Three-dimensional volume data is routinely produced, at increasingly high spatial resolution, in computer simulations and image acquisition tasks. In-situ visualization, the visualization of an experiment or simulation while it is running, enables new modes of interaction, including simulation steering and experiment control. These can provide the scientist a deeper understanding of the underlying phenomena, but require interactive visualization with smooth viewpoint changes and zooming to convey depth perception and spatial understanding. As the size of the volume data increases, however, it is increasingly challenging to achieve interactive visualization with smooth viewpoint changes. This thesis presents an end-to-end solution for interactive in-situ visualization based on novel extensions proposed to the Volumetric Depth Image (VDI) representation. VDIs are view-dependent, compact representations of volume data than can be rendered faster than the original data. Novel methods are proposed in this thesis for generating VDIs on large data and for rendering them faster. Together, they enable interactive in situ visualization with smooth viewpoint changes and zooming for large volume data. The generation of VDIs involves decomposing the volume rendering integral along rays into segments that store composited color and opacity, forming a representation much smaller than the volume data. This thesis introduces a technique to automatically determine the sensitivity parameter that governs the decomposition of rays, eliminating the need for manual parameter tuning in the generation of a VDI. Further, a method is proposed for sort-last parallel generation and compositing of VDIs on distributed computers, enabling their in situ generation with distributed numerical simulations. A low latency architecture is proposed for the sharing of data and hardware resources with a running simulation. The resulting VDI can be streamed for interactive visualization. A novel raycasting method is proposed for rendering VDIs. Properties of perspective projection are exploited to simplify the intersection of rays with the view-dependent segments contained within the VDI. Spatial smoothness in volume data is leveraged to minimize memory accesses. Benchmarks are performed showing that the method significantly outperforms existing methods for rendering the VDI, and achieves responsive frame rates for High Definition (HD) display resolutions near the viewpoint of generation. Further, a method is proposed to subsample the VDI for preview rendering, maintaining high frame rates even for large viewpoint deviations. The quality and performance of the approach are analyzed on multiple datasets, and the contributions are provided as extensions of established open-source tools. The thesis concludes with a discussion on the strengths, limitations, and future directions for the proposed approach.

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[pt] Neste trabalho apresentamos os aspectos da visualização volumétrica de horizontes em dados sísmicos 3D. Consideramos as abordagens de visualização volumétrica direta e indireta. Na abordagem direta investigamos o problema da seleção de horizontes usando funções de transferência. Apresentamos a técnica de opacidade 2D, que busca aumentar a capacidade de seleção dos horizontes para visualização. Comparamos a utilização dos atributos de fase instantânea, fase ajustada e fase desenrolada como segunda dimensão, enquanto a primeira é a amplitude sísmica. Ainda na abordagem direta, mostramos que o gradiente da amplitude sísmica não aproxima bem os vetores normais nos horizontes sísmicos. Sugerimos o gradiente da fase instantânea como solução para este problema. Na abordagem de visualização volumétrica indireta introduzimos uma modelagem de otimização para o problema de rastreamento de horizontes. Sugerimos um método heurístico baseado em uma estratégia gulosa para encontrar soluções que são boas aproximações para os horizontes mesmo na presença de estruturas geológicas complexas. / [en] This work presents aspects of volume visualization of seismic horizons in 3-D seismic data. We consider both the direct and indirect approaches of volume visualization. In the direct approach we investigate the problem of selecting horizons using transfer functions. We present the 2-D opacity technique, which seeks to increase the ability to select horizons for visualization. We compare the use of instantaneous phase, adjusted phase and unwrapped phase as the second dimension, while seismic amplitude is the first dimension. Also in the direct approach, we show that the seismic amplitude gradient is not a good approximation for the normal vectors in seismic horizons. We suggest the gradient of instantaneous phase as a solution to this problem. In the indirect volume visualization approach we introduce a new optimization model to overcome the seismic horizon tracking problem. We present a heuristic method based on a greedy strategy to find solutions that are good approximations of the horizon of interest, even for complex geological structures.

