EG2006

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https://diglib.eg.org/handle/10.2312/253

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Efficient Sorting and Searching in Rendering Algorithms
(The Eurographics Association, 2006) Havran, Vlastimil; Bittner, Jiri; Nadia Magnenat-Thalmann and Katja Bühler
In the proposed tutorial we would like to highlight the connection between rendering algorithms and sorting and searching as classical problems studied in computer science. We will provide both theoretical and empirical evidence that for many rendering techniques most time is spent by sorting and searching. In particular we will discuss problems and solutions for visibility computation, density estimation, and importance sampling. For each problem we mention its specific issues such as dimensionality of the search domain or online versus offline searching. We will present the underlying data structures and their enhancements in the context of specific rendering algorithms such as ray shooting, photon mapping, and hidden surface removal.
HOPI: A Novel High Order Parametric Interpolation in 2D
(The Eurographics Association, 2006) Xu, Jia; Huang, Zhiyong; Dieter Fellner and Charles Hansen
This paper presents a novel smooth and convergent high order parametric interpolation method called HOPI with a formal treatment. It employs high order derivatives information and provides more freedom on control of curves. It can be applied to shape design and analysis using curves. This paper reports the work in 2D.
Long Distance Distribution of Educational Augmented Reality Applications
(The Eurographics Association, 2006) Kaufmann, Hannes; Csisinko, Mathis; Totter, Alexandra; Judy Brown and Werner Hansmann
For distance education utilizing shared Virtual or Augmented Reality (VR/AR) applications, reliable network distribution of educational content is of prime importance. In this paper we summarize the development of software components enabling stable and reliable distribution of an existing educational AR application for geometry education. Our efforts focus on three main areas: (1) For long distance distribution of Open Inventor scene graphs, throughout a wide area IP network, a TCP based network protocol was implemented in Distributed Open Inventor. (2) A tracking middleware was extended to support sending tracking data unicast instead or in addition to sending multicast messages. (3) Multiple adaptations in our geometry application were required to improve scalability, robustness and reliability. We present an early evaluation with high school students in a distant learning, distributed HMD setup and highlight final results.
Real-time Inhabited Virtual Worlds and Interaction - interactive virtual worlds module
(The Eurographics Association, 2006) Magnenat-Thalmann, Nadia; Papagiannakis, George; Egges, Arjan; Lyard, Etienne; Nadia Magnenat-Thalmann and Katja Bühler
Virtual Worlds [MK94] and their concept of cyber-real space interplay invoke such interactive digital narratives that promote new patterns of understanding. However, the "narrative" and "interactive" part, which refers to a set of events happening during a certain period of time and providing aesthetic, dramaturgical and emotional elements, objects and attitudes ([NM00], [TYK01]) is still an early topic of research. Mixing such aesthetic ambiences with interactive virtual character augmentations [CMM*03] and adding dramatic tension has developed very recently these narrative patterns into an exciting new edutainment medium [LHM03]. With the interplay of a modern real-time framework for integrated interactive virtual character simulation, we can enhance the experience with full virtual character simulations.
Rendering Plasma Phenomena: Applications and Challenges
(The Eurographics Association, 2006) Baranoski, G. V. G.; Rokne, J. G.; Brian Wyvill and Alexander Wilkie
Plasmas are ubiquitous in the Universe. An understanding of plasma phenomena is therefore of importance for almost every area of astrophysics, from stellar atmospheres to star clusters. Plasmas also occur in daily life both in industrial processes and in consumer products. Recent groundbreaking data is making this the golden age of plasma science. Although direct observations and analysis of data provide important physical evidence for plasma phenomena, they do not necessarily explain the phenomena. Hence, recent discoveries in this area might not only arise out of observations, but also from visual simulations of the phenomena supported by advanced rendering technologies. This report describes the state of art of such simulations, and examines practical issues often overlooked in the literature. Their educational and public outreach applications are also discussed. Although the emphasis is on the predictive rendering of plasma processes, the simulation guidelines and trade-offs addressed in this report can be extended to the general simulation of natural phenomena. The report closes with a discussion of further avenues of research involving the simulation of plasma phenomena.
