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Item Efficient CPU-based Volume Ray Tracing Techniques(The Eurographics Association and Blackwell Publishing Ltd, 2008) Marmitt, Gerd; Friedrich, Heiko; Slusallek, PhilippRecent research on high-performance ray tracing has achieved real-time performance even for highly complex surface models already on a single PC. In this report, we provide an overview of techniques for extending real-time ray tracing also to interactive volume rendering. We review fast rendering techniques for different volume representations and rendering modes in a variety of computing environments. The physically-based rendering approach of ray tracing enables high image quality and allows for easily mixing surface, volume and other primitives in a scene, while fully accounting for all of their optical interactions. We present optimized implementations and discuss the use of upcoming high-performance processors for volume ray tracing.Item Improving Multipath Radiosity with Bundles of Parallel Lines(The Eurographics Association and Blackwell Publishing Ltd, 2008) Martinez, Roel; Sbert, Mateu; Szirmay-Kalos, LaszloMonte Carlo approaches use random lines to distribute the light power in the scene but the cost of creating a set of random single lines is very costly. In this paper, we present several software and hardware techniques in order to reduce the computational cost of the generation of random single lines by using bundles of parallel lines. The bundle of parallel lines is simulated with a general purpose polygon filling algorithm, like the painter s algorithm. We also present two graphics hardware implementations. The first approach uses two depth buffers in order to represent stochastically a bundle of parallel global lines. The second one uses multiple depth buffers and the aim is to exploit coherence between projection planes for each iteration. All algorithms were implemented with the multipath method.Item Statistical optimization of octree searches(The Eurographics Association and Blackwell Publishing Ltd, 2008) Castro, Rener; Lewiner, Thomas; Lopes, Helio; Tavares, Geovan; Bordignon, AlexThis work emerged from the following observation: usual search procedures for octrees start from the root to retrieve the data stored at the leaves. But as the leaves are the farthest nodes to the root, why start from the root? With usual octree representations, there is no other way to access a leaf. However, hashed octrees allow direct access to any node, given its position in space and its depth in the octree. Search procedures take the position as an input, but the depth remains unknown. This work proposes to estimate the depth of an arbitrary node through a statistical optimization of the average cost of search procedures. As the highest costs of these algorithms are obtained when starting from the root, this method improves on both the memory footprint by the use of hashed octrees, and execution time through the proposed optimization.Item Interference Shaders of Thin Films(The Eurographics Association and Blackwell Publishing Ltd, 2008) Sun, Yinlong; Wang, QiqiThis paper presents a systematic study of light interferences at single thin films. Based on Fresnel s law, we have derived generic expressions of reflectance and transmittance for film interference, as well as specific expressions for free thin films and films coated on transparent or opaque objects. By combining film interference and volume absorption, we have obtained the reflectances and transmittances of film-coated thin objects such as ribbons. Illumination models for all interference cases of single thin films are presented, and they have been implemented and tested for various structures and materials.Item Computational Geometry Education for Computer Graphics Students(The Eurographics Association and Blackwell Publishing Ltd, 2008) Kolingerova, I.The paper surveys main features of computational geometry and presents the argument that a course oriented to applied computational geometry should be a part of the computer graphics curriculum, as it teaches effective algorithmic methods and helps to develop abstract thinking. Possible contents of the course and forms suitable and interesting for computer graphics students are discussed. The students feedback on such a course has been mostly positive.Item Computational Aesthetics 2008(The Eurographics Association and Blackwell Publishing Ltd, 2008)Item Displacement Mapping on the GPU - State of the Art(The Eurographics Association and Blackwell Publishing Ltd, 2008) Szirmay-Kalos, Laszlo; Umenhoffer, TamasThis paper reviews the latest developments of displacement mapping algorithms implemented on the vertex, geometry, and fragment shaders of graphics cards. Displacement mapping algorithms are classified as per-vertex and per-pixel methods. Per-pixel approaches are further categorized as safe algorithms that aim at correct solutions in all cases, to unsafe techniques that may fail in extreme cases but are usually much faster than safe algorithms, and to combined methods that exploit the robustness of safe and the speed of unsafe techniques. We discuss the possible roles of vertex, geometry and fragment shaders to implement these algorithms. Then the particular GPU-based bump, parallax, relief, sphere, horizon mapping, cone stepping, local ray tracing, pyramidal and view-dependent displacement mapping methods, as well as their numerous variations are reviewed providing also implementation details of the shader programs. We present these methods using uniform notations and also point out when different authors called similar concepts differently. In addition to basic displacement mapping, self-shadowing and silhouette processing are also reviewed. Based on our experiences gained having reimplemented these methods, their performance and quality are compared, and the advantages and disadvantages are fairly presented.Item Practical HDR Texture Compression(The Eurographics Association and Blackwell Publishing Ltd, 2008) Munkberg, J.; Clarberg, P.; Hasselgren, J.; Akenine-Moeller, T.The use of high dynamic range (HDR) textures in real-time graphics applications can increase realism and provide a more vivid experience. However, the increased bandwidth and storage requirements for uncompressed HDR data can become a major bottleneck. Hence, several recent algorithms for HDR texture compression have been proposed. In this paper, we discuss several practical issues one has to confront in order to develop and implement HDR texture compression schemes. These include improved texture filtering and efficient offline compression. For compression, we describe how Procrustes analysis can be used to quickly match a predefined template shape against chrominance data. To reduce the cost of HDR texture filtering, we perform filtering prior to the colour transformation, and use a simple trick to reduce the incurred errors. We also introduce a number of novel compression modes, which can be combined with existing compression schemes, or used on their own.Item Computational Aesthetics 2009 Call for papers(The Eurographics Association and Blackwell Publishing Ltd, 2008)Item New EUROGRAPHICS Fellows(The Eurographics Association and Blackwell Publishing Ltd, 2008)