Search Results

Now showing 1 - 10 of 30
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    Heightfield and spatially varying BRDF Reconstruction for Materials with Interreflections
    (The Eurographics Association and Blackwell Publishing Ltd, 2009) Ruiters, Roland; Klein, Reinhard
    Photo-realistic reproduction of material appearance from images has widespread use in applications ranging from movies over advertising to virtual prototyping. A common approach to this task is to reconstruct the small scale geometry of the sample and to capture the reflectance properties using spatially varying BRDFs. For this, multi-view and photometric stereo reconstruction can be used, both of which are limited regarding the amount of either view or light directions and suffer from either low- or high-frequency artifacts, respectively. In this paper, we propose a new algorithm combining both techniques to recover heightfields and spatially varying BRDFs while at the same time overcoming the above mentioned drawbacks. Our main contribution is a novel objective function which allows for the reconstruction of a heightfield and high quality SVBRDF including view dependent effects. Thereby, our method also avoids both low and high frequency artifacts. Additionally, our algorithm takes inter-reflections into account allowing for the reconstruction of undisturbed representations of the underlying material. In our experiments, including synthetic and real-world data, we show that our approach is superior to state-of-the-art methods regarding reconstruction error as well as visual impression. Both the reconstructed geometry and the recovered SVBRDF are highly accurate, resulting in a faithful reproduction of the materials characteristic appearance, which is of paramount importance in the context of material rendering.
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    Data Preparation for Real-time High Quality Rendering of Complex Models
    (The Eurographics Association and Blackwell Publishing, Inc, 2006) Klein, Reinhard
    The capability of current 3D acquisition systems to digitize the geometry reflection behaviour of objects as well as the sophisticated application of CAD techniques lead to rapidly growing digital models which pose new challenges for interaction and visualization. Due to the sheer size of the geometry as well as the texture and reflection data which are often in the range of several gigabytes, efficient techniques for analyzing, compressing and rendering are needed. In this talk I will present some of the research we did in our graphics group over the past years motivated by industrial partners in order to automate the data preparation step and allow for real-time high quality rendering e.g. in the context of VR-applications. Strength and limitations of the different techniques will be discussed and future challenges will be identified. The presentation will go along with live demonstrations.
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    Efficient and Realistic Visualization of Cloth
    (The Eurographics Association, 2003) Sattler, Mirko; Sarlette, Ralf; Klein, Reinhard; Philip Dutre and Frank Suykens and Per H. Christensen and Daniel Cohen-Or
    Efficient and realistic rendering of cloth is of great interest especially in the context of e-commerce. Aside from the simulation of cloth draping, the rendering has to provide the "look and feel" of the fabric itself. In this paper we present a novel interactive rendering algorithm to preserve this "look and feel" of different fabrics. This is done by using the bidirectional texture function (BTF) of the fabric, which is acquired from a rectangular probe and after synthesis, mapped onto the simulated geometry. Instead of fitting a special type of bidirectional reflection distribution function (BRDF) model to each texel of our BTF, we generate view-dependent texture-maps using a principal component analysis of the original data. These view-dependent texture maps are then illuminated and rendered using either point-light sources or high dynamic range environment maps by exploiting current graphics hardware. In both cases, self-shadowing caused by geometry is taken into account. For point light sources, we also present a novel method to generate smooth shadow boundaries on the geometry. Depending on the geometrical complexity and the sampling density of the environment map, the illumination can be changed interactively. To ensure interactive frame rates for denser samplings or more complex objects, we introduce a principal component based decomposition of the illumination of the geometry. The high quality of the results is demonstrated by several examples. The algorithm is also suitable for materials other than cloth, as far as these materials have a similar reflectance behavior.
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    Fast Generation of Multiresolution Surfaces from Contours
    (The Eurographics Association, 1998) Schilling, Andreas; Klein, Reinhard; Bartz, Dirk
    Surface reconstruction from contours is an important problem especially in medical applications. Other uses include reconstruction from topographic data, or isosurface generation in general. The drawback of existing reconstruction algorithms from contours is, that they are relatively complicated and often have numerical problems. Furthermore, algorithms to generate multiresolution surface models do not exploit the special situation having contours. In this paper we describe a new robust and fast reconstruction algorithm from contours that delivers a multiresolution surface with controlled distance from the original contours. Supporting selective refinement in areas of interest, this multiresolution model can be handled interactively without giving up accuracy.
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    Preserving Realism in Real-Time Rendering of Bidirectional Texture Functions
    (The Eurographics Association, 2003) Meseth, Jan; Müller, Gero; Klein, Reinhard; Dirk Reiners
    The Bidirectional Texture Function (BTF) is a suitable representation for the appearance of highly detailed surface structures under varying illumination and viewing conditions. Since real-time rendering of the full BTF data is currently not feasible, approximations of the six-dimensional BTF are used such that the amount of data is reduced and current graphics hardware can be exploited. While existing methods work well for materials with low depth variation, realism is lost if the depth variation grows. In this paper we analyze this problem and devise a new real-time rendering method, which provides signi cant improvements with respect to realism for such highly structured materials without sacri cing the general applicability and speed of previous algorithms. We combine our approach with texture synthesis methods to drastically reduce the texture memory requirements and demonstrate the capabilities of our new rendering method with several examples.
