This paper presents methods for photo-realistic rendering using strongly spatially variant illumination captured from real scenes. The illumination is captured along arbitrary paths in space using a high dynamic range, HDR, video camera system with position tracking. Light samples are rearranged into 4-D incident light fields (ILF) suitable for direct use as illumination in renderings. Analysis of the captured data allows for estimation of the shape, position and spatial and angular properties of light sources in the scene. The estimated light sources can be extracted from the large 4D data set and handled separately to render scenes more efficiently and with higher quality. The ILF lighting can also be edited for detailed artistic control.

The need for efficient interference detection frequently arises in computer graphics, robotics, virtual prototyping, surgery simulation, computer games, and visualization. To prevent bodies passing directly through each other, the simulation system must be able to track touching or intersecting geometric primitives. In interactive simulations, in which millions of geometric primitives may be involved, highly efficient collision detection algorithms are necessary. For these reasons, new adaptive collision detection algorithms for rigid and different types of deformable polygon meshes are proposed in this thesis. The solutions are based on adaptive bounding volume hierarchies. For deformable body simulation, different refit and reconstruction schemes to efficiently update the hierarchies as the models deform are presented. These methods permit the models to change their entire shape at every time step of the simulation. The types of deformable models considered are (i) polygon meshes that are deformed by arbitrary vertex repositioning, but with the mesh topology preserved, (ii) models deformed by linear morphing of a fixed number of reference meshes, and (iii) models undergoing completely unstructured relative motion among the geometric primitives. For rigid body simulation, a novel type of bounding volume, the slab cut ball, is introduced, which improves the culling efficiency of the data structure significantly at a low storage cost. Furthermore, a solution for even tighter fitting heterogeneous hierarchies is outlined, including novel intersection tests between spheres and boxes as well as ellipsoids and boxes. The results from the practical experiments indicate that significant speedups can be achieved by using these new methods for collision queries as well as for ray shooting in complex deforming scenes.

This thesis present an efficient approach for performing smoke simulation on curvilinear grids. The solution of the Navier-Stokes equations on curvilinear is made on three steps: advection, pressure solving and velocity projection. The proposed advection method is simple, fast and unconditionally-stable. Our solution is able to maintain a staggered-grid variable arrangement, and includes an efficient solution to enforce mass conservation. Compared to approaches based on regular grids traditionally used in computer graphics, our method allows for better representation of boundary conditions, lending to more realistic results, with just a small increment in computational cost. Moreover, we are able to condensate cells where interesting artifacts tend to appear, like swirling vortices or turbulence. We demonstrate the effectiveness of our approach, both in 2-D and 3-D, through a variety of high-quality smoke simulations and animations. These examples show the integration of our method with overlapping grids and multigrid techniques.

This thesis present an efficient approach for performing smoke simulation on curvilinear grids. The solution of the Navier-Stokes equations on curvilinear is made on three steps: advection, pressure solving and velocity projection. The proposed advection method is simple, fast and unconditionally-stable. Our solution is able to maintain a staggered-grid variable arrangement, and includes an efficient solution to enforce mass conservation. Compared to approaches based on regular grids traditionally used in computer graphics, our method allows for better representation of boundary conditions, lending to more realistic results, with just a small increment in computational cost. Moreover, we are able to condensate cells where interesting artifacts tend to appear, like swirling vortices or turbulence. We demonstrate the effectiveness of our approach, both in 2-D and 3-D, through a variety of high-quality smoke simulations and animations. These examples show the integration of our method with overlapping grids and multigrid techniques.

This thesis present an efficient approach for performing smoke simulation on curvilinear grids. The solution of the Navier-Stokes equations on curvilinear is made on three steps: advection, pressure solving and velocity projection. The proposed advection method is simple, fast and unconditionally-stable. Our solution is able to maintain a staggered-grid variable arrangement, and includes an efficient solution to enforce mass conservation. Compared to approaches based on regular grids traditionally used in computer graphics, our method allows for better representation of boundary conditions, lending to more realistic results, with just a small increment in computational cost. Moreover, we are able to condensate cells where interesting artifacts tend to appear, like swirling vortices or turbulence. We demonstrate the effectiveness of our approach, both in 2-D and 3-D, through a variety of high-quality smoke simulations and animations. These examples show the integration of our method with overlapping grids and multigrid techniques.

[pt] Com a evolução tecnológica, ambientes virtuais em 3D crescem continuamente em complexidade; este é o caso de ambientes multiescala, i.e., ambientes que contêm grupos de objetos com níveis de escala extremamente divergentes. Tal variação em escala dificulta a navegação interativa neste tipo de ambiente dado sua demanda repetitiva e não-intuitiva de ajustes em tanto velocidade quanto escala, levando em consideração os objetos que estão próximos ao observador, para garantir uma navegação estável e confortável. Esforços recentes tem sido desenvolvidos trabalhando com soluções fortemente baseadas na GPU que nem sempre podem ser viáveis dependendo da complexidade de uma cena. Nós apresentamos uma heurística de particionamento espacial para o ajuste automático de velocidade de navegação 3D em um ambiente multiescala virtual, minimizando o esforço computacional e transferindo este para a CPU, permitindo que a GPU possa focar na renderização. Nossa proposta descreve uma estratégia geométrica durante a fase de pré-processamento que nos permite estimar, em tempo real, qual é a menor distância entre o observador e o objeto mais próximo dele. A partir desta informação única, somos capazes de ajustar automaticamente a velocidade de navegação de acordo com a caraterística de escala da região na qual o observador se encontra. Com a informação topológica da cena obtida na fase de pré-processamento, somos capazes de responder, em tempo real, qual é o objeto mais próximo assim como o objeto visível mais próximo, que nos permite propor duas diferentes heurísticas de velocidade de navegação automática. Finalmente, com o objetivo de verificar o ganho de usabilidade alcançado com as abordagens propostas, foram realizados testes de usuário para avaliar a eficiência e precisão da navegação, assim como a satisfação subjetiva do usuário. Os resultados foram particularmente significantes ao demonstrar o ganho em precisão da navegação ao utilizar as abordagens propostas, tanto para usuários experientes quanto para leigos. / [en] With technological evolution, 3D virtual environments continuously increase in complexity; such is the case with multiscale environments, i.e., environments that contain groups of objects with extremely diverging levels of scale. Such scale variation makes it difficult to interactively navigate in this kind of environment since it demands repetitive and unintuitive adjustments in either velocity or scale, according to the objects that are close to the observer, in order to ensure a comfortable and stable navigation. Recent efforts have been developed working with heavy GPU based solutions that are not feasible depending on the complexity of the scene. We present a spatial partitioning heurístic for automatic adjustment of the 3D navigation speed in a multiscale virtual environment minimizing the workload and transferring it to the CPU, allowing the GPU to focus on rendering. Our proposal describes a geometric strategy during the preprocessing phase that allows us to estimate, in real-time phase, which is the shortest distance between the observer and the object nearest to him. From this unique information, we are capable to automatically adjusting the speed of navigation according to the characteristic scale of the region where the observer is. With the scene topological information obtained in a preprocessing phase, we are able to obtain, in real-time, the closest object and the visible objects, which allows us to propose two different heurístics for automatic navigation velocity. Finally, in order to verify the usability gain in the proposed approaches, user tests were conducted to evaluate the accuracy and echiency of the navigation, and users subjective satisfaction. Results were particularly significant for demonstrating accuracy gain in navigation while using the proposed approaches for both laymen and advanced users.