GRAPP 2008 Abstracts


Area 1 - Geometry and Modeling

Full Papers
Paper Nr: 117
Title:

APPROXIMATE G1 CUBIC SURFACES FOR DATA APPROXIMATION

Authors:

Yingbin Liu and Stephen Mann

Abstract: This paper presents a piecewise cubic approximation method with approximate G1 continuity. For a given triangular mesh of points with arbitrary topology, one cubic triangular Be´zier patch surface is constructed. The resulting surfaces have G1 continuity at the vertex points, but only requires approximate G1 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.
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Paper Nr: 132
Title:

EFFICIENT FACE-BASED NON-SPLIT CONNECTIVITY COMPRESSION FOR QUAD AND TRIANGLE-QUAD MESHES

Authors:

Dina Khattab, Yasser Abd El-latif, Saeed Abd El-wahab and Fahmy 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 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.
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Paper Nr: 148
Title:

SURFACE-SURFACE INTERSECTION BY HERMITE INTERPOLATION

Authors:

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 either 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.
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Paper Nr: 160
Title:

MESH SIMPLIFICATION USING DISTANCE LABELS FOR VIEW-INDEPENDENT SILHOUETTE PRESERVATION

Authors:

Susana Mata, Luis Pastor and Angel Rodríguez

Abstract: Multiresolution modelling is a good method to achieve both quality and performance in the rendering of complex scenes. Within this framework, the detection and preservation of outstanding features, such us silhouettes, become very important. The goal of this paper is to present a technique based on Distance Transforms that allows to classify the elements of the mesh according to their proximity to both the internal and the external contours and makes use of this information for weighting the approximation error which will be tolerated during the mesh simplification process. The approach used in this work precomputes silhouettes for a given set of cameras and performs an estimation for any other point of view. The results obtained are evaluated in two ways: visually and using an objective metric that measures the geometrical difference between two polygonal meshes.
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Paper Nr: 161
Title:

CONTROL POLYGON BASED TEXTURE SYNTHESIS ON BIQUADRATIC BĒZIER RATIONAL SURFACES

Authors:

Rupesh 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.
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Paper Nr: 163
Title:

EXPERIMENTAL STUDY OF BOUNDING BOX ALGORITHMS

Authors:

Darko Dimitrov, Mathias Holst, Christian Knauer and Klaus Kriegel

Abstract: The computation of the minimum-volume bounding box of a point set in R3 is a hard problem. The best known exact algorithm requires O(n3 ) 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. Here, we study the impact of the recent theoretical results on applications of several PCA variants in practice. We give the closed form solutions for the case when the point set is a polyhedron or a polyhedral surface. To the best of our knowledge, the continuous PCA over the volume of a 3D body is considered for the first time. We analyze the advantages and disadvantages of the different variants on realistic inputs, randomly generated inputs, and specially constructed (worst case) instances. The results reveal that for most of the realistic inputs the qualities of the discrete PCA and the continuous PCA bounding boxes are comparable. As it was expected the discrete PCA versions are much faster, but behave bad on the clustered inputs. In addition, we evaluate and compare the performances of several existing bounding box algorithms.
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Short Papers
Paper Nr: 134
Title:

ANALYSIS OF POINT CLOUDS - Using Conformal Geometric Algebra

Authors:

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.
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Paper Nr: 135
Title:

GEOMETRIC ALGORITHMS ON CUDA

Authors:

Antonio Rueda and Lidia M. 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.
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Paper Nr: 136
Title:

THE GROUNDED HEIGHTMAP TREE - A New Data Structure for Terrain Representation

Authors:

Jesus Alonso and Robert 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.
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Paper Nr: 138
Title:

IMAGE-BASED 3D TORSO BODY MODELING - 3D Female Body Modeling for Breast Surgery Simulation

Authors:

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 realistic visualization.
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Paper Nr: 146
Title:

QUALITY PERCEPTION OF SIMPLIFIED MODELS: NSA V S. QSLIM

Authors:

