EG2002

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3D Data Acquisition
(Eurographics Association, 2002) Scopigno,Roberto; Andujar, Carlos; Goesele,Michael; Lensch, Hendrik P. A.
3D scanners and image acquisition systems are rapidly becoming more affordable and allow to build highly accurate models of real 3D objects in a cost- and time-effective manner. This tutorial will present the potential of this technology, review the state of the art in model acquisition methods, and will discuss the 3D acquisition pipeline from physical acquisition until the final digital model. First, different scanning techniques such as time-of-flight or structured light approaches will briefly be presented. Other acquisition related issues including the design of the scanning studio will be discussed and evaluated. In the area of registration, we will consider both the problems of initially aligning individual scans, and of refining this alignment with variations of the Iterative Closest Point method. For scan integration and mesh reconstruction, we will compare various methods for computing interpolating and approximating surfaces. We will then look at various ways in which surface properties such as color and reflectance can be extracted from acquired imagery. Finally, we will examine techniques for the efficient management and rendering of very large, attribute-rich meshes, including methods for the construction of simplified triangle-based representation and sample-based rendering approaches.
3D Scanning Technology: Capabilities and Issues
(Eurographics Association, 2002) Scopigno, Roberto
The recent evolution of graphics technology makes it possible to manage very complex models on inexpensive platforms. These impressive rendering capabilities should be paired with detailed and accurate digital models. The construction of high quality 3D models is made easier by the increasing diffusion of automatic 3D measuring devices (often called 3D scanners). These allow to build highly accurate models of real 3D objects in a cost- and time-effective manner. The talk will present the capabilities of this technology focusing mainly on a particular application context: the acquisition of Cultural Heritage artifacts. The peculiar requirements of this domain (high accuracy in the acquisition of both shape and surface appearance, expected low cost and easiness of use of the tools) make it a perfect application example. This talk aims also at presenting and discussing the main issues in the acquisition of accurate 3D models, together with some limitations of current hardware and software tools. Some examples of the results of current projects will be shown.
Adaptive Compression of Human Animation Data
(Eurographics Association, 2002) Ahmed, Amr Adel Hassan; Hilton, Adrian; Mokhtarian, Farzin
In this paper we introduce an adaptive motion compression technique using the discrete wavelet transform. Based on the analysis of human animation data, and its frequency contents, the wavelet analysis is utilised to achieve motion compression. It has been found that even with high compression ratios (up to 86%), the compressed animation is visually very close to the original animation. This property is potentially useful for many areas of animation such as motion interpolation/blending and networked virtual environments. One of our motivations is that motion blending/interpolation between motion capture samples is one of the successful techniques for synthesis of novel realistic human animation. One of the major concerns of that method is the increase of the database size with the large number of samples required to synthesise a wide range of movements. Previous research has addressed this issue by trying to reduce the number of samples required for interpolation. The approach that we introduce in this paper is to reduce the individual sample’s size using compression. Integration of both these approaches promises to allow a realistic animation with reduced database size. In networked virtual environments and on-line games, compressing the animation data can reduce the transmission load and help in achieving real-time performance and realism with reduced cost.
Adaptive Tessellation for Trimmed NURBS Surface
(Eurographics Association, 2002) YingLiang, Ma; Hewitt, Terry
We present an adaptive method for tessellating the trimmed NURBS surface in the parametric domain. Given a model space tolerance ε, the algorithm first splits the NURBS surface in both the U and V directions to fit within the bounding box of the outer trimming loop. Then we subdivide the surface into Bézier patches recursively until the control net of the Bézier patch is flat enough and within the tolerance ε. By building up the quadtrees of inner trimming loops, we use the scanline algorithm to remove the patches inside the inner trimming loops. Finally, we close the inner trimming loops with a set of triangles. The resulting tessellation contains both quadrilaterals and triangles.
