Short Papers 2007

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https://diglib.eg.org/handle/10.2312/261

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Reeb Chart Unfolding Based 3D Shape Signatures
(The Eurographics Association, 2007) Tierny, Julien; Vandeborre, Jean-Philippe; Daoudi, Mohamed; Paolo Cignoni and Jiri Sochor
This paper presents a novel surface parameterization based technique that addresses the pose insensitive shape signature problem for surface models of arbitrary genus. It is based on the key idea that two surface models are similar if the canonical mappings of their sub-parts introduce similar distortions. First, a Reeb graph of the shape is computed so as to segment it into charts of controlled topology, denoted as Reeb charts, that have either disk or annulus topology. Next, we define for each Reeb chart a straightforward mapping to the canonical planar domain. Then, we compute a stretching signature of the canonical mapping based on an area distortion evaluation. Finally, the input shape is represented by the set of the stretching signatures. An application to pose-insensitive shape similarity is proposed by comparing the signatures of the different Reeb charts. Promising experimental results are presented and compared to state-of-the-art techniques. The gain provided by this new signature as well as its interest for partial shape similarity are demonstrated.
Exemplar-based Worn Edges
(The Eurographics Association, 2007) Brachmann, Christoph; Walther-Franks, Benjamin; JörnLoviscach,; Paolo Cignoni and Jiri Sochor
To counteract the sterile look of computer-generated worlds, we introduce a procedural model for worn edges that can be seen in buildings and stones: edges that have suffered minor damage at multiple points, resulting in material being chipped off. Employing data gathered from photographs, the method adds minute detail along exposed edges. The deformed geometry may be simulated with normal maps to also support real-time applications.
Stabilized Noise
(The Eurographics Association, 2007) Yoon, Jong-Chul; Lee, In-Kwon; Paolo Cignoni and Jiri Sochor
Perlin noise is generated by interpolation of a pre-defined random number table. However since the random number table is generated without considering the ideal properties of noise for computer graphics, the resulting noise function does not have these properties. We improve the properties of noise for Perlin s and similar algorithms, by stabilizing the random number table itself. We create the noise function using well-known statistical tools that measure the degree of stability of a random number table. These tools are used within an optimization procedure to create a random number table with a uniform random distribution, without periodicity, and having a band-limited property.
State-of-the-Art Computer Graphics in Neurosurgical Planning and Risk Assessment
(The Eurographics Association, 2007) Köhn, Alexander; Weiler, Florian; Klein, Jan; Konrad, Olaf; Hahn, Horst; Peitgen, Heinz-Otto; Paolo Cignoni and Jiri Sochor
We present a novel software assistant that unlocks new potentials in neurosurgical planning and risk assessment. It allows surgeons to approach the task in an intuitive manner, by providing them with the possibility to simultaneously observe all relevant data of a case in synchronized 2D and 3D views. State-of-the-art technologies from the field of computer graphics are combined to allow simultaneous interactive rendering of anatomical and functional MR data in combination with manually segmented objects and slice-based overlays. This allows surgeons to perceive a clearer impression of the anatomical and functional structures affected by an intervention, and especially the way they are related to each other. Thus, it significantly facilitates the finding of an optimal intervention strategy.
Imperceptible Calibration for Radiometric Compensation
(The Eurographics Association, 2007) Zollmann, Stefanie; Bimber, Oliver; Paolo Cignoni and Jiri Sochor
We present a novel multi-step technique for imperceptible geometry and radiometry calibration of projectorcamera systems. Our approach can be used to display geometry and color corrected images on non-optimized surfaces at interactive rates while simultaneously performing a series of invisible structured light projections during runtime. It supports disjoint projector-camera configurations, fast and progressive improvements, as well as real-time correction rates of arbitrary graphical content. The calibration is automatically triggered when misregistrations between camera, projector and surface are detected
A Unified Interpolatory and Approximation sqrt-3 Subdivision Scheme
(The Eurographics Association, 2007) Lin, Shujin; Luo, Xiaonan; Paolo Cignoni and Jiri Sochor
We have found that there is a relationship between the cubic B-spline and four-point curve subdivision method. In the paper it is used to deduce interpolatory subdivision schemes from cubic B-spline based approximation subdivision schemes directly and construct unified schemes for compositing approximation and interpolatory subdivision. A new interpolatory p3 subdivision scheme and a interpolatory and approximation blended p3 subdivision scheme are created by this straightforward method. The former produces C1 limit surface and avoids the problem in the exsiting interpolatory p3 subdivision mask where the weight coefficients on extraordinary vertices can not be described by explicit formulation. The latter can be used to solve the "popping effect" problem when switching between meshes at different levels of resolution, provide the possibility to locally choose an interpolating variant of the conventionally approximating subdivision scheme, and give more flexibility for feature modeling. These are realized by only changing the value of a parameter. The method is thoroughly simple without needs of constructing and solving equations.