3D Role-Playing Games as Language Learning Tools
(The Eurographics Association, 2006) Rankin, Yolanda; Gold, Rachel; Gooch, Bruce; Judy Brown and Werner Hansmann
Leveraging the experiential cognition and motivational factors of 3D games, we conduct a pilot study that utilizes Ever Quest 2 as pedagogical learning tool for English as a second language (ESL) students. We combine the benefits of massive multiplayer online role-playing games (MMORPGs) and second language methodology to create a digital learning environment for second language acquisition (SLA). Rather than using traditional computerassisted language learning (CALL) software, we explore the immersive, virtual environment of Ever Quest 2 as ESL participants assume virtual identities and engage in social interactions within the game world. We suggest that language becomes a crucial artifact for character development and completion of game tasks in the virtual world. Preliminary results demonstrate that Ever Quest 2 intermediate and advanced ESL students increase their English vocabulary by 40% as result of game play interactions with non-playing characters (NPCs). Furthermore, intermediate and advanced ESL students practice their conversational skills with playing characters (PCs), generating a 100% increase in chat messages during eight sessions of game play. These results lead to the conclusion that MMORPGs can provide motivation and adequate language learning support for intermediate and advanced ESL students.
Fast and Realistic Display of Clouds Using a Recording Matrix
(The Eurographics Association, 2006) Wu, Y.; Allgöwer, B.; Nüesch, D.; Dieter Fellner and Charles Hansen
For volumetric cloud models, traditional ray tracing methods and graphics hardware acceleration methods can result in photorealistic images, but with considerably expensive costs. Hence, real-time rendering can be achieved only under the condition of a static relationship between light sources and clouds. This paper presents a new method to accelerate the rendering process for animated clouds. In order to display visually convincing self-shading properties of clouds, multiple scattering among their internal particles is taken into account with the help of a recording matrix, which only requires small intermediate saving space. This method is not only flexible and easy to use, but also capable of rendering other dynamic gaseous phenomena such as smoke in a fast and efficient manner.
Geometric Modeling Based on Triangle Meshes
(The Eurographics Association, 2006) Botsch, Mario; Pauly, Mark; Rössl, Christian; Bischoff, Stephan; Kobbelt, Leif; Nadia Magnenat-Thalmann and Katja Bühler
In the last years triangle meshes have become increasingly popular and are nowadays intensively used in many different areas of computer graphics and geometry processing. In classical CAGD irregular triangle meshes developed into a valuable alternative to traditional spline surfaces, since their conceptual simplicity allows for more flexible and highly efficient processing. Moreover, the consequent use of triangle meshes as surface representation avoids error-prone conversions, e.g., from CAD surfaces to meshbased input data of numerical simulations. Besides classical geometric modeling, other major areas frequently employing triangle meshes are computer games and movie production. In this context geometric models are often acquired by 3D scanning techniques and have to undergo postprocessing and shape optimization techniques before being actually used in production.This course discusses the whole geometry processing pipeline based on triangle meshes. We will first introduce general concepts of surface representations and point out the advantageous properties of triangle meshes in Section 2, and present efficient data structures for their implementation in Section 3. The different sources of input data and types of geometric and topological degeneracies and inconsistencies are described in Section 4, as well as techniques for their removal, resulting in clean two-manifold meshes suitable for further processing. Mesh quality criteria measuring geometric smoothness and element shape together with the corresponding analysis techniques are presented in Section 6. Mesh smoothing reduces noise in scanned surfaces by generalizing signal processing techniques to irregular triangle meshes (Section 7). Similarly, the underlying concepts from differential geometry are useful for surface parametrization as well (Section 8). Due to the enormous complexity of meshes acquired by 3D scanning, mesh decimation techniques are required for error-controlled simplification (Section 9). The shape of triangles, which is important for the robustness of numerical simulations, can be optimized by general remeshing methods (Section 10). After optimizing meshes with respect to the different quality criteria, we finally present techniques for intuitive and interactive shape deformation (Section 11). Since solving linear systems is a commonly required component for many of the presented mesh processing algorithms, we will discuss their efficient solution and compare several existing libraries in Section 12.
Computer Graphics Applications in the Education Process of People with Learning Difficulties
(The Eurographics Association, 2006) Vera, Lucia; Campos, Ruben; Herrera, Gerardo; Sebastian, Beleu; Judy Brown and Werner Hansmann
This paper describes the use of Real Time graphic applications as educational tools, specifically oriented to working with people who have certain learning difficulties. We first focus on identifying the most relevant traits (from a psychological point of view) of those disorders, then we continue by analysing the advantages of graphics in Real Time in this context, and how they can be used to complement the conventional teaching methods. Finally, we review the main characteristics of two applications belonging to this category, which serve as a practical example of this encounter between education and technology.
