25-Issue 1

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https://diglib.eg.org/handle/10.2312/124

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    16th Eurographics Workshop on Rendering Konstanz, Germany, 29th June-1st July 2005
    (The Eurographics Association and Blackwell Publishing Ltd., 2006) Konstanz, Oliver Deussen
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    4th International Workshop on Volume Graphics
    (The Eurographics Association and Blackwell Publishing Ltd., 2006)
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    Classification of Illumination Methods for Mixed Reality
    (The Eurographics Association and Blackwell Publishing Ltd., 2006) Jacobs, Katrien; Loscos, Celine
    A mixed reality (MR) represents an environment composed both by real and virtual objects. MR applications are used more and more, for instance in surgery, architecture, cultural heritage, entertainment, etc. For some of these applications it is important to merge the real and virtual elements using consistent illumination. This paper proposes a classification of illumination methods for MR applications that aim at generating a merged environment in which illumination and shadows are consistent. Three different illumination methods can be identified: common illumination, relighting and methods based on inverse illumination. In this paper a classification of the illumination methods for MR is given based on their input requirements: the amount of geometry and radiance known of the real environment. This led us to define four categories of methods that vary depending on the type of geometric model used for representing the real scene, and the sdifferent radiance information available for each point of the real scene. Various methods are described within their category.The classification points out that in general the quality of the illumination interactions increases with the amount of input information available. On the other hand, the accessibility of the method decreases since its pre-processing time increases to gather the extra information. Recent developed techniques managed to compensate unknown data with clever techniques using an iterative algorithm, hardware illumination or recent progress in stereovision. Finally, a review of illumination techniques for MR is given with a discussion on important properties such as the possibility of interactivity or the amount of complexity in the simulated illumination.
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    Computational Aesthetics 2005 Eurographics Workshop on Computational Aesthetics in Graphics, Visualization and Imaging Girona, Spain, 18-20 May 2005
    (The Eurographics Association and Blackwell Publishing Ltd., 2006) Neumann, Laszlo; Sbert, Mateu; Gooch, Bruce; Purgathofer, Werner
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    Editorial
    (The Eurographics Association and Blackwell Publishing Ltd., 2006) Duke, David; Scopigno, Roberto
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    Eurographics Symposium on Natural Phenomena
    (The Eurographics Association and Blackwell Publishing Ltd., 2006) Galin, Eric; Poulin, Pierre
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    Image Registration in a Coarse Three-Dimensional Virtual Environment
    (The Eurographics Association and Blackwell Publishing Ltd., 2006) Laycock, R. G.; Day, A. M.
    In recent years, the availability of off-the-shelf geometric data for an urban environment has increased. During rendering, ground level images are mapped onto the facades of the buildings to improve the visual quality of the scene. This paper focuses on a technique that enables ground level images to be automatically integrated into an existing coarse three-dimensional environment. The approach utilises the planar nature of architectural scenes to enable the automatic extraction of a building facade from an image and its registration into the virtual environment.
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    In Memoriam: Juergen Schoenhut
    (The Eurographics Association and Blackwell Publishing Ltd., 2006) Duce, David
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    In Memoriam: Professor Dick Grimsdale 1929-2005
    (The Eurographics Association and Blackwell Publishing Ltd., 2006) Willis, Phil
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    Particle Oriented Collision Detection using Simplicial Coverings and Tetra-Trees
    (The Eurographics Association and Blackwell Publishing Ltd., 2006) Jimenez, Juan Jose; Feito, Francisco R.; Segura, Rafael J.; Ogayar, Carlos J.
    Collision detection (CD) among complex objects in motion is an open question because of its algorithmic complexity. In this paper, we present a CD algorithm between a particle and a complex rigid solid. In order to represent solids, we use a simplicial covering scheme by means of 3-simplices. With this representation system, complex polyhedra and closed triangle meshes can be represented and used in CD with a particle. A particle can be represented by a point, where the real dimensions of the particle are not important. This CD algorithm has been extended for a particle represented by a sphere which in turn represents an approximation to the particle dimensions. In order to efficiently classify the particles and the simplices of the polyhedra covering, we use a new hierarchical data structure named tetra-tree that decomposes the space into tetra-cones. These algorithms also use bounding volumes and temporal and geometric coherence, as well as incremental calculations in order to determine the collision in an efficient and exact way. Because of the use of sign operations with signed volumes and barycentric coordinates, we conclude that operations carried out using this method are more robust and efficient than those used in classic algorithms.
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    A PBL Experience in the Teaching of Computer Graphics
    (The Eurographics Association and Blackwell Publishing Ltd., 2006) Marti, E.; Gil, D.; Julia, C.
