Short Presentations

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https://diglib.eg.org/handle/10.2312/239

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Accurate Dense Stereo Reconstruction using Graphics Hardware
(Konrad, 2003) Zach, Christopher; Klaus, Andreas; Hadwiger, Markus; Karner, Konrad
Vertex programs and pixel shaders found in modern graphics hardware are commonly used to enhance the realism of rendered scenes. Recently these hardware facilities were exploited to obtain interactive non-photorealistic effects and to perform low-level image processing tasks like texture filtering for volume visualization. We exploit modern graphics hardware to accomplish the higher level vision task of dense stereo reconstruction. In our system almost every stage of the matching procedure is executed on 3D graphics hardware, therefore utilizing the parallel vertex and pixel pipelines. Our implementation performs accurate calculations and does not suffer from the limited precision of color channels. On state of the art PC hardware our algorithm requires less than one second to reconstruct a dense mesh with subpixel accuracy for input images with one megapixel resolution.
ActiveInk
(Eurographics Association, 2003) Tobita, Hiroaki; Rekimoto, Jun
The ActiveInk system integrates the advantages of real world painting techniques with computer graphics (CG) effects such as natural phenomenon animations (e.g., water, fire, snow, and clouds), attributes (e.g., rubber, cloth, and land), surface materials (e.g., texture effects, metal, and glass), and so on. Most conventional paint systems mainly allow users to set a simple and static color. Also, they require users to control many parameters if the user applies complex effects. However, the ActiveInk system treats many behaviors as separate behavior inks (e.g., water, cloud, and cloth ink), so a user can add effects by selecting a behavior ink and painting it onto objects to realize CG effects. Moreover, the system has a palette area that is similar in function to an actual painters palette, so the user can create a new ink by mixing different types of behavior ink and can control the behavior in the palette area directly. In this paper, we describe a prototype of the ActiveInk system, explain how it allows CG effects to be applied through simple and easy manipulations, and discuss its implementation.
Adaptive quantization with error bounds for compressed view-dependent multiresolution meshes
(Eurographics Association, 2003) Grabner, Markus; Zach, Christopher
We present a simple method to adaptively determine compression parameters according to the given input data. Our method allows to make better use of the available dynamic range (number of bits per component of vertex locations) than with a given fixed-point representation. Moreover, the number of bits per component is also determined adaptively under a user-specified upper bound for the quantization error. Our adaptive quantization method can handle models with largely non-uniform geometric resolution. This is typically the case for manually created models or models derived from different sensors. The experiments we performed demonstrate the benefits of the proposed method.
Animatope: A Manga-Styled Animation Expression Toolkit
(Eurographics Association, 2003) Tohda, Asuka; Hasegawa, Sho; Inakage, Masa
Manga, a Japanese comic style, is becoming widely accepted within comic readers worldwide. In Manga, mimetic symbols and onomatopoeia symbols are heavily used to express emotions and various movements in a comic frame. In this paper, we present a toolkit named "Animatope", to emulate Manga-style symbols in a non-photorealisitc animation. Animatope transfers the Manga-sytle symbol grammar to 3D animation. We extend Manga symbols to Meta-symbols, or animated symbols, to enrich the emotional expressions and subtle behaviors. Meta-symbols are categorized into several classifications in Animatope Toolkit. Meta-symbols are controlled with basic parameters, shape of emitters, and motion handles.
Automatic High Level Avatar Guidance Based on Affordance of Movement
(Eurographics Association, 2003) Michael, Despina; Chrysanthou, Yiorgos
As virtual cities become ever more common and more extensive, the need to populate them with virtual pedestrians grows. One of the problems to be resolved for the virtual population is the behaviour simulation. Currently specifying the behaviour requires a lot of laborious work. In this paper we propose a method for automatically deriving the high level behaviour of the avatars. We introduce to the Graphics community a new method adapted from ideas recently presented in the Architecture literature. In this method, the general avatar movements are derived from an analysis of the structure of the architectural model. The analysis tries to encode Gibsons 7 principle of affordance, interpreted here as: pedestrians are more attracted towards directions with greater available walkable surface. We have implemented and tested the idea in a 2x2 km2 model of the city of Nicosia. Initial results indicate that the method, although simple, can automatically and efficiently populate the model with realistic results.
