Short Papers 2007

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

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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.
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.
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.
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.
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.
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.
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.
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.
Preface and Table of Contents
(The Eurographics Association, 2007) -; Paolo Cignoni and Jiri Sochor
Preface and Table of Contents
Pareto-Based Perceptual Metric for Imperceptible Simplification on Mobile Displays
(The Eurographics Association, 2007) Wu, Fan; Agu, Emmanuel; Lindsay, Clifford; Paolo Cignoni and Jiri Sochor
Graphics on mobile devices has become popular because untethered computing is convenient and increases pro- ductivity. Mobile displays come in different resolutions that affect the scene Level-of-Detail (LoD) that users can perceive: smaller displays show less detail, making lower resolution meshes and textures acceptable. Mobile de- vices frequently have limited battery energy, low memory and disk space. To minimize wasting system resources, we try to render mobile graphics scenes at the lowest LoD at which users do not perceive distortion due to sim- plification. We call this LoD the Point of Imperceptibility (PoI). The PoI LoD depends on several factors including screen size, scene geometry and lighting levels. We propose a perceptual metric that identifies the PoI LoD of a target mobile display and accounts for object geometry, lighting and shading. Our perceptual metric generates a screen-dependent pareto distribution with a knee point that corresponds to the PoI. We employ wavelets for simplification, which gives direct access to the mesh undulation frequency that we then use to parametrize the perceptual CSF curve.
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.
Spinoff - Transferring Energy between Real and Virtual Worlds
(The Eurographics Association, 2007) Groenegress, Christoph; Slater, Mel; Tamke, Martin; Thomsen, Mette Ramsgard; Paolo Cignoni and Jiri Sochor
There is a widening gap between interaction devices for Virtual Environments and other factors such as graphical realism, accessibility and complexity. To address this problem, we developed a Mixed Reality environment that allows participants to interact with virtual entities using an existing toy a Hula Hoop. In a subsequent user study we attempted to correlate the use of real artefacts as input devices towards increased interactivity.
Fast Hierarchical Methods to Detect Collisions between Deformable Objects: A Comparison
(The Eurographics Association, 2007) Madera, Francisco; Day, A. M.; Laycock, S. D.; Paolo Cignoni and Jiri Sochor
The time complexity of a collision detection algorithm can be reduced to logarithmic in the number of tests performed when the objects are decomposed into a Bounding Volume (BV) tree hierarchy. It is well known that the Sphere Bounding Volume (SBV) and the Axis Aligned Bounding Box (AABB) hierarchies require inexpensive overlapping tests. However, we present a method called the Distance Hierarchy (DH) which is more suitable for deformable objects and is very simple to implement. It uses a hierarchical tree to decompose each object into regions. Each region requires just one parameter, its radius. In this work we compare three methods, AABB hierarchy, Sphere hierarchy, and DH, where the focus is on the intersection test, computation time, and the use of memory.
Real-Time 3D Lettering with a 2D Font Engine
(The Eurographics Association, 2007) Heise, Sebastian; Loviscach, Jörn; Paolo Cignoni and Jiri Sochor
Standard texturing shows a number of problems with 3D objects such as road signs, labels, or books. If letters are displayed at too large a scale, textures show blurred instead of hard edges; if letters are displayed at tiny sizes, textures appear either too pixelated or too blurry, but seldom well readable. In 2D as opposed to 3D, letters are created on demand in the required size by a sophisticated font rendering engine, a standard component of today s operating systems. A number of specific improvements such as hinting and RGB subpixel rendering are available. This paper demonstrates how these partially proprietary and patented 2D functions can be leveraged for 3D rendering. The price to pay is a loss in geometric precision, since typical 2D font rendering engines only handle affine transformations, which can merely approximate perspective projection. However, in most situations this is outweighed easily by the gain in clarity.
An Accurate Implicit Field Representation for Meshes and Its Adapted Triangulation Algorithms
(The Eurographics Association, 2007) Fournier, Marc; Dischler, J. - M.; Bechmann, D.; Paolo Cignoni and Jiri Sochor
The classic implicit scalar field distance transform representation of a mesh is very useful to perform many mesh processing operations and to obtain better results than with other methods. In this paper we propose a new and more accurate implicit vector field distance transform representation of a mesh. We adapt Marching Cube and Marching Triangle, the two most widely used triangulation algorithms, to our new vector field representation to correctly reconstruct the final mesh after data processing in the implicit domain. According to a reliable surface error metric, we show our new vector field is more accurate than the classic scalar field to implicitly represent a mesh. We adapt to our vector field a previously introduced mesh denoising algorithm performed on the scalar field. Results show mesh denoising with our vector field outperforms the one with classic scalar field in terms of an error metric comparison.
Analysis of the Pulmonary Vein Ostia using Cardiac 4DCT for Radiosurgical Ablation
(The Eurographics Association, 2007) Sumanaweera, Thilaka; Conti, Francois; Maguire, Patrick; Paolo Cignoni and Jiri Sochor
A software tool to analyze 4D cardiac CT data sets for planning radiosurgical ablations in the heart is presented. Volume rendering and data processing are performed using a GPU. The user visualizes the data from inside the left atrium and defines the target in 3D using an intuitive user interface. A haptic input device lets the user measure motion at the ostia of the pulmonary veins for radiosurgical treatment planning. This tool has been used effectively for generating radiation treatment plans for animal studies.
High Speed Skin Color Detection and Localization on a GPU
(The Eurographics Association, 2007) Seshadrinathan, Manoj; Dempski, Kelly; Paolo Cignoni and Jiri Sochor
In this paper, we present a simple yet novel method for high speed skin color detection and localization on images and video using the Graphics Processing Unit (GPU) and common graphics programming techniques. Our approach is innovative in that it provides a system for skin recognition and localization on the GPU at a speed much higher than that on the CPU. We also test in detail, the performance of different classes of cards and data buses.

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