Frutuoso Silva and Samuel 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 are of 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 of the models. The comparison of results was made using the PolyMeCo tool, which enables the analysis and comparison of meshes by providing an environment where several visualization options and metrics are available and can be used in a coordinated way.
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Paper Nr: 156
Title:

HAPCO: REAL TIME SIMULATION OF INTERACTION BETWEEN DEFORMABLE OBJECTS WITH HAPTIC FEEDBACK FOR SOLVING FRICTION MULTIPLE CONTACTS

Authors:

Talbi nadjet, Joli Pierre, Feng Zhi-Qiang and kheddar abderrahmane

Abstract: This paper deals principally with the comparison of two efficient algorithms to solve multi-contact problems with friction between two deformable bodies. 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 an unique mathematical operator of projection as well as a better force feedback stability of the friction contact force. For reasons of modular programming, a method to decouple the contact solver from the displacement solver is presented. A Haptic Contact simulator called “HapCo” has been developed as a prototype to test contact algorithms between two deformable objects in the context of interactive simulation with a haptic device.
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Paper Nr: 164
Title:

VORONOI DIAGRAM AND ITS APPLICATION TO SPATIAL CALIBRATION FOR GAMMA CAMERA IMAGES

Authors:

Brian Maisler , Hong Liu, John 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.
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Paper Nr: 168
Title:

GPU-BASED NORMAL MAP GENERATION

Authors:

Jesús Gumbau, Carlos González 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 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.
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Paper Nr: 170
Title:

A HIERARCHICAL SPATIAL INDEX FOR TRIANGULATED SURFACES

Authors:

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.
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Paper Nr: 178
Title:

GEOMETRICAL DEGENERACY REMOVAL BY VIRTUAL DISTURBANCES - An Application to Surface Reconstruction from Point Slice Samples

Authors:

Oscar Ruiz-Salguero, Eliana Vasquez, Sebastian Pena 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 properties of the surface. Topological methods classify the transitions occurred in the 2-manifold between two consecutive slices i and i + 1. Geometrical methods synthesize the surface based on local proximity of the contours in consecutive slices. Superimposed 2D Voronoi Diagrams V Di and V Di+1 for slices i and i + 1, respectively, present topological problems if, for example, a site of V Di lies on an site or an edge of V Di+1 . The usual treatment of this problem in literature is to apply a geometrical disturbance to either V Di or V Di+1 , thus eliminating the degeneracy. In contrast, this article presents the implementation of a method which identifies the degenerate situation, constructs un-instantiated topological constructs, choses a geometrical instantiation based on a virtual disturbance introduced to the actual configuration. The algorithm was successfully applied to remove non-manifold topologies produced by well known algorithms in surface reconstruction.
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Paper Nr: 181
Title:

A PEN AND PAPER METAPHOR FOR ORCHID MODELING

Authors:

Glen McCord, Burkhard Wuensche, 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 extend the pen and paper metaphor with a paper sculpting metaphor which is applied to sketched shapes. 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 created by an inexperienced, non-artistic user in a short period of time.
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Paper Nr: 145
Title:

CORNER DETECTION ON CURVES

Authors:

Neeta Nain, Vijay laxmi and Bhavitavya Bhadviya

Abstract: Detection of discontinuity plays an important role in image registration, comparison, segmentation, time sequence analysis and object recognition. In this paper we address some aspects of analyzing the content of an image. A point is classified as a corner where there are abrupt changes in the curvature of the curve. This paper presents a new approach for corner detection using first order difference of chain codes. Since the proposed method is based on integer operations it is simple to implement and efficient. Preliminary results are presented and evaluation with respect to standard corner detectors is done as a benchmark.
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Paper Nr: 150
Title:

DETECTION OF FACES IN WIRE-FRAME POLYHEDRA - Interactive Modelling of Uniform Polyhedra

Authors:

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 system can be applied to recreational mathematics, computer assisted education of the graph theory, and so on.
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Paper Nr: 169
Title:

VISUALIZING MULTIPLE SCALAR FIELDS ON A SURFACE

Authors:

