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Item Translucent Shadow Maps(The Eurographics Association, 2003) Dachsbacher, Carsten; Stamminger, Marc; Philip Dutre and Frank Suykens and Per H. Christensen and Daniel Cohen-OrShadow maps are a very efficient means to add shadows to arbitrary scenes. In this paper, we introduce Translucent Shadow Maps, an extension to shadow maps which allows very efficient rendering of sub-surface scattering. Translucent Shadow Maps contain depth and incident light information. Sub-surface scattering is computed on-the-fly during rendering by filtering the shadow map neighborhood. This filtering is done efficiently using a hierarchical approach. We describe optimizations for an implementation of Translucent Shadow Maps on contemporary graphics hardware, that can render complex translucent objects with varying light and material properties in real-time.Item Interactive Sampling and Rendering for Complex and Procedural Geometry(The Eurographics Association, 2001) Stamminger, Marc; Drettakis, George; S. J. Gortle and K. MyszkowskiWe present a new sampling method for procedural and complex geometries, which allows interactive point-based modeling and rendering of such scenes. For a variety of scenes, object-space point sets can be generated rapidly, resulting in a sufficiently dense sampling of the final image. We present an integrated approach that exploits the simplicity of the point primitive. For procedural objects a hierarchical sampling scheme is presented that adapts sample densities locally according to the projected size in the image. Dynamic procedural objects and interactive user manipulation thus become possible. The same scheme is also applied to on-the-fly generation and rendering of terrains, and enables the use of an efficient occlusion culling algorithm. Furthermore, by using points the system enables interactive rendering and simple modification of complex objects (e.g., trees). For display, hardware-accelerated 3-D point rendering is used, but our sampling method can be used by any other point-rendering approach.Item Realtime Isosurface Extraction with Graphics Hardware(Eurographics Association, 2004) Reck, Frank; Dachsbacher, Carsten; Grosso, Roberto; Greiner, Günther; Stamminger, Marc; M. Alexa and E. GalinIn this paper we introduce a method for the display of isosurfaces extracted from unstructured tetrahedral grids. Our algorithm completely runs on the graphics hardware. The tetrahedra are streamed into a vertex program, which extracts the surface for the given isovalue and immediately renders it. The triangles are not stored explicitly but are computed during rendering time, so the user can modify the isovalue with immediate feedback. If the tetrahedra entirely fit into video memory, we achieve a throughput of more than nine million tetrahedra per second. Our performance can be further improved by using a hybrid method which pre-selects tetrahedra containing the isovalue. We compare our approach with a pure CPU based implementation which achieves about half the performance of our hardware accelerated method.Item Fast GPU-based Adaptive Tessellation with CUDA(The Eurographics Association and Blackwell Publishing Ltd, 2009) Schwarz, Michael; Stamminger, MarcCompact surface descriptions like higher-order surfaces are popular representations for both modeling and animation. However, for fast graphics-hardware-assisted rendering, they usually need to be converted to triangle meshes. In this paper, we introduce a new framework for performing on-the-fly crack-free adaptive tessellation of surface primitives completely on the GPU. Utilizing CUDA and its flexible memory write capabilities, we parallelize the tessellation task at the level of single surface primitives. We are hence able to derive tessellation factors, perform surface evaluation as well as generate the tessellation topology in real-time even for large collections of primitives. We demonstrate the power of our framework by exemplarily applying it to both bicubic rational Bezier patches and PN triangles.Item Animation of Open Water Phenomena with coupled Shallow Water and Free Surface Simulations(The Eurographics Association, 2006) Thürey, Nils; Rüde, Ulrich; Stamminger, Marc; Marie-Paule Cani and James O'BrienThe goal of this paper is to perform simulations that capture fluid effects from small drops up to the propagation of large waves. To achieve this, we present a hybrid simulation method, that couples a two-dimensional shallow water simulation with a full three-dimensional free surface fluid simulation. We explain the approximations imposed by the shallow water model, and how to parametrize it according to the parameters of a 3D simulation. Each simulation is used to initialize double layered boundary conditions for the other one. The area covered by the 2D region can be an order of magnitude larger than the 3D region without significantly effecting the overall computation time. The 3D region can furthermore be easily moved within the 2D region during the course of the simulation. To achieve realistic results we combine our simulation method with a physically based model to generate and animate drops. For their generation we make use of the fluid turbulence model, and animate them with a simplified drag calculation. This allows simulations with relatively low resolutions.Item GPU Accelerated Normalized Mutual Information and B-Spline