Beyond Image Quality Comparison
(Eurographics Association, 2003) Bornik, Alexander; Cech, Peter; Ferko, Andrej; Perko, Roland
We solve the problem of quantitative measuring of image quality, beyond the widely used MSE (mean square error) or even visual comparison. We combine eight feature-based and perceptually-oriented image quality metrics. The need for this comes from virtual archaeology, where various image acquisitions, antialiasing, multiresolution, image reconstruction or texturing methods produce very similar images. The proposed evaluation framework is suitable for any image quality decision-making, being not restricted to virtual archaeology. In particular, we compare a representative database of visually indistiguishable image pairs from different cameras, anisotropic texture filters and various antialiasing methods. For image registration we propose a modified video processing step. The results support the selection beyond commonly used visual comparison.
Continuous Local Parameterization of Polygons
(Eurographics Association, 2003) Maillot, Jerome
Texture mapping has now become a standard technique for adding visual details to 3d models. Nevertheless, intuitive mapping tools have made little progress in the past decade, compared to other computer graphics areas: defining a good quality parameterization is still a tedious process, requiring experienced and skilled users. In this paper, we specifically address the problem of finding automatically a parameterization of a reasonably small portion of the surface. This method is simple and efficient, which makes it suitable for interactive applications. It is also continuous in terms of the user input, so that it is stable during animation and interaction. Finally, it only requires the user to define a small set of intuitive parameters, mostly position, size and orientation of the area to be parameterized. Thus, it can be used by inexperienced users and easily connected to existing applications. We show how our method can improve 3D-paint systems and decal placement on surfaces. The same approach can also be used to adapt 2D image processing tools to geometry filtering.
Crosstalk reduction in passive stereo-projection systems
(Eurographics Association, 2003) Klimenko, Stanislav; Frolov, Pavel; Nikitina, Lialia; Nikitin, Igor
We describe a scheme for reduction of depolarization artefacts in passive stereo-projection systems. These problems appear due to non-perfectness of stereo-projection equipment: depolarization of the light due to reflection from the screen or due to the passage through the screen, non-ideality of polarizing filters, mixing of left- and right-eye images in a change of relative orientation of the filters, which together produce a strong crosstalk effect, resulting to difficulting stereo-perception. The artefacts are eliminated by software methods, using linear filtering of the image before its projection to the screen. We have implemented this algorithm in VE system Avango 1 by means of texture mappings. All necessary operations are performed by the graphics board, thus providing the real-time rendering rate. The described method considerably improves stability of stereo-perception, making high-quality performances of virtual environment possible on affordable equipment.
Cyclification of Human Motion for Animation Synthesis
(Eurographics Association, 2003) Ahmed, Amr; Mokhtarian, Farzin; Hilton, Adrian
In this paper, new techniques are introduced for matching cyclic motion boundaries by using simple animation processing algorithms based on some observed characteristics from different families of cyclic motions. Matching the cycle boundaries is one of the essential stages in generating a stream of animation of cyclic human movements. If the cycle boundaries are not matched, noticeable artefacts and flickers will appear regardless of how realistic the available motion cycle is. The proposed techniques are developed to modify the motion cycle even in the case, where only one cycle is provided. These techniques do not only match the cycle boundaries but also correct other parts of the cycle and motion constraints. The techniques are computationally efficient as they work directly on the animation data (without conversion to intermediate representations such as spline or time-frequency transforms). Moreover, many aspects of animation (including joint limits and important motion constraints) are preserved as the modification is guided by the original motions. A simple framework for automatic detection of gait phases timing is also introduced.
