5 research outputs found
Object Hierarchies for Efficient Rendering
This thesis covers the efficient visualization of complex 3d scenes using various rendering methods such as photo-realistic and real-time rendering. Especially the important role of bounding volume hierarchies is discussed in detail in the context of illumination and visibility algorithms. We present a novel approach for automatic generation of object hierarchies and apply the resulting data structure to several rendering techniques. In the field of ray tracing we describe a novel ray acceleration method that combines objects hierarchies and regular grids. We demonstrate how radiosity computations may benefit from available scene hierarchies to determine the radiant flux between object clusters. Finally, we present an adaptive interactive rendering algorithm that may dramatically reduce the number of visibility tests in an occlusion culling framework for interactive real-time visualization.Diese Dissertation untersucht unterschiedliche Verfahren zur effizienten Visualisierung grosser dreidimensionaler Szenengeometrien, sowohl im Bereich des Photorealismus wie auch bei der Echtzeit-Visualisierung. Hierbei wird insbesondere die Nützlichkeit von Hüllkörperhierarchien bei der Beleuchtungsrechnung und bei der Beantwortung von Sichtbarkeitsfragen herausgearbeitet. Ein neuartiges, kostenbasiertes Verfahren zur automatischen Konstruktion von Objekthierarchien wird präsentiert sowie dessen Anwendung für alle gängigen Darstellungsverfahren. Zusätzlich beschreibt diese Disseration im Bereich Ray Tracing ein neues Verfahren zur Szenenstrukturierung, welches die Vorteile von Hüllkörperhierarchien und regulären Gittern kombiniert. Im Bereich der Radiosity wird gezeigt, wie sich Szenenhierarchien ideal zur Berechnung des Lichtflusses zwischen Objekt-Clustern nutzen lassen und im Bereich Echtzeit-Rendering wird ein adaptives Verfahren vorgestellt, dass die Zahl teurer Sichtbarkeitstests beim Occlusion-Culling deutlich reduziert
Tighter bounding volumes for better occlusion culling performance
Bounding volumes are used in computer graphics to approximate the actual geometric shape of an object in a scene. The main intention is to reduce the costs associated with visibility or interference tests. The bounding volumes most commonly used have been axis-aligned bounding boxes and bounding spheres. In this paper, we propose the use of discrete orientation polytopes (\kdops) as bounding volumes for the specific use of visibility culling. Occlusion tests are computed more accurately using \kdops, but most importantly, they are also computed more efficiently. We illustrate this point through a series of experiments using a wide range of data models under varying viewing conditions. Although no bounding volume works the best in every situation, {\kdops} are often the best, and also work very well in those cases where they are not the best, therefore they provide good results without having to analyze applications and different bounding volumes
Approximate convex decomposition and its applications
Geometric computations are essential in many real-world problems. One important
issue in geometric computations is that the geometric models in these problems
can be so large that computations on them have infeasible storage or computation
time requirements. Decomposition is a technique commonly used to partition complex
models into simpler components. Whereas decomposition into convex components results
in pieces that are easy to process, such decompositions can be costly to construct
and can result in representations with an unmanageable number of components. In
this work, we have developed an approximate technique, called Approximate Convex
Decomposition (ACD), which decomposes a given polygon or polyhedron into "approximately
convex" pieces that may provide similar benefits as convex components,
while the resulting decomposition is both significantly smaller (typically by orders of
magnitude) and can be computed more efficently. Indeed, for many applications, an
ACD can represent the important structural features of the model more accurately
by providing a mechanism for ignoring less significant features, such as wrinkles and
surface texture. Our study of a wide range of applications shows that in addition to
providing computational efficiency, ACD also provides natural multi-resolution or hierarchical
representations. In this dissertation, we provide some examples of ACD's
many potential applications, such as particle simulation, mesh generation, motion
planning, and skeleton extraction