Camera Control in Computer Graphics
(The Eurographics Association, 2006) Christie, Marc; Olivier, Patrick; Brian Wyvill and Alexander Wilkie
Progress in modeling, animation and rendering means that rich, high fidelity interactive virtual worlds are now commonplace. But as photographers and cinematographers know, achievement of the intended informational and aesthetic goals is highly dependent on the position and motion of the camera in relation to the elements of the scene. Camera control encompasses interactive approaches, semi-automatic camera positioning, and fully declarative approaches to the management of a user's viewpoint on a scene. Camera control is required in nearly all interactive 3D applications and presents a particular combination of technical challenges for which there have been a number of recent proposals (e.g. specific path-planning, management of occlusion, modeling of high-level communicative goals). We present, classify the approaches, analyze the requirements and limits of solving techniques and explore in detail the main difficulties and challenges in automatic camera control.
Solving Local Reflections: a Direct Methodology
(The Eurographics Association, 2006) Jeremias, P.; Chavarria, O.; Garcia, O.; Carrillo, X.; Cuñado, A.; Dieter Fellner and Charles Hansen
Reflection and refraction are key processes intended for realism within simulation platforms. There are several parameters related to those techniques whose values have been traditionally selected by using subjective criteria. This paper presents an interactive water rendering model where the adjustment of the local perturbation parameters has been revised, ensuring physical correctness. Therefore we present new tuning paradigms, based on physical, optical and, besides that, objective constraints.
Teaching, Exploring, Learning Developing Tutorials for In-Class Teaching and Self-Learning
(The Eurographics Association, 2006) Beckhaus, Steffi; Blom, Kristopher J.; Judy Brown and Werner Hansmann
This paper presents an experience report on a novel approach for a course on intermediate and advanced computer graphics topics. The approach uses Teachlet Tutorials, a combination of traditional seminar type teaching with interactive exploration of the content by the audience, plus development of self-contained tutorials on the topic. Additionally to a presentation, an interactive software tool is developed by the students to assist the audience in learning and exploring the topic's details. This process is guided through set tasks. The resulting course material is developed for two different contexts: a) for classroom presentation and b) as an interactive, self-contained selflearning tutorial. The overall approach results in a more thorough understanding of the topic both for the student teachers as well as for the class participants. In addition to detailing the Teachlet Tutorial approach, this paper presents our experiences implementing the approach in our Advanced Computer Graphics course, and presents the resultant varied projects. Most of the final Teachlet Tutorials were surprisingly good, and we had excellent feedback of the students on approach and course.
Graphics-Based Learning in First-Year Computer Science
(The Eurographics Association, 2006) Davis, Timothy A.; Judy Brown and Werner Hansmann
This paper proposes a method for teaching a first-year course in computer science using graphicsbased problems as the teaching medium. Specifically, we present a method for instruction in programming using a semester-long project of developing a ray tracer. This effort is part of a larger project, in which a broad range of undergraduate courses are taught using computer graphics as the motivating application. An overview of this project is provided, along with description and results from the first trial CS2 course instructed using this technique.
Lighting-Up Geometry: Accurate 3D Modelling of Museum Artifacts with a Torch and a Camera
(The Eurographics Association, 2006) Vogiatzis, G.; Hernández, C.; Cipolla, R.; Dieter Fellner and Charles Hansen
This paper addresses the problem of obtaining complete, very detailed reconstructions of shiny objects such as glazed ceramics. We present an algorithm which uses silhouettes of the object, as well as images obtained under changing illumination conditions. In contrast with previous photometric stereo techniques, ours is not limited to a single viewpoint but produces accurate reconstructions in full 3D. A number of images of the object are obtained from multiple viewpoints, under varying lighting conditions. Starting from the silhouettes, the algorithm recovers camera motion and constructs the object s visual hull. This is then used to recover the illumination and initialise a multi-view photometric stereo scheme to obtain a closed surface reconstruction. The algorithm has been implemented as a practical model acquisition system. Here, we present a number of complete reconstructions of challenging real objects.
