EG2005

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https://diglib7.eg.org/handle/10.2312/247

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A 3D Perceptual Metric using Just-Noticeable-Difference
(The Eurographics Association, 2005) Cheng, Irene; Boulanger, Pierre; John Dingliana and Fabio Ganovelli
In multimedia applications, it is essential to distribute resources efficiently among different types of data in order to optimize overall quality. We propose a perceptual metric using Just-Noticeable-Difference (JND) to identify redundant mesh data so that available bandwidth can be allocated to improve texture resolution. Evaluation of perceptual impact during runtime is based on statistics in a lookup table generated during preprocessing. If the impact is less than the JND, no mesh refinement is performed. We apply Weber s fraction to compute the JND threshold, which is verified by perceptual evaluations. Experimental result shows that our JND model can accurately predict perceptual impact based on the human visual system.
Carving, Painting, and Printing with a Pen Tablet
(The Eurographics Association, 2005) Mizuno, Shinji; Kobayashi, Daigo; Okada, Minoru; Toriwaki, Junichiro; Yamamoto, Shinji; John Dingliana and Fabio Ganovelli
We discuss on an interactive CG system with a pressure sensitive pen tablet. This system is based on the virtual sculpting and printing method which are simulations of real sculpting and woodblock printing. In the sculpting process, the user operates virtual chisels with a pen to carve a virtual wooden object which has a 3D shape. The user can control the carving depth and the carving angle to the surface of the object with the pressure applied to the pen. In the painting process, the user paints ink with a pen on a 3D virtual sculpture created in the sculpting process. The painting result is determined by the surface shape of the sculpture and the pressure to the pen. In the printing process, a pen is used to operate a Japanese printing squeegee, Baren. The user can control the thickness of the print by changing the thickness of ink on the virtual woodblock and the pressure of printing operation.
Collision Handling in Dynamic Simulation Environments
(The Eurographics Association, 2005) Teschner, M.; Heidelberger, B.; Manocha, D.; Govindaraju, N.; Zachmann, G.; Kimmerle, S.; Mezger, J.; Fuhrmann, A.; Ming Lin and Celine Loscos
This tutorial will discuss collision detection algorithms with a special emphasis on the provided collision information. The potential combination with collision response schemes will be explained which is particular important for using collision detection algorithms in dynamic simulation environments. The tutorial will cover a large variety of relevant techniques. The tutorial starts with basic concepts, such as boundingvolume hierarchies, spatial partitioning, distance fields, and proximity queries. The idea of image-space collision detection is derived as a special case of spatial partitioning and it is illustrated how graphics hardware can be used to accelerate these methods. Based on the provided collision information, the potential combination with collision response schemes will be discussed for all techniques. The tutorial proceeds with further collision detection challenges that are particular important for dynamic simulation environments. Approaches to self-collision detection, as they can occur in deformable modeling, will be discussed. Stochastic methods, that can be used for time-critical collision detection, will be explained. Further, continuous collision detection will be introduced which aims at solving problems related to discrete-time simulations.
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.
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.
Deforming and Animating Discretely Sampled Object Representations
(The Eurographics Association, 2005) Chen, M.; Correa, C.; Islam, S.; Jones, M. W.; Shen, P.-Y.; Silver, D.; Walton, S. J.; Willis, P. J.; Yiorgos Chrysanthou and Marcus Magnor
A discretely sampled object representation (DSOR) defines a graphical model using data obtained by a sampling process, which takes a collection of samples at discrete positions in space in order to capture certain geometrical and physical properties of one or more objects of interest. Examples of DSORs include images, videos, volume datasets and point datasets. Unlike many commonly used data representations in computer graphics, DSORs lack in geometrical, topological and semantic information, which is much needed for controlling deformation and animation. Hence it poses a significant scientific and technical challenge to develop deformation and animation methods that operate upon DSORs. Such methods can enable computer graphics and computer animation to benefit enormously from the advances of digital imaging technology. In this state of the art report, we survey a wide-range of techniques that have been developed for manipulating, deforming and animating DSORs. We consider a collection of elementary operations for manipulating DSORs, which can serve as building blocks of deformation and animation techniques. We examine a collection of techniques that are designed to transform the geometry shape of deformable DSORs and pay particular attention to their deployment in surgical simulation. We review a collection of techniques for animating digital characters in DSORs, focusing on recent developments in volume animation.
Differential Photon Mapping - Consistent Augmentation of Photographs with Correction of all Light Paths
(The Eurographics Association, 2005) Grosch, Thorsten; John Dingliana and Fabio Ganovelli
Augmenting images with consistent lighting is possible with differential rendering. This composition technique requires two lighting simulations, one simulation with only real geometry and another one with additional virtual objects. The difference of the two simulations can be used to modify the original pixel colors. The main drawback of differential rendering is that not all modified light paths can be displayed: The result of the lighting simulation is visible in a reflective object instead of the real environment, augmented with virtual objects. Moreover, many regions in the photograph remain unchanged and the same work is done twice without any visual effect. In this paper we present a new approach for augmenting a photograph with only a single photon mapping simulation. The changes in lighting introduced by a virtual object are directly simulated using a differential photon map. All light paths intersecting the virtual object are corrected. To demonstrate the correctness of our approach, we compare our simulation results with real photographs.
