GRAPP 2008 Abstracts
Conference
Area 1 - Geometry and Modeling
Area 2 - Rendering
Area 3 - Animation and Simulation
Area 4 - Interactive Environments

Special Sessions
Art, Science and Technology, Virtual tools for Cultural Heritage
Multimedia Collaborative Virtual Environments



Area 1 - Geometry and Modeling

Paper Nr.:
59
Title:
GEOMETRIC ALGORITHMS ON CUDA
Author(s):
Antonio J. Rueda and Lidia Ortega
Abstract:
The recent launch of the NVIDIA CUDA technology has opened a new era in the young field of GPGPU (General Purpose computation on GPUs). This technology allows the design and implementation of parallel algorithms in a much simpler way than previous approaches based on shader programming. The present work explores the possibilities of CUDA for solving basic geometric problems on 3D meshes like the point inclusion test or the self-intersection detection. A solution to these problems can be implemented in CUDA with only a small fraction of the effort required to design and implement an equivalent solution using shader programming, and the results are impressive when compared to a CPU execution.

Paper Nr.:
60
Title:
VORONOI DIAGRAM AND ITS APPLICATION TO SPATIAL CALIBRATION FOR GAMMA CAMERA IMAGES
Author(s):
Brian D. Maisler, Hong Liu, J. E. McKisson, Yishi Li and Eric Kvam
Abstract:
Gamma camera images obtained from PSPMT detectors and segmented crystal scintillators to be used for scintimammography are often distorted and blurred. Our software application is used to restore flood-field gamma camera images and map the peak positions of individual charge clusters back to the positions of the corresponding source scintillations. Since the exact position of scintillation in a crystal grain is not controllable due to the randomness of scattering, a region-to-region location map is more statistically sound than a point-to-point position map. Traditionally, an array of rectangles centered at the restored peaks of charge clusters is mapped to an array of crystal grains from which the source scintillations are emitted. We observe that the mapping is essentially a nearest neighborhood problem and innovatively introduce the Voronoi diagram to replace the rectangular array. The natural fit of the Voronoi diagram to the essence of neighborhood problem significantly improves the likelihood of correct mapping. It also makes our mapping method adaptable to apply to crystal plates in other geometric configurations. We implement the computations of Voronoi diagrams via OpenGL. As an empirical software solution, the images restored from raw flood field images illustrate high level uniformity and linearity.

Paper Nr.:
63
Title:
CORNER DETECTION ON CURVES
Author(s):
Neeta Nain, Vijay Laxmi and Bhavitavya Bhadviya
Abstract:
Detection of discontinuity plays an important role in image registration, image comparison, image segmentation, time sequence analysis and object recognition. This paper presents a new approach for Corner Detection using First Order Difference Chain-Encoding. Since the proposed method is based on integer operations it is very simple and efficient. Preliminary results are presented and evaluation with respect to standard corner detectors is done as a benchmark.

Paper Nr.:
71
Title:
QUALITY PERCEPTION OF SIMPLIFIED MODELS: NSA VS QSLIM
Author(s):
Frutuoso G. M. Silva and Samuel S. Silva
Abstract:
Quality perception of simplified models is an important aspect for several applications. But, it is normally evaluated only based on the analysis of geometrical errors of the simplified models. However, the analysis of geometrical errors is not enough to evaluate the quality of the simplified models. The quality of the simplified models and the execution times are the main aspects that distinguish the simplification algorithms. These algorithms have a great interest in a variety of areas, since they allow the replacement of large models by approximations with far fewer cells for manipulation and visualization purposes. This paper presents a comparison between two simplification algorithms, NSA and Qslim, and shows the difference between geometrical and graphical quality. The comparison of results was made using the PolyMeCo tool. It is a tool which enhances how users perform mesh analysis and comparison, by providing an environment where several visualization options and metrics are available and can be used in a coordinated way.

Paper Nr.:
82
Title:
ANALYSIS OF POINT CLOUDS - Using Conformal Geometric Algebra
Author(s):
Dietmar Hildenbrand and Eckhard Hitzer
Abstract:
This paper presents some basics for the analysis of point clouds using the geometrically intuitive mathematical framework of conformal geometric algebra. In this framework it is easy to compute with osculating circles for the description of local curvature. Also methods for the fitting of spheres as well as bounding spheres are presented. In a nutshell, this paper provides a starting point for shape analysis based on this new, geometrically intuitive and promising technology.

Paper Nr.:
85
Title:
DETECTION OF FACES IN WIRE-FRAME POLYHEDRA - Interactive Modelling of Uniform Polyhedra
Author(s):
Hidetoshi Nonaka
Abstract:
This paper presents an interactive modelling system of uniform polyhedra including regular polyhedra, semi-regular polyhedra, and intersected concave polyhedra. In our system, user can virtually "make" and "handle" them interactively. The coordinate of vertices are computed without the knowledge of faces, solids, or metric information, but only with the isomorphic graph structure. After forming a wire-frame polyhedron, the faces are detected semi-automatically through user-computer interaction. This sytem can be applied to recreational mathematics, computer assisted education of the graph theory, and so on.

Paper Nr.:
86
Title:
MESH SIMPLIFICATION USING DISTANCE LABELS FOR VIEW-INDEPENDENT SILHOUETTE PRESERVATION
Author(s):
Susana Mata, Luis Pastor and Angel Rodríguez
Abstract:
Multiresolution modelling presents itself as a good approach in order to reach a compromise between quality and performance in the rendering of complex scenes. Within this framework, the detection and preservation of outstanding features, such us silhouettes, become of great importance. The goal of this paper is to present a technique based on Distance Transforms that allows to classify the mesh's elements according to their proximity to \nuevo{both the internal and }the external contour and makes use of this information for weighting the approximation error which will be tolerated during the mesh simplification process. The approach followed in this work precomputes silhouettes for a given set of cameras and performs an estimation for any other point of view. The obtained results are evaluated in two ways: visually and using an objective metric that measures the geometrical difference between two polygonal meshes.

Paper Nr.:
96
Title:
THE GROUNDED HEIGHTMAP TREE - A New Data Structure for Terrain Representation
Author(s):
J. Alonso and R. Joan-Arinyo
Abstract:
Terrain modeling is a fast growing field with many applications such as computer graphics, resource management, Earth and environmental sciences, civil and military engineering, surveying and photogrammetry and games programming. One of the most widely used terrain model is the Digital Elevation Model (DEM). A DEM is a simple regularly spaced grid of elevation points that represent the continuous variation of relief over space. DEMs require simple storage and are compatible with satellite data. However, they do not easily account for overhangs. In this work we report on the Grounded Heightmap Tree, a new data structure for terrain representation built as a generalization of the DEM. The new data structure allows to naturally represent terrain overhangs. We illustrate the performance of the Grounded Heightmap Tree when applied to represent terrains that undergo big changes.

Paper Nr.:
98
Title:
EXPERIMENTAL STUDY OF BOUNDING BOX ALGORITHMS
Author(s):
Darko Dimitrov, Mathias Holst, Christian Knauer and Klaus Kriegel
Abstract:
The computation of the minimum-volume bounding box of a point set in R^3 is a hard problem. The best known exact algorithm requires O(n^3) time, so several approximation algorithms and heuristics are preferred in practice. Among them, the algorithm based on PCA (Principal Component Analysis) plays an important role. Recently, it has been shown that the discrete PCA algorithm may fail to approximate the minimum-volume bounding box even for a large constant factor. Moreover, this happens only for some very special examples with point clusters. As an alternative, it has been proven that the continuous version of PCA overcomes these problems. The contribution of this paper is two-fold. First, we study the impact of the recent theoretical results on applications of several PCA variants in practice. We analyze the advantages and disadvantages of the different variants on realistic inputs, randomly generated inputs, and specially constructed (worst case) instances. Second, we evaluate and compare the performances of several existing bounding box algorithms.

