High-dynamic-range rendering

Abstract: Photo-realistic rendering of virtual objects into real scenes is one of the most important research problems in computer graphics. Methods for capture and rendering of mixed reality scenes are driven by a large number of applications, ranging from augmented reality to visual effects and product visualization. Recent developments in computer graphics, computer vision, and imaging technology have enabled a wide range of new mixed reality techniques including methods for advanced image based lighting, capturing spatially varying lighting conditions, and algorithms for seamlessly rendering virtual objects directly into photographs without explicit measurements of the scene lighting. This report gives an overview of the state-of-the-art in this field, and presents a categorization and comparison of current methods. Our in-depth survey provides a tool for understanding the advantages and disadvantages of each method, and gives an overview of which technique is best suited to a specific problem.

Abstract: Rendering global illumination effects for dynamic scenes at interactive frame rates is a computationally challenging task. Much of the computation time needed is spent during visibility queries between individual scene elements, and it is almost illusive to update this information at realtime even for moderately complex scenes. In this paper, we propose a global illumination approach for dynamic scenes that runs at near-real-time frame rates on a single PC. Our method is inspired by the principles of hierarchical radiosity and tackles the visibility problem by implicitly evaluating mutual visibility while constructing a hierarchical link structure between scene elements. By means of the same efficient and easy-to-implement framework, we are able to reproduce a large variety of complex lighting effects for moderately sized scenes, such as interreflections, environment map lighting as well as area light sources.

Abstract: Recently several distributed rendering systems have been developed that exploit a cluster of commodity computers by connecting host graphics cards over a fast network to form a compositing pipeline. This paper introduces an algorithm for one such system to parallelize contributions from arbitrary numbers of OpenGL lights, for example to compute approximate soft shadows by sampling area light sources. The algorithm renders multiple shadow maps across nodes of the cluster by factoring the OpenGL lighting equation into illumination and material properties. Additional parallelism is achieved by utilizing multiple texture units within each graphics card. Illumination by L point sources can be rendered by (L/K) + 1 nodes where K is the number of texture units on each graphics card. For walkthrough applications each node requires a single rendering pass, while for scenes with dynamic lights or geometry K+ 1 passes are needed per node. We present results using fragment shaders on nVidia Ge- Force4 Ti4600 and ATI Radeon 8500 graphics cards, and a cycle-accurate simulation of the compositing operators. These results show interactive frame rates for walkthroughs and dynamic models rendering shadows with 32 light sources on 9 nodes of a Sepia-2a distributed rendering cluster.