Efficient Sampling of Textured Scenes in Vertex Tracing
(Eurographics Association, 2003) Ullmann, Thomas; Preidel, Thomas; Bruderlin, Beat
We present vertex tracing, an adaptive progressive ray tracing approach for efficient sampling of the radiance function, based on refinement in object space and subsequent reconstruction, using standard 3D graphics accelerator hardware. The main focus of this paper is the reconstruction of reflected and transmitted texture maps. By taking advantage of the newest graphics hardware features (such as the pixel shader) even higher levels of recursion can be supported without explicit sampling of the textures. In addition, the graphics hardware is used for an efficient visibility test, which leads to a further reduction of ray samples, and for the rendering of diffuse local illumination effects, as well as for progressive rendering of the global illumination effects, which are superimposed over the hardware-rendered scene in object space. With this approach, interactive performance for realistically rendered illumination effects of scenes of average complexity, can be achieved on a standard PC with off-the-shelf 3D graphics accelerators.
Estimating Positions and Radiances of a Small Number of Light Sources for Real-Time Image-Based Lighting
(Eurographics Association, 2003) Madsen, Claus B.; Sorensen, Mads K. D.; Vittrup, Michael
Image-based lighting (IBL) of virtual objects has become a popular approach to blending virtual and real scenes. In IBL an omni-directional image of a scene is used as the illumination environment for rendering virtual objects. Typically, this rendering is based on global illumination techniques which are far from capable of real-time performance. In this paper we describe how to estimate the positions and radiances of a small number of point light sources, e.g., on the order of 5 to 10, which will produce virtual object appearances which are consistent with those obtained using IBL. The estimated light source parameters can be used directly in OpenGL rendering for real-time performance. We demonstrate the approach on natural scenes.
Evolutionary Design of BRDFs
(Eurographics Association, 2003) Meyer-Spradow, Jennis; Loviscach, Joern
The look of a non-transparent material is determined by its bidirectional reflection distribution function (BRDF). To design 3-D objects for example for games or animation films thus includes to design BRDFs. However, as functions defined on a four-dimensional domain, these form a vast space that is very difficult to explore interactively. Typically, the infinite number of degrees of freedom is reduced to a tractable handful of parameters by introducing simplified physical models or heuristic approximations such as Phongs. As the complexity of such approaches increases, they become difficult to master for a human operator. Even if many parameters are made accessible, an infinite variety of useful and/or interesting BRDFs remains hidden and inaccessible. We therefore propose a method of constructing BRDFs through genetic programming with a human operator making choices based on his or her preferences. With the pixel shader programmability of modern graphics cards this can be performed in real time.
Extending the Immediate Buckling Model to Triangular Meshes for Simulating Complex Clothes
(Eurographics Association, 2003) Choi, Kwang-Jin; Ko, Hyeong-Seok
The immediate buckling model is an essential element for simulating realistic cloth animations without introducing buckling instability. The original model is restricted to structured regular quad meshes, by which its use is severely limited. This paper extends the immediate buckling model from its original formulation in terms of regular quad meshes to irregular triangular meshes, thereby significantly increasing the applicability of the technique. Using a model that included cloth-specific buckling and anisotropy, we produced realistic animations of quite complex clothes.
A Framework for Video-based and Hardware-Accelerated Remote 3D-Visualization
(Eurographics Association, 2003) Goetz, Frank; Domik, Gitta
This paper presents a framework for video-based and hardware-accelerated remote 3d-visualization that produces and delivers high quality video streams at an accurate frame rate. The framework is based on the portable scenegraph system OpenSG, the MPEG4IP package and the Apple Darwin Streaming Server. In realtime generated visualizations will be multicast as an ISO MPEG-4 compliant video stream over the RealTime Streaming Protocol from a server to a client computer. On the client computer a Java program and an ISO MPEG-4 compliant video player are used to interact with the delivered visualization. While using MPEG-4 video streams we can achieve high image quality at a low bandwidth.
Generation of Radiosity Texture Atlas for Realistic Real-Time Rendering
(Eurographics Association, 2003) Ray, Nicolas; Ulysse, Jean-Christophe; Cavin, Xavier; Levy, Bruno
Radiosity methods are a both physically correct and efficient way to compute the global illumination giving the visual atmosphere to a 3D scene. In this paper, we present a new approach to optimizing the visualization of meshed models illuminated using these methods. Our approach is based on a texture atlas, which makes it possible to store the global illumination in a set of textures, that can be mapped in real-time onto the model by the graphics hardware. Our contribution is a new robust atlas generation method well adapted to the visualization of illuminated complex meshed models, and based on a tight cooperation between the segmentation and the parameterization algorithms. In our segmentation method, the combinatorial information of the mesh is systematically preferred over the geometry whenever possible, which makes the algorithm both simpler and more robust. Large industrial models with complex topologies and poor mesh qualities can be efficiently processed. The paper concludes with some results, showing our method applied to architectural and car design industry models, and demonstrating that it both speeds up the visualization and is easy to integrate into existing advanced rendering software.