Paper Nr.:
101
Title:
IMAGE-BASED 3D TORSO BODY MODELING
Author(s):
YoungJun Kim, Kunwoo Lee and Wontae Kim
Abstract:
This paper proposes an image-based 3D modeling algorithm for a 3D torso of the human body. This approach provides an easy and practical way of modeling so that doctors can obtain the subject’s 3D data without additional equipment such as a 3D scanner or MRI. To achieve this goal, a 3D template model with feature points is prepared, and then a 3D model of the subject is reconstructed from orthogonal photographs by deforming the 3D template model. An appropriate number of feature points and their positions are derived. Procrustes Analysis and Radial Basis Functions (RBFs) are applied for the deformation. After the deformations, images are mapped onto the mesh for visualization.

Paper Nr.:
102
Title:
SURFACE-SURFACE INTERSECTION BY HERMITE INTERPOLATION
Author(s):
Eng-Wee Chionh
Abstract:
A fast heuristic to approximate the intersection curve of two surface patches was originally proposed by Sederberg and Nishita. The patches are rationally parametrized and they cut each other transversely. This paper reports a simple generalization that greatly improves the accuracy of the original heuristic. The generalization eihter avoids or attenuates the approximation error. Avoidance is achieved when the improved heuristic produces the exact intersection curve; attenuation is accomplished with an aggregate square distance formula guiding the selection of a generalized constraint for a better fit.

Paper Nr.:
105
Title:
A HIERARCHICAL SPATIAL INDEX FOR TRIANGULATED SURFACES
Author(s):
Leila De Floriani, Marianna Facinoli, Paola Magillo and Debora Dimitri
Abstract:
We present the PM2-Triangle quadtree (PM2T-quadtree), a new hierarchical spatial index for triangle meshes which has been designed for performing spatial queries on triangle-based terrain models. The PM2T-quadtree is based on a recursive space decomposition into square blocks. Here, we propose a highly compact data structure encoding a PM2T-quadtree, which decouples the spatial indexing structure from the combinatorial description of the mesh. We compare the PM2T-quadtree against other spatial indexes by considering the structure of the underlying domain subdivision, the storage costs of their data structures and the performance in geometric queries.

Paper Nr.:
108
Title:
EFFICIENT FACE-BASED NON-SPLIT CONNECTIVITY COMPRESSION FOR QUAD AND TRIANGLE-QUAD MESHES
Author(s):
D. R. Khattab, Y. M. Abd El-Latif, M. S. Abdel Wahab and M. F. Tolba
Abstract:
In this paper we present an efficient face based connectivity coding technique for the special class of quadrilateral and the hybrid triangular-quadrilateral meshes. This work extends the main ideas of non-split encoding presented by the first contribution of the authors (Khattab, Abd El-Latif, Abdel Wahab and Tolba, 2007) for triangle meshes and improves over the compression results provided so far for existing face based connectivity compression techniques. It achieves an average compression ratio of 2.17 bits per quad and bit per vertex for simple quadrilateral meshes and bit rates of 1.84 bits per polygon and 1.85 bits per vertex for the simple hybrid triangle-quad meshes

Paper Nr.:
116
Title:
APPROXIMATE G1 CUBIC SURFACES FOR DATA APPROXIMATION
Author(s):
Yingbin Liu and Stephen Mann
Abstract:
This paper presents a piecewise cubic approximation method with approximate $G^1$ continuity. For a given triangular mesh of points with arbitrary topology, one cubic triangular B\'ezier patch surface is constructed. The resulting surfaces have $G^1$ continuity at the vertex points, but only requires approximate $G^1$ continuity along the macro-patch boundaries so as to lower the patch degree. While our scheme cannot generate the surfaces in as high quality as Loop's sextic scheme, they are of half the polynomial degree, and of far better shape quality than the results of interpolating split domain schemes.

Paper Nr.:
120
Title:
CONTROL POLYGON BASED TEXTURE SYNTHESIS ON BIQUADRATIC BĒZIER RATIONAL SURFACES
Author(s):
Rupesh N. Shet, H. E. Bez and E. A. Edirisinghe
Abstract:
Existing texture synthesis algorithms fail to deliver effectively in application areas where progressive rendering of texture is required. To provide a practical solution to this problem we propose a novel algorithm for progressive-texture synthesis on surfaces, which makes use of the Embedded Zero-tree of Wavelet (EZW) idea proposed by Shapiro et al., 1993 which is capable of prioritising the coefficients of a DWT decomposed image according to their visual significance. We demonstrate the use of the proposed algorithm on texturing a single biquadratic surface and two smoothly joined biquadratic surfaces. It is further shown that the proposed texture synthesis approach on Bézier patches allows the algorithm's general use in texture synthesis on many common surface topologies and can be generalised for arbitrarily shaped surfaces. We provide experimental results to prove the effectiveness of the proposed approach, when synthesising textures of regular, irregular and stochastic nature. Further experimental results are provided to illustrate the practical use of the proposed texture synthesis algorithm in resource constrained application domains.

Paper Nr.:
122
Title:
GEOMETRICAL DEGENERACY REMOVAL BY VIRTUAL DISTURBANCES - An Application to Surface Reconstruction from Point Slice Samples
Author(s):
Oscar Ruiz, Eliana Vasquez, Sebastian Peña and Miguel Granados
Abstract:
In surface reconstruction from slice samples (typical in medical imaging, coordinate measurement machines, stereolithography, etc.) the available methods attack the geometrical and topological aspects or a combination of these. Topological methods classify the events occurred in the 2-manifold between two consecutive slices. Geometrical methods synthesize the surface based on local proximity of contours in consecutive slices. Many of these methods work with modifications of Voronoi - Delaunay (VD) techniques, applied on slices i and i+1. Superimposed 2D Voronoi Diagrams VDi and VDi+1 (used in surface reconstruction) present topological problems if, for example, a site of VDi lies on an site or an edge of VDi+1. The usual treatment of this problem in literature is to apply a geometrical disturbance to either VDi or VDi+1, thus eliminating the degeneracy. Recent works seek to quantify the amount of the disturbance applied in relation to the probability distribution of the event “change in the topology of VD”. In this article, in contrast, virtual disturbances are proposed and implemented, which allow for the application of subsequent steps of the algorithm at hand (in this case, tetrahedra construction for surface reconstruction) regardless of to the geometrical exception. Tetrahedra (or any other downstream constructs) can then be instantiated as per non-degenerate conditions. Although this method is applied for surface reconstruction, it gives insight as to how to circumvent degeneracies in procedures based on VD methods.

Paper Nr.:
123
Title:
VISUALIZING MULTIPLE SCALAR FIELDS ON A SURFACE
Author(s):
Mohammed Mostefa Mesmoudi, Leila De Floriani and Paola Magillo
Abstract:
In (Mesmoudi et al., 2007b), the authors presented a theoretical visualization technique, called Atmosphere Upper Bound Level (AUBL) that allows to a scalar field to be visualized on a surface. They showed how this visualization technique can be used to extract the morphology of the scalar field and how can be used in other applications. In this paper, we present our experimental results obtained from the implementation of AUBL technique. Furthermore, we generalize the AUBL concept to a new visualization technique that allows a graphical representation of more than one scalar field defined on the surface. This later technique that we call Generalized AUBL (GAUBL), has the advantage to be interactive and displays the scalar fields separately and uses transparencies for comparison purposes or displays them simultaneously to highlight the dependencies and interactions between scalar fields. As a special case, a multi-valued scalar field can be handled by GAUBL.

Paper Nr.:
124
Title:
GPU-BASED NORMAL MAP GENERATION
Author(s):
Jesus Gumbau, Carlos Gonzalez and Miguel Chover
Abstract:
This work presents a method for the generation of normal maps from two polygonal models: a very detailed one with a high polygonal density, and a coarser one which will be used for the real-time rendering. This method generates the normal map of the high resolution model which can be applied to the coarser model to improve its shading. The normal maps are completely generated on the graphics hardware.

