EG2011
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Item A Survey on Video-based Graphics and Video Visualization(The Eurographics Association, 2011) Borgo, Rita; Chen, Min; Daubney, Ben; Grundy, Edward; Heidemann, Gunther; Höferlin, Benjamin; Höferlin, Markus; Jänicke, Heike; Weiskopf, Daniel; Xie, Xianghua; N. John and B. WyvillIn recent years, a collection of new techniques which deal with video as input data, emerged in computer graphics and visualization. In this survey, we report the state of the art in video-based graphics and video visualization. We provide a comprehensive review of techniques for making photo-realistic or artistic computer-generated imagery from videos, as well as methods for creating summary and/or abstract visual representations to reveal important features and events in videos. We propose a new taxonomy to categorize the concepts and techniques in this newlyemerged body of knowledge. To support this review, we also give a concise overview of the major advances in automated video analysis, as some techniques in this field (e.g., feature extraction, detection, tracking and so on) have been featured in video-based modeling and rendering pipelines for graphics and visualization.Item PhD Education Through Apprenticeship(The Eurographics Association, 2011) Patel, Daniel; Gröller, M. Eduard; Bruckner, Stefan; S. Maddock and J. JorgeWe describe and analyze the PhD education in the visualization group at the Vienna University of Technology and set the education in a larger perspective. Four central mechanisms drive the PhD education in Vienna. They are: to require an article-based PhD; to give the student freedom to choose research direction; to let students work in shared offices towards joint deadlines; and to involve students in reviewing articles. This paper describes these mechanisms in detail and illustrates their effect.Item An Error Bound for Decoupled Visibility with Application to Relighting(The Eurographics Association, 2011) Schwenk, Karsten; Fellner, Dieter W.; N. Avis and S. LefebvreMonte Carlo estimation of direct lighting is often dominated by visibility queries. If an error is tolerable, the calculations can be sped up by using a simple scalar occlusion factor per light source to attenuate radiance, thus decoupling the expensive estimation of visibility from the comparatively cheap sampling of unshadowed radiance and BRDF. In this paper we analyze the error associated with this approximation and derive an upper bound. We demonstrate in a simple relighting application how our result can be used to reduce noise by introducing a controlled error if a reliable estimate of the visibility is already available.Item Interactive Character Animation using Simulated Physics(The Eurographics Association, 2011) Geijtenbeek, Thomas; Pronost, Nicolas; Egges, Arjan; Overmars, Mark H.; N. John and B. WyvillPhysics simulation offers the possibility of truly responsive and realistic animation. Despite wide adoption of physics simulation for the animation of passive phenomena, such as rigid objects, fluids, cloths and rag-doll characters, commercial applications still resort to kinematics-based approaches for the animation of actively controlled characters. However, in recent years, research on interactive character animation using simulated physics has resulted in tremendous improvements in controllability, robustness, visual quality and usability. In this review, we present a structured evaluation of relevant aspects, approaches and techniques regarding interactive character animation using simulated physics, based on over two decades of research. We conclude by pointing out some open research areas and possible future directions.Item Improving Shadow Map Filtering with Statistical Analysis(The Eurographics Association, 2011) Gumbau, Jesus; Szirmay-Kalos, László; Sbert, Mateu; Sellés, Miguel Chover; N. Avis and S. LefebvreShadow maps are widely used in real-time applications. Shadow maps cannot be filtered linearly as regular textures, thus undersampling leads to severe aliasing. This problem has been attacked by methods that transform the depth values to allow approximate linear filtering and to approaches based on statistical analysis, which suffer from light bleeding artifacts. In this paper we propose a new statistical filtering method for shadow maps, which approximates the cumulative distribution function (CDF) of depths with a power function. This approximation significantly reduces light bleeding artifacts, maintaining performance and spatial costs. Like existing techniques, the algorithm is easy to implement on the graphics hardware and is fairly scalable.Item A Sparse Parametric Mixture Model for BTF Compression, Editing and Rendering(The Eurographics Association and Blackwell Publishing Ltd., 2011) Wu, Hongzhi; Dorsey, Julie; Rushmeier, Holly; M. Chen and O. DeussenBidirectional texture functions (BTFs) represent the appearance of complex materials. Three major shortcomings with BTFs are the bulky storage, the difficulty in editing and the lack of efficient rendering methods. To reduce storage, many compression