Short Presentations

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

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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.
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.
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.
On the characterization of avatars in Distributed Virtual Worlds
(Eurographics Association, 2003) Morillo, Pedro; Fernandez, Marcos; Orduna, Juan Manuel
Current Distributed Virtual Environment (DVE) systems run simulations based on a server-network architecture, where the population of avatars should be properly assigned to the servers in the DVE. This goal, called partitioning problem, is a hot research problem in the field of networked 3D real time graphics. Some approaches have been proposed for resolving this problem, all of them based on a very basic model which describes the behaviour of an avatar in a virtual world. This model estimates the workload that a given avatar adds to its server as an independent and static value. In order to design scalable and accurate partitioning schemes we propose a new characterization of the workload generated by the avatars in the system. In this model, the workload is computed as a function of two factors: avatar movement rate and factor of presence. Evaluation results show that this proposed model correlates with real systems properly, providing an accurate abstraction of avatars for load balancing purposes.
Skeleton Subspace Deformation with Displacement Map
(Eurographics Association, 2003) Liu, Feng; Liang, Ronghua; Ye, Dahai
Skeleton Subspace Deformation (SSD) is a novel Free Form Deformation technology (FFD), and plays an important role in character animation, interactive game and other fields. In this paper, we present a new layered algorithm of SSD. After a preliminary conventional SSD, a displacement map is constructed based on the pose of the skeleton and the original surface. And then synthesize the displacement map with the defectively deformed surface and thus solve the inherent problems of conventional SSD, called "collapse" and "pinch". The experiment shows the effectiveness of this algorithm to create the realistic skin for an animated character.
PREFACE
(Eurographics Association, 2003)
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.
Occlusion Culling for Image-Based Rendering withWarping
(Eurographics Association, 2003) Soner, I. Sen; Atalay, Volkan
The basic idea of the proposed algorithm is to reduce the number of depth pixels in Layer Depth Images (LDI) by culling the occluded ones before warping. The method combines the octree spatial subdivision concept with LDI concept, using the implicit geometry stored in depth pixels. The algorithm uses an octree to group depth pixels in a hierarchical way. The proposed algorithm is very effective when used in highly occluded scenes, and the density of the depth pixels should be high enough to get a high performance from the algorithm
Parameter-driven freeform deformations
(Eurographics Association, 2003) Song, Y.; Vergeest, J.S.M.; Saakes, D.P.
High-level parameters offer user an easy and intuitive tool to modify an existing model. In this paper, an approach of deforming freeform shapes using intrinsic parameters is proposed, where those parameters were not part of the model. Instead the parameters are introduced by user at the time he/she needs them. To achieve this, different from existing freeform deformation methods, a deformable template defined by intrinsic parameters is used as the bridge to link the original freeform shape and the user actions. Those templates can be defined by the user or simply derived from freeform feature concepts. With shape similarity analysis, a user-defined region of interest in the freeform shape is matched, or fitted, to a deformable shape template. By several different kinds of R3 to R3 functions, the region of interest is mapped to the fitted deformable shape template. Thus template parameters can be transferred to the original freeform shape. Through those quantitative intrinsic parameters, the user can easily modify the freeform shape. Several simple implementations were conducted in order to verify the proposed method. It is also described how the proposed technique can be applied in practical shape modelling applications.
Interactive Dynamic Environments Using Image-Based Modeling and Rendering (393.4 kB) Timothy A. Davis, Stephen P. Ficklin An approach to construct augmented CAD models using acquired digital images
(Eurographics Association, 2003) Bianconi, Francesco; Conti, Paolo
An approach for integrating CAD models and information associated with digital images is discussed in this paper. The main objective of the proposed framework is the construction of augmented CAD models using digital images acquired on real components of that models. An approach to associate general shape surfaces with related images is discussed. The proposed method can be used to associate engineering information retrieved through optical methods (thermoelasticity, photoelasticity, surface analysis and similar) with CAD models. The overall architecture and the first outcomes of the implementation of the framework are presented.
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.
Information Visualization using Transparent Shape Impostors
(Eurographics Association, 2003) Seipel, Stefan