GPU-Based Hierarchical Texture Decompression
(The Eurographics Association, 2006) Stachera, J.; Rokita, P.; Dieter Fellner and Charles Hansen
We propose a hierarchical texture compression algorithm for real-time decompression on the GPU. Our algorithm is characterized by low computational complexity, random access and hierarchical structure which allow us to access first three levels of encoded mip-map pyramid. The hierarchical texture compression algorithm HiTCg is based on block-wise approach, where each block is subject to local fractal transform.
Fast Skeletal Animation by skinned Arc-Spline based Deformation
(The Eurographics Association, 2006) Forstmann, Sven; Ohya, Jun; Dieter Fellner and Charles Hansen
Presented is a novel skeletal animation system for providing high quality geometric deformations in real-time. Each bone of the skeleton is therefore represented by a spline, rather than using conventional matrix rotation. In our approach, each vertex of the animated character can be influenced by a maximum of three spline-curves, which is sufficient for skinned animation. One spline is parameterized by three control points and a possible twist. As opposed to conventional Bézier curves does our arc-spline rely on trigonometric functions for providing better curvatures. The optimized implementation using the OpenGL-shading language shows very promising results for real-time character animation, as even about 1 Million vertices were able to be transformed at interactive 43 frames per second on a GeForce 7800 GTX graphics card.
A Programmable Tutor for OpenGL Transformations
(The Eurographics Association, 2006) Andújar, Carlos; Vázquez, Pere-Pau; Judy Brown and Werner Hansmann
Computer Graphics is a growing field that is becoming more and more present in Computer Science studies at University level. This has lead to the creation of a large number of support materials, such as tutorials, white papers, and teaching books. Geometric transforms is commonly one of the topics that all Computer Graphics courses must deal with, and, traditionally, is one of the issues that students find difficult to master. Some of the problems come from the difficulty of using a blackboard to represent 3D objects, and it is therefore very convenient to have tutorial applications that are able to help through the learning process. In light of this, we have built a geometric transformation tutor that is intended to improve student understanding of the operations that are carried out on the OpenGL transformation matrices, and the results in terms of visualization. The application achieves a nice balance between the flexibility provided by a script language and the easiness of use. A key benefit of the application is the possibility of writing interactive tutorials demonstrating topics such as camera and object animation.
Clothing the Masses: Real-Time Clothed Crowds With Variation
(The Eurographics Association, 2006) Dobbyn, S.; McDonnell, R.; Kavan, L.; Collins, S.; O'Sullivan, C.; Dieter Fellner and Charles Hansen
The animation and rendering of crowds of realistically clothed characters presents a difficult challenge in computer graphics, which is further exacerbated when real-time frame rates are required. To date, due to real-time constraints, standard skinning methods have been used to animate the clothes of individuals in real-time crowds, which does not create the appropriate secondary motion for flowing garments. However, plausible cloth simulation is vital for the depiction of realistic characters, so we have developed a novel crowd system in which the individuals are endowed with realism and variety through the addition of physically simulated clothing and hardware assisted pattern variation.
Competitive Runtime Performance for Inverse Kinematics Algorithms using Conformal Geometric Algebra
(The Eurographics Association, 2006) Hildenbrand, Dietmar; Fontijne, Daniel; Wang, Yusheng; Alexa, Marc; Dorst, Leo; Dieter Fellner and Charles Hansen
Conformal geometric algebra is a powerful tool to find geometrically intuitive solutions. We present an approach for the combination of compact and elegant algorithms with the generation of very efficient code based on two different optimization approaches with different advantages, one is based on Maple, the other one is based on the code generator Gaigen 2. With these results, we are convinced that conformal geometric algebra will be able to become fruitful in a great variety of applications in Computer Graphics.
GPUGI: Global Illumination Effects on the GPU
(The Eurographics Association, 2006) Szirmay-Kalos, Laszlo; Szecsi, Laszlo; Sbert, Mateu; Nadia Magnenat-Thalmann and Katja Bühler
In this tutorial we explain how global illumination rendering methods can be implemented on Shader Model 3.0 GPUs. These algorithms do not follow the conventional local illumination model of Di- rectX/OpenGL pipelines, but require global geometric or illumination information when shading a point. In addition to the theory and state of the art of these approaches, we go into the details of a few algorithms, including mirror reflections, reflactions, caustics, diffuse/glossy indirect illumination, precomputation aided global illumination for surface and volumetric models, obscurances and tone mapping, also giving their GPU implementation in HLSL or Cg language.

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