EG2005

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https://diglib.eg.org/handle/10.2312/247

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Progressive Cartesian Inequality Constraints for the Inverse Kinematic Control of Articulated Chains
(The Eurographics Association, 2005) Peinado, Manuel; Boulic, Ronan; Callennec, Benoit Le; Meziat, D.; John Dingliana and Fabio Ganovelli
We propose an Inverse Kinematic Control architecture capable of handling tasks that are expressed in terms of inequality constraints in the Cartesian space. These inequality constraints are progressive in the sense that their influence manifests itself in a zone of finite thickness by damping the progression toward the strict limit of the constraint. We show how to enforce this family of constraints in a two stage process with our prioritized IK sheme. Various examples highlight the potential of this approach for managing complex articulated chains in cluttered environments where obstacles are modelled with this type of constraints.
A PBL Experience in the Teaching of Computer Graphics
(The Eurographics Association, 2005) Marti, E.; Gil, D.; Julia, C.; Jean-Jacques Bourdin and Hugh McCabe
Project Based Learning (PBL) is an educational strategy to improve students learning capability which, in recent years, has had a progressive acceptation 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 ECTS (European Credit Transfer System). PBL is currently applied in undergraduate studies needing of 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 which already includes lighting functions, perspective projection with mouse interaction to change the point of view and 3 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 on 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.
Laplacian Mesh Processing
(The Eurographics Association, 2005) Sorkine, Olga; Yiorgos Chrysanthou and Marcus Magnor
Surface representation and processing is one of the key topics in computer graphics and geometric modeling, since it greatly affects the range of possible applications. In this paper we will present recent advances in geometry processing that are related to the Laplacian processing framework. This framework is based on linear operators defined on polygonal meshes, and furnishes a variety of processing applications, such as shape approximation and compact representation, mesh editing, filtering, watermarking and morphing. The core of the framework is the mesh Laplacian operator, which allows to define differential coordinates and new bases for efficient mesh geometry representation.
Constriction Computation using Surface Curvature
(The Eurographics Association, 2005) Hétroy, F.; John Dingliana and Fabio Ganovelli
This paper provides a curvature-based algorithm to compute locally shortest geodesics on closed triangulated surfaces. These curves, which are called "constrictions", are useful for shape segmentation. The key idea of the algorithm is that constrictions are almost plane curves; it first finds well-located simple, plane, closed curves, and then slides them along the surface until a shortest geodesic is reached. An initial curve is defined as a connected component of the intersection between the surface and a plane going through an initial vertex. Initial vertices and planes are determined using approximations of surface curvature.
Perception-Based Rendering: Eyes Wide Bleached
(The Eurographics Association, 2005) Gutierrez, Diego; Anson, Oscar; Munoz, Adolfo; Seron, Francisco J.; John Dingliana and Fabio Ganovelli
Perception issues are a key factor in rendering Vision-Realistic images. This paper develops a novel spectral sensitive model of the Human Visual System (HVS) in order to simulate the bleaching effect in retinal photopigments. First, the Stiles-Crawford effect is taken into account to determine the pupil size of the adapted eye and to compute the directional sensitivity of the photoreceptors in the retina. After that, the percentage of bleached pigment based on the incident retinal illuminance is calculated to simulate the loss of spectral sensitivity of the human observer seeing the scene.
Predicting Natural Hair Shapes by Solving the Statics of Flexible Rods
(The Eurographics Association, 2005) Bertails, Florence; Audoly, Basile; Querleux, Bernard; Leroy, Frédéric; Lévêque, Jean-Luc; Cani, Marie-Paule; John Dingliana and Fabio Ganovelli
This paper presents a new physically-based method for predicting natural hairstyles in the presence of gravity and collisions. The method is based upon a mechanically accurate model for static elastic rods (Kirchhoff model), which accounts for the natural curliness of hair, as well as for hair ellipticity. The equilibrium shape is computed in a stable and easy way by energy minimization. This yields various typical hair configurations that can be observed in the real world, such as ringlets. As our results show, the method can generate different hair types with a very few input parameters, and perform virtual hairdressing operations such as wetting, cutting and drying hair.
Efficient, Physically Plausible Finite Elements
(The Eurographics Association, 2005) Nesme, Matthieu; Payan, Yohan; Faure, François; John Dingliana and Fabio Ganovelli
This paper discusses FEM-based simulations of soft bodies in terms of speed and robustness. To be physically plausible, three fundamental laws must be respected: rotational invariance, Newton's law and Euler's law. We show that precomputed strain-displacement matrices generate nonphysical torques which can lead to visual artifacts. We then derive the fastest FEM-based method meeting our criteria of plausibility and robustness and discuss their limitations.