Transformation(The Eurographics Association, 2008) Teßmann, Matthias; Eisenacher, Christian; Enders, Frank; Stamminger, Marc; Hastreiter, Peter; Charl Botha and Gordon Kindlmann and Wiro Niessen and Bernhard PreimVisualization of multimodal images in medicine and other application areas requires correct and efficient registration. Optimally, the alignment operation is made an integral part of the rendering process. Voxel based approaches using mutual information ensure high quality similarity measurement. As a limiting factor, high computational load is caused since for every iteration of the optimization procedure one volume is transformed into the coordinate system of the other, a 2D histogram is generated and mutual information is computed. The expensive trilinear interpolation operations are well supported by 3D texture mapping hardware. However, existing strategies compute the histogram and mutual information on the CPU and thus require a cost intensive data transfer. Overcoming this considerable bottleneck, we introduce a new approach that efficiently supports all computations on modern graphics cards. This makes expensive data transfers from GPU to main memory dispensable. Due to its modularity, the presented approach can be integrated into general frameworks. As a major result, the speed improvement over existing GPU-CPU strategies amounts to a factor of 4 and over pure conventional CPU techniques to more than a factor of 10. Overall, the suggested strategy contributes considerably to integration of multimodal registration directly into interactive volume visualization.Item Rendering Procedural Terrain by Geometry Image Warping(The Eurographics Association, 2004) Dachsbacher, Carsten; Stamminger, Marc; Alexander Keller and Henrik Wann JensenWe describe an approach for rendering large terrains in real-time. A digital elevation map defines the rough shape of the terrain. During rendering, procedural geometric and texture detail is added by the graphics hardware. We show, how quad meshes can be generated quickly that have a locally varying resolution that is optimized for the inclusion of procedural detail.We obtain these distorted meshes by importance based warping of geometry images. The resulting quad mesh can then be rendered very efficiently by graphics hardware, which also adds all visible procedural detail using vertex and fragment programs.Item Efficient Glossy Global Illumination with Interactive Viewing(Blackwell Publishers Ltd and the Eurographics Association, 2000) Stamminger, Marc; Scheel, Annette; Granier, Xavier; Perez-Cazorla, Frederic; Drettakis, George; Sillion, FrancoisThe ability to perform interactive walkthroughs of global illumination solutions including glossy effects is a challenging open problem. In this paper we overcome certain limitations of previous approaches. We first introduce a novel, memory- and compute-efficient representation of incoming illumination, in the context of a hierarchical radiance clustering algorithm. We then represent outgoing radiance with an adaptive hierarchical basis, in a manner suitable for interactive display. Using appropriate refinement and display strategies, we achieve walkthroughs of glossy solutions at interactive rates for non-trivial scenes. In addition, our implementation has been developed to be portable and easily adaptable as an extension to existing, diffuse-only, hierarchical radiosity systems. We present results of the implementation of glossy global illumination in two independent global illumination systems.Item Thrifty Final Gather for Radiosity(The Eurographics Association, 2001) Scheel, Annette; Stamminger, Marc; Seidel, Hans-Peter; S. J. Gortle and K. MyszkowskiFinite Element methods are well suited to the computation of the light distribution in mostly diffuse scenes, but the resulting mesh is often far from optimal to accurately represent illumination. Shadow boundaries are hard to capture in the mesh, and the illumination may contain artifacts due to light transports at different mesh hierarchy levels. To render a high quality image a costly final gather reconstruction step is usually done, which re-evaluates the illumination integral for each pixel. In this paper an algorithm is presented which significantly speeds up the final gather by exploiting spatial and directional coherence information taken from the radiosity solution. Senders are classified, so that their contribution to a pixel is either interpolated from the radiosity solution or recomputed with an appropriate number of new samples. By interpolating this sampling pattern over the radiosity mesh, continuous solutions are obtained.Item Tone Mapping in VR Environments(Eurographics Association, 2004) Hausner, Alexander; Stamminger, Marc; M. Alexa and E. GalinTone mapping is the process of mapping high dynamic range images to the low dynamic range of current displays. So far, tone mapping research was focused on static images, but with powerful graphics hardware available today, real time tone mapping becomes possible. In this paper we describe tone mapping within a VR environment. The tone mapping operator utilizes information about the user's line of sight obtained by a tracking system. Adaptation is optimized for the current view point and costly image operations are restricted to the central view field. Since all computations are completely performed by graphics hardware, we achieve interactive frame rates.