Automated Combination of Real-Time Shader Programs
(The Eurographics Association, 2007) Trapp, Matthias; Döller, Jürgen; Paolo Cignoni and Jiri Sochor
This work proposes an approach for automatic and generic runtime-combination of high-level shader programs. Many of recently introduced real-time rendering techniques rely on such programs. The fact that only a single program can be active concurrently becomes a main conceptual problem when embedding these techniques into middleware systems or 3D applications. Their implementations frequently demand for a combined use of individual shader functionality and, therefore, need to combine existing shader programs. Such a task is often timeconsuming, error-prone, requires a skilled software engineer, and needs to be repeated for each further extension. Our extensible approach solves these problems efficiently: It structures a shader program into code fragments, each typed with a predefined semantics. Based on an explicit order of those semantics, the code fragments of different programs can be combined at runtime. This technique facilitates the reuse of shader code as well as the development of extensible rendering frameworks for future hardware generations. We integrated our approach into an object-oriented high-level rendering system.
Volumetric Normal Mapping in Rendering of Multivariate Volume Data
(The Eurographics Association, 2007) Seipel, Stefan; Paolo Cignoni and Jiri Sochor
The work presented in this paper introduces volumetric normal maps for producing visual structure in direct volume rendering (DVR) of 3D data for the purpose of visualizing multiple attributes in a 3D volume. We use volumetric normal maps to represent normal vector glyphs that are subsequently applied to warp the gradients in the primary volume data. This method is intended to visualize some secondary attribute in DVR. We demonstrate that our method can render visual structures in DVR without the need of explicit surface reconstruction and texturing.
Adaptive Abstraction of 3D scenes in Real-Time
(The Eurographics Association, 2007) Redmond, Niall; Dingliana, John; Paolo Cignoni and Jiri Sochor
We present an approach for creating abstracted renderings of 3D scenes in real-time. We create painterly renderings with edge detail using varying levels of abstraction dependent on regions of interest within a scene. Image space techniques are used to make the system real-time and as non-invasive as possible. This approach can also use object space information to segment the scene into visually important objects and unimportant data and background. Interactive frame rates are achieved by using graphics hardware to perform the computations.
Shape Analysis for Augmented Topological Shape Descriptor
(The Eurographics Association, 2007) Symonova, Olga; Amicis, Raffaele De; Paolo Cignoni and Jiri Sochor
In this work we propose a scheme for analysis of the shape of a 3D model.We use Extended Reeb Graph to describe the topological structure of the model which we further enrich with extracted geometrical features. The nodes of the graph represent different components of the model, and we propose to analyze their shape separately. Shape characteristics such as taper/enlargement, average curvature, bending are revealed through tracing changes in cross sections of each shape component. Finally the topological structure together with the associated geometrical characteristics represents the shape descriptor of the 3D model.
Virtual Agent Navigation in Open Spaces using Iterative Shrinking Polygons
(The Eurographics Association, 2007) Haciomeroglu, Murat; Laycock, Robert; Day, Andy; Paolo Cignoni and Jiri Sochor
Populating an urban environment with a virtual crowd provides a dynamic element to an otherwise static scene; bringing the virtual environment to life. One of the fundamental components governing the fidelity of the scene is the realistic simulation of the crowd behaviour. To create a believable crowd simulation one group of methods considers constructing a graph covering the space available to the virtual agents and subsequently performing path planning to allow the agents to navigate their environment by traversing the edges of the graph. To avoid computationally expensive path planning algorithms there exists a tradeoff between the number of edges in the graph and the amount of available space which an agent can visit. In order to alleviate this problem we propose to compute the straight skeleton to provide an initial covering of the environment. This is subsequently augmented using iterative shrinking polygons to generate additional edges in the larger open spaces. The technique developed requires limited knowledge of the urban environment, processes the relevant information automatically and is illustrated in this paper to control the behaviour of a virtual crowd in real time.
Bridging Semantic Web and Digital Shapes
(The Eurographics Association, 2007) Papaleo, Laura; Floriani, Leila De; Hendler, Jim; Paolo Cignoni and Jiri Sochor
Since the volume of multimedia content available on the Web is continuously increasing, a clear need for advanced techniques capable of performing an effective retrieval and management of such data. In this context, in order to reason on digital shapes and their associated semantic, we see a growing interest in exploiting the potential of the Semantic Web in different research fields. We present here the design and initial development of our new system, that we call be-SMART for inspecting digital 3D shapes by extracting geometrical and topological information from them and for structuring and annotating these shapes using ontology-driven metadata. We describe the general structure of the system, its modules and their mutual relations. We also provide motivations for further work in developing new techniques for managing 3D models on the Web.
Object-Oriented Shader Design
(The Eurographics Association, 2007) Kuck, Roland; Paolo Cignoni and Jiri Sochor
We present an extremely lightweight object-oriented framework for writing shaders. It provides a way to invoke methods of objects from the shading language and to use references of objects as normal variables. Classes are declared and instantiated in the application language using proxy classes. We then apply object-oriented design to several typical shading problems showing their strength compared to the standard methods.
