Doctor's Theses (authored and supervised):
"Accelerating the Rendering Process Using Impostors";
Supervisor, Reviewer: H. Schumann;
Institut für Computergraphik und Algorithmen,
The interactive rendering of three-dimensional geometric models is a research area of big interest in computer graphics. The generation of a fluent animation for complex models, consisting of multiple million primitives, with more than 60 frames per second is a special challenge. Possible applications include ship-, driving- and flight simulators, virtual reality and computer games. Although the performance of common computer graphics hardware has dramatically increased in recent years, the demand for more realism and complexity in common scenes is growing even faster. This dissertation is about one approach for accelerating the rendering of such complex scenes. We take advantage of the fact that the appearance of distant scene parts hardly changes for several successive output images. Those scene parts are replaced by precomputed image-based representations, so-called impostors. Impostors are very fast to render while maintaining the appearance of the scene part as long as the viewer moves within a bounded viewing region, a so-called view cell. However, unsolved problems of impostors are the support of a satisfying visual quality with reasonable computational effort for the impostor generation, as well as very high memory requirements for impostors for common scenes. Until today, these problems are the main reason why impostors are hardly used for rendering acceleration. This thesis presents two new impostor techniques that are based on partitioning the scene part to be represented into image layers with different distances to the observer. A new error metric allows a guarantee for a minimum visual quality of an impostor even for large view cells. Furthermore, invisible scene parts are efficiently excluded from the representation without requiring any knowledge about the scene structure, which provides a more compact representation. One of the techniques combines every image layer separately with geometric information. This allows a fast generation of memory-efficient impostors for distant scene parts. In the other technique, the geometry is independent from the depth layers, which allows a compact representation for near scene parts. The second part of this work is about the efficient usage of impostors for a given scene. The goal is to guarantee a minimum frame rate for every view within the scene while at the same time minimizing the memory requirements for all impostors. The presented algorithm automatically selects impostors and view cells so that for every view, only the most suitable scene parts are represented as impostors. Previous approaches generated numerous similar impostors for neighboring view cells, thus wasting memory. The new algorithm overcomes this problem. i The simultaneous use of additional acceleration techniques further reduces the required impostor memory and allows making best use of all available techniques at the same time. The approach is general in the sense that it can handle arbitrary scenes and a broad range of impostor techniques, and the acceleration provided by the impostors can be adapted to the bottlenecks of different rendering systems. In summary, the provided techniques and algorithms dramatically reduce the required impostor memory and simultaneously guarantee a minimum output image quality. This makes impostors useful for numerous scenes and applications where they could hardly be used before.
Created from the Publication Database of the Vienna University of Technology.