Paper Nr.:
126
Title:
HAPCO: REAL TIME SIMULATION OF INTERACTION BETWEEN DEFORMABLE OBJECTS WITH HAPTIC FEEDBACK FOR SOLVING FRICTION MULTIPLE CONTACTS
Author(s):
Nadjet Talbi, Pierre Joli, Zhi-Qiang Feng and Abderrahmane Kheddar
Abstract:
In this paper we present HapCo, a real time physics-based simulator of interaction between deformable objects with haptic force feedback for scenarios involving friction multiple contacts. The discrete modeling of the elastic bodies is achieved by the Finite Element Method (FEM). In real time, the rigid displacements are applied to an elastic object by means of a PHANTOM desktop. A force is computed and returned to this haptic device when a collision occurs with a second clamped elastic solid. This force feedback takes into account the linear elasticity laws and the friction contact laws (Signorini and Coulomb) of the elastic bodies in contact. So, we introduce two algorithms to calculate efficiently the friction multi-contact forces occurring between two deformable objects. These two algorithms are based on the bi-potential formulation of the contact laws, offering the control of the solution at each contact point through a unique operator of projection as well as a better force feedback stability . According to the rendering visual feedback given, the elastic deformations of the bodies computed by the Finite Element Method look physically realistic.

Paper Nr.:
145
Title:
AN EXTENSION TO THE BEZIER SUB-DIVISION METHOD TO COMPLETELY APPROXIMATE CURVES AND SURFACES
Author(s):
Andreas Savva, Vasso Stylianou and George Portides
Abstract:
Sub-division splines generate a number of new control points calculated fron the old control points. Both control polygons/grids define the same curve/surface. At each iteration the resulting new points are much greater in number than the old points and lie nearer to the actual curves. After a number of iterations, the generated points lie on the actual curve, very close to each other, and by displaying them on a computer screen the result is a smooth curve/surface. This paper describes a method, which is an extension to the Bezier sub-division method, where the resulting curve is an approximation curve which interpolates only the first and the last control points. The method is also derived for surfaces and some results are illustrated.

Paper Nr.:
149
Title:
A PEN AND PAPER METAPHOR FOR ORCHID MODELING
Author(s):
Burkhard Wuensche, Glen McCord, Beryl Plimmer, Greg Gilbert and Christian Hirsch
Abstract:
The creation of 3D computer models is an essential task for many applications in science, engineering and arts and is frequently performed by untrained users. In many cases speed and simplicity of the modeling process is more important than matching the geometry of the modeled object exactly. Sketch-based modeling has been suggested as an important tool for such applications. In this paper we take the pen and paper metaphor a step further and introduce a paper sculpting metaphor. Using these techniques we present an efficient and effective tool for orchid modeling. We discuss the inherent properties of orchid flowers and use them to develop constraints for representing the complex surface shapes of orchids with simple 2D sketches. Surface details are added using noise functions. Additional surface modifications are possible using the paper sculpting metaphor. By computing inherent bending axis from the skeleton of a sketched 2D shape the user is able to warp leaf-like structures like if they were cut from a piece of paper. The intuitive object manipulation of our tool means that an otherwise complex model can be rapidly created by an inexperienced, non-artistic user in a short period of time.

Paper Nr.:
187
Title:
BEYOND GRAPHICS: INFORMATION - An Overview of Infovis Practices in the Field of the Architectural Heritage
Author(s):
J. Y. Blaise and I. Dudek
Abstract:
Understanding and representing the evolution of architectural artefacts over time requires a careful examination of heterogeneous, questionable pieces of data. Accordingly, our position is that computer graphics can and will support such investigation if and only if they are designed, above all, as information visualisation disposals (may the visual result be realistic or not). But contemporary practices often fail to reach this goal. In this paper, we propose possible explanations, and argue why we believe the problem has more to do with a lack of appropriate methodology than with technologies. As an answer, we introduce a global methodological framework that claims to be at the intersection of figurative architectural representation and of information visualisation. We finally back up this claim by presenting past and contemporary examples showing there has been a bridge between the above mentioned fields, a bridge that we today need to rebuild with or against computer technologies.

Area 2 - Rendering

Paper Nr.:
11
Title:
FINE ARTS EDUTAINMENT- The Amateur Painter
Author(s):
João Rodrigues, Daniel Almeida, Samuel Nunes, João Carvalho, Vera Brito and Hans du Buf
Abstract:
A new scheme for painterly rendering (NPR) has been developed. This scheme is based on visual perception, in particular the multi-scale line/edge representation in the visual cortex. The Amateur Painter (TAP) is the user interface on top of the rendering scheme. It allows to (semi)automatically create paintings from photographs, with different types of brush strokes and colour manipulations. In contrast to similar painting tools, TAP has a set of menus that reflects the procedure followed by a normal painter. In addition, menus and options have been designed such that they are very intuitive, avoiding a jungle of sub-menus with options from image processing that children and laymen do not understand. Our goal is to create a tool that is extremely easy to use, with the possibility that the user becomes interested in painting techniques, styles, and fine arts in general.

Paper Nr.:
58
Title:
FROM VOLUME SPLATTING TO RAYCASTING - A Smooth Transition
Author(s):
Guillaume Gilet, Jean-Michel Dischler and Luc Soler
Abstract:
Splatting-based methods are well suited to render large hierarchical structured or unstructured point-based volumetric datasets. However, as for most object-order volume rendering methods, one major problem still remains the processing of huge amount of elements usually necessary to represent highly detailed densely sampled datasets, which can lead to poor performance. Resampling into 3D textures to apply hardware-based raycasting is a common way of improving framerate in such cases but often with a certain precision loss related to limited texture memory. Switching between these two rendering techniques is interesting in order to keep the advantages of both and has thus been proposed before, but not in a smooth and hierarchical manner. In this paper, we show that for most point-based volumetric datasets, some parts of the model can be rendered more efficiently with a texture-based method, whereas other parts can be rendered as usual using splatting. We address the issue of providing a smooth hierarchical transition between the two methods using a data-dependent approach based on a per-pixel ray-driven rendering scheme. In practice, our transition scheme allows users a good control of the performance/quality trade-off. Through a comparison with standard hierarchical EWA splatting, we show that our smooth transition can lead to an improvement of framerate without introducing visual inconsistencies or artifacts.

Paper Nr.:
80
Title:
GENERIC BRDF SAMPLING - A Sampling Method for Global Illumination
Author(s):
Rosana Montes, Carlos Ureña, Ruben Garcia and Miguel Lastra
Abstract:
This paper introduces a new BRDF sampling method with reduced variance, which is based on a hierarchical adaptive parameterless PDF. This PDF is based also on rejection sampling with a bounded average number of trials, even in regions where the BRDF does exhibit high variations. Our algorithm works in an appropiate way with both physical and analytical reflectance models. Reflected directions are sampled by using importance sampling of the BRDF times the cosine term. This fact improves computation of reflected radiance when Monte-Carlo integration is used in Global Illumination. Test images have been obtained by using a Monte-Carlo rendering system, and they show reduced variance as compared with those obtained by other known techniques.

Paper Nr.:
81
Title:
TIME-VARYING MULTIMODAL VOLUME RENDERING WITH 3D TEXTURES
Author(s):
Pascual Abellán, Sergi Grau and Dani Tost
Abstract:
In this paper, we propose a rendering method for multimodal and time-varying data based on 3D texture mapping. Our method takes as input two registered voxel models: one with static data and the other with time-varying values. It visualizes the fusion of data through time steps of different sizes, forward and backward. At each frame we use one 3D texture for each modality. We compute and compose a set of view-aligned texture slices. For each texel of a slice, we perform a fetch to each 3D texture and realize fusion and shading using a fragment shader. We codify the two shading transfer functions on auxiliary 1D textures. Moreover, the weight of each modality in fusion is not constant but defined through a 2D fusion transfer function implemented as a 2D texture. We benefit from frame-to-frame coherence to avoid reloading the time-varying data texture at each frame. Instead, we update it at each frame using a 2D texture that run-length encodes the variation of property values through time. The 3D texture updating is done entirely on the GPU, which significantly speeds up rendering. Our method is fast and versatile and it provides a good insight into multimodal data.

