Dissertations / Theses on the topic 'Voxel Graphic'

Кваліфікаційна робота включає пояснювальну записку (54 с., 19 рис., 2 табл., список використаної літератури з 15 найменувань, 3 додатки). Метою дипломного проєкту є розробка простого графічного редактору з використанням 3D моделі Voxel, який дозволяє дослідити можливості використання даної технології на сучасних персональних комп’ютерах. Розроблений графічний редактор дозволяє: створювати воксельну модель з існуючої моделі іншого типу; візуалізувати створені воксельні моделі; виконувати перетворення воксельних моделей з використанням буферів глибини. В процесі розробки були використані власні реалізації технології Voxel, розрідженого воксельного дерева та стандарт графічних адаптерів OpenGL 3.3. В ході розробки: - реалізовано об’єкт Voxel, що інкапсулює нюанси реалізації технології в умовах відсутності апаратної підтримки; - реалізовано розріджене воксельне дерево, що використовується для представлення об’єкту типу Voxel; - реалізовані алгоритми побудови, візуалізації та редагування воксельних об’єктів; - реалізовано простий графічний редактор з підтримкою розроблених алгоритмів. Результати дипломного проєкту можуть бути використані для оцінки можливостей воксельної технології та доцільності її використання.
Qualification work includes an explanatory note (54 p., 19 figs., 2 tables., list of references with 15 items, 3 appendices). The purpose of the thesis project is to develop a simple graphic editor using the 3D model Voxel, to explore the possibility of using technology on modern PCs. Developed graphic editor allows you to: create a voxel model from an existing model of another type; visualize the created voxel models; perform voxel model transformations using depth buffers. In the development process, we used our own implementations of Voxel technology, sparse voxel octree and the OpenGL 3.3 graphics adapter standard. During development: - implemented Voxel object, which encapsulates the nuances of technology implementation in the absence of hardware support. - sparse voxel octree used to represent a Voxel object is implemented. - implemented algorithms for building, visualizing and editing voxel objects. - implemented a simple graphical editor with support for developed algorithms. The results of the thesis project can be used to assess the capabilities of voxel technology and the feasibility of its use

The field of Procedural Generation is being increasingly used in modern content generation for its ability to significantly decrease the cost and time involved. One such area of Procedural Generation is Shape Grammars, a type of formal grammar that operates on geometric shapes instead of symbols. Conventional shape grammar implementations use mesh representations of shapes, but this has two significant drawbacks. Firstly, mesh representations make Boolean geometry operations on shapes difficult to accomplish. Boolean geometry operations allow us to combine shapes using Boolean operators (and, or, not), producing complex, composite shapes. A second drawback is that sub-, or trans-shape detailing is challenging to achieve. To address these two problems with conventional mesh-based shape grammars, we present a novel extension to shape grammars, in which a voxel representation of the generated shapes is used. We outline a five stage algorithm for using these extensions and discuss a number of optional enhancements and optimizations. The final output of the algorithm is a detailed mesh model, suitable for use in real-time or offline graphics applications. We also test our extension’s performance and range of output with three categories of testing: performance testing, output range testing, and variation testing. The results of the testing with our proof-of-concept implementation show that our unoptimized algorithm is slower than conventional shape grammar implementations, with a running time that is O(N^3) for an N^3 voxel grid. However, there is scope for further optimization to our algorithm, which would significantly reduce running times and memory consumption. We outline and discuss several such avenues for performance enhancement. Additionally, testing reveals that our algorithm is able to successfully produce a broad range of detailed outputs, exhibiting many features that would be very difficult to accomplish using mesh-based shape grammar implementations. This range of 3D models includes fractals, skyscraper buildings, space ships, castles, and more. Further, stochastic rules can be used to produce a variety of models that share a basic archetype, but differ noticeably in their details.