Efficient Architecture for Low-Cost Adaptive 3D Graphics-Based E-Learning Applications
(The Eurographics Association, 2005) Salgado, Luis; Bescos, Jesus; Moran, Francisco; Cabrera, Julian; Estalayo, Enrique; Cubero, Jose; Jean-Jacques Bourdin and Hugh McCabe
This work describes the design and implementation of the Virtual Reality Tool (VRT), a core component within the educational platform developed for the European research project IST-2001-33184, SLIM-VRT (Self Learning Integrated Methodology Virtual Reality Tool). The main objective of this project is to propose an alternative for integrated maritime self-learning on board and ashore based on the use of interactive multimedia and low-cost 3D graphics technologies. The integration of the Virtual Reality Tool in the educational platform involves the incorporation of 3D graphic experiences to the educational process. Based on VRML and other standard tools, the VRT-enabled case studies are used for those learning activities in which the students interact with a virtual environment either to access multimedia information associated to relevant objects/devices in the scene, or to manipulate those devices to carry out specific simulations of operational tasks identified in the case study. With the aim of fulfilling the user s requirements and learning needs identified within this field of application, the design of the VRT has required specific developments to overcome VRML limitations and make it possible to: (i) customize dynamically both the education programme and the multimedia content according to the specific user s and terminal profiles; (ii) manage efficiently the interactivity with the virtual environment to adapt in realtime the learning process, according to student s actions; and (iii) design and implement multiple case studies based on the same virtual environments, thus minimizing the modelling effort.
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.
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
Estimating Mobile Memory Requirements and Rendering Time for Remote Execution of the Graphics Pipeline
(The Eurographics Association, 2005) Banerjee, Kutty; Wu, Fan; Agu, Emmanuel; John Dingliana and Fabio Ganovelli
Mobile devices have limited processing power, memory and battery power. Remote execution, wherein part or entire graphics pipeline is offloaded to a powerful surrogate server, is an attractive solution for low end mobile devices such as PDAs and cell phones that lack floating point units or GPUs. We have found that remote execution of floating-point-intensive pipeline stages such as transform and geometry operations can produce speedups of up to 10 times for a low-end mobile device. We introduce generalized pipeline-splitting, a paradigm whereby 15 sub-stages of the graphics pipeline are instrumented with networking code such that they can run either on a mobile client or a surrogate server. To validate our concepts, we create Remote Mesa (RMesa). As a foundation for deciding which stages of the pipeline would benefit from remote execution, this paper presents analytical models for the overall rendering time, memory requirements and roundtrip network delay incurred by RMesa.
Facial Motion Cloning Using Global Shape Deformation
(The Eurographics Association, 2005) Fratarcangeli, Marco; Schaerf, Marco; John Dingliana and Fabio Ganovelli
We present a novel Facial Motion Cloning method relying on the combination of the radial basis functions (RBF) based scattered data interpolation with the encoding capabilities of the MPEG-4 Facial and Body Animation (FBA) international standard. Beside from an initial manual selection of feature points, our method works fully automatically without user interaction. The produced talking head is able to perform generic face animation which is stored in a MPEG-4 FBA data stream.
Fast and Controllable 3D Modelling From Silhouettes
(The Eurographics Association, 2005) Prasad, Mukta; Fitzgibbon, Andrew; Zisserman, Andrew; John Dingliana and Fabio Ganovelli
We show how a 3D model of a complex curved object can be easily extracted from a single 2D image. A userdefined silhouette is the key input; and we show that finding the smoothest 3D surface which projects exactly to this silhouette can be expressed as a quadratic optimization, a result which has not previously appeared in the large literature on the shape-from-silhouette problem. For simple models, this process can immediately yield a usable 3D model; but for more complex geometries the user will wish to further shape the surface. We show that a variety of editing operations which can be defined either in the image or in 3D can also be expressed as linear constraints on the 3D shape parameters. We extend the system to fit higher genus surfaces. Our method has several advantages over the system of Zhang et al. [ZDPSS01] and over systems such as SKETCH and Teddy.
Fast Body-Cloth simulation with moving humanoids
(The Eurographics Association, 2005) Rodriguez-Navarro, Javier; Sainz, Miguel; Susin, Antonio; John Dingliana and Fabio Ganovelli
In this paper we present a very fast method for body-cloth animation. The usual bottle-neck in cloth simulation performance is collision detection, which becomes more difficult to solve when a complex geometry, like a human body, is involved. Recent image based methods, that use depth images to detect collisions, usually relays on CPU for collision correction. In our work we implement a GPU based simulation that takes care both of cloth simulation and body-cloth collisions when the humanoid is moving. Our solution is based on a hierarchic depth map structure. A high frame rate is obtained with both structured and unstructured cloth meshes with thousands of particles.