Paper Nr.:
89
Title:
OBJECTIVE QUALITY SELECTION FOR HYBRID LOD MODELS
Author(s):
Tom Jehaes, Wim Lamotte and Klaas Tack
Abstract:
The problem of rendering large virtual 3D environments at interactive framerates has traditionally been solved by using polygonal Level-of-Detail (LoD) techniques, for which either a series of discrete models or one progressive model were determined during preprocessing. At runtime, several metrics such as distance, projection size and scene importance are used to scale the objects to such a resolution that a target framerate is maintained in order to provide a satisfactory user experience. In recent years however, image-based techniques have received a lot of interest from the research community because of their ability to represent complex models in a compact way, thereby also decreasing the time needed for rendering. One of the questions however that should be given some more consideration is when to switch from polygonal rendering to image-based rendering. In this paper we explore this topic further and provide a solution using an objective image quality metric which tries to optimize render quality. We test the presented solution on both desktop and mobile systems.

Paper Nr.:
90
Title:
QUASI-CONVOLUTION PYRAMIDAL BLURRING
Author(s):
Martin Kraus
Abstract:
Efficient image blurring techniques based on the pyramid algorithm can be implemented on modern graphics hardware; thus, image blurring with arbitrary blur width is possible in real time even for large images. However, pyramidal blurring methods do not achieve the image quality provided by convolution filters; in particular, the shape of the corresponding filter kernel varies locally, which potentially results in objectionable rendering artifacts. In this work, a new analysis filter is designed that significantly reduces this variation for a particular pyramidal blurring technique. Moreover, an efficient implementation for programmable graphics hardware is presented. The proposed method is named "quasi-convolution pyramidal blurring" since the resulting effect is very close to image blurring based on a convolution filter for many applications.

Paper Nr.:
99
Title:
A DIRECT VOLUME RENDERING FRAMEWORK FOR THE INTERACTIVE EXPLORATION OF HIGHER-ORDER AND MULTIFIELD DATA
Author(s):
Felix Manke and Burkhard Wünsche
Abstract:
Direct Volume Rendering is a popular method for displaying volumetric data sets without generating intermediate representations. The technique is most frequently applied to scalar data and few specialized techniques exist for visualizing higher-order data, such as tensor fields, directly. This is a serious limitation because progress in medical imaging, satellite technology and numerical simulations has made higher-order and multifield data sets a common entity in medicine, science and engineering. In this paper we present a framework for the interactive exploration of complex data sets using direct volume rendering. This is achieved by applying modern SE design technologies to modularize the direct volume rendering pipeline and by exploiting the latest advances in graphics hardware and shading languages to modify rendering effects and to compute derived data sets at runtime. We discuss how the framework can be used to mimic the latest specialized direct volume rendering algorithms and to interactively explore and gain new insight into high-order and multifield data sets. The capabilities of the framework are demonstrated by two simple case studies and the efficiency and effectiveness of the framework is evaluated.

Paper Nr.:
104
Title:
REAL-TIME VIEW-DEPENDENT VISUALIZATION OF REAL WORLD GLOSSY SURFACES
Author(s):
Claus B. Madsen, Bjarne K. Mortensen and Jens R. Andersen
Abstract:
A technique for real-time visualization of glossy surfaces is presented. The technique is aimed at recreating the view-dependent appearance of glossy surfaces under some fixed illumination conditions. The visualized surfaces can be actual real world surfaces or they can be surfaces for which the appearance is precomputed with a global illumination renderer. The approach taken is to image to surface from a large number of viewpoints distributed over the viewsphere. From these images the reflected radiance in different direction is sampled and a parameterized model is fitted to these radiance samples. Two different models are explored: a very low parameter model inspired by the Phong reflection model, and a general Spherical Harmonics model. It is concluded that the Phong-based model is best suited for this type of application.

Paper Nr.:
107
Title:
A GENERALIZATION APPROACH FOR 3D VIEWING DEFORMATIONS OF SINGLE-CENTER PROJECTIONS
Author(s):
Matthias Trapp and Jürgen Döllner
Abstract:
This paper presents a novel image-based approach to efficiently generate real-time non-planar projections of arbitrary 3D scenes such as panorama and fish-eye views. The real-time creation of such projections has a multitude of applications, e.g., in geovirtual environments and in augmented reality. Our rendering technique is based on dynamically created cube map textures in combination with shader programs that calculate the specific projections. We discuss two different approaches to create such cubemaps and introduce possible optimizations. Our technique can be applied within a single rendering pass, is easy to implement, and exploits the capability of modern programmable graphics hardware completely. Further, we present an approach to customize and combine different planar as well as non-planar projections. We have integrated our technique into an existing real-time rendering framework and demonstrate its performance on large scale datasets such as virtual 3D city and terrain models.

Paper Nr.:
110
Title:
SUGGESTIVE CONTOURS OVER POINT-SET IMPLICITS
Author(s):
João Proença, Joaquim Jorge and Mario Costa Sousa
Abstract:
We present a system that combines large point-set implicit surfaces with fast line-based rendering. We devised a new process for extracting suggestive contours quickly by using particles scattered throughout the surface to identify areas of interest, followed by clustering and line-fitting. Furthermore, we improve on state-of-the-art methods for extracting silhouettes and feature-lines by harnessing the descriptive power of the surface representation. This provides heuristics for fast determination of curvature and allows for the local regeneration of shape-depicting line elements after editing operations. While visual examples illustrate the high quality of the drawings obtained with our application, as well as the high detail it can provide for more complex models, run-times show comparatively higher performance over similar approaches for the same number of points.

Paper Nr.:
128
Title:
A Psychophysical Study of Foveal Gradient Based Selective RenderingA PSYCHOPHYSICAL STUDY OF FOVEAL GRADIENT BASED SELECTIVE RENDERING
Author(s):
Veronica Sundstedt
Abstract:
High-fidelity rendering of complex scenes at interactive rates is one of the primary goals of computer graphics. Since high-fidelity rendering is computationally expensive, perceptual strategies such as visual attention have been explored to achieve this goal. Inattentional Blindness (IB) experiments have shown that observers conducting a task can fail to see an object, although it is located within the foveal region (2°). However, previous attention based algorithms assumed that IB would be restricted to the area outside the foveal region, selectively rendering the areas around task-related objects in high quality and the surrounding areas in lower quality. This paper describes a psychophysical forced-choice preference experiment assessing if participants, performing a task or free-viewing animations, would fail to notice rendering quality degradation within the foveal region. The effect of prior knowledge on the level of perceived quality is also studied. The study involves 64 participants in four conditions: performing a task, or free-viewing a scene, while being naive or informed about assessing rendering quality. Our results show that participants fail to notice the additional reduction in quality, decreasing the overall computation 13 times. There was also a significant difference in the results if free-viewing participants were informed.

Paper Nr.:
140
Title:
DISPLACEMENT PATCHES FOR GPU-ORIENTED VIEW-DEPENDENT RENDERING
Author(s):
Yotam Livny, Gilad Bauman and Jihad El-Sana
Abstract:
In this paper we present a new approach for interactive view-dependent rendering of large polygonal datasets, which relies on advanced features of modern graphics hardware. Our preprocessing algorithm starts by generating a simplified representation of the input mesh. It then builds a multiresolution hierarchy for the simplified model. For each face in the hierarchy, it generates and assigns a displacement map that resembles the original surface represented by that face. At runtime, the multiresolution hierarchy is used to select a coarse view-dependent level-of-detail representation, which is sent to the graphics hardware. The GPU then refines the coarse representation by replacing each face with a planar patch, which is elevated according to the assigned displacement map. Experimental results show that our implementation achieves quality images at high rates.

Paper Nr.:
183
Title:
REAL-TIME MIXED REALITY WITH GPU TECHNIQUES
Author(s):
Tobias Franke and Yvonne Jung
Abstract:
In this paper, we propose a combination of modern GPU-based methods that are able to generate high-quality, interactive real-time rendering for augmented and mixed reality applications. We also present a new approach to estimate surface reflection functions and materials from images using genetic algorithms.

