University, Diss., 2000--Dortmund. / Dateiformat: PDF.

University, Diss., 2001--Tübingen.

University, Diss., 2001--Mannheim.

Techn. University, Diss., 2002--Darmstadt.

University, Diss., 2003--Tübingen.

Nürnberg, University, Diss., 2005--Erlangen.

My work consists of a written part including images of practical investigations and references. The thesis is best read in chronological order, including images.

abstract: The video game graphics pipeline has traditionally rendered the scene using a polygonal approach. Advances in modern graphics hardware now allow the rendering of parametric methods. This thesis explores various smooth surface rendering methods that can be integrated into the video game graphics engine. Moving over to parametric or smooth surfaces from the polygonal domain has its share of issues and there is an inherent need to address various rendering bottlenecks that could hamper such a move. The game engine needs to choose an appropriate method based on in-game characteristics of the objects; character and animated objects need more sophisticated methods whereas static objects could use simpler techniques. Scaling the polygon count over various hardware platforms becomes an important factor. Much control is needed over the tessellation levels, either imposed by the hardware limitations or by the application, to be able to adaptively render the mesh without significant loss in performance. This thesis explores several methods that would help game engine developers in making correct design choices by optimally balancing the trade-offs while rendering the scene using smooth surfaces. It proposes a novel technique for adaptive tessellation of triangular meshes that vastly improves speed and tessellation count. It develops an approximate method for rendering Loop subdivision surfaces on tessellation enabled hardware. A taxonomy and evaluation of the methods is provided and a unified rendering system that provides automatic level of detail by switching between the methods is proposed. / Dissertation/Thesis / Ph.D. Computer Science 2011

En Computación Gráfica uno de los conceptos más importantes es el \emph{Rendering}, definido como el proceso que a partir de los datos de una escena tridimensional genera una imagen en una ventana de visualización en 2 dimensiones. El rendering siempre se ha enfocado en generar imágenes fotorrealistas, aunque para diversas aplicaciones y escenarios se desea una imagen abstracta y/o estilizada. El proceso que puede generar ese tipo de imágenes es llamado Rendering No Fotorrealista, o NPR por sus siglas en inglés (Non Photorealistic Rendering). El NPR integra conceptos de Computación Gráfica y de Geometría Diferencial, y puede aplicarse en visualización científica e ilustración técnica, con el fin de destacar áreas o contornos de los objetos que son de interés para el observador; en la producción de imágenes que imiten medios tradicionales como la pintura o la acuarela; y en la generación de imágenes que imiten dibujos animados, entre otras áreas. En esta memoria se diseña e implementa un marco de trabajo (framework en inglés) para Computación Gráfica que permite desarrollar técnicas NPR y de rendering tradicional. El diseño del marco de trabajo contempla el estudio de los puntos comunes de diferentes técnicas de NPR y de las áreas asociadas, y, siguiendo el paradigma de la Orientación a Objetos, define distintas componentes internas que pueden ser extendidas para implementar técnicas de NPR y de rendering tradicional. La implementación se realiza en el lenguaje de programación C++ utilizando bibliotecas de código abierto o compatibles con código abierto: se utilizan la biblioteca gráfica OpenGL y el lenguaje Cg para comunicarse con los procesadores de la tarjeta de vídeo (GPU). El marco de trabajo incluye técnicas ya implementadas: para el rendering tradicional se implementaron graficadores de Gouraud y de Phong, mientras que para las técnicas NPR se implementaron graficadores de dibujado animado (Cel-Shading) y de modelos de tonos (Gooch Shading). Se implementaron extractores de líneas de interés (Siluetas y Contornos Sugestivos), así como una clase abstracta que permite definir nuevos tipos de líneas a extraer. La demostración de estas implementaciones se realiza mediante una aplicación de prueba que permite cargar modelos tridimensionales estáticos y animados; los resultados obtenidos se muestran mediante imágenes de los modelos tridimensionales cargados en la aplicación de prueba. Finalmente se realiza una discusión sobre el trabajo futuro, sobre las posibles líneas de investigación a seguir en estudios de post-grado y sobre el uso del marco de trabajo para implementar técnicas de rendering no NPR. Se concluye que el marco de trabajo se puede utilizar para el desarrollo de técnicas NPR y de rendering tradicional, que su desempeño es adecuado para el rendering en tiempo real para escenas tridimensionales de tamaño medio y que puede ser utilizado en aplicaciones reales.

Due to the rapid development of 3D display market, the protection and authentication of the intellectual property rights of 3D multimedia has become an essential concern. As a consequence, the digital watermarking for 3D image and video is attracting considerable attention. The depth-image-based rendering (DIBR) technique has been playing a critical role in 3D contents representation because of its numerous advantages. A good digital watermarking algorithm should be robust to various possible attacks, including geometric distortions and compressions. And di erent from ordinary 2D digital watermarking, there are more speci c requirements for 3D watermarking, especially for DIBR 3D image watermarking. Not only the center view, but also the virtual left and right views can be illegally distributed. Therefore, the embedded watermark information should be accurately extracted from these three views individually for content authentication, even under attacks. In this thesis, we focus on the research of digital watermarking and watermarking based quality evaluation for DIBR 3D images. We first present a 2D image and video watermarking method based on contourlet transform, which is then extended to a robust contourlet-based watermarking algorithm for DIBR 3D images. The watermark is embedded into the center view by quantizing certain contourlet coe cients. The virtual left and right views are synthesized from the watermarked center view and the corresponding depth map. One advantage of our algorithm is its simplicity and practicality. However, the performance on watermark extraction needs to be further improved. As an improvement, a blind watermarking algorithm for DIBR 3D images based on feature regions and ridgelet transform is proposed. The watermarked view has good perceptual quality under both the objective and subjective image quality measures. Compared with other related and state-of-the-art methods, the proposed algorithm shows superiority in terms of watermark extraction and robustness to various attacks. Furthermore, as one of the most promising techniques for quality evaluation, a watermarking based quality evaluation scheme is developed for DIBR 3D images. The qualities of the watermarked center view and the synthesized left and right views under distortions can be estimated by examining the degradation of corresponding extracted watermarks. The simulation results demonstrate that our scheme has good performance of quality evaluation for DIBR 3D images under the attacks.