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Item Optimizing Stereo-to-Multiview Conversion for Autostereoscopic Displays(The Eurographics Association and John Wiley and Sons Ltd., 2014) Chapiro, Alexandre; Heinzle, Simon; Aydin, Tunç Ozan; Poulakos, Steven; Zwicker, Matthias; Smolic, Aljosa; Gross, Markus; B. Levy and J. KautzWe present a novel stereo-to-multiview video conversion method for glasses-free multiview displays. Different from previous stereo-to-multiview approaches, our mapping algorithm utilizes the limited depth range of autostereoscopic displays optimally and strives to preserve the scene s artistic composition and perceived depth even under strong depth compression. We first present an investigation of how perceived image quality relates to spatial frequency and disparity. The outcome of this study is utilized in a two-step mapping algorithm, where we (i) compress the scene depth using a non-linear global function to the depth range of an autostereoscopic display, and (ii) enhance the depth gradients of salient objects to restore the perceived depth and salient scene structure. Finally, an adapted image domain warping algorithm is proposed to generate the multiview output, which enables overall disparity range extension.Item BetweenIT: An Interactive Tool for Tight Inbetweening(The Eurographics Association and Blackwell Publishing Ltd, 2010) Whited, Brian; Noris, Gioacchino; Simmons, Maryann; Sumner, Robert W.; Gross, Markus; Rossignac, JarekThe generation of inbetween frames that interpolate a given set of key frames is a major component in the production of a 2D feature animation. Our objective is to considerably reduce the cost of the inbetweening phase by offering an intuitive and effective interactive environment that automates inbetweening when possible while allowing the artist to guide, complement, or override the results. Tight inbetweens, which interpolate similar key frames, are particularly time-consuming and tedious to draw. Therefore, we focus on automating these high-precision and expensive portions of the process. We have designed a set of user-guided semi-automatic techniques that fit well with current practice and minimize the number of required artist-gestures. We present a novel technique for stroke interpolation from only two keys which combines a stroke motion constructed from logarithmic spiral vertex trajectories with a stroke deformation based on curvature averaging and twisting warps. We discuss our system in the context of a feature animation production environment and evaluate our approach with real production data.Item Are Points the Better Graphics Primitives?(Eurographics Association, 2001) Gross, MarkusSince the early days of graphics the computer based representation of three-dimensional geometry has been one of the core research fields. Today, various sophisticated geometric modelling techniques including NURBS or implicit surfaces allow the creation of 3D graphics models with increasingly complex shape. In spite of these methods the triangle has survived over decades as the king of graphics primitives meeting the right balance between descriptive power and computational burden. As a consequence, today's consumer graphics hardware is heavily tailored for high performance triangle processing. In addition, a new generation of geometry processing methods including hierarchical representations, geometric filtering, or feature detection fosters the concept of triangle meshes for graphics modelling. Unlike triangles, points have amazingly been neglected as a graphics primitive. Although being included in APIs since many years, it is only recently that point samples experience a renaissance in computer graphics. Conceptually, points provide a mere discretization of geometry without explicit storage of topology. Thus, point samples reduce the representation to the essentials needed for rendering and enable us to generate highly optimized object representations. Although the loss of topology poses great challenges for graphics processing, the latest generation of algorithms features high performance rendering, point/pixel shading, anisotropic texture mapping, and advanced signal processing of point sampled geometry. This talk will give an overview of how recent research results in the processing of triangles and points are changing our traditional way of thinking of surface representations in computer graphics - and will discuss the question: Are Points the Better Graphics Primitives?Item Point-Based Computer Graphics(Eurographics Association, 2003) Alexa, Marc; Dachsbacher, Carsten; Gross, Markus; Pauly, Mark; van Baar, Jeroen; Zwicker, Matthias-Item Spatio-Temporal Geometry Fusion for Multiple Hybrid Cameras using Moving Least Squares Surfaces(The Eurographics Association and John Wiley and Sons Ltd., 2014) Kuster, Claudia; Bazin, Jean-Charles; Öztireli, Cengiz; Deng, Teng; Martin, Tobias; Popa, Tiberiu; Gross, Markus; B. Levy and J. KautzMulti-view reconstruction aims at computing the geometry of a scene observed by a set of cameras. Accurate 3D reconstruction of dynamic scenes is a key component for a large variety of applications, ranging from special effects to telepresence and medical imaging. In this paper we propose a method based on Moving Least Squares surfaces which robustly and efficiently reconstructs dynamic scenes captured by a calibrated set of hybrid color+depth cameras. Our reconstruction provides spatio-temporal consistency and seamlessly fuses color and geometric information. We illustrate our approach on a variety of real sequences and demonstrate that it favorably compares to state-of-the-art methods.Item Dynamic Sampling and