EG2002

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On the Integration of Synthetic Objects with Real-World Scenes
(Eurographics Association, 2002) Abad, Francisco; Camahort, Emilio; Vivó, Roberto
This paper presents a method for integrating synthetic objects in real-world photographs. We take a set of photographs of a real scene and build a simple image-based model. We use high dynamic range images to build an accurate representation of the lighting in the scene. Then we insert a synthetic object into the model and compute its illumination and shading using the lighting information. Illumination changes produced by the synthetic object are also applied to the background plane in the real-world photograph. We show how easy it is to achieve photorealistic results without specialized hardware. Our approach takes advantage of techniques like automatic camera calibration, high-dynamic range image capture and image-based lighting. We show preliminary results obtained with our application. We also present two improvements that we are currently studying. They are aimed at improving the quality of the resulting images and decreasing the computational resources needed by the process.
Point Based Computer Graphics
(Eurographics Association, 2002) Gross, Markus; Pfister, Hanspeter; Zwicker, Matthias; Pauly, Mark; Stamminger, Marc; Alexa, Marc
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Texture Minification using Quad-trees and Fipmaps
(Eurographics Association, 2002) Bornik, Alexander; Ferko, Andrej
The paper extends the recently published methods for image reconstruction and texture minification using the generalized ripmap method, named fipmap, and quad-trees. Fipmap is based on the technique of partitioned iterated function systems, used in fractal image compression. The quad-tree texture reconstruction algorithm works well for many standard cases. The special cases can be solved using the fipmap minification. The approach was applied for textures from architectural image sequences and the results are very promising.
View Interpolation for Dynamic Scenes
(Eurographics Association, 2002) Xiao, Jiangjian; Rao, Cen; Shah, Mubarak
This paper describes a novel technique for synthesizing a dynamic scene from two images without the use of a 3D model. A scene containing rigid or non-rigid objects, in which each object can move in any orientation or direction, is considered. It is shown that such a scene can be converted into several equivalent static scenes, where each scene only includes one rigid object. Our method can generate a series of continuous and realistic intermediate views from only two reference images without 3D knowledge. The procedure consists of three main steps: segmentation, morphing and postwarping. The key frames are first segmented into several layers. Each layer can be realistically morphed after determining its fundamental matrix. Based on the decomposition of 3D rotation matrix, an optimized and unique postwarping path is automatically determined by the least distortion method and boundary connection constraint. Finally, four experiments, which include morphing of a rotating rigid object in presence of occlusion and morphing of non-rigid objects (human), are demonstrated.
Feature Extraction and Visualisation of Flow Fields
(Eurographics Association, 2002) Post, Frits H.; Vrolijk, Benjamin; Hauser, Helwig; Laramee, Robert S.; Doleisch, Helmut
Flow visualisation has already been a very attractive part of visualisation research for a long time. Usually very large data sets need to be processed, which often consist of multivariate data with a large number of sample locations, often arranged in multiple time steps. Recently, the steadily increasing performance of computers again has become a driving factor for a new boom in flow visualisation, especially in techniques based on feature extraction, vector field clustering, and topology extraction. In this state-of-the-art report, an attempt was made to (1) provide a useful categorisation of FlowVis solutions, (2) give an overview of existing solutions, and (3) focus on recent work, especially in the field of feature extraction. In separate sections we describe (a) direct visualisation techniques such as hedgehog plots, (b) visualisation using integral objects, such as streamlines, (c) texture-based techniques, including spot noise and line integral convolution, and (d) techniques based on extraction of features or flow topology.
Simulation of Cumuliform Clouds Based on Computational Fluid Dynamics
(Eurographics Association, 2002) Miyazaki, Ryo; Dobashi, Yoshinori; Nishita, Tomoyuki
Simulation of natural phenomena is one of the important research fields in computer graphics. In particular, clouds play an important role in creating images of outdoor scenes. Fluid simulation is effective in creating realistic clouds because clouds are the visualization of atmospheric fluid. In this paper, we propose a simulation technique, based on a numerical solution of the partial differential equation of the atmospheric fluid model, for creating animated cumulus and cumulonimbus clouds with features formed by turbulent vortices.
Eurographics 2002 - Presentation of European Groups doing Computer Graphics Research
(Eurographics Association, 2002)
This brochure contains a concentrated description of many European Computer Graphics research labs. It was produced to accompany a track of lab presentations at the annual conference Eurographics’2002 in Saarbrücken in September 2002. European CG researchers were invited through the call for participation to present their research unit to a broader audience, including the readers of this booklet. In addition we have invited the leaders of the most active labs personally to send their contributions. We believe that only relatively few important CG institutes and research organisations are missing, and that this brochure therefore gives a nice overview of what is going on in Europe in Computer Graphics. Most of the labs collected in this brochure presented themselves with a short talk during the conference, often given by their heads in person, and participants had the oportunity to ask a few rather organisational questions.
