EG2005

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

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Virtual Reality Course - A Natural Enrichment of Computer Graphics Classes
(The Eurographics Association, 2005) Zara, J.; Jean-Jacques Bourdin and Hugh McCabe
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, the 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 six years. Our experience clearly demonstrates that students appreciate its contents even if they already completed courses on 3D graphics.
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.
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 Marching Cubes on the Vertex Shader
(The Eurographics Association, 2005) Goetz, Frank; Junklewitz, Theodor; Domik, Gitta; John Dingliana and Fabio Ganovelli
In this paper we propose a new approach for visualizing volumetric datasets by their isosurfaces. For an interactive isosurface reconstruction an optimized version of the well-known marching cubes algorithm is used. We extend the original algorithm by an additional vertex shader program. Contrary to other hardware-accelerated solutions our program is not based on a tetrahedral algorithm and thus the implementation for structured grids is more effective. Furthermore, surfaces of time-varying datasets at distinguished threshold values can be extracted in real-time.
Preface
(The Eurographics Association, 2005) -; John Dingliana and Fabio Ganovelli
Preface and Table of Contents
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.
Proactive Steering Toward Oriented Targets
(The Eurographics Association, 2005) Boulic, Ronan; 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.
Preface
(The Eurographics Association, 2005) Boulic, Ronan; Ronan Boulic
Preface
Walking with Pens
(The Eurographics Association, 2005) Kolhoff, Philipp; Preuß, Jacqueline; Loviscach, Jörn; John Dingliana and Fabio Ganovelli
Believable 3D animation of walking or running characters still requires complex motion capture technology or extensive skills in manual keyframing. We present an inexpensive, yet natural input method: The user walks on a digital graphics tablet, striding over the surface with two pens in his or her hands, where each pen represents one leg. This technique leverages the popular graphics tablets that can track two drawing tools at the same time. We implemented recording software and a plug-in to use the data in off-the-shelf 3D animation software.
Simulation of Light Interaction with Human Skin
(The Eurographics Association, 2005) Baranoski, G.V.G.; Krishnaswamy, A.; Ming Lin and Celine Loscos
Despite the notable progress in physically-based rendering, there is still a long way to go before one can automatically generate predictable images of organic materials such as human skin. In this tutorial, the main physical and biological aspects involved in the processes of propagation and absorption of light by skin tissues are examined. These processes affect not only skin s appearance, but also its health. For this reason, they have also been the object of study in biomedical research. The models of light interaction with human skin developed by the biomedical community are mainly aimed at the simulation of skin spectral properties which are used to determine the concentration and distribution of various natural pigments. In computer graphics, the focus has been on the simulation of light scattering properties that affect skin appearance. Computer models used to simulate these spectral and scattering properties are described, and their strengths and limitations examined in detail in this tutorial. The emphasis of the discussions is on the predictive rendering of human skin, and open problems and new avenues of research in this area are also addressed.
Preface
(The Eurographics Association, 2005) -; Jean-Jacques Bourdin and Hugh McCabe
Preface and Table of Contents
Leaf Cluster Impostors for Tree Rendering with Parallax
(The Eurographics Association, 2005) Garcia, Ismael; Sbert, Mateu; Szirmay-Kalos, László; John Dingliana and Fabio Ganovelli
This paper presents a simple method to render complex trees on high frame rates while maintaining parallax effects. Based on the recognition that a planar impostor is accurate if the represented polygon is in its plane, we find an impostor for each of those groups of tree leaves that lie approximately in the same plane. The groups are built automatically by a clustering algorithm. Unlike billboards, these impostors are not rotated when the camera moves, thus the expected parallax effects are provided. On the other hand, clustering allows the replacement of a large number of leaves by a single semi-transparent quadrilateral, which improves rendering time considerably. Our impostors well represent the tree from any direction and provide accurate depth values, thus the method is also good for shadow computation.
Multimodal Interfaces: an Introduction to ENACTIVE systems
(The Eurographics Association, 2005) Bergamasco, Massimo; Ming Lin and Celine Loscos
Enactive Interfaces are related to a fundamental "interaction" concept which is not exploited by most of the existing human-computer interface technologies. The traditional interaction with the information mediated by a computer is mostly based on symbolic or iconic knowledge, and not on enactive knowledge. While in the symbolic way of learning knowledge is stored as words, mathematical symbols or other symbol systems, in the iconic stage knowledge is stored in the form of visual images, such as diagrams and illustrations that can accompany verbal information. On the other hand, enactive knowledge is a form of knowledge based on the active use of the hand for apprehension tasks. Enactive knowledge is not simply multisensory mediated knowledge, but knowledge stored in the form of motor responses and acquired by the act of "doing". A typical example of enactive knowledge is constituted by the competence required by tasks such as typing, driving a car, dancing, playing a musical instrument, modelling objects from clay, which would be difficult to describe in an iconic or symbolic form. This type of knowledge transmission can be considered the most direct, in the sense that it is natural and intuitive, since it is based on the experience and on the perceptual responses to motor acts.
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
A Scalable Hardware and Software System for the Holographic Display of Interactive Graphics Applications
(The Eurographics Association, 2005) Balogh, Tibor; Forgács, Tamás; Agács, Tibor; Balet, Olivier; Bouvier, Eric; Bettio, Fabio; Gobbetti, Enrico; Zanetti, Gianluigi; John Dingliana and Fabio Ganovelli
We present a scalable holographic system design targeting multi-user interactive computer graphics applications. The display uses a specially arranged array of micro-displays and a holographic screen. Each point of the holographic screen emits light beams of different color and intensity to the various directions, in a controlled manner. The light beams are generated through a light modulation system arranged in a specific geometry and the holographic screen makes the necessary optical transformation to compose these beams into a perfectly continuous 3D view. With proper software control, the light beams leaving the various pixels can be made to propagate in multiple directions, as if they were emitted from physical objects at fixed spatial locations. The display is driven by DVI streams generated by multiple consumer level graphics boards and decoded in real-time by image processing units that feed the optical modules at high refresh rates. An OpenGL compliant library running on a client PC redefines the OpenGL behavior to multicast graphics commands to server PCs, where they are re-interpreted for implementing holographic rendering. The feasibility of the approach has been successfully evaluated with a working hardware and software 7.4M pixel prototype driven at 10-15Hz by three DVI streams.
Rendering Realistic Trees and Forests in Real Time
(The Eurographics Association, 2005) Candussi, Alberto; Canduss, Nicola; Höllerer, Tobias; John Dingliana and Fabio Ganovelli
Real-Time rendering of realistic trees on common graphics hardware represents a big challenge due to their inherent geometric complexity. In most cases, trees are composed of hundreds of thousands of leaves and branches with complex lighting interrelations. We present novel techniques to render and animate photorealistic trees in real-time. The described techniques are easily implemented with commonly available graphics cards, making them suitable to applications such as visual simulations and video games. Polygon counts are significantly reduced by the use of simplified textured geometry for minor branches and billboarded leaf textures. Fast and realistic lighting and shadowing of the leaves and surroundings enhances realism. We animate the tree branches and leaf textures using simple vertex shaders, creating a realistic effect of the tree swaying in the wind. Discrete levels of detail allow rendering of a large number of trees, making it possible to represent realistic forest scenes made of 1000-1500 trees.
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.
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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