techniques have been applied to BTFs, but the results are difficult to edit. To facilitate editing, analytical models have been fit, but at the cost of accuracy of representation for many materials. It becomes even more challenging if efficient rendering is also needed. We introduce a high-quality general representation that is, at once, compact, easily editable, and can be efficiently rendered. The representation is computed by adopting the stagewise Lasso algorithm to search for a sparse set of analytical functions, whose weighted sum approximates the input appearance data. We achieve compression rates comparable to a state-of-the-art BTF compression method. We also demonstrate results in BTF editing and rendering.Item FEMONUM: A Framework for Whole Body Pregnant Woman Modeling from Ante-Natal Imaging Data(The Eurographics Association, 2011) Alcalde, Juan Pablo de la Plata; Anquez, Jérémie; Bibin, Lazar; Boubekeur, Tamy; Angelini, Elsa; Bloch, Isabelle; K. Buehler and A. VilanovaAnatomical models of pregnant women can be used in several applications such as numerical dosimetry to assess the potential effects of electromagnetic fields on biological tissues, or medical simulations for delivery planning. Recent advances in medical imaging have enabled the generation of realistic and detailed models of human beings. This paper describes FEMONUM, a complete methodological framework for the construction of pregnant woman models based on medical images and their segmentation. FEMONUM combines several computer graphics methods, such as surface reconstruction and physics-based computer animation to model and deform pregnant women abdomens, to simulate different fetal positions and sizes and also different morphologies of the mother, represented with a synthetic woman body envelope. A set of 16 models, anatomically validated by clinical experts, is presented and is made available online to the scientific community. These models include detailed information on the utero-fetal units and cover different gestational stages with various fetal positions.Item Predicted Virtual Soft Shadow Maps with High Quality Filtering(The Eurographics Association and Blackwell Publishing Ltd., 2011) Shen, Li; Guennebaud, Gaël; Yang, Baoguang; Feng, Jieqing; M. Chen and O. DeussenIn this paper we present a novel image based algorithm to render visually plausible anti-aliased soft shadows in a robust and efficient manner. To achieve both high visual quality and high performance, it employs an accurate shadow map filtering method which guarantees smooth penumbrae and high quality anisotropic anti-aliasing of the sharp transitions. Unlike approaches based on pre-filtering approximations, our approach does not suffer from light bleeding or losing contact shadows. Discretization artefacts are avoided by creating virtual shadow maps on the fly according to a novel shadow map resolution prediction model. This model takes into account the screen space frequency of the penumbrae via a perceptual metric which has been directly established from an appropriate user study. Consequently, our algorithm always generates shadow maps with minimal resolutions enabling high performance while guarantying high quality. Thanks to this perceptual model, our algorithm can sometimes be faster at rendering soft shadows than hard shadows. It can render game-like scenes at very high frame rates, and extremely large and complex scenes such as CAD models at interactive rates. In addition, our algorithm is highly scalable, and the quality versus performance trade-off can be easily tweaked.Item Rendering Interior Cultural Heritage Scenes Using Image-based Shooting(The Eurographics Association, 2011) Happa, Jassim; Bashford-Rogers, Tom; Debattista, Kurt; Chalmers, Alan; A. Day and R. Mantiuk and E. Reinhard and R. ScopignoRendering interior cultural heritage scenes using physically based rendering with outdoor environment maps is computationally expensive using ray tracing methods, and currently difficult for interactive applications without significant precomputation of lighting. In this paper, we present a novel approach to relight synthetic interior scenes by extending image-based lighting to generate fast high-quality interactive previews of these environments. Interior light probes are acquired from a real scene, then used to shoot light onto the virtual scene geometry to accelerate image synthesis by assuming the light sources shot act as the correct solution of light transport for that particular intersection point. We term this approach Image-Based Shooting. It is demonstrated in this paper with an approach inspired by Irradiance Cache Splatting. The methodology is well-suited for interior scenes in which light enters through narrow windows and doors, common at cultural heritage sites. Our implementation generates high-quality interactive preview renditions of these sites and can significantly aid documentation, 3D model validation and predictive rendering. The method can easily be integrated with existing cultural heritage reconstruction pipelines, especially ray tracing based renderers.Item Wavelet Rasterization(The