develop these fast fluid simulations, comprising different solid body dynamics, to find a viable time kinematic solution for robotics. The tested cases are: i) the case of a fluid in a closed channel flowing across a cylinder, ii) the case of a fluid flowing across a controlled profile, and iii), the case of a free surface fluid control during pouring. The implementation of the former cases settles the formulations and constraints to the latter applications. The results will allow the reader not only to sustain the implemented models but also to break down the software implementation concepts for better comprehension. A fast GPU-based fluid dynamics simulation is detailed in the main implementation. The results show that it can be used in real-time to allow robotics to perform a blind pouring task with a conventional controller and no special sensing systems nor knowledge-driven prediction models would be necessary.Aunque los sólidos y los fluidos pueden concebirse como medios continuos, las aplicaciones de la dinámica de sólidos y fluidos difieren mucho entre sí en sus modelos teóricos y su comportamiento físico. Es por eso que los simuladores por computadora de cada uno son muy dispares y están orientados al caso de su aplicación. El objetivo de este trabajo de investigación, capturado en este libro de tesis, es encontrar un modelo de dinámica de fluidos que se pueda implementar cercano al tiempo real con procesamiento GPU y que se pueda adaptar a escalas típicamente grandes que se encuentran en dispositivos robóticos en acción con medios fluidos. Específicamente, el propósito es desarrollar estas simulaciones de fluidos rápidos, que comprenden diferentes dinámicas de cuerpos sólidos, para encontrar una solución cinemática viable para robótica. Los casos probados son: i) el caso de un fluido en canal cerrado que fluye a través de un cilindro, ii) el caso de un fluido que fluye a través de un alabe controlado, y iii), el caso del control de un fluido de superficie libre durante el vertido. La implementación de estos primeros casos establece las formulaciones y limitaciones de aplicaciones futuras. Los resultados permitirán al lector no solo sostener los modelos implementados sino también desglosar los conceptos de la implementación en software para una mejor comprensión. En la implementación principal se consigue una simulación rápida de dinámica de fluidos basada en GPU. Los resultados muestran que esta implementación se puede utilizar en tiempo real para permitir que la robótica realice una tarea de vertido ciego con un controlador convencional sin que sea necesario algún sistema de sensado especial ni algún modelo predictivo basados en el conocimiento.Programa de Doctorado en Ingeniería Eléctrica, Electrónica y Automática por la Universidad Carlos III de MadridPresidente: Carmen Martínez Arévalo.- Secretario: Luis Santiago Garrido Bullón.- Vocal: Benjamín Hernández Arreguí

Visual Simulation of Multiple Fluids in Computer Graphics: A State-of-the-Art Report

Realistic animation of various interactions between multiple fluids, possibly undergoing phase change, is a challenging task in computer graphics. The visual scope of multi-phase multi-fluid phenomena covers complex tangled surface structures and rich color variations, which can greatly enhance visual effect in graphics applications. Describing such phenomena requires more complex models to handle challenges involving the calculation of interactions, dynamics and spatial distribution of multiple phases, which are often involved and hard to obtain real-time performance. Recently, a diverse set of algorithms have been introduced to implement the complex multi-fluid phenomena based on the governing physical laws and novel discretization methods to accelerate the overall computation while ensuring numerical stability. By sorting through the target phenomena of recent research in the broad subject of multiple fluids, this state-of-the-art report summarizes recent advances on multi-fluid simulation in computer graphics

Multiple-fluid SPH simulation using a mixture model

This article presents a versatile and robust SPH simulation approach for multiple-fluid flows. The spatial distribution of different phases or components is modeled using the volume fraction representation, the dynamics of multiple-fluid flows is captured by using an improved mixture model, and a stable and accurate SPH formulation is rigorously derived to resolve the complex transport and transformation processes encountered in multiple-fluid flows. The new approach can capture a wide range of real-world multiple-fluid phenomena, including mixing/unmixing of miscible and immiscible fluids, diffusion effect and chemical reaction, etc. Moreover, the new multiple-fluid SPH scheme can be readily integrated into existing state-of-the-art SPH simulators, and the multiple-fluid simulation is easy to set up. Various examples are presented to demonstrate the effectiveness of our approach