Mohammed Mostefa Mesmoudi, Leila De Floriani and Paola Magillo

Abstract: We present a new technique for the simultaneous visualization of an arbitrary number of scalar fields defined on a surface. The technique is called Generalized Atmosphere Upper Bound Level (GAUBL), since it is an evolution of our previous AUBL technique, that allowed for the visualization of a single scalar field. The generalized AUBL can highlight the dependencies and interactions between many scalar fields, and can handle a multi-valued scalar field as a special case. We have implemented the GAUBL into a visualization tool that handles triangle-based surface models, and we show here some experimental results.
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Paper Nr: 187
Title:

AN EXTENSION TO THE BEZIER SUB-DIVISION METHOD TO COMPLETELY APPROXIMATE CURVES AND SURFACES

Authors:

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.
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Paper Nr: 202
Title:

BEYOND GRAPHICS: INFORMATION - An Overview of Infovis Practices in the Field of the Architectural Heritage

Authors:

Jean-Yves Blaise and Iwona 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 can be a bridge between the above mentioned fields.
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Area 2 - Rendering

Full Papers
Paper Nr: 137
Title:

QUASI-CONVOLUTION PYRAMIDAL BLURRING

Authors:

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.
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Paper Nr: 152
Title:

DISPLACEMENT PATCHES FOR GPU-ORIENTED VIEW-DEPENDENT RENDERING

Authors:

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. Initial results show that our implementation achieves quality images at high rates.
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Paper Nr: 155
Title:

GENERIC BRDF SAMPLING - A Sampling Method for Global Illumination

Authors:

Rosana Montes, Carlos Ureña Almagro, 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.
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Paper Nr: 162
Title:

A DIRECT VOLUME RENDERING FRAMEWORK FOR THE INTERACTIVE EXPLORATION OF HIGHER-ORDER AND MULTIFIELD DATA

Authors:

Felix Manke and Burkhard Wuensche

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 sophisticated Software Engineering (SE) 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 three case studies and the efficiency and effectiveness of the framework is evaluated.
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Paper Nr: 171
Title:

A PSYCHOPHYSICAL STUDY OF FOVEAL GRADIENT BASED SELECTIVE RENDERING

Authors:

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.
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Paper Nr: 179
Title:

A GENERALIZATION APPROACH FOR 3D VIEWING DEFORMATIONS OF SINGLE-CENTER PROJECTIONS

Authors:

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.
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Paper Nr: 180
Title:

SUGGESTIVE CONTOURS OVER POINT-SET IMPLICITS

Authors:

Joao, Proenca, Joaquim Jorge and Mario Costa Sousa

Abstract: This paper presents 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 harness- ing 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.
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Short Papers
Paper Nr: 131
Title:

TIME-VARYING MULTIMODAL VOLUME RENDERING WITH 3D TEXTURES

Authors:

Pascual Abellán, Sergi Grau and Pascual Abellán

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.
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Paper Nr: 153
Title:

REAL-TIME VIEW-DEPENDENT VISUALIZATION OF REAL WORLD GLOSSY SURFACES

Authors:

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 directions 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.
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Paper Nr: 157
Title:

FROM VOLUME SPLATTING TO RAYCASTING - A Smooth Transition

Authors:

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 amounts of elements usually necessary to represent highly detailed densely sampled datasets, which can lead to poor performances. 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.
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Paper Nr: 188
Title:

OBJECTIVE QUALITY SELECTION FOR HYBRID LOD MODELS

Authors:

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 which we use to optimize render quality. We test the presented solution on both desktop and mobile systems.
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Paper Nr: 190
Title:

REAL-TIME MIXED REALITY WITH GPU TECHNIQUES

Authors:

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.
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Paper Nr: 133
Title:

FINE ARTS EDUTAINMENT - The Amateur Painter

Authors:

D. Almeida, S. Nunes, J. Carvalho, V. Brito, Joao Rodrigues and Hans D. 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.
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Paper Nr: 196
Title:

TOWARDS PROBE-LESS AUGMENTED REALITY - A Position Paper

Authors:

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 to be captured as a High Dynamic Range environment map. 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.
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Area 3 - Animation and Simulation