Paper Nr.:
195
Title:
TOWARDS PROBE-LESS AUGMENTED REALITY - A Position Paper
Author(s):
Claus B. Madsen and Michael Nielsen
Abstract:
The main problem area for Augmented Reality is ensuring that the illumination of the virtual objects is continuously consistent with the illumination in the real scene. State of the art in the area typically requires the real scene illumination conditions be captured as a High Dynamic Range environment map of the scene. The environment map is then used for shading and shadowing. Handling the real and the virtual shadows and their interaction is the single most difficult aspect. This paper presents a completely different approach to determining the illumination conditions in the real scene. Based on an assumption that the scene is outdoor we automatically detect shadows in the image and use this information to determine the ratio of sky irradiance to sun irradiance. We then present how to convert this information into radiance levels for both the sky and the sun. When combined with a computation of the Sun's position based on date, time and information about position on the Earth, we arrive at a full illumination model applicable for rendering virtual objects into real scenes.

Area 3 - Animation and Simulation

Paper Nr.:
56
Title:
MODELING AND SIMULATING MOBILE ROBOT ENVIRONMENTS
Author(s):
Oliver Kutter, Christian Hilker, Alexander Simon and Bärbel Mertsching
Abstract:
According to the requirements of our ongoing research on algorithms of robot vision and manipulation, we present a newly developed simulation framework for mobile robot environments called SIMORE. A dynamic 3D environment has been created in which simulated robots, sensors and actors can be manipulated. Multiple methods to operate a robot are provided including control by manual input devices, graphical user interface and program commands. The interface to the simulator is transparent so that the control commands can be directly transferred to the real hardware platform after successful simulation tests. In addition to the 3D graphics engine the simulator has a physics engine to guarantee a correct physical behavior. The modeling of all objects (visual and dynamic) can be done in modeling software. Simulations can run either in an offline mode, in which actions are predefined, or in an online mode, where an operator can directly manipulate the simulated system by manual input devices. The simulation framework is designed to be modular and flexible in order to allow future extensions and enhancements such as inclusion of additional sensors.

Paper Nr.:
72
Title:
DIRECTABLE AND STYLIZED HAIR SIMULATION
Author(s):
Yosuke Kazama, Eiji Sugisaki and Shigeo Morishima
Abstract:
Creating natural looking hair motion is considered as one of the most difficult and time consuming tasks in CG animation so that it has been challenging. A detailed physics model is an essential to create convincing hair animation. However, hair animation created by a detailed hair dynamics might not be desired result for creators. For this reason, both detailed and editable hair simulation system is required in contemporary CG world. In this paper, therefore, we propose External Force Field (EFF) for hair motion constructed by motion capture system. Furthermore, we develop a system for editing the obtained hair motion. First, we capture an environment around a subject by motion capture system, and then define EFF. Secondly, we develop a hair motion editing system based on EFF for creating creator-oriented hair animation. Consequently, our editing system enables creators to create desired hair animation intuitively without a physical discontinuity.

Paper Nr.:
79
Title:
EFFICIENT INVERSE KINEMATICS ALGORITHM BASED ON CONFORMAL GEOMETRIC ALGEBRA - Using Reconfigurable Hardware
Author(s):
Dietmar Hildenbrand, Holger Lange, Florian Stock and Andreas Koch
Abstract:
This paper presents a very efficient approach for algorithms developed based on conformal geometric algebra using reconfigurable hardware. We use the inverse kinematics of the arm of a virtual human as an example, but we are convinced that this approach can be used in a wide field of computer animation applications. We describe the original algorithm on a very high geometrically intuitive level as well as the resulting optimized algorithm based on symbolic calculations of a computer algebra system. The main focus then is to demonstrate our approach for the hardware implementation of this algorithm leading to a very efficient implementation.

Paper Nr.:
109
Title:
A FULLY GPU-IMPLEMENTED RIGID BODY SIMULATOR
Author(s):
Álvaro del Monte, Roberto Torres, Pedro J. Martín and Antonio Gavilanes
Abstract:
In this paper we study how to implement a fully GPU-based rigid body simulator by programming shaders for every phase of the simulation. We analyze the pros and cons of different approaches, and point out the bottlenecks we have detected. We also apply the developed techniques to two case studies, comparing them with the analogous versions running on CPU.

Paper Nr.:
112
Title:
DTW-CURVE FOR CLASSIFICATION OF LOGICALLY SIMILAR MOTIONS
Author(s):
Yang Yuedong, Zhao Qinping, Hao Aiminand Wu Weihe
Abstract:
Logical classification of motion data is the precondition of motion editing and behaviour recognition. The typical distance metrics of sequences can not identify logical relation between motions well. Based on the traditional DTW distance metrics, this paper proposes strategies bidirectional DTW and segment DTW, both of which could improve the robustness of identifying logically related motions, and then proposes a DTW-Curve method which is used to compare the logical similarity between the motions. The generation of DTW-Curve includes three steps. Firstly, motions should be normalized to remove the global translation and align the global orientation. Secondly, motions are resampled to cluster local frames and remove redundant frames. Finally, DTW-Curve is generated under the control of different thresholds. DTW-Curve may produce many statistical properties, which could be used to unsupervised logical classification of motions. We propose two types of statistical properties, and classify motion data by using hierarchical clustering procedure. The experiment results demonstrate that the logical classification based on DTW-Curve has better classification performance and robustness.

Paper Nr.:
117
Title:
INTERACTIVE RECONSTRUCTION AND VISUALIZATION OF DYNAMIC 3D ULTRASOUND DATA SETS
Author(s):
Timo Ropinski, Borislav Petkov, Larissa Fabritz and Klaus Hinrichs
Abstract:
In this paper we describe techniques which have been developed in order to interactively visualize dynamic 3D ultrasound (US) volume data sets acquired using a small animal 2D US scanner. The 2D frames are acquired at different spatial positions and gated based on the ECG signal. For the reconstruction process a user interface is specified, which allows the user to select 2D frames acquired during different ECG phases at different spatial locations. Thus it is possible to reconstruct and visualize a volumetric model based on several 2D frames for different phases of the heart cycle. To improve the interactive visualization, we facilitate filtering techniques, which have been implemented on the GPU.

Paper Nr.:
132
Title:
RAY-TRACED COLLISION DETECTION FOR DEFORMABLE BODIES
Author(s):
Everton Hermann, François Faure and Bruno Raffin
Abstract:
This paper presents a new approach to collision detection and modeling between deformable volumetric bodies. It allows deep intersections while alleviating the difficulties of distance field update. A ray is shot from each surface vertex in the direction of the inward normal. A collision is detected when the first intersection belongs to an inward surface triangle of another body. A contact force between the vertex and the matching point is then created. Experiments show that this approach is fast and more robust than traditional proximity-based collisions.

Paper Nr.:
134
Title:
REALISTIC RAIN RENDERING
Author(s):
Yoshiki Mizukami, Katsuhiro Sasaki and Katsumi Tadamura
Abstract:
This paper proposes a method for rendering realistic three-dimensional raining scene. This proposed method gives two main contributions to rendering raining scene. The first one is to propose a simple model that deals with temporal-spatial localities such as wind effect, density and intensity of rainfall, and raindrop brightness, so as to represent environmental conditions that differs on a scene-to-scene basis. The other one is to propose a raindrop trajectory computing method whose computation load immunes to the number of raindrop, wind effect and complicated camera movement. Due to the above-mentioned contributions, the proposed method can represent essential aspects in raining scene, such as spatial changes of rain in urban canyon or temporal changes due to the moving wisp of rain.