Modeling believable lighting is a crucial component of computer graphics applications, including games and modeling programs. Physically accurate lighting is complex and is not currently feasible to compute in real-time situations. Therefore, much research is focused on investigating efficient ways to approximate light behavior within these real-time constraints. In this thesis, we implement a general purpose algorithm for real-time applications to approximate indirect lighting. Based on voxel cone tracing, we use a filtered representation of a scene to efficiently sample ambient light at each point in the scene. We present an approach to scene voxelization using hardware tessellation and compare it with an approach utilizing hardware rasterization. We also investigate possible methods of warped voxelization. Our contributions include a complete and open-source implementation of voxel cone tracing along with both voxelization algorithms. We find similar performance and quality with both voxelization algorithms.

Ray tracing is a popular technique used in movies and video games to create compelling visuals. Ray traced computer images are increasingly becoming more realistic and almost indistinguishable from real-word images. Due to the complexity of scenes and the desire for high resolution images, ray tracing can become very expensive in terms of computation and memory. To address these concerns, researchers have examined data structures to efficiently store geometric and material information. Sparse voxel octrees (SVOs) and directed acyclic graphs (DAGs) have proven to be successful geometric data structures for reducing memory requirements. Moxel DAGs connect material properties to these geometric data structures, but experience limitations related to memory, build times, and render times. This thesis examines the efficacy of connecting an alternative material data structure to existing geometric representations. The contributions of this thesis include the creation of a new material representation using hashing to accompany DAGs, a method to calculate surface normals using neighboring voxel data, and a demonstration and validation that DAGs can be used to super sample based on proximity. This thesis also validates the visual acuity from these methods via a user survey comparing different output images. In comparison to the Moxel DAG implementation, this work increases render time, but reduces build times and memory, and improves the visual quality of output images.

In the field of Computer Graphics, Ray Tracing has so far been the the best algorithm for rendering of realistic three dimensional images created by mathematical models. Ray Tracing is also known for its very large computation times, where the computation depends on the picture resolution, the number of objects and the complexity of the scene.

As time goes on, the demand for higher resolution and more visually rich images only increases. Unfortunately, creating these more realistic computer graphics is pushing our computational resources to their limits. In realistic rendering, one of the common ways 3D objects are represented is as volumetric elements called voxels. Traditionally, voxel data structures are known for their high memory requirements. One of the standard ways these requirements are minimized is by storing the voxels in a sparse voxel octree (SVO). Very recently, a method called High Resolution Sparse Voxel DAGs was presented that can store binary voxel data orders of magnitudes more efficiently than SVOs. This memory efficiency is achieved by converting the tree into a directed acyclic graph (DAG). The method was also shown to have competitive rendering performance to recent GPU ray tracers. Unfortunately, it does not support storing collections of rendering attributes, commonly called materials. These represent a given object's reflectance properties, and are necessary for calculating its perceived color. We present a method for connecting material information to High Resolution Sparse Voxel DAGs for mid-level scenes, with multiple meshes, and several different materials. This is achieved using an extended Sparse Voxel DAG, called a Moxel DAG, and an external data structure for holding the material information, we call a Moxel Table. Our method is much more memory efficient than traditional SVOs, and only increases in efficiency in comparison when at higher resolutions. Because it stores the equivalent information as SVOs, it achieves the exact same visual quality at the same resolutions.

This thesis explores Voxel Cone Tracing as a possible Global Illumination solutionon mobile devices.The rapid increase of performance on low-power graphics processors hasmade a big impact. More advanced computer graphics algorithms are now possi-ble on a new range of devices. One category of such algorithms is Global Illumi-nation, which calculates realistic lighting in rendered scenes. The combinationof advanced graphics and portability is of special interest to implement in newtechnologies like Virtual Reality.The result of this thesis shows that while possible to implement a state of theart Global Illumination algorithm, the performance of mobile Graphics Process-ing Units is still not enough to make it usable in real-time.