Eurographics Association and Blackwell Publishing Ltd., 2011) Manson, Josiah; Schaefer, Scott; M. Chen and O. DeussenWe present a method for analytically calculating an anti-aliased rasterization of arbitrary polygons or fonts bounded by Bezier curves in 2D as well as oriented triangle meshes in 3D. Our algorithm rasterizes multiple resolutions simultaneously using a hierarchical wavelet representation and is robust to degenerate inputs. We show that using the simplest wavelet, the Haar basis, is equivalent to performing a box-filter to the rasterized image. Because we evaluate wavelet coefficients through line integrals in 2D, we are able to derive analytic solutions for polygons that have Bezier curve boundaries of any order, and we provide solutions for quadratic and cubic curves. In 3D, we compute the wavelet coefficients through analytic surface integrals over triangle meshes and show how to do so in a computationally efficient manner.Item GPU Based On-the-fly Light Emission-absorption Approximation for Direct Multi-volume Rendering(The Eurographics Association, 2011) Khlebnikov, Rostislav; Kainz, Bernhard; Roth, Bernhard; Muehl, Judith; Schmalstieg, Dieter; R. Laramee and I. S. LimWe present a novel on-the-fly scatter approximation scheme that can be applied concurrently to multiple volumetric datasets. We use a simplified version of the emission-absorption model, including single scattering and shadowing and guide the scatter sample positions and in-scatter coefficients by local gradients. This allows us to render multiple intersecting volumes with our rendering system with clearly visible improvements in rendering quality over local illumination models, while maintaining interactive frame-rates.Item Combinatorial Bidirectional Path-Tracing for Efficient Hybrid CPU/GPU Rendering(The Eurographics Association and Blackwell Publishing Ltd., 2011) Pajot, Anthony; Barthe, Loïc; Paulin, Mathias; Poulin, Pierre; M. Chen and O. DeussenThis paper presents a reformulation of bidirectional path-tracing that adequately divides the algorithm into processes efficiently executed in parallel on both the CPU and the GPU. We thus benefit from high-level optimization techniques such as double buffering, batch processing, and asyncronous execution, as well as from the exploitation of most of the CPU, GPU, and memory bus capabilities. Our approach, while avoiding pure GPU implementation limitations (such as limited complexity of shaders, light or camera models, and processed scene data sets), is more than ten times faster than standard bidirectional path-tracing implementations, leading to performance suitable for production-oriented rendering engines.Item Sketch Input of Engineering Solid Models(The Eurographics Association, 2011) Company, Pedro; Varley, Peter; Ralph Martin and Juan Carlos TorresIn this tutorial, we describe the state of the art of sketch input of engineering solid models. The tutorial is in four parts. In the first part, we show how sketching has historically been an important aspect of engineering culture,and remains a useful tool in the early design phase as it has been demonstrated that sketching enhances creativity.We discuss and classify various current approaches to computer interpretation of sketches.We introduce the problem of deducing design intent, which we understand as a mix of geometry, psychology and engineering, and note how no existing approach to interpretation of sketches has considered the explicit capture of design intent from the input sketch. In the second and third parts, we present our selection of the most important algorithms currently used for interpreting wireframe drawings (part two) and natural line drawings (part three) of engineering objects. In part two, the algorithms we look at are: for finding faces in wireframes; for inflating wireframes to 3D; and for processing rounds and fillets. In part three, we look at: line labelling; inflation to 2.5D; and deducing hidden topology. In part four, we discuss some of the most interesting open problems: making virtual paper and pencil more usable than actual paper and pencil; interpreting annotated engineering sketches; and creating assemblies from sketches.Item Realistic Simulation of Peripheral Vision Using An Aspherical Eye Model(The Eurographics Association, 2011) Wu, Jiaze; Zheng, Changwen; Hu, Xiaohui; Xu, Fanjiang; N. Avis and S. LefebvreA novel method is proposed to accurately simulate the peripheral vision under different visual perception. An accurate aspherical schematic eye model is firstly introduced to reasonably predict the anatomical and optical properties of the human eye. This eye model is composed of the Navarro schematic eye model with aspherical surfaces as a basic model, and a corresponding accommodation model, and both these models are combined to simulate the varying refractive power of the human eye. Finally, distributed ray tracing techniques is combined with this eye model to produce a variety of visual results.Item A Virtual Environment for Radiotherapy Training and Education - VERT(The Eurographics Association, 2011) Ward, James