1 Introduction Recent trends in realistic image synthesis have been towards a sepa-ration of the rendering process into two or more stages[10, 2, 9]. One of these stages solves for the global energy equilibrium throughoutthe environment. This process can be very expensive and its complexity grows rapidly with the number of objects in the environment.These computational demands generally limit the level of detail of environments that can be simulated. Furthermore, a solution to thisproblem must be computed before anything useful can be displayed.

We introduce a new approach for the computation of viewindependent solutions to the diffuse global illumination problem in polyhedral environments. The approach combines ideas from hierarchical radiosity and discontinuity meshing to yield solutions that are accurate both numerically and visually. First, we describe a modified hierarchical radiosity algorithm that uses a discontinuitydriven subdivision strategy to achieve better numerical accuracy and faster convergence. Second, we present a new algorithm based on discontinuity meshing that uses the hierarchical solution to reconstruct an object-space approximation to the radiance function that is visually accurate. Our results show significant improvements over both hierarchical radiosity and discontinuity meshing algorithms.

Abstract — This paper presents a new radiosity algorithm that allows the simultaneous computation of energy exchanges between surface elements, scattering volume distributions, and groups of surfaces, or object clusters. The new technique is based on a hierarchical formulation of the zonal method, and efficiently integrates volumes and surfaces. In particular no initial linking stage is needed, even for inhomogeneous volumes, thanks to the construction of a global spatial hierarchy. An analogy between object clusters and scattering volumes results in a powerful clustering radiosity algorithm, with no initial linking between surfaces and fast computation of average visibility information through a cluster. We show that the accurate distribution of the energy emitted or received at the cluster level can produce even better results than isotropic clustering at a marginal cost. The resulting algorithm is fast and, more importantly, truly progressive as it allows the quick calculation of approximate solutions with a smooth convergence towards very accurate simulations. I.

In this paper we present a new Monte Carlo rendering algorithm that seamlessly integrates the ideas of

Interactively manipulating the geometry of complex, globally illuminated scenes has to date proven an elusive goal. Previous attempts have failed to provide interactive updates of global illumination and have not been able to offer well-adapted algorithms controlling the frame rate. The need for such interactive updates of global illumination is becoming increasingly important as the field of application of radiosity algorithms widens. To address this need, we present a novel algorithm which provides interactive update rates of global illumination for complex scenes with moving objects. In the context of clustering for hierarchical radiosity, we introduce the idea of an implicit line-space hierarchy. This hierarchy is realized by augmenting the links between hierarchical elements (clusters or surfaces) with shafts, representing the set of lines passing through the two linked elements. We show how line-space traversal allows rapid identification of modified links, and simultaneous clean...

In this paper, we present a system for interactive computation of global illumination in dynamic scenes. Our system uses a novel scheme for caching the results of a high quality pixel-based renderer such as a bidirectional path tracer. The Shading Cache is an objectspace hierarchical subdivision mesh with lazily computed shading values at its vertices. A high frame rate display is generated from the Shading Cache using hardware-based interpolation and texture mapping. An image space sampling scheme refines the Shading Cache in regions that have the most interpolation error or those that are most likely to be affected by object or camera motion. Our system handles dynamic scenes and moving light sources efficiently, providing useful feedback within a few seconds and high quality images within a few tens of seconds, without the need for any pre-computation. Our approach allows us to significantly outperform other interactive systems based on caching ray-tracing samples, especially in dynamic scenes. Based on our results, we believe that the Shading Cache will be an invaluable tool in lighting design and modelling while rendering.

We present a new clustering algorithm for global illumination in complex environments. The new algorithm extends previous work on clustering for radiosity to allow for nondiffuse (glossy) reflectors. We represent clusters as points with directional distributions of outgoing and incoming radiance and importance, and we derive an error bound for transfers between these clusters. The algorithm groups input surfaces into a hierarchy of clusters, and then permits clusters to interact only if the error bound is below an acceptable tolerance. We show that the algorithm is asymptotically more efficient than previous clustering algorithms even when restricted to ideally diffuse environments. Finally, we demonstrate the performance of our method on two complex glossy environments.

We develop a radiance formulation for discrete three point transport, and a new measure and description of reflectance: area reflectance. This formulation and associated reflectance allow an estimate of error in the computation of radiance across triples of surface elements, and lead directly to a hierarchical refinement algorithm for global illumination. We have implemented and analyzed this algorithm over surfaces exhibiting glossy specular and diffuse reflection. Theoretical growth in light transport interactions is shown to be O(n log n) for sufficient refinement, where n is the number of elements at the finest level of subdivision within the environment --- in trials, this growth has been nearly linear. Naive implementation of three point transport would require O(n 3 ) element-triple interactions. CR Categories and Subject Descriptors: I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism. Key Words: adaptive meshing, global illumination, radiosity, ray-tracing. ...

Virtual environment research has focused on interactive image generation and has largely ignored acoustic modeling for spatialization of sound. Yet, realistic auditory cues can complement and enhance visual cues to aid navigation, comprehension, and sense of presence in virtual environments. A primary challenge in acoustic modeling is computation of reverberation paths from sound sources fast enough for real-time auralization. We have developed a system that uses precomputed spatial subdivision and "beam tree" data structures to enable real-time acoustic modeling and auralization in interactive virtual environments. The spatial subdivision is a partition of 3D space into convex polyhedral regions (cells) represented as a cell adjacency graph. A beam tracing algorithm recursively traces pyramidal beams through the spatial subdivision to construct a beam tree data structure representing the regions of space reachable by each potential sequence of transmission and specular reflection even...

This paper introduces importance-driven volume rendering as a novel technique for automatic focus and context display of volumetric data. It is a generalization of cut-away views, which - depending on the viewpoint - remove or suppress less important parts of a scene to reveal more important underlying information. We automatize and apply this idea to volumetric data. Each part of the volumetric data is assigned an object importance which encodes visibility priority. It determines which structures should be readily discernable and which structures are less important. In those image regions, where an object occludes more important structures it is displayed more sparsely than in those areas where no occlusion occurs. Thus the objects of interest are clearly visible. For each object several representations, i.e., levels of sparseness, are specified. The display of an individual object may incorporate different levels of sparseness. The goal is to emphasize important structures and to maximize the information content in the final image. This paper also discusses several possible schemes for level of sparseness specification and different ways how object importance can be composited to determine the final appearance of a particular object.