More than RGB: Spectral Trends in Color Reproduction
(Eurographics Association, 2002) Bell, Ian E.; Baranoski, Gladimir V. G.
Early rendering algorithms relied exclusively on three-dimensional spaces for color computation, such as RGB and CIE XYZ. Recent rendering advances use full spectral information for illuminants and surfaces, resulting in much greater accuracy and realism. These expensive computations can be wasted, however, if ad hoc methods are used to adjust the final image on the monitor, in film, or in print. Ineficiency and inaccuracy can be avoided with some knowledge of device gamuts and color reproduction algorithms. This course follows spectral data through the graphics pipeline, examining issues of rendering, color science, perception, gamut mapping, and color management. We conclude with a discussion of trends and open problems in managing spectral data for accurate color reproduction. Participants will learn not only the theoretical background of color and spectral reproduction, but practical guidelines often omitted in technical papers.
Tree balancing for mesh simplification
(Eurographics Association, 2002) Grabner, Markus
In this paper, a tree balancing technique is presented that reduces the number of hierarchy levels in typical paircontraction based mesh simplification methods. A well-balanced hierarchy is essential for data structures that explicitly represent vertices as the corresponding paths through the simplification hierarchy. The quality of the generated meshes is evaluated by three methods. The deviation between the simplified and the original mesh is measured by the Hausdorff distance. The shape of the individual triangles is evaluated by Guéziec’s compactness value. Finally, a plot showing the shape distribution of all triangles in the mesh is given. The experiments show that tree balancing has no significant impact on triangle quality.
Global Illumination for Interactive Applications and High-Quality Animations
(Eurographics Association, 2002) Damez, Cyrille; Dmitriev, Kirill; Myszkowski, Karol
One of the main obstacles to the use of global illumination in image synthesis industry is the considerable amount of time needed to compute the lighting for a single image. Until now, this computational cost has prevented its widespread use in interactive design applications as well as in computer animations. Several algorithms have been proposed to address these issues. In this report, we present a much needed survey and classification of the most up-to-date of these methods. Roughly, two families of algorithms can be distinguished. The first one aims at providing interactive feedback for lighting design applications. The second one gives higher priority to the quality of results, and therefore relies on offline computations. Recently, impressive advances have been made in both categories. Indeed, with the steady progress of computing resources and graphics hardware, and the current trend of new algorithms for animated scenes, common use of global illumination seems closer than ever.
Tutorial on Inhabited Virtual Heritage
(Eurographics Association, 2002) Magnenat-Thalmann, Nadia; Chalmers, Alan; Fua, Pascal; Thalmann, Daniel
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3D Scanning Technology: Capabilities and Issues
(Eurographics Association, 2002) Scopigno, Roberto
The recent evolution of graphics technology makes it possible to manage very complex models on inexpensive platforms. These impressive rendering capabilities should be paired with detailed and accurate digital models. The construction of high quality 3D models is made easier by the increasing diffusion of automatic 3D measuring devices (often called 3D scanners). These allow to build highly accurate models of real 3D objects in a cost- and time-effective manner. The talk will present the capabilities of this technology focusing mainly on a particular application context: the acquisition of Cultural Heritage artifacts. The peculiar requirements of this domain (high accuracy in the acquisition of both shape and surface appearance, expected low cost and easiness of use of the tools) make it a perfect application example. This talk aims also at presenting and discussing the main issues in the acquisition of accurate 3D models, together with some limitations of current hardware and software tools. Some examples of the results of current projects will be shown.
A Method for Creating Mosaic Images Using Voronoi Diagrams
(Eurographics Association, 2002) Dobashi, Yoshinori; Haga, Toshiyuki; Johan, Henry; Nishita, Tomoyuki
This paper proposes a non-photorealistic rendering method that creates an artistic effect called mosaicing. The proposed method converts images provided by the user into the mosaic images. Commercial image editing applications also provide a similar function. However, these applications often trade results for low-cost computing. It is desirable to create high quality images even if the computational cost is increased. We present an automatic method for mosaicing images by using Voronoi diagrams. The Voronoi diagrams are optimized so that the error between the original image and the resulting image is as small as possible. Next, the mosaic image is generated by using the sites and edges of the Voronoi diagram. We use graphics hardware to efficiently generate Voronoi diagrams. Furthermore, we extend the method to mosaic animations from sequences of images.
Visual Data Mining
(Eurographics Association, 2002) Keim, Daniel A.; Müller, Wolfgang; Schumann, Heidrun
Never before in history has data been generated at such high volumes as it is today. Exploring and analyzing the vast volumes of data has become increasingly difficult. Information visualization and visual data mining can help to deal with the flood of information. The advantage of visual data exploration is that the user is directly involved in the data mining process. There are a large number of information visualization techniques that have been developed over the last two decades to support the exploration of large data sets. In this star report, we provide an overview of information visualization and visual data mining techniques, and illustrate them using a few examples.