Artificial Animals and Humans: From Physics to Intelligence
(Eurographics Association, 2002) Terzopoulos, Demetri
The confluence of virtual reality and artificial life, an emerging discipline that spans the computational and biological sciences, has yielded synthetic worlds inhabited by realistic, artificial flora and fauna. Artificial animals are complex synthetic organisms that possess functional biomechanical bodies, sensors, and brains with locomotion, perception, behavior, learning, and cognition centers. Artificial humans and other animals are of interest in computer graphics because they are self-animating characters that dramatically advance the state of the art of production animation and interactive game technologies. More broadly, these biomimetic autonomous agents in their realistic virtual worlds also foster deeper, computationally oriented insights into natural living systems.
Automated Enhancement of 3D Models
(Eurographics Association, 2002) Torres-Mendez, L.A.; Dudek, G.
The acquisition of a 3D model of a real environment can be accomplished using range sensors. In practice, suitable sensors to densely cover a large environment are often impractical. This paper presents ongoing work on the synthesis of 3D environment models from as little as one intensity image and sparse range data. Our method is based on interpolating the available range data using statistical inferences learned from the available intensity image and from those (sparse) regions where both range and intensity information is available. Since we compute the relationship between extisting range data and the images we start with, we do not need to make any strong assumptions about the kind of surfaces in the world (for example we do not need to assume the world exhibits only diffuse reflectance). Experimental results show the feasibility of our method.
Automatic Data Acquisition and Visualization for Usability Evaluation of Virtual Reality Systems
(Eurographics Association, 2002) Holm, Roland; Priglinger, Markus; Stauder, Erwin; Volkert, J.; Wagner, R.
Evaluating the usability of a Virtual Reality system is a common practice nowadays. However, gathering and analyzing the necessary data are time-consuming tasks and sometimes involve inconvenient changes to the system. The VR-based safety training system SAVE suffered from this problem. Therefore, independent modules have been developed to acquire and visualize usability relevant data to allow extensive evaluation sessions to be performed efficiently. Interaction and simulation data is acquired automatically and joined with external physiological data to be visualized inside a complete 3D representation of the training scenario. Visualizations can be performed in real-time while acquiring the data during a session, or from recorded data after the session has been completed. Because the visualization is coupled with a VR authoring tool, it is also possible to analyze the usability of a VR scenario and perform changes instantly.
Cloth Animation and Rendering
(Eurographics Association, 2002) Hauth, Michael; Etzmuss, Olaf; Eberhardt, Bernd; Klein, Reinhard; Sarlette, Ralf; Sattler, Mirko; Daubert, Katja; Kautz, Jan
The area of physically-based modeling is situated in the intersection of computer science, mathematics, and physics. The animation of cloth is a particularly interesting application of physically-based modeling, because it aims at fast animation solutions for rather difficult physical problems. Moreover, it addresses one of the major difficulties in creating realistic scenes with virtual actors. The challenge of computer animation is to break down physical models for complex structures as textiles, approximate them efficiently, and run fast simulations with intelligent numerical methods. Furthermore, interactivity and collisions with other objects in the scene are challenges that have motivated much creative work over the recent years. The range of methods proposed in literature is quite large. The techniques vary from simplified methods designed for real-time applications to sophisticated methods that were designed to reproduce measured material properties. Rendering cloth is especially difficult because of its complex material properties. Software rendering can deal with these properties fairly easily, once they have been acquired, but remains too slow for interactive applications. Hardware accelerated rendering often provides a way to achieve interactive renderings, unfortunately complex materials aren’t directly supported. We will demonstrate how interactive rendering with complex materials can nonetheless be achieved
Concise Tour to the Virtual Old Prague
(Eurographics Association, 2002) Zara, Jiri
This paper describes a structure and a user interface of the Internet based 3D presentation of existing historical part of city Prague. The application offers a smooth tour to selected regions of the real city, utilizing number of standard and modern technologies including VRML, Java, and PHP. The architecture of the whole virtual model is presented together with several advanced and specific features like dynamic loading und unloading objects or newly proposed LOD for urban scenes. This running web application seems to be currently unique in terms of complexity, functionality, and scaleability for further growth. The paper introduces methodology suitable for immediate creation of arbitrary virtual city according to a real one.