Paper Nr.:
153
Title:
SIMULATION OF CONSTRUCTION PROCESSES WITHIN VIRTUAL ENVIRONMENTS
Author(s):
Alcínia Zita Sampaio and Pedro Gameiro Henriques
Abstract:
Three-dimensional geometric models have been used to present architectural and engineering works, showing their final configuration. But, when the clarification of a detail or the constitution of a construction step in needed, these models are not appropriate because they do not allow the observation of the construction activity. Models that could present dynamically changes of the building geometry are a good support on education in civil engineering domain. Techniques of geometric modelling and virtual reality were used to obtain interactive models that could visually simulate the construction activity. The applications explain the construction work of a cavity wall and a bridge. These models allow the visualization of the physical progression of the work following a planned construction sequence, the observation of details of the form of every component of the works and support the study of the type and method of operation of the equipment applied in the construction. The models present distinct advantage as educational aids in first-degree courses in Civil Engineering. The use of Virtual Reality techniques in the development of educational applications brings new perspectives to the teaching of subjects related to the field of civil construction

Paper Nr.:
194
Title:
AUTOMATIC COMPOSITION OF DRAMATIC MOVEMENT - Analysis and Algorithm for Creating Contemporary Dance Sequences
Author(s):
Asako Soga and Bin Umino
Abstract:
We have developed an automatic composition system for contemporary dance by using 3DCG animation. Our goal is to develop some useful tools in dance education such as creation-support system for teachers and self-study system for students. Our approach is not creating natural connection but creating conceptual sequences. As a result of previous experiment, we recognize the connecting method is not so important for contemporary dancers. We try to create short sequences that have dramatic stories according to the structure of Chinese poetry in ancient times. The basic movements of contemporary dance are classified and analyzed. The algorithm for automatic composition is integrated to create utilitarian choreographies for lessons. This system is valuable for online virtual dance experimentation and exploration by teachers and choreographers involved in creative practices, improvisation, creative movement, or dance composition.

Area 4 - Interactive Environments

Paper Nr.:
44
Title:
LOCALIZATION IN AN INTERACTIVE SYSTEM
Author(s):
Juan J. Jiménez, Francisco R. Feito and Rafael J. Segura
Abstract:
The localization of the nearest parts of an object to a device is usually solved by means of a proximity measurement of each one of the features that form this object to the device. In order to perform this efficiently, hierarchical decompositions of the space or of the object are used, so that the features of objects are classified into several types of cells, usually rectangular. In this paper we propose a solution based on the classification of a set of points located on the device in a spatial decomposition named tetra-tree. Using this type of spatial decomposition gives us several qualitative properties that allow us a more realistic and intuitive visual interaction. In order to show these properties we have compared an interaction system based on tetra-trees to one based on octrees.

Paper Nr.:
61
Title:
IMAGE QUALITY IN IMAGE-BASED REPRESENTATIONS OF REAL-WORLD ENVIRONMENTS - Perceived Smoothness of Viewpoint Transitions
Author(s):
Filippo Speranza, Akshay Bhatia and Robert Laganière
Abstract:
In this study, we investigated the effect of viewpoint density and speed of motion on perceived smoothness of viewpoint transitions. The effect of viewpoint density was examined for two types of viewer motion: forward and lateral motion. In both cases, we found that perceived smoothness varies with viewpoint density. We also found the number of viewpoints required to maintain a certain level of perceived smoothness varies inversely with speed of movement represented.

Paper Nr.:
73
Title:
A SIP SPATIAL AUDIO SERVER FOR THE EVE PLATFORM
Author(s):
Ch. Bouras, V. Triglianos and Th. Tsiatsos
Abstract:
When it comes to 3D Virtual Environments it is well known that 3D sound is of great importance to the whole interactive experience. The percept of sound is a major counterpart for the eyesight, since it describes the location, the momentum and the attitude towards the listener, of each surrounding entity. The sound can offer precision of spatial perception that cannot be achieved by the eye itself. Thus the support of 3D surround sound of high fidelity is mandatory for a 3D Virtual platform. The evolution of Internet telephony led to the introduction of new session establishment and management protocols. The most important of them, the Session Initiation Protocol (SIP), is a robust, lightweight reliable and fast application-layer control (signaling) protocol that is highly adopted for creating, modifying and terminating sessions. This protocol can be of extreme importance in establishing audio sessions for multi-user platforms. This paper presents the work done for developing a SIP 3D spatial audio server for a multi-user virtual environments platform, called EVE, in order to support 3D spatial audio

Paper Nr.:
74
Title:
A MULTI-CAMERA FRAMEWORK FOR INTERACTIVE VIDEO GAMES
Author(s):
Tom Cuypers, Cedric Vanaken, Yannick Francken, Frank Van Reeth and Philippe Bekaert
Abstract:
We present a framework that allows for a straightforward development of multi-camera controlled interactive video games. Compared to traditional gaming input devices, cameras provide players with many degrees of freedom and a natural kind of interaction. The use of cameras can even obsolete the need for special clothing or other tracking devices. This partly accounted for the success of the currently popular single-camera video games like the Sony Eyetoy. However, these games are fairly limited in the use of 3D scene information. Using multi-camera setups, this limitation can be surpassed, but typically many different image processing and computer vision techniques are involved. Our framework divides multi-camera based games into basic algorithms that are easily combinable into several sequentially executed stages. Therefore the amount of effort to develop new games can significantly be reduced. The capabilities of our framework are demonstrated with a number of conceptual games, proving that multi-camera controlled video games can be created with off-the-shelf hardware.

Paper Nr.:
84
Title:
A 3D SIMULATION OF A GAME OF BILLIARDS USING A HAPTIC DEVICE
Author(s):
Lucio Tommaso De Paolis, Giovanni Aloisio and Marco Pulimeno
Abstract:
Recently the computer entertainment technology has generated a great deal of interest among researchers and developers who have recognized the potential to create new and exciting forms of human computer interaction. Performance improvements in graphics hardware and the diffusion of the low cost haptic interfaces have made it possible to visualize complex virtual environments and provided opportunities to interact with these in a more realistic way. In this paper a Virtual Reality application of a game of billiards is presented. By means of a commercial haptic interface a force feedback is provided, thus rendering the interaction realistic and exciting to the user; the introduction of the force feedback allows the user to actually feel the contact between cue and ball. The virtual environment has been built using the development environment XVR and rigid body dynamics have been simulated utilizing the ODE library.

Paper Nr.:
119
Title:
GENERATING HUMAN INTERACTIVE BEHAVIOURS USING THE WINDOWED VITERBI ALGORITHM
Author(s):
Yue Zheng, Yulia Hicks, Dave Marshall and Darren Cosker
Abstract:
In this paper, we propose a new approach for generating interactive behaviours for virtual characters, namely the windowed Viterbi algorithm, capable of doing so in real-time. Consequently, we compare the performance of the standard Viterbi algorithm and the windowed Viterbi algorithm within our system. Our system tracks and analyses the behaviour of a real person in video input and produces a fully articulated three dimensional (3D) character interacting with the person in the video input. Our system is model-based. Prior to tracking, we train a collection of dual Hidden Markov Model (HMM) on 3D motion capture (MoCap) data representing a number of interactions between two people. Then using the dual HMM, we generate a moving virtual character reacting to (the motion of) a real person. In this article, we present the detailed evaluation of using the windowed Viterbi algorithms within our system, and show that our approach is suitable for generating interactive behaviours in real-time.

Paper Nr.:
121
Title:
A TOOL SUPPORTING MODEL BASED USER INTERFACE DESIGN IN 3D VIRTUAL ENVIROMENTS
Author(s):
Joan De Boeck, Chris Raymaekers and Karin Coninx
Abstract:
Although interactive virtual environments (IVE) have the capability to offer intuitive and easy to use interfaces, their creation is often a long and expensive process, in which specialists play a key role. The –Project– approach investigates how the use of high-level specifications may help to overcome this problem: instead of coding an IVE using a low level programming language, high-level models are used. As such a modelbased process combines a series of models containing a mixture of manual and automatic processes. The usefulness of a model based process relies on available tool support. Supporting the –Project– process, this paper introduces –Tool–. This tool has been used in order to develop a series of demonstrators, all based on real-life cases. From this experience, the –Project– approach and more particular –Tool– have proven to be useful to develop interactive virtual environments using high-level specifications.

