Spatial Sound Rendering – A Survey

Simulating propagation of sound and audio rendering can improve the sense of realism and the immersion both in complex acoustic environments and dynamic virtual scenes. In studies of sound auralization, the focus has always been on room acoustics modeling, but most of the same methods are also applicable in the construction of virtual environments such as those developed to facilitate computer gaming, cognitive research, and simulated training scenarios. This paper is a review of state-of-the-art techniques that are based on acoustic principles that apply not only to real rooms but also in 3D virtual environments. The paper also highlights the need to expand the field of immersive sound in a web based browsing environment, because, despite the interest and many benefits, few developments seem to have taken place within this context. Moreover, the paper includes a list of the most effective algorithms used for modelling spatial sound propagation and reports their advantages and disadvantages. Finally, the paper emphasizes in the evaluation of these proposed works

Radioptimization - Goal based rendering

Journal ArticleThis paper presents a method for designing the illumination in an environment using optimization techniques applied to a radiosity based image synthesis system. An optimization of lighting parameters is performed based on user specified constraints and objectives for the illumination of t h e environment. The system solves for t h e "best" possible settings for: light source emissivities, element reflectivities, and spot light directionality parameters so that the design goals, such as to minimize energy or to give the the room an impression of privacy, are met. The system absorbs much of the burden for searching the design space allowing the user to focus on the goals of the illumination design rather than the intricate details of a complete lighting specification. A software implementation is described and some results of using the system are reported. The system employs an object space perceptual model based on work by Tumblin and Rushmeier to account for psychophysical effects such as subjective brightness and the visual adaptation level of a viewer. This provides a higher fidelity when comparing the illumination in a computer simulated environment against what would be viewed in the "real" world. Optimization criteria are based on subjective impressions of illumination with qualities such as "pleasantness", and "privateness". The qualities were selected based on Flynn's work in illuminating engineering. These criteria were applied to the radiosity context through an experiment conducted with subjects viewing rendered images, and the respondents evaluated with a Multi-Dimensional Scaling analysis

Efficient From-Point Visibility for Global Illumination in Virtual Scenes with Participating Media

Sichtbarkeitsbestimmung ist einer der fundamentalen Bausteine fotorealistischer Bildsynthese. Da die Berechnung der Sichtbarkeit allerdings äußerst kostspielig zu berechnen ist, wird nahezu die gesamte Berechnungszeit darauf verwendet. In dieser Arbeit stellen wir neue Methoden zur Speicherung, Berechnung und Approximation von Sichtbarkeit in Szenen mit streuenden Medien vor, die die Berechnung erheblich beschleunigen, dabei trotzdem qualitativ hochwertige und artefaktfreie Ergebnisse liefern

A Gathering and Shooting Progressive Refinement Radiosity Method

This paper presents a gathering and shooting progressive refinement radiosity method. Our method integrates the iterative process of light energy gathering used in the standard full matrix method and the iterative process of light energy shooting used in the conventional progressive refinement method. As usual, in each iteration, the algorithm first selects the patch which holds the maximum unprocessed light energy in the environment as the shooting patch. But before the shooting process is activated, a light energy gathering process takes place. In this gathering process, the amount of the unprocessed light energy which is supposed to be shot to the current shooting patch from the rest of the environment in later iterations is pre-accumulated. In general, this extra amount of gathered light energy is far from trivial since it comes from every patch in the environment from which the current shooting patch can be seen. However, with the reciprocity relationship for form-factors, still only one hemi-cube of the form-factors is needed in each iteration step. Based on a concise record of the history of the unprocessed light energy distribution in the environment, a new progressive refinement algorithm with revised gathering and shooting procedures is then proposed. With little additional computation and memory usage compared to the conventional progressive refinement radiosity method, a solid convergence speedup is achieved. This gathering and shooting approach extends the capability of the radiosity method in accurate and efficient simulation of the global illuminations of complex environments

A bidirectional formulation for Walk on Spheres

Poisson’s equations and Laplace’s equations are important linear partial differential equations (PDEs)widely used in many applications. Conventional methods for solving PDEs numerically often need todiscretize the space first, making them less efficient for complex shapes. The random walk on spheresmethod (WoS) is a grid-free Monte-Carlo method for solving PDEs that does not need to discrete thespace. We draw analogies between WoS and classical rendering algorithms, and find that the WoSalgorithm is conceptually identical to forward path tracing.We show that solving the Poisson’s equation is equivalent to solving the Green’s function for everypair of points in the domain. Inspired by similar approaches in rendering, we propose a novel WoSreformulation that operates in the reverse direction. Besides this, using the corrector function enablesus to use control variates to estimate the Green’s function. Implementations of this algorithm showimprovement over classical WoS in solving Poisson’s equation with sparse sources. Our approachopens exciting avenues for future algorithms for PDE estimation which, analogous to light transport,connect WoS walks starting from sensors and sources and combine different strategies for robustsolution algorithms in all cases

GPU-Based Global Illumination Using Lightcuts

Global Illumination aims to generate high quality images. But due to its highrequirements, it is usually quite slow. Research documented in this thesis wasintended to offer a hardware and software combined acceleration solution toglobal illumination. The GPU (using CUDA) was the hardware part of the wholemethod that applied parallelism to increase performance; the “Lightcuts”algorithm proposed by Walter (2005) at SIGGRAPH 2005 acted as the softwaremethod. As the results demonstrated in this thesis, this combined method offersa satisfactory performance boost effect for relatively complex scenes

Master of Science

thesisVirtual point lights (VPLs) provide an effective solution to global illumination computation by converting the indirect illumination into direct illumination from many virtual light sources. This approach results in a less noisy image compare to Monte Carlo methods. In addition, the number of VPLs to generate can be specified in advance; therefore, it can be adjusted depending on the scene, desired quality, time budget, and the available computational power. In this thesis, we investigate a new technique that carefully places VPLs for providing improved rendering quality for computing global illumination using VPLs. Our method consists of three different passes. In the first pass, we randomly generate a large number of VPLs in the scene starting from the camera to place them in positions that can contribute to the final rendered image. Then, we remove a considerable number of these VPLs using a Poisson disk sample elimination method to get a subset of VPLs that are uniformly distributed over the part of the scene that is indirectly visible to the camera. The second pass is to estimate the radiant intensity of these VPLs by performing light tracing starting from the original light sources in the scene and scatter the radiance of light rays at a hit-point to the VPLs close to that point. The final pass is rendering the scene, which consists of shading all points in the scene visible to the camera using the original light sources and VPLs