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Item A Dynamic Caching System for Rendering an Animated Crowd in Real-Time(The Eurographics Association, 2009) Lister, Wayne; Laycock, Robert G.; Day, Andrew M.; P. Alliez and M. MagnorWe present a method to accelerate the rendering of large crowds of animated characters. Recent trends have seen matrix-palette skinning become the prevalent approach due to its low memory overhead and fully dynamic geometry. However, the performance of skeletal animation remains modest in comparison to static rendering since neither temporal nor intra-frame coherency can be exploited. We cast crowd rendering as a memory-management problem and allocate a small geometry cache on the GPU within which animated characters can be stored. This serves to augment matrix-palette skinning with baked geometry and allows animation frames to be re-used by multi-pass rendering, between multiple agents and across multiple frames. Our method builds its cache dynamically and adapts to the current simulation state through use of the page-replacement algorithms traditionally employed by virtual-memory systems. In many cases this negates the need for skinning altogether and enables thousands of characters to be rendered in real-time, each independently animated and without loss of fidelity.Item A Real-time Interactive Tool for Image Cutout(The Eurographics Association, 2009) Liu, Chen; Li, Fengxia; Zhang, Yan; Zhan, Shouyi; P. Alliez and M. MagnorWe present an interactive tool for extracting foreground objects from image in real-time. As seen from the object boundary, the segmentation is to split pixel-pairs right on the boundary. The system utilizes the user input while the user roughly paints the stroke along the object boundary. Either side of the stroke is assumed to lie in foreground or background, and the mouse trace is supposed to coarsely indicate the object contour. We use the appearance, gradient and contour information to formulate the segmentation problem to an energy minimization problem, which is solved by graph cut. The appearance model is built via local sampling, since it often provides more discriminative model in local areas than that from global sampling. In addition, our system can dynamically adjust the stroke and the optimization region for which segmentation needs to be computed. The optimization region is much smaller than the whole image. This greatly reduces the computational complexity in each iteration and also gives the system the ability of incrementally segmenting. Experiments show the effectiveness of our methods in improving the segmentation performance.Item Continuous Search and Replace in Vector Graphics(The Eurographics Association, 2009) Loviscach, Joern; P. Alliez and M. MagnorMany types of vector graphics comprise large numbers of almost identical partial shapes such as serifs in typeface design, ornaments in illustrations, and stylistic elements in icon design. As of today, later design changes of such shapes require the user to edit every instance on its own. Standard features of vector graphics software help with the automated replacement of stand-alone graphical objects, but do not cover partial shapes. Hence, a geometric search & replace function is needed, which is exacerbated by the circumstance that the repeated shapes construction from curve segments tends to vary from instance to instance, which requires a continuous approach that does not rely on a fixed division of a path into segments. This paper presents a geometric search and replace function that addresses these issues, possesses adjustable tolerance against orientation and size changes between the search pattern shape and the retrieved shapes, and is integrated with a standard vector graphics program.Item Dent Removal: Geodesic Curve-Based Mesh Fairing(The Eurographics Association, 2009) Pinskiy, Dmitriy; P. Alliez and M. MagnorThis paper presents a novel mesh fairing method to remove unwanted geometric artifacts such as dents. The key element of the proposed method is our unique algorithm for the assignment of weights in the discrete Laplacian. Our weights reflect the orientation of the first ring of vertices around a given vertex with respect to the whole dented region, rather than the ring's local geometry (e.g. Gauss or mean curvature flow that needs to be reestimated per each iteration). To establish the dent region s global behavior, we perform principal curvature analysis to determine representative geodesic curves for the surface. Our method is efficient as it only needs to compute the geodesic curves once, and then it uses them to guide subsequent iterations of anisotropic relaxation.Item Real-time Volumetric Lighting in Participating Media(The Eurographics Association, 2009) Toth, Balazs; Umenhoffer, Tamas; P. Alliez and M. MagnorSimulating light scattering in participating media, such as dust, fog or smoke, can greatly improve the overall realism of the images. This volumetric effect has been well studied in the context of off-line rendering but is still challenging for interactive applications. In this paper we present a GPU-based algorithm to compute volumetric light-shafts generated by single scattering in participating media. The proposed method uses shadow maps to account for shadowing and interleaved sampling to maintain high frame rates without sacrificing image quality.Item Preface and Table of Contents(The Eurographics Association, 2009) Alliez, P.; Magnor, M.; P. Alliez and M. MagnorPreface and Table of ContentsItem Tile-based Image Forces for Active Contours on GPU(The Eurographics Association, 2009) Kienel, Enrico; Brunnett, Guido; P. Alliez and M. MagnorActive contours have been proven to be powerful semiautomatic image segmentation tools. We present an adaptive image force computation scheme in order to minimize both computational and memory requirements. Hence, we are able to perform a fast semiautomatic contour detection in huge images. We present an efficient implementation of this approach on the basis of general purpose GPU processing providing a visual continuous active contour deformation.Item Video-Realistic Image-based Eye Animation System(The Eurographics Association, 2009) Weissenfeld, Axel; Liu, Kang; Ostermann, J.; P. Alliez and M. MagnorIn this work we elaborate on a novel image-based system for creating video-realistic eye animations to arbitrary spoken output. These animations are useful to give a face to multimedia applications such as virtual operators in dialog systems. Our eye animation system consists of two parts: eye control unit and rendering engine. The designed eye control unit is based on the statistical analysis of recorded human subjects. We design a new model, which fully automatically couples eye blinks and movements with phonetic as well as prosodic information extracted from spoken language. Subjective tests showed that participants are not able to distinguish between real eye motions and our animations, which has not been achieved before.Item Volume Conserving Simulation of Deformable Bodies(The Eurographics Association, 2009) Diziol, Raphael; Bender, Jan; Bayer, Daniel; P. Alliez and M. MagnorWe present a new method for simulating volume conserving deformable bodies using an impulse-based approach. In order to simulate a deformable body a tetrahedral model is generated from an arbitrary triangle mesh. All resulting tetrahedrons are assigned to volume constraints which ensure the conservation of the total volume. For the simulation of such a constraint impulses are computed and applied to the particles of the assigned tetrahedrons. The algorithm is easy to implement and ensures exact volume conservation in each simulation step.Item A Precalculated Point Set for Caching Shading Information(The Eurographics Association, 2009) Bikker, Jacco; Reijerse, Roel; P. Alliez and M. MagnorIn this short paper, we present a caching scheme for low-frequent shading information. The scheme consists of a precalculated, carefully constructed sparse set of points, the density of which adapts to local shading requirements, which we estimate by calculating the ambient occlusion. This fixed set of points is then used to store shading information. This shading information is calculated once, or updated prior to rendering each frame. Finally, during rendering, the shading information stored in the point set is used to estimate shading for any point in the scene using interpolation. We apply this scheme to render soft shadows and indirect lighting in a real-time ray traced game environment.
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