A Convolution-Based Algorithm for Animated Water Waves
(Eurographics Association, 2002) Loviscach, Jörn
A non-linear partial differential equation solver is too sophisticated for computer graphics applications if they are only used to render effects like circular waves and ship wakes. We present an approach which simulates waves through a convolution algorithm. It handles both gravity waves and capillary waves; the latter are often neglected even though they dominate small-scale behavior. The algorithm can be integrated into a complete solution architecture: First, standard commercial 3-D software is used to prepare an animated scene with objects traveling on a water surface. Based on the movements of these objects, waves are calculated and added as bump and displacement maps to the 3-D model.
Dependent Tests Driven Filtering in Monte-Carlo Global Illumination
(Eurographics Association, 2002) Csonka, Ferenc; Szirmay-Kalos, Laszlo; Kelemen, Csaba; Antal, György
This paper presents a multi-phase algorithm to solve the global illumination problem. In the first phase dependent tests are applied, i.e. the random walks of different pixels are built from the same random numbers. The result of the first phase is used to identify homogeneous pixel groups in the image. The criterion of the formation of such groups is that averaging the color inside these groups should result in less error than handling the pixels independently. The second phase of the algorithm is a conventional random walk method that uses independent random samples in different pixels. The final result is calculated as the average of the results of the dependent tests and the lowpass filtered version of the independent tests. This low-pass filter averages the pixel values inside the homogenous groups. The algorithm takes advantage of the fact that the image can contain larger homogeneous regions that can be calculated from much less number of samples. Thus we can focus on those pixels where significant changes happen.
Digital Watermarking for Volumetric Datasets
(Eurographics Association, 2002) Dimitrov, Leonid I.; Sramek, Milos
An idea for digitaly watermarking volumetric datasets (VDS) and preliminary results from a test implementation are presented. It consists of a combination of filtering and rendering operations on volumetric data allowing for identification of the voxels suitable for hiding the watermark and spreading the information in the gradients of the selected voxels. Thus, a secure and robust method for watermarking VDS could be developed which takes into account the specific properties of volumetric data and advantageously utilizes them.
Distance fields applied to character animation
(Eurographics Association, 2002) Rudomin, Isaac; Castillo, J.
A general hybrid geometric-physical method that is useful for animating characters with skin, clothing and a MPEG-4 compatible face is presented. This method uses an approximation to the underlying musculo-skeletal structure of the body and face to generate a distance field, used for collision detection purposes, and skin/clothing consisting of a particle-spring mesh. The results obtained deliver animation with plausible dynamics for fairly detailed models at around 60fps on a PIII computer with Nvidia Gforce2 graphics. The main contribution is to show that similar algorithms can be used for skin, clothing and facial animation, at interactive rates.
Dynamic Motion Models
(Eurographics Association, 2002) Grünvogel, Stefan Michael; Lange, Thorsten; Piesk, Jens
Real-time animation of virtual characters is a demanding task. We propose dynamic motion models which can create the motion of a virtual character in different styles and have the ability to change the animation while it is played. The motions are created by blending and changing given base motions which contain animation data and additional information. The blending and manipulation operations on the animation data build up a motion tree which can be altered dynamically in real-time. This allows to change the animation of a motion model while its animation is played. Motion trees of different motion models are blended together to build a motion tree which represents the complete animation of the character. This tree is constructed and dynamically changed according to user commands.
Dynamics-Based Motion Synthesis by Simple Learning Control
(Eurographics Association, 2002) Kiriazov, Petko
Point-to-point motion of a humanoid agent (or any mobile creature) is considered as a composition of basic movements related to the degrees of freedom. With time/energy performance criteria, such movements can be synthesized by using simple control functions. Natural looking animation can be achieved employing even very simplified dynamics models. Their parameters can be estimated or identified using motion capture data. In case no appropriate dynamic model is available, we propose an efficient procedure of direct motion editing. The captured motion can be re-used in order to animate the original or other characters in a variety of similar motion tasks. The proposed approach for motion synthesis is applied in the case of a six-link biped. Two examples are considered: one for editing captured walking motion and the other of direct motion synthesis for climbing stairs. The proposed methodology is very appropriate for interactive character animation.