Real-time Upper Body 3D Pose Estimation from a Single Uncalibrated Camera
(The Eurographics Association, 2005) Micilotta, Antonio Salvatore; Ong, Eng Jon; Bowden, Richard; John Dingliana and Fabio Ganovelli
In this paper we introduce a real-time steering controller ensuring the reach of a (possible mobile) target position and orientation, without requiring to build/update the full trajectory to that target. We name it the funnelling control. The final orientation is achieved through the continuous adjustment of the heading direction. This control mode is proactive in the sense that it anticipates the success/failure of the reach and adjusts the desired speed accordingly. Both features rely on an heterogeneously sampled table of radial-tangential seek angles obtained when the controller reaches a desired position target without prescribed orientation. By construction, the control update has a constant computing cost, even with variable target characteristics. Its low update cost makes it particularly suited for controlling a large number of mobile entities in real-time. The present exposition is made for an obstacle-free context.This paper outlines a method of estimating the 3D pose of the upper human body from a single uncalibrated camera. The objective application lies in 3D Human Computer Interaction where hand depth information offers extended functionality when interacting with a 3D virtual environment, but it is equally suitable to animation and motion capture. A database of 3D body configurations is built from a variety of human movements using motion capture data. A hierarchical structure consisting of three subsidiary databases, namely the frontal-view Hand Position (top-level), Silhouette and Edge Map Databases, are pre-extracted from the 3D body configuration database. Using this hierarchy, subsets of the subsidiary databases are then matched to the subject in real-time. The examples of the subsidiary databases that yield the highest matching score are used to extract the corresponding 3D configuration from the motion capture data, thereby estimating the upper body 3D pose.
EG 2005 Tutorial on Mixed Realities in Inhabited Worlds
(The Eurographics Association, 2005) Magnenat-Thalmann, Nadia; Thalmann, Daniel; Fua, Pascal; Vexo, Frederic; Kim, HyungSeok; Ming Lin and Celine Loscos
1. Outline of the tutorial 1.1 Concepts and State of the Art of mixed realities in inhabited worlds 1.1.1 Mixed Realities in inhabited worlds 1.1.2 Believability and Presence 1.2 Perception, Sensors and Immersive hardware for MR in Inhabited Worlds 1.2.1 Vision Based 3D Tracking and Pose Estimation for MR 1.2.2 Perception and sensors for Virtual Humans 1.2.3 Hardware for mixed reality inhabited virtual world 1.2.4 Emotional and conversational virtual humans 1.3 MR in various applications 1.3.1 Simulating Life in mixed realities Pompei world 1.3.2 Simulating actors and audiences in ancient theaters 1.3.3 MR in STAR, an industrial project 1.3.4 Feeling presence in the treatment of social phobia 2. Syllabus 3. Resume of the presenters 4. Selected Publications
Computer Graphics Courseware
(The Eurographics Association, 2005) Ullrich, T.; Fellner, Dieter W.; Jean-Jacques Bourdin and Hugh McCabe
A lot of courseware tools suffer from the almost mutually exclusive goals of ease of usability on the one hand and extensibility and flexibility on the other hand. In most cases the tools are either ready-to-use applications (e.g. a virtual lab) or complex tool sets which need a long period of domain-specific adjustment. This paper presents the courseware environment AlgoViz which primarily addresses this problem. The AlgoViz project provides a software collection which is currently focused on the visualization of fundamental computer graphics algorithms and geometric modeling concepts. The intention is to build a collection of components, that can easily be combined to new applications. Supporting a purely visual programming paradigm, AlgoViz offers the possibility to create new demonstration applications without having to write a single line of source code. To demonstrate its potential AlgoViz comes with a variety of examples already forming a valuable computer graphics tutorial.
Image-based Representations for Accelerated Rendering of Complex Scenes
(The Eurographics Association, 2005) Jeschke, Stefan; Wimmer, Michael; Purgathofer, Werner; Yiorgos Chrysanthou and Marcus Magnor
This paper gives an overview of image-based representations commonly used for reducing the geometric complexity of a scene description in order to accelerate the rendering process. Several different types of representations and ways for using them have been presented, which are classified and discussed here. Furthermore, the overview includes techniques for accelerating the rendering of static scenes or scenes with animations and/or dynamic lighting effects. The advantages and drawbacks of the different approaches are illuminated, and unsolved problems and roads for further research are shown.
Interactive Shape Modeling
(The Eurographics Association, 2005) Alexa, Marc; Angelidis, Alexis; Cani, Marie-Paule; Singh, Karan; Zorin, Denis; Ming Lin and Celine Loscos
The course will present the state-of-the-art in digital modeling techniques, both in commercial software and academic research. The goal of this course is to impart the audience with an understanding of the big open questions as well as the skills to engineer recent research in interactive shape modeling applications.
A Visual Quality Prediction Model for 3D Texture
(The Eurographics Association, 2005) Cheng, Irene; Boulanger, Pierre; John Dingliana and Fabio Ganovelli
Online bandwidth limitations and fluctuations impose a major challenge in estimating the amount of data to transmit in a given time period. Over or under estimation of bandwidth can jeopardize the visual fidelity of the transmitted and related multimedia data. We propose a Visual Quality Prediction (VQP) model which supports an adaptive fragmented texture transmission approach taking bandwidth fluctuations into consideration, and adjusts the data size (and thus quality) of the next block of texture data to be transmitted. The transmission depends on a set of predictors used to optimize an overall best effort visual quality.