Rendering of Algebraic Point Set Surfaces(The Eurographics Association and Blackwell Publishing Ltd, 2008) Guennebaud, Gael; Germann, Marcel; Gross, MarkusAlgebraic Point Set Surfaces (APSS) define a smooth surface from a set of points using local moving least-squares (MLS) fitting of algebraic spheres. In this paper we first revisit the spherical fitting problem and provide a new, more generic solution that includes intuitive parameters for curvature control of the fitted spheres. As a second contribution we present a novel real-time rendering system of such surfaces using a dynamic up-sampling strategy combined with a conventional splatting algorithm for high quality rendering. Our approach also includes a new view dependent geometric error tailored to efficient and adaptive up-sampling of the surface. One of the key features of our system is its high degree of flexibility that enables us to achieve high performance even for highly dynamic data or complex models by exploiting temporal coherence at the primitive level. We also address the issue of efficient spatial search data structures with respect to construction, access and GPU friendliness. Finally, we present an efficient parallel GPU implementation of the algorithms and search structures.Item Manufacturing Layered Attenuators for Multiple Prescribed Shadow Images(The Eurographics Association and John Wiley and Sons Ltd., 2012) Baran, Ilya; Keller, Philipp; Bradley, Derek; Coros, Stelian; Jarosz, Wojciech; Nowrouzezahrai, Derek; Gross, Markus; P. Cignoni and T. ErtlWe present a practical and inexpensive method for creating physical objects that cast different color shadow images when illuminated by prescribed lighting configurations. The input to our system is a number of lighting configurations and corresponding desired shadow images. Our approach computes attenuation masks, which are then printed on transparent materials and stacked to form a single multi-layer attenuator. When illuminated with the input lighting configurations, this multi-layer attenuator casts the prescribed color shadow images. Alternatively, our method can compute layers so that their permutations produce different prescribed shadow images under fixed lighting. Each multi-layer attenuator is quick and inexpensive to produce, can generate multiple full-color shadows, and can be designed to respond to different types of natural or synthetic lighting setups. We illustrate the effectiveness of our multi-layer attenuators in simulation and in reality, with the sun as a light source.Item Computational Design of Rubber Balloons(The Eurographics Association and John Wiley and Sons Ltd., 2012) Skouras, Mélina; Thomaszewski, Bernhard; Bickel, Bernd; Gross, Markus; P. Cignoni and T. ErtlThis paper presents an automatic process for fabrication-oriented design of custom-shaped rubber balloons. We cast computational balloon design as an inverse problem: given a target shape, we compute an optimal balloon that, when inflated, approximates the target as closely as possible. To solve this problem numerically, we propose a novel physics-driven shape optimization method, which combines physical simulation of inflatable elastic membranes with a dedicated constrained optimization algorithm. We validate our approach by fabricating balloons designed with our method and comparing their inflated shapes to the results predicted by simulation. An extensive set of manufactured sample balloons demonstrates the shape diversity that can be achieved by our method.Item Scalable Music: Automatic Music Retargeting and Synthesis(The Eurographics Association and Blackwell Publishing Ltd., 2013) Wenner, Simon; Bazin, Jean-Charles; Sorkine-Hornung, Alexander; Kim, Changil; Gross, Markus; I. Navazo, P. PoulinIn this paper we propose a method for dynamic rescaling of music, inspired by recent works on image retargeting, video reshuffling and character animation in the computer graphics community. Given the desired target length of a piece of music and optional additional constraints such as position and importance of certain parts, we build on concepts from seam carving, video textures and motion graphs and extend them to allow for a global optimization of jumps in an audio signal. Based on an automatic feature extraction and spectral clustering for segmentation, we employ length-constrained least-costly path search via dynamic programming to synthesize a novel piece of music that best fulfills all desired constraints, with imperceptible transitions between reshuffled parts. We show various applications of music retargeting such as part removal, decreasing or increasing music duration, and in particular consistent joint video and audio editing.Item Iterative Image Warping(The Eurographics Association and John Wiley and Sons Ltd., 2012) Bowles, Huw; Mitchell, Kenny; Sumner, Robert W.; Moore, Jeremy; Gross, Markus; P. Cignoni and T. ErtlAnimated image sequences often exhibit a large amount of inter-frame coherence which standard rendering algorithms and pipelines are ill-equipped to exploit, limiting their efficiency. To address this inefficiency we transfer rendering results across frames using a novel image warping algorithm based on fixed point iteration. We analyze the behavior of the iteration and describe two alternative algorithms designed to suit different performance requirements. Further, to demonstrate the versatility of our approach we apply it to a number of spatio-temporal rendering problems including 30-to-60Hz frame upsampling, stereoscopic 3D conversion, defocus and motion blur. Finally we compare our approach against existing image warping methods and demonstrate a significant performance improvement.