    Project-Based Learning (PBL) is an educational strategy to improve student s learning capability that, in recent years, has had a progressive acceptance in undergraduate studies. This methodology is based on solving a problem or project in a student working group. In this way, PBL focuses on learning the necessary tools to correctly find a solution to given problems.Since the learning initiative is transferred to the student, the PBL method promotes students own abilities. This allows a better assessment of the true workload that carries out the student in the subject. It follows that the methodology conforms to the guidelines of the Bologna document, which quantifies the student workload in a subject by means of the European credit transfer system (ECTS).PBL is currently applied in undergraduate studies needing strong practical training such as medicine, nursing or law sciences. Although this is also the case in engineering studies, amazingly, few experiences have been reported. In this paper we propose to use PBL in the educational organization of the Computer Graphics subjects in the Computer Science degree.Our PBL project focuses in the development of a C++ graphical environment based on the OpenGL libraries for visualization and handling of different graphical objects. The starting point is a basic skeleton that already includes lighting functions, perspective projection with mouse interaction to change the point of view and three predefined objects. Students have to complete this skeleton by adding their own functions to solve the project. A total number of 10 projects have been proposed and successfully solved. The exercises range from human face rendering to articulated objects, such as robot arms or puppets. In the present paper we extensively report the statement and educational objectives for two of the projects: solar system visualization and a chess game.We report our earlier educational experience based on the standard classroom theoretical, problem and practice sessions and the reasons that motivated searching for other learning methods. We have mainly chosen PBL because it improves the student learning initiative. We have applied the PBL educational model since the beginning of the second semester. The student s feedback increases in his interest for the subject. We present a comparative study of the teachers and students workload between PBL and the classic teaching approach, which suggests that the workload increase in PBL is not as high as it seems.
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    Principles and Applications of Computer Graphics in Medicine
    (The Eurographics Association and Blackwell Publishing Ltd., 2006) Vidal, Franck; Bello, F.; Brodlie, K.W.; John, N.W.; Gould, D.; Phillips, R.; Avis, N.J.
    The medical domain provides excellent opportunities for the application of computer graphics, visualization and virtual environments, with the potential to help improve healthcare and bring benefits to patients. This survey paper provides a comprehensive overview of the state-of-the-art in this exciting field. It has been written from the perspective of both computer scientists and practising clinicians and documents past and current successes together with the challenges that lie ahead. The article begins with a description of the software algorithms and techniques that allow visualization of and interaction with medical data. Example applications from research projects and commercially available products are listed, including educational tools; diagnostic aids; virtual endoscopy; planning aids; guidance aids; skills training; computer augmented reality and use of high performance computing. The final section of the paper summarizes the current issues and looks ahead to future developments.
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    Rendering Soft Shadows using Multilayered Shadow Fins
    (The Eurographics Association and Blackwell Publishing Ltd., 2006) Cai, Xiao-Hua; Jia, Yun-Tao; Wang, Xi; Hu, Shi-Min; Martin, Ralph R.
    Generating soft shadows in real time is difficult. Exact methods (such as ray tracing, and multiple light source simulation) are too slow, while approximate methods often overestimate the umbra regions. In this paper, we introduce a new algorithm based on the shadow map method to quickly and highly accurately render soft shadows produced by a light source. Our method builds inner and outer translucent fins on objects to represent the penumbra area inside and outside hard shadows, respectively. The fins are traced into multilayered light space maps to store illuminance adjustment to shadows. The viewing space illuminance buffer is then calculated using those maps. Finally, by blending illuminance and shading, a scene with highly accurate soft shadow effects is produced. Our method does not suffer from umbra overestimation. Physical relations between light, objects and shadows demonstrate the soundness of our approach.
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    Speed-up Technique for a Local Automatic Colour Equalization Model
    (The Eurographics Association and Blackwell Publishing Ltd., 2006) Artusi, A.; Gatta, C.; Marini, D.; Purgathofer, W.; Rizzi, A.
    In this paper we propose a speed-up technique for a local automatic colour equalization operator derived from a model of the human vision system. This method is characterized by local and global filtering effects, that simultaneously achieve different equalization tasks e.g. performing colour and lightness constancy, realizing dynamic image data driven stretching, controlling the contrast. We describe a way to quickly create a filtering mapping function to perform the global component of the mapping. This method is based on singular value decomposition (SVD) applied to sampled and filtered points in the input image. Then, the local information is added computing the basic algorithm on a neighbourhood of each input pixel. A slight quality loss is the price that we have to pay for a speed-up of more than two orders of magnitude of the basic algorithm. We present the results on several images and discuss the efficiency and the drawbacks of the speed-up technique.
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    VAST 2005 November 7-11, Pisa, Italy
    (The Eurographics Association and Blackwell Publishing Ltd., 2006) Mudge, Mark; Ryan, Nick; Scopigno, Roberto
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    Virtual Reality Course-A Natural Enrichment of Computer Graphics Classes
    (The Eurographics Association and Blackwell Publishing Ltd., 2006) Zara, J.
    This paper shows how the Virtual Reality (VR) course can naturally extend and practice a wide range of Computer Graphics (CG) principles and programming techniques. Thanks to real-time processing requirements, attention is paid to efficient modeling conventions, time-saving rendering approaches, and user interfaces allowing a smooth navigation in a virtual environment. All these issues play an important role especially when designing virtual worlds targeted to the web, i.e. utilizing VRML/X3D standards. The paper presents a structure and related information of the VR course that has been taught at various universities during the last 6 years. Our experience clearly demonstrates that students appreciate its contents even if they already completed courses on 3D graphics.
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    A Weighted Error Metric and Optimization Method for Antialiasing Patterns
    (The Eurographics Association and Blackwell Publishing Ltd., 2006) Laine, S.; Aila, T.
    Displaying a synthetic image on a computer display requires determining the colors of individual pixels. To avoid aliasing, multiple samples of the image can be taken per pixel, after which the color of a pixel may be computed as a weighted sum of the samples. The positions and weights of the samples play a major role in the resulting image quality, especially in real-time applications where usually only a handful of samples can be afforded per pixel. This paper presents a new error metric and an optimization method for antialiasing patterns used in image reconstruction. The metric is based on comparing the pattern against a given reference reconstruction filter in spatial domain, and it takes into account psychovisually measured angle-specific acuities for sharp features.