Paper Nr.:
125
Title:
A DIYD (DO IT YOURSELF DESIGN) SYSTEM FOR VEHICLE DESIGN BASED ON 3D VISUALIZATION AND ONTOLOGIES
Author(s):
Lambros Makris, Nikolaos Karatzoulis, Dimitrios Tzovaras and Evangelos Bekiaris
Abstract:
The customization level of vehicles is growing in order to deal with increasing user needs. Web browsers are becoming the focal point of vehicle customization, forming personalized market places where users can select and preview various setups. However the state of the art for the completion of the transaction is still very much characterized by a face-to-face sales situation. Direct sales over the internet, without sales person contacts, are still a small segment of the market, of only a few percent, for European manufacturers. This paper presents an Intelligent DIY e-commerce system for vehicle design, based on 3D Visualization and Ontologies that aims at enabling a suitable representation of products with the most realistic possible visualization outcome in order to help prospective customers in their decision. The platform, designed for the vehicle sector, includes all the practicable electronic commerce variants and its on-line product configuration process is controlled by an ontology that was created using the OWL Web Ontology Language.

Paper Nr.:
127
Title:
ANIMATING AND RENDERING VIRTUAL HUMANS - Extending X3D for Real Time Rendering and Animation of Virtual Characters
Author(s):
Yvonne Jung
Abstract:
In this paper, we focus on the different aspects of real time visualization and animation of realistic virtual characters. The common goal was to come up with solutions based on the concepts of the open ISO standard X3D and if necessary to propose generalized extensions to the standard. First we describe the high level control language PML and its implementation, which is also suitable for non-graphics experts. Then we focus on realistic rendering, how X3D must be extended to allow special effects and realization of novel rendering algorithms, including skin and emotion rendering. Next we explain the challenges of dynamics related to virtual characters covering play-back and blending of pre-defined animations, online simulation of locomotion and last but not least hair simulation.

Paper Nr.:
129
Title:
AUGMENTING 3D CITY MODELS WITH VISUALIZATION OF REAL-TIME METEOROLOGICAL PHENOMENA
Author(s):
Frank Steinicke, Jörg Mensmann, Klaus Hinrichs, Jan de Buhr, Kai Rothaus and Antonio Krüger
Abstract:
General interest in visualizations of digital 3D city models is growing rapidly, and several applications are already available that display such models very realistically. Many authors have emphasized the importance of the effects of realistic illumination for computer generated images, and this applies especially to the context of 3D city visualization. However, current 3D city visualization applications rarely implement techniques for achieving realistic illumination, in particular the effects caused by current weather-related phenomena. At most, some geospatial visualization systems render artificial skies—sometimes with a georeferenced determination of the sun position—to give the user the impression of a real sky. However, such artificial renderings are not sufficient for real simulation purposes. In this paper we present techniques to augment visualizations of digital 3D city models with real-time display of georeferenced meteorological phenomena. For this purpose we retrieve weather information from different sources, i. e., real-time images from cameras and radar data from web-based weather services, and we use this information in the rendering process for realistic visualization of different weather-related issues, such as clouds, rain, fog, etc. Our approach is not limited to a specific setup, and we have evaluated the results in a user study presented in this paper.

Paper Nr.:
130
Title:
A FRAMEWORK FOR 4-D BIOMEDICAL IMAGE PROCESSING, VISUALIZATION AND ANALYSIS
Author(s):
Matteo Campana, Barbara Rizzi, Camilo Melani, Paul Bourgine, Nadine Peyrieras and Alessandro Sarti
Abstract:
Today, studies on biological systems are often realized acquiring, processing and analyzing 4-D image datasets. In this paper we present a software framework that aims at providing support for managing multidimensional biological images, designing and validating new image processing algorithms, and analyzing processed images through different visualization techniques. Finally we present a real scenario where the framework has been used for the segmentation of biological cell membranes and nuclei imaged from live zebrafish embryos.

Paper Nr.:
141
Title:
AN INTERACTIVE 3D VISUALIZATION MODEL BY LIVE STREAMING FOR REMOTE SCIENTIFIC VISUALIZATION
Author(s):
Eriko Touma, Satomi Hara, Mari Kurumi, Yuri Shirakawa, Chisato Ishikawa, Masami Takata, Takeshi Horinouchi and Kazuki Joe
Abstract:
Recent improvement of high-end GPUs has made it possible to perform real-time 3D visualization such as volume rendering and 3D contour plot for scientific data locally. A web browser based remote 3D visualization by visualization servers is attractive, but data transfer overhead prevents from performing interactive operations. We propose an interactive remote 3D visualization model by live streaming for geophysical fluids research. In this model, we use live streaming flash media for the web browser based operations keeping minimum quality of data analysis and minimum bit rate for live streaming of flash media. Preliminary experiments with a prototype system validate the effectiveness of our proposing model.

Paper Nr.:
179
Title:
A SCIENCE OF INTERACTION - A Multidimensional Canvas
Author(s):
Robert Spence
Abstract:
A recently proposed search for a science of interaction will involve the creation of a multidimensional canvas composed of many features: complex perceptual and cognitive processes, the many approaches to interaction design, the many models of interaction and the vast range of interaction modalities. In any attempt to meet this challenge this paper urges emphasis on precise definitions, especially for visualization and interaction, and reports the results of an exploratory study.

Paper Nr.:
185
Title:
SPLITTING THE SCENE GRAPH - Using Spatial Relationship Graphs Instead of Scene Graphs in Augmented Reality
Author(s):
Florian Echtler, Manuel Huber, Daniel Pustka, Peter Keitler and Gudrun Klinker
Abstract:
Scene graphs have been a core element of 3D graphics since the publication of Inventor. However, in Virtual and Augmented Reality applications, 3D graphics are often interleaved with and controlled by real-world data provided by pose trackers, cameras and other kinds of sensors. In such a setup, the generalized concept of a Spatial Relationship Graph (SRG) might be better suited as an underlying data structure to describe the application and its components. In this paper, we will give an overview of the SRG concept, describe its difference to a scene graph and provide an example AR application built upon a SRG-based tracking library.

Paper Nr.:
189
Title:
REGISTRATION APPROACHES FOR AUGMENTED REALITY - A Crucial Aspect for Successful Industrial Application
Author(s):
Katharina Pentenrieder and Peter Meier
Abstract:
In the past years, a variety of Augmented Reality (AR)-based applications were created, aiming to support industrial processes. Although these first demonstrator applications or prototypes cover all parts of the industrial product process - design, planning and production, service and maintenance - only a few of them actually turned into established and applied solutions. Reasons for this lack of acceptance are - amongst others - their insufficient usability and accuracy. One crucial step in the accuracy chain for an Augmented Reality system is the registration of real and virtual world. This paper presents different approaches for industrial registration, which are being investigated in the context of an Augmented Reality based factory planning application. The resulting toolbox promises to be helpful and valuable for general application in industrial AR. To support the choice for an optimal registration method for a given scenario, the toolbox is currently being evaluated according to usability and accuracy criteria. The current state of this evaluation as well as future planned studies are also outlined here.

Paper Nr.:
191
Title:
THE FUTURE OF PARALLEL COMPUTING: GPU VS CELL - General Purpose Planning against Fast Graphical Computation Architectures, which is the Best Solution for General Purposes Computation?
Author(s):
Luca Bianchi, Riccardo Gatti and Luca Lombardi
Abstract:
Complex models require high performance computing (HPC) which means Parallel Computing. That is a fact. The question we try to address in this paper is "which is the best suitable solution for HPC contexts such as rendering? Will it be possible to use it in General Purpose elaborations?" We start from these questions and analyze two different approaches, IBM CELL and the well known GPGPU, showing how changing our minds and breaking some assumptions can lead to unexpected results and open a whole set of new possibilities. We talk about rendering, but quickly move slightly towards general purpose computation, because many algorithms used in Visual Simulations are not only referred to rendering issues but to a wider range of problems.