Transparency is a graphical effect used in visualizations to present co-located graphical glyphs. Accomplishing a visually convincing transparency effect requires complex calculations of light absorption and refraction in object space. Alternatively, screen-space sorted rendering of graphical primitives using colour- blending techniques can be used for interactive applications. In this paper an efficient way is presented to render transparent glyphs for information visualization. The technique combines random dot surface plots with pre-computed transparent shape impostors to present different levels of transparency for co-located graphical glyphs. It is shown that this rendering method is faster than ordered polygon rendering using blending.
VelvetPath - Layout Design System with Sketch and Paint Manipulations
(Eurographics Association, 2003) Tobita, Hiroaki
We describe the VelvetPath system, a system that allows users to design layouts for visualized information by using sketch and paint manipulations. Many systems enable users to visually search and browse through information by treating the data as visualized nodes (e.g., related images and simple figures). While these layouts are pre-defined and useful for the applications considered by the designers, users cannot freely change or redesign the layouts. In contrast, users of the VelvetPath system can freely design and change layouts by simply drawing strokes. Since the information layouts are defined automatically according to the users strokes, the user can create layouts based on his/her own needs and retrieve information using these layouts. Moreover, because all the manipulations in the system are based on simple sketching and painting interactions, the system is easy to use. These simple manipulations are useful not only for information retrieval, but also for a wide variety of applications such as 2D and 3D content creation, preparing slide presentations, and communication through a computer. In this paper, we describe our VelvetPath system and how it can be effectively applied.
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.
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.
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.
Mobile Augmented Reality for Environmental Management (MARE)
(Eurographics Association, 2003) Danado, Jose; Dias, Eduardo; Romao, Teresa; Correia, Nuno; Trabuco, Adelaide; Santos, Carlos; Araujo, David; Duarte, Pedro; Rebocho, Rui; Palmeiro, Jose; Serpa, Joao; Costa, Manuel; Camara, Antonio
Access to real-time data while in field observations is often a requested issue in environmental management. Additionally, it is easier to see that information spatially distributed where it makes sense, leveraging users of the task of searching for the context where the retrieved information can be applied. Augmented Reality (AR) is a technology that allows the superimposition of synthetic images over real images, providing augmented knowledge about the environment in the users vicinity. AR will also make the task more pleasant and effective for the user, since the required information is spatially superimposed over real information related to it. This short paper describes ANTS (Augmented Environments), an AR project for environmental management providing geo-referenced information to the user. The systems architecture has a flexible design based on a client/ server model, where several independent, but functionally interdependent modules are articulated. Therefore, modules can be moved from the server side to the client side or vice-versa, according to the client processing capacity. The system is being deployed in laptop computers and work is in progress to deploy the system using Personal Digital Assistant (PDA) devices. A 3D model and a geo-referenced database are used in the server for user positioning, and presentation components are used in the client to superimpose synthetic information over real images. Several applications for the system are being developed and will also be discussed in this short paper.
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.
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.
Multilevel modelling and rendering of architectural scenes
(Eurographics Association, 2003) Kushal, Akash M.; Chanda, Gaurav; Shrivastava, Kanishka; Gupta, Mohit; Sanyal, Subhajit; Sriram, T. V. N.; Kalra, Prem; Banerjee, Subhashis
We present a novel approach for multilevel modelling and rendering of architectural scenes using a small set of photographs. Our approach is based on interactive probing of intuitive measures like lengths, widths and heights using single view metrology. These measures can then be aggregated with additional input if need be, for defining high-level primitives such as planes, prismatic blocks, cuboids, spheres, and general surfaces of translation and revolution. The modelling approach is modular and incremental which enables ease and flexibility in building large architectural scenes. Further, our approach allows multilevel modelling and rendering. That is, the model can be enhanced/reduced both in terms of changing details at the primitive level and at the model level. This requires inter-registration of two or more images with common contents. Our approach is computationally simple, fast and robust. We demonstrate our results by building a model of a magnificent historical monument in Delhi - Humayunss tomb.

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