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    Visualization Framework for the Integration and Exploration of Heterogeneous Geospatial Data
    (The Eurographics Association, 2009) Greß, Alexander; Klein, Reinhard; D. Ebert and J. Krüger
    This paper presents an interactive visualization framework for heterogeneous geospatial data developed in context of an interdisciplinary research project that aims at the risk analysis of sea-dumped chemical weapons in the Baltic Sea. In the focus of the analysis are geophysical, hydrographical, geochemical, and biological data acquired on research cruises as well as data produced by toxic compound migration and bioaccumulation modeling. These different types of data to be visualized are represented as height fields, 2D vector maps, seismic profiles, and time-dependent scalar and vector fields. In general, these datasets are given at largely varying resolutions and geospatial extents, which makes their integration into one visualization especially challenging and requires efficient level-of-detail techniques. Furthermore, special care is taken on the appropriate integration and efficient 3D visualization of all different types of data at the same time. Several examples demonstrate the effectiveness of the resulting visualizations for collaborative analysis of the data.
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    Cloth Animation and Rendering
    (Eurographics Association, 2002) Hauth, Michael; Etzmuss, Olaf; Eberhardt, Bernd; Klein, Reinhard; Sarlette, Ralf; Sattler, Mirko; Daubert, Katja; Kautz, Jan
    The area of physically-based modeling is situated in the intersection of computer science, mathematics, and physics. The animation of cloth is a particularly interesting application of physically-based modeling, because it aims at fast animation solutions for rather difficult physical problems. Moreover, it addresses one of the major difficulties in creating realistic scenes with virtual actors. The challenge of computer animation is to break down physical models for complex structures as textiles, approximate them efficiently, and run fast simulations with intelligent numerical methods. Furthermore, interactivity and collisions with other objects in the scene are challenges that have motivated much creative work over the recent years. The range of methods proposed in literature is quite large. The techniques vary from simplified methods designed for real-time applications to sophisticated methods that were designed to reproduce measured material properties. Rendering cloth is especially difficult because of its complex material properties. Software rendering can deal with these properties fairly easily, once they have been acquired, but remains too slow for interactive applications. Hardware accelerated rendering often provides a way to achieve interactive renderings, unfortunately complex materials aren’t directly supported. We will demonstrate how interactive rendering with complex materials can nonetheless be achieved
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    Photo-realistic Rendering of Metallic Car Paint from Image-Based Measurements
    (The Eurographics Association and Blackwell Publishing Ltd, 2008) Rump, Martin; Mueller, Gero; Sarlette, Ralf; Koch, Dirk; Klein, Reinhard
    State-of-the-art car paint shows not only interesting and subtle angular dependency but also significant spatial variation. Especially in sunlight these variations remain visible even for distances up to a few meters and give the coating a strong impression of depth which cannot be reproduced by a single BRDF model and the kind of procedural noise textures typically used. Instead of explicitly modeling the responsible effect particles we propose to use image-based reflectance measurements of real paint samples and represent their spatial varying part by Bidirectional Texture Functions (BTF). We use classical BRDF models like Cook-Torrance to represent the reflection behavior of the base paint and the highly specular finish and demonstrate how the parameters of these models can be derived from the BTF measurements. For rendering, the image-based spatially varying part is compressed and efficiently synthesized. This paper introduces the first hybrid analytical and image-based representation for car paint and enables the photo-realistic rendering of all significant effects of highly complex coatings.
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    Markerless Visual Human Movement Tracking for HCI: What Frequency?
    (The Eurographics Association, 2009) Kahlesz, Ferenc; Klein, Reinhard; Wen Tang and John Collomosse
    This paper tries to establish a minimal tracking frequency limit for visual human movement tracking algorithms that intend to be useful for the realization of some kind Human-Computer-Interaction (HCI) metaphor. More specifically, we examine the question of this minimal frequency for Augmented/Virtual Reality (AR/VR) navigation and 3D object manipulation. We approach the question from three different perspectives: shortly reviewing non-visual and visual marker-based solutions integrated regularly into AR/VR systems, spectral analysis of human movement and latency implications for AR/VR settings. Finally, we conclude the paper by combining and discussing the results from these different areas. We find that tracking with update rates as low as 12.5Hz can provide a usable basis for interaction. The most important message of the paper is that stable and working (even if slow, when compared to other techniques) markerless tracking algorithms are desperately needed because only working online with and based on such systems can the pros and cons of markerless tracking be evaluated.
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    BAT - a Distributed Meta-tracking System
    (The Eurographics Association, 2008) Kahlesz, Ferenc; Klein, Reinhard; Robert van Liere and Betty Mohler
    This paper describes the design of the 'BAT' (Bonn Articulated Tracker) visual tracking framework. This system allows the easy implementation of real-time, multi-camera motion tracking that can be distributed (also in multithreaded sense) across several computing nodes (or CPU cores). The system in itself does not realize any specific tracking system, but manages a meta-algorithm flow between processing blocks. An actual tracking implementation is realized by specifying the processing blocks through plugins. Depending on the plugins supplied, 'BAT' is capable to instantiate a wide-variety of systems ranging from object-detection methods to model-based deformable object tracking based on time-coherence, allowing also for hybrid algorithms. Being a meta dataflow system , 'BAT' also naturally facilitates sensor fusion. Moreover, it can be used as a testbed to compare and evaluate different kind of tracking algorithms or algorithm substeps.