The work described in this thesis is part of the Open Space project, a collaboration between Linköping University, NASA and the American Museum of Natural History. The long-term goal of Open Space is a multi-purpose, open-source scientific visualization software. The thesis covers the research and implementation of a pipeline for preparing and rendering volumetric data. The developed pipeline consists of three stages: A data formatting stage which takes data from various sources and prepares it for the rest of the pipeline, a pre-processing stage which builds a tree structure of of the raw data, and finally an interactive rendering stage which draws a volume using ray-casting. The pipeline is a fully working proof-of-concept for future development of Open Space, and can be used as-is to render space weather data using a combination of suitable data structures and an efficient data transfer pipeline. Many concepts and ideas from this work can be utilized in the larger-scale software project.

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Para estimar a dose absorvida pelo paciente em uma série de exames de raios-X diagnóstico, é necessário realizar simulações utilizando um modelo computacional de exposição. Tais modelos são compostos, fundamentalmente, por um simulador antropomórfico (fantoma) e um código Monte Carlo. O acoplamento de um fantoma de voxels a um código Monte Carlo é um processo complexo e quase sempre resulta na solução de um problema particular. Isto significa que é inviável a utilização destas ferramentas computacionais na rotina de clínicas e hospitais que realizam exames de raios-X, porque as simulações com modelo computacional de exposição demandam tempo, conhecimento do código utilizado e diversos ajustes a serem implementados de uma simulação para outra. Neste contexto, foi desenvolvido em C++ a GUI (Graphics User Interface) VoxelDose que cria arquivos de dados com o resultado da simulação de diversos exames e utiliza estes arquivos de dados para fornecer as informações dosimétricas. O arquivo de dados foi construído usando os fantomas de voxels MAX (Male Adult voXel) e FAX (Female Adult voXel), e o código Monte Carlo EGS4 (Electron Gamma Shower, versão 4). O software permite ao usuário criar os arquivos de dados, inserir novos exames, visualizar a região do exame e a posição da fonte, obter coeficientes de conversão e calcular dose. Os resultados dosimétricos e as imagens podem ser salvos ou impressos

Zoomable user interfaces (ZUIs) have been studied for a long time and many applications are built upon them. Most applications, however, only use two dimensions to express the content. This report presents a solution using all three dimensions where the base features are built as a framework with uniform grids and scene graphs as primary data structures. The purpose of these data structures is to improve performance while maintaining flexibility when creating and handling three-dimensional objects. A 3D-ZUI is able to represent the view of the world and its objects in a more lifelike manner. It is possible to interact with the objects much in the same way as in real world. By developing a prototype framework as well as some example applications, the usefulness of 3D-ZUIs is illustrated. Since the framework relies on abstraction and object-oriented principles it is easy to maintain and extend it as needed. The currently implemented data structures are well motivated for a large scale 3D-ZUI in terms of accelerated collision detection and picking and they also provide a flexible base when developing applications. It is possible to further improve performance of the framework, for example by supporting different types of culling and levels of detail