Eurographics 2002 - Presentation of European Groups doing Computer Graphics Research
(Eurographics Association, 2002)
This brochure contains a concentrated description of many European Computer Graphics research labs. It was produced to accompany a track of lab presentations at the annual conference Eurographics’2002 in Saarbrücken in September 2002. European CG researchers were invited through the call for participation to present their research unit to a broader audience, including the readers of this booklet. In addition we have invited the leaders of the most active labs personally to send their contributions. We believe that only relatively few important CG institutes and research organisations are missing, and that this brochure therefore gives a nice overview of what is going on in Europe in Computer Graphics. Most of the labs collected in this brochure presented themselves with a short talk during the conference, often given by their heads in person, and participants had the oportunity to ask a few rather organisational questions.
Extraction of Critical Points and Nets Based on Discrete Gradient Vector Field
(Eurographics Association, 2002) De Floriani, Leila; Mesmoudi, Mohammed Mostefa; Danovaro, Emanuele
In this paper we address the problem of representing the topology of discrete scalar fields defined on triangulated domains. To this aim, we use the notion of discrete gradient vector field that we have introduced in [4] to classify the critical points of a scalar field defined over a two-dimensional domain that generalizes the nature of critical points in the differentiable case. Then we sketch an algorithm for extracting a critical net in the discrete case.
Facial Modeling and Animation
(Eurographics Association, 2002) Haber, Jörg; Magnenat-Thalmann, Nadia; Terzopoulos, Demetri; Vetter, Thomas; Blanz, Volker; Kähler, Kolja
Fast Volume Carving
(Eurographics Association, 2002) Pyo, Soon Hyoung; Shin, Yeong Gil
In recent years, the volumetric scene representation has been widely used in the fields of computer graphics and computer vision. In computer graphics, the representation is used to visualize and reconstruct 3D internal structures of 2D human-body medical data obtained from Magnetic Resonance Imaging (MRI) or Computed Tomography (CT). On the other hand, the volumetric representation is used to model 3D objects from a sequence of 2D images in computer vision. In both cases, eliminating some unnecessary part of the volumetric data is sometimes needed. For example, we need to remove skin or tissue which hides the target organ of human in volume rendering, or empty region of 3D objects being modeled in image-based modeling. In this paper, we propose a fast carving algorithm which can be applied in volume rendering and image-based modeling. The memory usage is minimized by using 1-bit field of a voxel to represent whether the voxel is carved or not. Our experiments show that we can carve out any part of the 5123 volume data in about a second. The carving speed is not affected by the complexity of objects.
Feature Extraction and Visualisation of Flow Fields
(Eurographics Association, 2002) Post, Frits H.; Vrolijk, Benjamin; Hauser, Helwig; Laramee, Robert S.; Doleisch, Helmut
Flow visualisation has already been a very attractive part of visualisation research for a long time. Usually very large data sets need to be processed, which often consist of multivariate data with a large number of sample locations, often arranged in multiple time steps. Recently, the steadily increasing performance of computers again has become a driving factor for a new boom in flow visualisation, especially in techniques based on feature extraction, vector field clustering, and topology extraction. In this state-of-the-art report, an attempt was made to (1) provide a useful categorisation of FlowVis solutions, (2) give an overview of existing solutions, and (3) focus on recent work, especially in the field of feature extraction. In separate sections we describe (a) direct visualisation techniques such as hedgehog plots, (b) visualisation using integral objects, such as streamlines, (c) texture-based techniques, including spot noise and line integral convolution, and (d) techniques based on extraction of features or flow topology.

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