Construction of Non-Blobby Surface from Particles
(The Eurographics Association, 2007) Harada, Takahiro; Koshizuka, Seiichi; Kawaguchi, Yoichiro; Paolo Cignoni and Jiri Sochor
This paper presents a method that can construct a surface with a thin region or sharp edges from particles. The surface is constructed in two stages. An implicit surface is generated by assigning a density distribution to each particle in the first step and then the surface constructed from the density distribution is changed to a surface with a thin region or sharp edges. Furthermore, the method can generate various kinds of surfaces because a surface is controlled by several parameters. Therefore, the present technique increases the range of expression of particle-based simulations. In this paper, some calculation results are presented and finally an application from the results of particle-based fluid simulation is discussed.
Enforcing Scene Constraints in Single View Reconstruction
(The Eurographics Association, 2007) Lourakis, Manolis; Argyros, Antonis; Paolo Cignoni and Jiri Sochor
Three-dimensional reconstruction from a single view is an under-constrained process that relies critically upon the availability of prior knowledge about the imaged scene. This knowledge is assumed to be supplied by a user in the form of geometric constraints such as coplanarity, parallelism, perpendicularity, etc, based on his/her interpretation of the scene. In the presence of noise, however, most of the existing methods yield reconstructions that only approximately satisfy the supplied geometric constraints. This paper proposes a novel single view reconstruction method that provides reconstructions which exactly satisfy all user-supplied constraints. This is achieved by first obtaining a preliminary reconstruction and then refining it in an extendable, constrained optimization framework.
Exact Computation of the Hausdorff Distance between Triangular Meshes
(The Eurographics Association, 2007) Straub, Raphael; Paolo Cignoni and Jiri Sochor
We present an algorithm that computes the exact Hausdorff distance between two arbitrary triangular meshes. Our method computes squared distances for each point on each triangle of one mesh to all relevant triangles of the other mesh yielding a continuous, piecewise convex quadratic polynomial over domains bounded by conics. The maximum of this polynomial is the one-sided Hausdorff distance from one to the other mesh. We ensure the efficiency of our approach by employing a voxel grid for searching relevant triangles and an attributed half-edge data structure for representing the squared distance function.
Fast Hierarchical 3D Distance Transforms on the GPU
(The Eurographics Association, 2007) Cuntz, Nicolas; Kolb, Andreas; Paolo Cignoni and Jiri Sochor
This paper describes a fast approximate approach for the GPU-based computation of 3D Euclidean distance transforms (DT), i.e. distance fields with associated vector information to the closest object point. Our hierarchical method works on discrete voxel grids and uses a propagation technique, both on a single hierarchy level and between the levels. Using our hierarchical approach, the effort to compute the DT is significantly reduced. It is well suited for applications that mainly rely on exact distance values close to the boundary. Our technique is purely GPU-based. All hierarchical operations are performed on the GPU. A direct comparison with the Jump Flooding Algorithm (JFA) shows that our approach is faster and provides better scaling in speed and precision, while JFA should be preferred in applications that require a more precise DT.
Preface and Table of Contents
(The Eurographics Association, 2007) -; Paolo Cignoni and Jiri Sochor
Preface and Table of Contents
Liquid Diffusion Model that Accounts for a Variety of Dyeing Parameters
(The Eurographics Association, 2007) Yuki, Morimoto; Tanaka, Masayuki; Tsuruno, Reiji; Tomimatsu, Kiyoshi; Paolo Cignoni and Jiri Sochor
This paper describes a method for simulating and visualizing dyeing based on weave patterns and the physical parameters of the threads and the dye. We apply Fick s second law with a variable diffusion coefficient, which is calculated using the porosity, tortuosity, and the dye concentration based on the physical chemistry of dyeing. The tortuosity of the channel was incorporated in order to consider the effect of weave patterns on diffusion. The total mass is conserved in this model. We describe the cloth model using a two-layered cellular model that includes the minimum factors required for representing the weft and warp. Our model also includes a simple dyeing technique that produces dyeing patterns by interrupting the diffusion of the dye in a cloth using a press. The results obtained using our model demonstrate that it is capable of modeling many of the characteristics of dyeing.
A Pen-based Interface for Generating Graphical Reports of Findings in Cardiac Catheterization
(The Eurographics Association, 2007) Mori, Yuki; Igarashi, Takeo; Haraguchi, Ryo; Nakazawa, Kazuo; Paolo Cignoni and Jiri Sochor
This paper introduces a pen-based interface for the graphical reporting of findings in cardiac catheterization. The user can interactively draw, erase, move, and deform coronary arteries as well as record stenoses on them. The lo-cation and degree of each stenosis is represented visually and the doctor can record various treatments such as by-passes and stents on the diagram. In addition, the system automatically extracts semantic information from the graphical representation and stores it in XML format. The system can also generate a table in the format specified by the American Heart Association. This system is useful not only as a tool for efficiently generating reports of findings but also as an effective explanation tool for patients.

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