Art, Science and Technology, Virtual tools for Cultural Heritage

Paper Nr.:
115
Title:
VIRTUAL RESTORATION OF A MEDIEVAL POLYCHROME SCULPTURE - Experimentation, Modelization, Validation and Visualization in Spectral Ray-tracing
Author(s):
Sylvain Dumazet, Patrick Callet and Ariane Genty
Abstract:
A pluridisciplinary work always in progress involving 3D digitization, simulation, rapid prototyping, virtual restoration of a french medieval sculpture is presented. This work is led in the framework of a general collaboration between three academic labs, industrial partners and Cultural institutions. The main purpose is to virtually represent a polychrome statue of the XIIIth century in high quality spectral rendering, to simulate its visual and original appearance at that period. The complete process used throughout all the phases of the project mainly involves optical devices that ensure no physical contact with the museum object. This article describes the complete chain of engineering resources and the main models we used for accomplishing our objective. From 3D capture without contact to plaster replica, the complete process will be described and illustrated with images and objects during the conference. Some sequences extracted from the didactic and scientific movies produced will also be presented.

Paper Nr.:
143
Title:
VIRTUAL ART GALLERY TOOL
Author(s):
Pedro Miguel Semião and Maria Beatriz Carmo
Abstract:
This paper describes a set of two applications comprising the Virtual Art Gallery tool: the Space Picker application and the Virtual Exhibition Builder application. The purpose of this tool is to allow users to interactively create a virtual exhibition of artworks in a pre-built virtual model. We use X3D for the models and Java with Xj3D for the display and handling. The works of art are handled through a MySQL database. The solution is entirely based in free soft-ware.

Paper Nr.:
165
Title:
STUDYING USERS’ ACCEPTABILITY TOWARDS 3D IMMERSIVE ENVIRONMENTS - Virtual Tours: A Case Study
Author(s):
Karina Rodriguez Echavarria, Craig Moore, David Morris, David Arnold, A. Delaney and R. Heath
Abstract:
If information is considered the key in today’s information society, then museums and heritage sites are of critical importance as they are places for knowledge to be shared and experienced by individuals. For this reason, presenting and distributing information through ICT forms could play a critical role for the museum in order to empower the public in their understanding of the past. The view of using ICT contextualisation mechanisms, such as 3D immersive virtual environment, in museums and heritage sites is explored in this research. Hence, this paper describes efforts towards exploring the acceptability of the interfaces and interaction techniques for Virtual Tours. We acknowledge the difficulty of the task as 3D immersive environment do not have defined interfaces nor visitor are believed to have replicable experiences. However, we believe that a significant amount of studies of this type might provide some answers to a field full of expectations but not enough experience in the ICT field.

Paper Nr.:
170
Title:
UNDERWATER PHOTOGRAMMETRY FOR ARCHAEOLOGY, THE VENUS PROJECT FRAMEWORK
Author(s):
P. Drap, D. Scaradozzi, P. Gambogi and F. Gauch
Abstract:
This article describes on-going developments of the VENUS European Project (Virtual ExploratioN of Underwater Sites, http://www.venus-project.eu) concerning the first mission to sea in Pianosa Island, Italy in October 2006. The VENUS project aims at providing scientific methodologies and technological tools for the virtual exploration of deep underwater archaeological sites. The VENUS project will improve the accessibility of underwater sites by generating thorough and exhaustive 3D records for virtual exploration. In this paper we focus on the underwater photogrammetric approach used to survey the archaeological site of Pianosa. After a brief presentation of the archaeological context we shall see the calibration process in such a context. The next part of this paper is dedicated to the survey: it is divided into two parts: a DTM of the site (combining acoustic bathymetry and photogrammetry) and a specific artefact plotting dedicated to the amphorae present on the site.

Paper Nr.:
192
Title:
GPU SPECTRAL VIEWER - A Tool for an Enhanced Colorimetric Perspective of Cultural Heritage
Author(s):
Denis Pitzalis, Philippe Colantoni, Ruven Pillay and Genevieve Aitken
Abstract:
During the EU IST project CRISATEL the consortium made around one hundred multispectral scans of paintings conserved in several museums. The high resolution images obtained allow us to not only have an accurate colour image but also to perform in depth quantitative scientific measures in the colour structure of works of art. One of these paintings in particular required special attention. It was Leonardo da Vinci’s “Mona Lisa”. In order to study it a special GPU oriented software was developed. In this paper we will present how the GPU computation and the computer vision can deliver the high performance and the analysis capability required to study complex and subtle works of art.

Multimedia Collaborative Virtual Environments

Paper Nr.:
144
Title:
A REVIEW OF COLLABORATIVE VIRTUAL ENVIRONMENT (CVE) EVALUATION METHODOLOGIES
Author(s):
Thrasyvoulos Tsiatsos and Konstantinidis Andreas
Abstract:
This paper presents several methodologies concerning the evaluation of Collaborative Virtual Environments (CVEs). In doing so, the authors aim to compensate for the absence of a CVE evaluating standard, with the goal of aid-ing future evaluators in their task. Initially, the paper discusses the general benefits of CVEs and computer supported collaborative learning (CSCL). Based on the examined research it continues with suggested evaluation criteria and the division of evaluation into partitions. Following that, we discuss rec-ommended evaluator profiles and data mining practices. The paper concludes with a description of appropriate data analysis procedures. In the final section, some closing remarks are made and future work is discussed.

Paper Nr.:
161
Title:
DEVELOPMENT OF THE VIRTUAL ELA®-HOUSE
Author(s):
Milán Horváth, Csaba Dániel, Jacqueline Stark and Cecília Sik Lanyi
Abstract:
In this paper, the rationale for the development and the process of creating the Virtual ELA®-House are described. The Virtual ELA®-House is an innovative therapy program designed for use with clients with language and speech disorders and/or with other cognitive neuropsychological disorders, which result from brain damage, e.g. aphasia, apraxia of speech, neglect, etc. The Virtual Reality setting is chosen as a modern and relevant therapy setting which imitates real everyday life scenarios. Computer supported cognitive and language therapy allows for repetitive application in the clinical and home setting which is necessary for learning to take place. The advantages of employing a software program based on a Virtual Environment, in particular the ELA®-virtual house, are discussed.

Paper Nr.:
163
Title:
PRESENTING INTERACTIVE MULTIMEDIA DOCUMENTS WITHIN VIRTUAL ENVIRONMENTS
Author(s):
Paulo N. M. Sampaio, Laura M. Rodriguez Peralta and João Pedro D. Pereira
Abstract:
Different languages and tools have been used for the modelling and building Virtual Reality applications which can be applied in different domains. These tools are each time more sophisticated providing means for the author of a 3D environment to build his model intuitively. However, these languages and APIs used for building virtual environments are still limited when it comes to integrate multimedia content inside these applications. This paper presents a generic and extensible solution for the presentation of integrated Interactive Multimedia Documents within Virtual Reality applications.

Paper Nr.:
164
Title:
EMBEDDING MULTIMEDIA CONTENT WITHIN VIRTUAL ENVIRONMENTS - The OGRE Approach
Author(s):
Paulo N. M. Sampaio, Roberto Ivo C. de Freitas and Gonçalo Nuno P. Cardoso
Abstract:
Most of the tools and languages for modeling Virtual Reality environments, such as VRML, X3D, Java3D, etc. do not provide means of describing the synchronized presentation of multimedia content inside these environments. Multimedia has demonstrated its capabilities of motivating users and capturing their attention, which is an interesting characteristic when we want to provide a higher degree of immersion inside Virtual Reality applications. This paper presents a robust and generic solution for the integrated presentation of different kinds of media objects inside virtual environments based on the Graphical Engine OGRE.

Paper Nr.:
172
Title:
A MODEL FOR WIRELESS SENSOR NETWORKS SUPPORTED COOPERATIVE WORK
Author(s):
Lina M. Pestana Leão de Brito and Laura M. Rodríguez Peralta
Abstract:
Collaboration is essential to Wireless Sensor Networks due to the typical resource limitations of the sensor nodes. In fact, the main functions of the network cannot be accomplished without collaboration among sensor nodes. Most of the work found in literature only focuses a specific type of collaboration, associated with the accomplishment of a certain task, such as signal processing, computing, routing, etc. In this paper, we present a graph-based model of cooperative work for WSNs. This model is called Wireless Sensor Networks Supported Cooperative Work (WSNSCW) and considers the specific requirements of the WSNs.