Made available in DSpace on 2014-12-17T14:55:01Z (GMT). No. of bitstreams: 1 CarlosML.pdf: 1974392 bytes, checksum: 7dc32733a49e5db708c65fe1d883a3ae (MD5) Previous issue date: 2005-11-28 / In the recovering process of oil, rock heterogeneity has a huge impact on how fluids move in the field, defining how much oil can be recovered. In order to study this variability, percolation theory, which describes phenomena involving geometry and connectivity are the bases, is a very useful model. Result of percolation is tridimensional data and have no physical meaning until visualized in form of images or animations. Although a lot of powerful and sophisticated visualization tools have been developed, they focus on generation of planar 2D images. In order to interpret data as they would be in the real world, virtual reality techniques using stereo images could be used. In this work we propose an interactive and helpful tool, named ZSweepVR, based on virtual reality techniques that allows a better comprehension of volumetric data generated by simulation of dynamic percolation. The developed system has the ability to render images using two different techniques: surface rendering and volume rendering. Surface rendering is accomplished by OpenGL directives and volume rendering is accomplished by the Zsweep direct volume rendering engine. In the case of volumetric rendering, we implemented an algorithm to generate stereo images. We also propose enhancements in the original percolation algorithm in order to get a better performance. We applied our developed tools to a mature field database, obtaining satisfactory results. The use of stereoscopic and volumetric images brought valuable contributions for the interpretation and clustering formation analysis in percolation, what certainly could lead to better decisions about the exploration and recovery process in oil fields / No processo da recupera??o do petr?leo, a heterogeneidade das rochas exerce um impacto enorme na forma como os l?quidos se movem no reservat?rio, definindo quanto petr?leo pode ser recuperado. A fim de estudar esta variabilidade, a teoria da percola??o, que descreve fen?menos envolvendo geometria e conectividade ? um modelo muito ?til. Os resultados da simula??o de percola??o s?o de car?ter tridimensional e n?o t?m nenhum significado f?sico at? que sejam visualizados em imagens ou anima??es. Embora ferramentas poderosas e sofisticadas de visualiza??o tenham sido desenvolvidas, estas transformam grandes volumes de dados em imagens 2D. A fim de interpretarmos os dados como eles aparecem no mundo real, t?cnicas de realidade virtual baseadas principalmente em estereoscopia podem ser usadas. Neste trabalho, propomos uma ferramenta interativa, denominada ZSweepVR, baseada em t?cnicas de realidade virtual, que permite uma melhor compreens?o dos dados volum?tricos gerados por simula??es de percola??o din?mica. O sistema desenvolvido tem a capacidade de renderizar imagens utilizando duas t?cnicas diferentes: renderiza??o de superf?cie e renderiza??o de volumes. A renderiza??o de superf?cie ? realizada utilizando diretivas OpenGL, enquanto que a renderiza??o volum?trica ? realizada pelo algoritmo de renderiza??o volum?trica direta ZSweep. No caso da renderiza??o volum?trica, implementamos algoritmo para gerar imagens est?reo. N?s tamb?m propomos melhorias no algoritmo original de percola??o din?mica visando melhorar sua efici?ncia. Aplicamos as ferramentas desenvolvidas a dados de campos maduros, obtendo resultados satisfat?rios. O uso de imagens estereosc?picas e volum?tricas trouxe contribui??es valiosas para a interpreta??o e analise da forma??o dos aglomerados na percola??o, o que certamente pode levar a decis?es melhores sobre a explora??o e recupera??o de petr?leo

This thesis discusses possibilities of accelerated 3D scene displaying in a Web browser. In more detail, it deals with WebGL standard and its use in real applications. An application for visualization of volumetric medical data based on JavaScript, WebGL and Three.js library was designed and implemented. Image data are loaded from Google Drive cloud storage. An important part of the application is 3D visualization of the volumetric data based on volume rendering technique called Ray-casting.

Diplomová práce je zaměřena na metody zobrazování skalárních dat v pevné datové mřížce, konkrétně dat získaných užitím fluorescenčního konfokálního mikroskopu. Teoretická část textu začíná představením fungování konfokálních mikroskopů a zasazení problematiky zkoumaných grafických metod do matematického kontextu. Následující kapitola se věnuje odvození integrálu pro zobrazování objemů a z něj vyplývající back-to-front metodu. Teoretická část je zakončena představením metod vhodných pro zobrazování trojrozměrných skalárních dat při použití back-to-front algoritmu. V praktické části je pak popsán implementovaný algoritmus.

The first part of this project is focused on theoretical analysis of methods for rendering volume data. Both methods are analyzed showing the volume data using triangle mesh, and methods for direct volume rendering. Ray Casting is presented in detail. Possible way of its realization using graphics card is the subject of implementation part. The paper presents several methods that could be applied to ray casting and achieve different results of visualization of the same data. The work also aims to create a  graphical user interface that allows interactive visualizations.