Full Papers
Paper Nr: 130
Title:

DTW-CURVE FOR CLASSIFICATION OF LOGICALLY SIMILAR MOTIONS

Authors:

Yuedong Yang, Zhao Qinping, Aimin Hao and 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.
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Paper Nr: 154
Title:

REALISTIC RAIN RENDERING

Authors:

Yoshiki Mizukami, Katsuhiro Sasaki and Katsumi Tadamura

Abstract: We propose a method for rendering realistic three-dimensional raining scene. The 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.
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Short Papers
Paper Nr: 139
Title:

EFFICIENT INVERSE KINEMATICS ALGORITHM BASED ON CONFORMAL GEOMETRIC ALGEBRA - Using Reconfigurable Hardware

Authors:

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.
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Paper Nr: 147
Title:

DIRECTABLE AND STYLIZED HAIR SIMULATION

Authors:

Yosuke Kazama, Eiji Sugisaki and Shigeo Morishima

Abstract: Creating natural looking hair motion is considered to be one of the most difficult and time consuming challenges in CG animation. A detailed physics-based model is essential in creating convincing hair animation. However, hair animation created using detailed hair dynamics might not always be the result desired by creators. For this reason, a hair simulation system that is both detailed and editable is required in contemporary Computer Graphics. In this paper we therefore, propose the use of External Force Field (EFF) to construct hair motion using a motion capture system. Furthermore, we have developed a system for editing the hair motion obtained using this process. First, the environment around a subject is captured using a motion capture system and the EFF is defined. Second, we apply our EFF-based hair motion editing system to produce creator-oriented hair animation. Consequently, our editing system enables creators to develop desired hair animation intuitively without physical discontinuity.
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Paper Nr: 147
Title:

DIRECTABLE AND STYLIZED HAIR SIMULATION

Authors:

Yosuke Kazama, Eiji Sugisaki and Shigeo Morishima

Abstract: Creating natural looking hair motion is considered to be one of the most difficult and time consuming challenges in CG animation. A detailed physics-based model is essential in creating convincing hair animation. However, hair animation created using detailed hair dynamics might not always be the result desired by creators. For this reason, a hair simulation system that is both detailed and editable is required in contemporary Computer Graphics. In this paper we therefore, propose the use of External Force Field (EFF) to construct hair motion using a motion capture system. Furthermore, we have developed a system for editing the hair motion obtained using this process. First, the environment around a subject is captured using a motion capture system and the EFF is defined. Second, we apply our EFF-based hair motion editing system to produce creator-oriented hair animation. Consequently, our editing system enables creators to develop desired hair animation intuitively without physical discontinuity.
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Paper Nr: 167
Title:

INTERACTIVE RECONSTRUCTION AND VISUALIZATION OF DYNAMIC 3D ULTRASOUND DATA SETS

Authors:

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.
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Paper Nr: 176
Title:

RAY-TRACED COLLISION DETECTION FOR DEFORMABLE BODIES

Authors:

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.
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Paper Nr: 191
Title:

SIMULATION OF CONSTRUCTION PROCESSES WITHIN VIRTUAL ENVIRONMENTS

Authors:

Alcínia Z. 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. 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.
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Paper Nr: 201
Title:

AUTOMATIC COMPOSITION OF DRAMATIC MOVEMENT - Analysis and Algorithm for Creating Contemporary Dance Sequences

Authors:

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 recognized the connecting method was 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.
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Paper Nr: 173
Title:

MODELING AND SIMULATING MOBILE ROBOT ENVIRONMENTS

Authors:

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.
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Paper Nr: 182
Title:

A FULLY GPU-IMPLEMENTED RIGID BODY SIMULATOR

Authors:

Alvaro del Monte, Roberto Torres, Pedro Jesus Martin de la Calle 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.
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Area 4 - Interactive Environments

Full Papers
Paper Nr: 158
Title:

A DIYD (DO IT YOURSELF DESIGN) SYSTEM FOR VEHICLE DESIGN BASED ON 3D VISUALIZATION AND ONTOLOGIES

Authors:

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.
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Paper Nr: 172
Title:

GENERATING HUMAN INTERACTIVE BEHAVIOURS USING THE WINDOWED VITERBI ALGORITHM

Authors:

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.
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Paper Nr: 174
Title:

A TOOL SUPPORTING MODEL BASED USER INTERFACE DESIGN IN 3D VIRTUAL ENVIRONMENTS

Authors:

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 VR-DeMo 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 model-based 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 VR-DeMo process, this paper introduces CoGenIVE. This tool has been used in order to develop a series of demonstrators, all based on real-life cases in different domains. From this experience, the VR-DeMo approach and more particular CoGenIVE have proven to be useful to develop interactive virtual environments using high-level specifications.
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Paper Nr: 177
Title:

AUGMENTING 3D CITY MODELS WITH VISUALIZATION OF REAL-TIME METEOROLOGICAL PHENOMENA

Authors:

Frank Steinicke, Jörg Mensmann, Klaus Hinrichs, Swenja Rothaus, Jan de Buhr 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.
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Short Papers
Paper Nr: 128
Title:

ANIMATING AND RENDERING VIRTUAL HUMANS - Extending X3D for Real Time Rendering and Animation of Virtual Characters

Authors:

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.
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Paper Nr: 149
Title:

A SIP SPATIAL AUDIO SERVER FOR THE EVE PLATFORM

Authors:

Christos 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.
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Paper Nr: 151
Title:

AN INTERACTIVE 3D VISUALIZATION MODEL BY LIVE STREAMING FOR REMOTE SCIENTIFIC VISUALIZATION

Authors:

Eriko Touma, Satomi Hara, Mari Kurumi 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.
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Paper Nr: 159
Title:

A FRAMEWORK FOR 4-D BIOMEDICAL IMAGE PROCESSING, VISUALIZATION AND ANALYSIS

Authors:

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 3D-time lapse images. Different structures of the organism can be simultaneously observed by acquiring multi-channel image datasets. In this paper we present a software framework that aims at providing support for managing these kinds of multidimensional images, designing and validating new image processing algorithms, and analyzing processed images through different visualization techniques. We present a real scenario where the framework has been used for the detection and segmentation of biological cell membranes and nuclei imaged from live zebrafish embryos.
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Paper Nr: 197
Title:

A SCIENCE OF INTERACTION - A Multidimensional Canvas

Authors:

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.
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Paper Nr: 198
Title:

REGISTRATION APPROACHES FOR AUGMENTED REALITY - A Crucial Aspect for Successful Industrial Application

Authors:

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.
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Paper Nr: 200
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?

Authors:

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.
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Paper Nr: 200
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?

Authors:

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.
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Paper Nr: 129
Title:

LOCALIZATION IN AN INTERACTIVE SYSTEM

Authors:

Juan José Jiménez-Delgado, 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.
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Paper Nr: 165
Title:

IMAGE QUALITY IN IMAGE-BASED REPRESENTATIONS OF REAL-WORLD ENVIRONMENTS - Perceived Smoothness of Viewpoint Transitions

Authors:

Filippo Speranza, Akshay Bhatia and Robert Laganiere

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.
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Paper Nr: 166
Title:

A MULTI-CAMERA FRAMEWORK FOR INTERACTIVE VIDEO GAMES

Authors:

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.
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Paper Nr: 175
Title:

A 3D SIMULATION OF A GAME OF BILLIARDS USING A HAPTIC DEVICE

Authors:

Lucio Tommaso De Paolis, Giovanni Aloisio and Marco Pulimeno

Abstract: 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. Since in the real game it is possible to use the left hand when aiming and striking the ball, in the play modality it is possible to fix the cue movement in the desired direction in order to allow a more careful aim and a more stable interaction in the virtual environment. In addition it is possible to choose the force with which the ball is hit.
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Paper Nr: 199
Title:

SPLITTING THE SCENE GRAPH - Using Spatial Relationship Graphs Instead of Scene Graphs in Augmented Reality

Authors:

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 an SRG-based tracking library.
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