Function-based Shape Modeling Framework in Multilevel Education
(The Eurographics Association, 2005) Pasko, A.; Adzhiev, V.; Goto, Y.; Vilbrandt, C.; Jean-Jacques Bourdin and Hugh McCabe
We describe how an approach to the development of a shape modeling and visualization framework based on the rapidly progressing function representation can be used in education. The modeling language and software tools are being developed within an international HyperFun Project. We applied the theoretical framework and software tools on different levels of education starting from elementary schools to doctoral thesis research in various areas related to mathematics, computer graphics, programming languages, artistic design and animation. We illustrate the presented approach by the practical experience examples from different educational institutions and countries
High Dynamic Range Techniques in Graphics: from Acquisition to Display
(The Eurographics Association, 2005) Goesele, Michael; Heidrich, Wolfgang; Höfflinger, Bernd; Krawczyk, Grzegorz; Myszkowski, Karol; Trentacoste, Matthew; Ming Lin and Celine Loscos
This course is motivated by tremendous progress in the development and accessibility of high dynamic range technology (HDR) that happened just recently, which creates many interesting opportunities and challenges in graphics. The course presents a complete pipeline for HDR image and video processing from acquisition, through compression and quality evaluation, to display. Also, successful examples of the use of HDR technology in research setups and industrial applications are provided. Whenever needed relevant background information on human perception is given which enables better understanding of the design choices behind the discussed algorithms and HDR equipment.
Illustrative Visualization
(The Eurographics Association, 2005) Viola, Ivan; Gröller, Meister E.; Hadwiger, Markus; Bühler, Katja; Preim, Bernhard; Ebert, David; Ming Lin and Celine Loscos
The tutorial presents state-of-the-art visualization techniques inspired by traditional technical and medical illustrations. Such techniques exploit the perception of the human visual system and provide effective visual abstractions to make the visualization clearly understandable. Visual emphasis and abstraction has been used for expressive presentation from prehistoric paintings to nowadays scientific and medical illustrations. Many of the expressive techniques used in art are adopted in computer graphics, and are denoted as illustrative or non-photorealistic rendering. Different stroke techniques, or brush properties express a particular level of abstraction. Feature emphasis or feature suppression is achieved by combining different abstraction levels in illustrative rendering. Challenges in visualization research are very large data visualization as well as multi-dimensional data visualization. To effectively convey the most important visual information there is a significant need for visual abstraction. For less relevant information the dedicated image space is reduced to enhance more prominent features. The discussed techniques in the context of scientific visualization are based on iso-surfaces and volume rendering. Apart from visual abstraction, i.e., illustrative representation, the visibility of prominent features can be achieved by illustrative visualization techniques such as cut-away views or ghosted views. The structures that occlude the most prominent information are suppressed in order to clearly see more interesting parts. Another smart way to provide information on the data is using exploded views or other types of deformation. Illustrative visualization is demonstrated via application-specific tasks in medical visualization. An important aspect as compared to traditional medical illustrations is the interactivity and real-time manipulation of the acquired patient data. This can be very useful in anatomy education. Another application area is surgical planning which is demonstrated with two case studies: neck dissection and liver surgery planning.
Image Reconstruction Invariant to Relighting
(The Eurographics Association, 2005) Georgiev, Todor; John Dingliana and Fabio Ganovelli
This paper describes an improvement to the Poisson image editing method for seamless cloning. Our approach is based on minimizing an energy expression invariant to relighting. The improved method reconstructs seamlessly the selected region, matching both pixel values and texture contrast of the surrounding area, while previous algorithms matched pixel values only. Our algorithm solves a deeper problem: It performs reconstruction in terms of the internal working mechanisms of human visual system. Retinex-type effects of adaptation are built into the structure of the mathematical model, producing results that change covariantly with lighting.
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.
Improving the Experience of Scenes with a Large Field of View using Shift Lens Perspective
(The Eurographics Association, 2005) Hoeben, Aldo; Stappers, Pieter Jan; John Dingliana and Fabio Ganovelli
In interactive computer graphics such as games and interactive panoramic photos, users are often presented a view with a larger field of view than would correspond to the distance to and size of the screen on which the graphics are viewed. This makes looking at the scene a less claustrophobic experience, showing more of the environment than that which is strictly ahead. In many applications however, where the goal is to get a sense of presence and ambiance of the depicted scene, the large field of view distracts the observer with extreme converging lines when looking up or down. Even though these converging lines are perspectively correct, the resulting image does not match the way we normally perceive the world around us. In this paper we discuss modifying the perspective to reduce the distortions caused by the large field of view, to enhance the experience of these scenes.

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