W.; Phillips, R.; Boejen, Annette; Grau, Cai; Jois, Deepak; Beavis, Andy W.; K. Buehler and A. VilanovaA report in 2007 to the UK Government identified a crisis in England for training staff and students for the radiotherapy treatment of cancer. The Hull authors have developed an immersive life size virtual environment of a radiotherapy treatment room, known as VERT, to address this problem. VERT provides the trainee with models, simulation, enhanced visualization and training aids for treatment of virtual patients in a virtual treatment room. In 2007 VERT systems for radiotherapy training were established for training purposes at the University Aarhus Hospital (Denmark), Birmingham City University (UK) and the University of Ulster (UK). There are now some 70 VERT systems around the world. This paper reports on the simulation and visualization capabilities and reports on the use of VERT from the Aarhus University hospital and on the national evaluation of VERT in the UK [AC10]. These reports clearly indicate the clinical benefit of using a virtual environment approach, such as VERT, for training and education in radiotherapy.Item Dynamic Display of BRDFs(The Eurographics Association and Blackwell Publishing Ltd., 2011) Hullin, Matthias B.; Lensch, Hendrik P. A.; Raskar, Ramesh; Seidel, Hans-Peter; Ihrke, Ivo; M. Chen and O. DeussenThis paper deals with the challenge of physically displaying reflectance, i.e., the appearance of a surface and its variation with the observer position and the illuminating environment. This is commonly described by the bidirectional reflectance distribution function (BRDF). We provide a catalogue of criteria for the display of BRDFs, and sketch a few orthogonal approaches to solving the problem in an optically passive way. Our specific implementation is based on a liquid surface, on which we excite waves in order to achieve a varying degree of anisotropic roughness. The resulting probability density function of the surface normal is shown to follow a Gaussian distribution similar to most established BRDF models.Item Goal-based Caustics(The Eurographics Association and Blackwell Publishing Ltd., 2011) Papas, Marios; Jarosz, Wojciech; Jakob, Wenzel; Rusinkiewicz, Szymon; Matusik, Wojciech; Weyrich, Tim; M. Chen and O. DeussenWe propose a novel system for designing and manufacturing surfaces that produce desired caustic images when illuminated by a light source. Our system is based on a nonnegative image decomposition using a set of possibly overlapping anisotropic Gaussian kernels. We utilize this decomposition to construct an array of continuous surface patches, each of which focuses light onto one of the Gaussian kernels, either through refraction or reflection. We show how to derive the shape of each continuous patch and arrange them by performing a discrete assignment of patches to kernels in the desired caustic. Our decomposition provides for high fidelity reconstruction of natural images using a small collection of patches. We demonstrate our approach on a wide variety of caustic images by manufacturing physical surfaces with a small number of patches.Item Image and Video Abstraction by Coherence-Enhancing Filtering(The Eurographics Association and Blackwell Publishing Ltd., 2011) Kyprianidis, Jan Eric; Kang, Henry; M. Chen and O. DeussenIn this work, we present a non-photorealistic rendering technique to create stylized abstractions from color images and videos. Our approach is based on adaptive line integral convolution in combination with directional shock filtering. The smoothing process regularizes directional image features while the shock filter provides a sharpening effect. Both operations are guided by a flow field derived from the structure tensor. To obtain a high-quality flow field, we present a novel smoothing scheme for the structure tensor based on Poisson's equation. Our approach effectively regularizes anisotropic image regions while preserving the overall image structure and achieving a consistent level of abstraction. Moreover, it is suitable for per-frame filtering of video and can be efficiently implemented to process content in real-time.Item Artistic Stylisation of Images and Video(The Eurographics Association, 2011) Collomosse, John; Kyprianidis, Jan Eric; Ralph Martin and Juan Carlos TorresThe half-day tutorial provides an introduction to Non- Photorealistic Rendering (NPR), targeted at both students and experienced researchers of Computer Graphics who have not previously explored NPR in their work. The tutorial focuses on two-dimensional (2D) NPR, specifically the transformation of photos or videos into synthetic art concepts will be introduced gently and no prior knowledge is assumed beyond a working knowledge of filtering and convolution operations. Some elements of the course will touch upon GPU implementation, but GPU concepts will be described at a high level of abstraction without need for detailed working knowledge of GPU programming.Item Rendering with Layered Materials(The Eurographics Association, 2011) Wilkie, Alexander; Weidlich, Andrea; Ralph Martin and Juan Carlos TorresAbstract to follow.