Cone Beam Computed Tomography (CBCT) is a medical imaging technique routinely employed for diagnosis and treatment of patients with cranio-maxillo-facial defects. CBCT 3D reconstruction and segmentation of bones such as mandible or maxilla are essential procedures in orthodontic treatments. However, CBCT images present characteristics that are not desirable for processing, including low contrast, inhomogeneity, noise, and artifacts. Besides, values assigned to voxels are relative Hounsfield Units (HU), unlike traditional Computed Tomography (CT). Such drawbacks render CBCT segmentation a difficult and time-consuming task, usually performed manually with tools designed for medical image processing. We introduce two interactive two-stage methods for 3D segmentation of CBCT data: i) we first reduce the CBCT image resolution by grouping similar voxels into super-voxels defining a graph representation; ii) next, seeds placed by users guide graph clustering algorithms, splitting the bones into mandible and skull. We have evaluated our segmentation methods intensively by comparing the results against ground truth data of the mandible and the skull, in various scenarios. Results show that our methods produce accurate segmentation and are robust to changes in parameter settings. We also compared our approach with a similar segmentation strategy and we showed that it produces more accurate segmentation of the mandible and skull. In addition, we have evaluated our proposal with CT data of patients with deformed or missing bones. We obtained more accurate segmentation in all cases. As for the efficiency of our implementation, a segmentation of a typical CBCT image of the human head takes about five minutes. Finally, we carried out a usability test with orthodontists. Results have shown that our proposal not only produces accurate segmentation, as it also delivers an effortless and intuitive user interaction.
Tomografia Computadorizada de Feixe Cônico (TCFC) é uma modalidade para obtenção de imagens médicas 3D do crânio usada para diagnóstico e tratamento de pacientes com defeitos crânio-maxilo-faciais. A segmentação tridimensional de ossos como a mandíbula e a maxila são procedimentos essências em tratamentos ortodônticos. No entanto, a TCFC apresenta características não desejáveis para processamento digital como, por exemplo, baixo contraste, inomogeneidade, ruído e artefatos. Além disso, os valores atribuídos aos voxels são unidades de Hounsfield (HU) relativas, diferentemente da Tomografia Computadorizada (TC) tradicional. Esses inconvenientes tornam a segmentação de TCFC uma tarefa difícil e demorada, a qual é normalmente realizada por meio de ferramentas desenvolvidas para processamento digital de imagens médicas. Esta tese introduz dois métodos interativos para a segmentação 3D de TCFC, os quais são divididos em duas etapas: i) redução da resolução da TCFC por meio da agrupamento de voxels em super-voxels, seguida da criação de um grafo no qual os vértices são super-voxels; ii) posicionamento de sementes pelo usuário e segmentação por algoritmos de agrupamento em grafos, o que permite separar os ossos rotulados. Os métodos foram intensamente avaliados por meio da comparação dos resultados com padrão ouro da mandíbula e do crânio, considerando diversos cenários. Os resultados mostraram que os métodos não apenas produzem segmentações precisas, como também são robustos a mudanças nos parâmetros. Foi ainda realizada uma comparação com um trabalho relacionado, gerando melhores resultados tanto na segmentação da mandíbula quanto a do crânio. Além disso, foram avaliadas TCs de pacientes com ossos faltantes e quebrados. A segmentação de uma TCFC é realizada em cerca de 5 minutos. Por fim, foram realizados testes com usuarios ortodontistas. Os resultados mostraram que nossa proposta não apenas produz segmentações precisas, como também é de fácil interação.

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.

Real-time global illumination has been a very important topic and is widely used in game industry. Previous offline rendering requires a large amount of time to converge and reduce the noise generated in Monte Carlo method. Thus, it cannot be easily adapted in real-time rendering. Using voxels in the field of global illumination has become a popular approach. While a naïve voxel grid occupies huge memory in video card, a data structure called sparse voxel octree is often implemented in order to reduce memory cost of voxels and achieve efficient ray casting performance in an interactive frame rate.

However, rendering of voxels can cause block effects due to the nature of voxel. One solution is to increase the resolution of voxel so that one voxel is smaller than a pixel on screen. But this is usually not feasible because higher resolution results in higher memory consumption. Thus, most of the global illumination methods of SVO (sparse voxel octree) only use it in visibility test and radiance storage, rather than render it directly. Previous research has tried to incorporate SVO in ray tracing, radiosity methods and voxel cone tracing, and all achieved real-time frame rates in complex scenes. However, most of them only focus on static scenes and does not consider dynamic updates of SVO and the influence of it on performance.

In this thesis, we will discuss the tradeoff of multiple classic real-time global illumination methods and their implementations using SVO. We will also propose an efficient approach to dynamic update SVO in animated scenes. The deliverables will be implemented in CUDA 11.0 and OpenGL.

The thesis analyzes the non-standard vowel length and shortness in the complete hymn book of Valentin Šubar, as it is presented in the edition published by the Utraquist Jiří Hanuš of Kronenfeld in 1612 (Knihopis K16012). Based on selected transliterated segments, the level of consistency in the marking of vowel quantity is identified, and the outcome is subsequently taken into account when interpreting individual non-standard forms. Consequently, the results of previous research on vowel length marking in the 17th century Czech prints are slightly modified and the incorrect datation of surviving exemplars of the hymn book is corrected.