Goniometric Diagram Mapping for Hemisphere
(Eurographics Association, 2003) Havran, Vlastimil; Dmitriev, Kirill; Seidel, Hans-Peter
Describing the light intensity over the hemisphere using a goniometric diagram is a common practice in the lighting industry and is prescribed for instance by IESNA (Illuminating Engineering Society of North America) standards. Goniometric diagram specifies the spatial distribution of the emitted power via a hemispherical surface subdivided by meridians and parallels. Similar tabulated representations are extensively used for complex bidirectional refiectance distribution functions (BRDF) that are difficult to approximate with analytical models. We present an approximative bicontinuous mapping from the unit square to a goniometric diagram on the hemisphere. This mapping has low distortion and the error of the approximation is low. The proposed mapping algorithm is obtained as a composition of four mappings. We outline its use for importance sampling of light sources described by goniometric diagrams and for the representation of BRDF.
High quality images from 2.5D video
(Eurographics Association, 2003) Berretty, Robert-Paul; Ernst, Fabian
Given a 2D video stream with an accompanying depth channel, we render high quality images from viewpoints close to the original one. This is for instance required to generate a 3D impression on stereoscopic or multiview screens. We propose a technique for video based rendering that supports higher order video filtering. We focus on screens that support horizontal parallax. We can optionally incorporate rendering of a so called hidden layer that contains data of parts of the scene that are hidden from the original viewpoint. We are able to render high quality images at only the added cost of the video filtering.
Implicit Surface Reconstruction and uniform Sampling by Striped Marching Triangles
(Eurographics Association, 2003) Leborán, Víctor; Pardo, Xose M.
The synthesis of computer models from real objects is a usual procedure in medical image processing and reverse engineering. In both cases, the main issues are to reach a topologically consistent and geometrically precise object reconstruction. Implicit surfaces provide a solution to this problem. They define a smooth surface surrounding objects which must be polygonized for an efficient visualization. Due to the increasing size of the application generated data, it becomes necessary to use precise and efficient methods. This work presents a modified method of implicit surface polygonization based on “Marching Triangles”. This modification assures the topological consistency with the initial dataset during the progressive reconstruction of the surface, avoiding overlapping triangles. In addition, a comparison of our method with the marching cubes and the adaptive skeleton climbing algorithms is provided.
Improved Indirect Photon Mapping withWeighted Importance Sampling
(Eurographics Association, 2003) Szirmay-Kalos, Laszlo; Szecsi, Laszl
This paper offers a novel approach to the indirect photon mapping method. The placement of photons acting as virtual light sources is regarded as a cheap sampling scheme, allowing for the reuse of a complete shooting path at the cost a single shadow ray. In order to counter for its shortcomings, the variance reduction technique called weighted importance sampling is applied. This allows for the extension of the indirect photon mapping method for specular settings, because the weighting function can mimic surface BRDF characteristics disregarded by the virtual light source placement. On the other hand, weighted importance sampling also helps to eliminate the "corner spikes" caused by the fact that shooting cannot mimic the geometric factor of the connection rays. Advantages and problems are examined for several weighting schemes.
Inelastic Scattering and Participating Media.Application to the ocean
(Eurographics Association, 2003) Cerezo, Eva; Seron, Francisco J.
A system, developed to treat general participating media, is generalized to make it capable of considering volumetric inelastic processes such as fluorescence. The system is based on the discrete ordinates method, and can treat complex participating medium such as natural waters. It can deal with highly-peaked anisotropic phase functions and can handle the spectral behavior of the medium's characteristic parameters.The system is applied to the study of fluorescence, the most common inelastic effect in natural waters.

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