Real-Time Animated Grass
(Eurographics Association, 2002) Bakay, Brook; Lalonde, Paul; Heidrich, Wolfgang
We present a simple method to render fields of grass, animated in the wind, in real-time. The technique employs vertex shaders to render displacement maps with Russian-doll style transparent shells. Animation is achieved by translating the surface according to a local wind vector while preserving the length of the blades of grass. This technique achieves convincing results on current consumer graphics hardware and can be applied to other similar surfaces such as hair and fur.
Image Editing with Intelligent Paint
(Eurographics Association, 2002) Reese, Jack; Barrett, William
Intelligent Paint provides a new tool for interactively selecting image objects or regions of interest, while simultaneously applying filters or effects directly to the selection(s). By coupling adaptive cost-ordered region growing with the high-level visual expertise of the user to indicate which objects are of interest, we are able to accurately select and edit complex, non-homogeneous objects in only a few seconds using simple mouse input gestures. Prior to selection, the image is oversegmented using a watershed (tobogganing) algorithm. Watershed catchment basins are assembled into an hierarchical image partition by grouping basins using the student’s t-distribution. Grouped basins, referred to as TRAPs (Tobogganed Region Accumulation Plateaus), reasonably capture sub-object detail. Object selection is accomplished by user-steered, adaptive, cost-ordered collection of TRAPs. Tinting or application of filters during object selection provides immediate visual feedback as to what is being selected as well as the suitability of the chosen digital effect. Intelligent Paint selection compares favorably with popular commercial tools in terms of efficiency, accuracy and reproducibility with the added benefit of on-the-fly filtering, while raising the granularity of image editing from the pixel to the object-level. Novel tools for object-centered image editing such as Intelligent Eraser and Intelligent Clone tools are also possible with this technique.
Information-Theoretic Oracle Based on Kernel Smoothness for Hierarchical Radiosity
(Eurographics Association, 2002) Feixas, Miquel; Rigau, Jaume; Bekaert, Philippe; Sbert, Mateu
One of the main problems in the radiosity method is how to discretise the surfaces of a scene into mesh elements that allow us to accurately represent illumination. In this paper we present a robust information-theoretic refinement criterion (oracle) based on kernel smoothness for hierarchical radiosity. This oracle improves on previous ones in that at equal cost it gives a better discretisation, approaching the optimal one from an information theory point of view, and also needs less visibility computations for a similar image quality.
Geometric Simplification of Foliage
(Eurographics Association, 2002) Remolar, Inmaculada; Chover, Miguel; Belmonte, Oscar; Ribelles, Jose; Rebollo, Cristina
One of the most important challenges in real-time rendering of outdoor scenes is the representation of vegetation. This is due to the vast amount of polygons that are used to model vegetable species. The present automatic simplification algorithms produce acceptable results in the trunks and the branches, but not in the foliage of a tree. After simplification with the existing methods, the trees seem to be less leafy. In this paper, a new automatic simplification algorithm for this part of the tree is presented, the Foliage Simplification Algorithm. It diminishes the number of polygons in the crown, while maintaining the appearance. It uses a new method, leaf collapse: two leaves disappear to create a new one. The leaves obtained after collapsing preserve an area similar to that of the collapsed leaves
Hardware-Assisted Relief Texture Mapping
(Eurographics Association, 2002) Fujita, Masahiro; Kanai, Takashi
Image-Based Rendering by Warping (IBRW) creates three-dimensional scene by deforming several 2D images with depth information. Image-based rendering has an advantage compared to traditional polygon rendering that the rendering time is still constant even if a scene becomes complex. Relief texture mapping decomposes IBRWinto a very simple 1D image operation and a traditional texture mapping, which allows more effective computations. In this paper, we try to apply some hi-quality shading effects such as reflection mapping for relief texture mapping. Their effects can be realized by per-pixel shading technology of today’s graphics hardware. Our method for relief texture mapping allows fast and almost the same shading as well as traditional polygon rendering.
Interpolating 2D Shape Hierarchically
(Eurographics Association, 2002) Johan, Henry; Nishita, Tomoyuki
Shape interpolation has been widely used in the field of computer graphics for modeling and for creating visual effects. This paper presents a novel hierarchical method to interpolate between two 2D shapes. A hierarchical representation, which is a hierarchy of triangles, is proposed to represent the interior and the details of each shape. By constructing the compatible hierarchical representations of the two shapes, the intermediate shapes are computed by interpolating the corresponding triangles at the lowest level to the highest level of the representations, From experimental results, the proposed method produces smooth interpolation sequences.

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