Theoretical part of this project is focused on rendering of volumetric data. It compares and appraise individual methods and thus readers get a good basic knowledge of commonnest causes of problems. Texture Mapped Volume Rendering and Volume Ray-casting methods are described in detail and the latter method is used in implementation of graphic system designed in this thesis. Secondary goals of this work are usage of less powerful hardware for volume-rendering, methods of optimization and dynamic change of output quality.

This work makes basic analysis of historical and current algorithms for smoke animation. Modern approaches to rendering volumetric data are briefly described. We choose algorithms for implementation on basis of this analysis. These algorithms are described in detail and we make emphasis on their important properties according to dedication of this work. Detailed description of implementation follows along with performance measurement. Conclusion evaluates results of work and proposes possible extensions.

Made available in DSpace on 2016-03-15T19:37:58Z (GMT). No. of bitstreams: 1 RODRIGO FREITAS LIMA.pdf: 13768169 bytes, checksum: 153d5257eed9a0961aaeaac94e224f89 (MD5) Previous issue date: 2015-08-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Paranasal sinus are important objects of study to rhinosinusitis diagnostic, having some papers related incidence between asthma and allergic rhinitis.Many applications can calculate to various parts of the human body, getting a CT scan or MRI input, and returning information about the region of interest observed as volume and area. The accumulated mucus in the sinuses is one of the areas of interest that have not yet been implemented methods for the calculation of volume and area. In the present scenario, the patient monitoring is done visually, depending largely on perception of the evaluator. Therefore, we seek to implement more accurate metrics to facilitate medical care to the patient and it can help prevent the worsening of rhinitis in a given patient, developing mechanisms of visual and numerical comparison, where it is possible observe the progress of treatment. This work contains a detailed study of how certain existing techniques, combined into one methodology can segment and calculate the accumulated mucus in the maxillary sinus. In addition to techniques such as Thresholding, Gaussian filter, Mathematical Morphology, Metallic Artifacts Reduction during processing and segmentation, MUNC and DTA to calculate the volume and area, and visualization techniques as the Marching Cubes, it was also necessary some adjustments in the algorithm for limit the region of interest where the thresholding combined with the gaussian filter has not been effective of retaining edges. The application will use two open source platforms, one for processing, ITK, and another for visualization, VTK. The results demonstrated that it is possible to perform segmentation and the calculation with the use of platforms as well as the methodology used is adequate to solve this problem. / Os seios paranasais são importantes objetos de estudo para o diagnóstico de rinossinusites, tendo alguns estudos relacionado a incidência de asma na fase adulta a quadros de rinite alérgica na infância. Muitas aplicações atendem a diversas partes do corpo humano, obtendo de entrada uma tomografia computadorizada ou ressonância magnética, e devolvendo, muitas vezes, números que dizem respeito ao objeto de interesse observado, como volume e área. O muco acumulado nos seios paranasais é uma das regiões de interesse que ainda não tiveram métodos implementados para o cálculo do volume e área. No cenário atual, o acompanhamento do paciente é feito de forma visual, dependendo muito da percepção do avaliador. Portanto, busca-se a implementação de métricas mais precisas para facilitar o acompanhamento médico ao paciente e ajudar na prevenção do agravamento de um quadro de rinite em um determinado paciente, criando mecanismos de comparação visual e numérica, onde é possível observar a evolução do tratamento. Este trabalho contém um estudo detalhado de como determinadas técnicas existentes, combinadas em uma metodologia, podem segmentar e calcular o muco acumulado nos seios paranasais maxilares. Além de técnicas como a Binarizacão, Filtro Gaussiano, Morfologia Matemática, Redução de Ruídos Metálico durante o processamento e segmentação, MUNC e DTA para o cálculo do volume e área, e técnicas de visualização como o Marching Cubes, foram necessários também ajustes no algoritmo para limitar a área segmentada onde a binarizacão combinada ao filtro não foi capaz de manter as bordas da região de interesse. A aplicação fará uso de duas plataformas de código livre, sendo uma para o processamento, ITK, e outra para visualização de imagens, VTK. Os resultados demonstraram que é possível realizar a segmentação e o cálculo com o uso das plataformas, bem como a metodologia empregada é adequada a resolução deste problema.