Short Presentations

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https://diglib.eg.org/handle/10.2312/231

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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.
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.
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.
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.
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.
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.
Improved Bump Mapping by using Quadratic Vector Interpolation
(Eurographics Association, 2002) Hast, Hans Anders; Barrera, Tony; Bengtsson, Ewert
Bump mapping is a technique that perturbs normals used in the illumination computation in order to make the surface appear rough or wrinkled. Standard graphics hardware linearly interpolates rotated vectors in the direction to the light source over the polygon. Then, a cube map is used to normalize these vectors. We propose the use of quadratic interpolation instead, which will make the normalization stage unnecessary. The result is faster bump mapping with quality near the quality obtained by using vector interpolation with normalization. Quadratic interpolation is already used for ordinary shading but has to our knowledge not previously been used for bump mapping. The fast setup we use in our new algorithm can also be applied to Phong shading resulting in increased performance. Similarly the same approach can be used for efficiently setting up the linear interpolation.
Multi-dimensional and Multi-scale Visualizer of Large XML Documents
(Eurographics Association, 2002) Jacquemin, Christian; Jardino, Michele
3D-XV (3-Dimensional XML Visualizer) is an interactive graphical interface for accessing large structured documents. It relies on a geometrical model that combines a sequential organization and a hierarchical structure. In the overview mode, the user can access information through natural language queries. In the browsing mode, the content of the paragraphs is displayed in a moving walkway fashion. The model is compared with previous studies on document visualization for passage retrieval. The merits of interactive 3D manipulation through the intuitively oriented 3D-XV geometrical model are outlined.
Adaptive Compression of Human Animation Data
(Eurographics Association, 2002) Ahmed, Amr Adel Hassan; Hilton, Adrian; Mokhtarian, Farzin
In this paper we introduce an adaptive motion compression technique using the discrete wavelet transform. Based on the analysis of human animation data, and its frequency contents, the wavelet analysis is utilised to achieve motion compression. It has been found that even with high compression ratios (up to 86%), the compressed animation is visually very close to the original animation. This property is potentially useful for many areas of animation such as motion interpolation/blending and networked virtual environments. One of our motivations is that motion blending/interpolation between motion capture samples is one of the successful techniques for synthesis of novel realistic human animation. One of the major concerns of that method is the increase of the database size with the large number of samples required to synthesise a wide range of movements. Previous research has addressed this issue by trying to reduce the number of samples required for interpolation. The approach that we introduce in this paper is to reduce the individual sample’s size using compression. Integration of both these approaches promises to allow a realistic animation with reduced database size. In networked virtual environments and on-line games, compressing the animation data can reduce the transmission load and help in achieving real-time performance and realism with reduced cost.
Rendering of Japanese Artcraft
(Eurographics Association, 2002) Durikovic, Roman; Kolchin, Kostantin; Ershov, Sergey
We present several methods for simulation of Japanese lacquer ware, a prominent Far East Asian handicraft art. We consider two most popular kinds of Japanese lacquer ware made by the makie and nashiji techniques. For rendering makie, we propose a method for preparing RGBA textures from digital photos of art items. The alpha channels of these textures control the weight with which color channels are blended with the measured biderectional reflectance distribution function (BRDF) of a metallic finish. Both ray tracing and hardware based rendering are demonstrated. In the latter case, we show how the calculation of a sphere map texture used for BRDF visualization can be accelerated using a special coordinate system for tabulated BRDF. The depth effect manifested by nashiji lacquer is simulated by the explicit modeling of metal platelets immersed in absorptive material.
Texturing Calibrated Head Model from Images
(Eurographics Association, 2002) Lempitsky, Victor; Ivanov, Denis; Kuzmin, Yevgeniy
In this paper we address a well-known problem of producing an animated model of a human head from a pair of orthogonal photographs and present a new technique of generating consistent high-quality texture for a polygonal 3D mesh which represents a personalized 3D head. The described technique is based on a combination of two different approaches to this problem and significantly extends them in order to produce optimal image in terms of minimizing visual artifacts and keeping level of details as high as possible. After a brief introduction to the complete calibration pipeline that we have used, we describe the stages of texture generation procedure, which consists of indexing available photographs with texture coordinates, finding optimal merging lines and balancing visual differences to allow for seamless merging while preserving high-frequency details. The presented technique has been evaluated within head animation software and demonstrated its ability of yielding high-quality textured model from photographs.
Visibility Preprocessing Using Spherical Sampling of Polygonal Patches
(Eurographics Association, 2002) Meruvia Pastor, Oscar E.
A technique is presented that permits fast view-reconstruction of individual objects. This method improves a previous approach to solve the problem of approximated view reconstruction by combining clustering of polygons with visibility bitfields to determine visibility for novel viewpoints. The technique consists of three steps: patch creation, spherical sampling, and rendering. In the first stage, the input 3D model is tiled in polygonal patches. In the sampling stage images of the model are taken from several points on the surface of a viewing sphere. Patch-ID bitfields, which are structures that contain visibility information, are computed for each picture. In the rendering stage, a subset of the viewpoints computed for sampling is selected depending on the viewers position on the viewing sphere and the bitfields of the selected viewpoints are used to rebuild the visible parts of the model from the new viewpoint. The overall system presented here makes a very efficient use of memory resources, and involves practically no overhead during rendering while significantly improving frame rate during interaction with large models. Although the technique is not conservative, our results show that the reconstructed views are practically identical to the original views of the model.
From Textual Chats to Interest Groups in 3D Virtual Space
(Eurographics Association, 2002) Masa, Michal; Zara, Jiri
While the textual chat is a highly popular tool for various kinds of social interactions, its extension to the visual three-dimensional domain remains almost untouched and without practical utilization yet. This paper discusses advantages and disadvantages of spatial virtual environment when used as a platform for connecting people and serving for social and cultural interaction. The differences between textual chat and interest groups in virtual reality are highlighted with the aim to overcome the gap between well-established chat technology and promising but still a bit exotic virtual reality approach. Theoretical analysis is followed by several examples taken from experimental setup.
Function-defined shape node for VRML
(Eurographics Association, 2002) Lai, Feng Min; Sourin, Alexei
This paper describes how the web-based visualisation can be greatly improved using the function-based shape modelling technique. We propose the function-defined VRML shape node, which allows the content creators to describe any complex models with relatively small functions compared to the large-size polygonal mesh based VRML nodes. The design, the implementation details, and the application examples of the proposed node are discussed. The software is available for downloading from the project website.

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