Scalar Tagged PN Triangles
(The Eurographics Association, 2005) Boubekeur, Tamy; Reuter, Patrick; Schlick, Christophe; John Dingliana and Fabio Ganovelli
This paper presents a new technique to convert a coarse polygonal geometric model into a smooth surface interpolating the mesh vertices, by improving the principle proposed by Vlachos et al. in their "Curved PN-Triangles". The key idea is to assign to each mesh vertex, a set of three scalar tags that act as shape controllers. These scalar tags (called sharpness, bias, and tension) are used to compute a procedural displacement map that enriches the geometry, and a procedural normal map that enriches the shading. The resulting technique offers two majors features: First, it can be applied on meshes of arbitrary topology while always generating surfaces with consistent behaviors across edge and vertex boundaries, second, it only involves operations that are purely local to each polygon, which means that it is very well suited for hardware implementations.
Physically Based Deformable Models in Computer Graphics
(The Eurographics Association, 2005) Nealen, Andrew; Müller, Matthias; Keiser, Richard; Boxerman, Eddy; Carlson, Mark; Yiorgos Chrysanthou and Marcus Magnor
Physically based deformable models have been widely embraced by the Computer Graphics community. Many problems outlined in a previous survey by Gibson and Mirtich [GM97] have been addressed, thereby making these models interesting and useful for both offline and real-time applications, such as motion pictures and video games. In this paper, we present the most significant contributions of the past decade, which produce such impressive and perceivably realistic animations and simulations: finite element/difference/volume methods, mass-spring systems, meshfree methods, coupled particle systems and reduced deformable models based on modal analysis. For completeness, we also make a connection to the simulation of other continua, such as fluids, gases and melting objects. Since time integration is inherent to all simulated phenomena, the general notion of time discretization is treated separately, while specifics are left to the respective models. Finally, we discuss areas of application, such as elastoplastic deformation and fracture, cloth and hair animation, virtual surgery simulation, interactive entertainment and fluid/smoke animation, and also suggest areas for future research.
A Survey of General-Purpose Computation on Graphics Hardware
(The Eurographics Association, 2005) Owens, John D.; Luebke, David; Govindaraju, Naga; Harris, Mark; Krüger, Jens; Lefohn, Aaron E.; Purcell, Timothy J.; Yiorgos Chrysanthou and Marcus Magnor
The rapid increase in the performance of graphics hardware, coupled with recent improvements in its programmability, have made graphics hardware a compelling platform for computationally demanding tasks in a wide variety of application domains. In this report, we describe, summarize, and analyze the latest research in mapping general-purpose computation to graphics hardware. We begin with the technical motivations that underlie general-purpose computation on graphics processors (GPGPU) and describe the hardware and software developments that have led to the recent interest in this field. We then aim the main body of this report at two separate audiences. First, we describe the techniques used in mapping general-purpose computation to graphics hardware. We believe these techniques will be generally useful for researchers who plan to develop the next generation of GPGPU algorithms and techniques. Second, we survey and categorize the latest developments in general-purpose application development on graphics hardware. This survey should be of particular interest to researchers who are interested in using the latest GPGPU applications in their systems of interest.
Preface
(The Eurographics Association, 2005) -; Yiorgos Chrysanthou and Marcus Magnor
Preface and Table of Contents
Real-Time Rendering of Cloudy Natural Phenomena with Hierarchical Depth Impostors
(The Eurographics Association, 2005) Ummenhoffer, Tamás; Szirmay-Kalos, László; John Dingliana and Fabio Ganovelli
This paper presents a real-time method to realistically render dynamic participating media under changing lighting conditions. In order to cope with performance requirements, the volume is built of instances of particle blocks. The simulation and rendering happen on two levels, on the block level and on the volume level. On the volume level blocks are replaced by depth impostors, which allows for very fast recalculation of the cloud illumination. Including depth information into block impostors our technique also eliminates billboard clipping artifacts when the participating medium contains objects. The proposed method can render swirling clouds and smoke on high frame rates, and can be used in real-time applications.
A Sharpness Dependent Approach to 3D Polygon Mesh Hole Filling
(The Eurographics Association, 2005) Chen, Chun-Yen; Cheng, Kuo-Young; Liao, H.Y. Mark; John Dingliana and Fabio Ganovelli
A sharpness dependent hole filling approach is proposed in this paper. The proposed method can fill the hole of a mesh-based model and recover its sharp feature located at the hole area. Interpolation based on radial basis function is applied to create a smooth implicit surface and this surface can approximate the shape of the missed data. Then, a regularized marching tetrahedral algorithm is adopted to triangulate the above implicit surface and to produce a polygonal hole patch. A repaired mesh model is obtained by stitching the hole patch and the hole boundary of the original model. Finally, a feature enhancement process is applied if there exists a sharp feature on the hole boundary of the original model. The introduction of a sharpness dependent filter enhances the sharp feature of a hole-filled model. Experiment results show that our approach can produce excellent reparation results especially for recovering sharp feature.
Preface
(The Eurographics Association, 2005) -; Jean-Jacques Bourdin and Hugh McCabe
Preface and Table of Contents

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