Short Papers 2007

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

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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.
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.
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.
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.
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.
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.
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.
Fast GPU-based Visibility Computation for Natural Illumination of Volume Data Sets
(The Eurographics Association, 2007) Ritschel, Tobias; Paolo Cignoni and Jiri Sochor
Pre-computed radiance transfer (PRT) has been used to render volumetric data under distant low-frequency illumination at real-time rates, including natural illumination, soft shadows, attenuation from semi-transparent occluders and multiple scattering. PRT requires a lengthy pre-process, which is acceptable only for static volume data. However, in practical volume rendering, general transfer functions are used. Manipulating such a transfer function will result in a dynamic radiance transfer which has to be re-computed. This work proposes a fast way for this re-computation. While previous work has used CPU Monte Carlo ray-tracing for pre-computation and requires time in the order of many minutes, our GPU implementation uses a hierarchical visibility approximation implemented entirely on the GPU and requires only a few seconds for typical scenes.
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.
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.
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.
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
Improved Skeleton Computation of an Encoded Volume
(The Eurographics Association, 2007) Ayala, Dolors; Paolo Cignoni and Jiri Sochor
In this communication, we present an improvement of an existing thinning algorithm that computes a surface skeleton from a binary volume. The method makes an intensive use of Boolean operations and works on a special encoding of the volume (the EVM encoding) in which Boolean operations are very efficient. The contribution of this work consists on a more suitable application of Boolean operations in the thinning algorithm. Computation time has been reduced more than a half.
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.
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.
Painterly Effects Rendering with Focus Based Level of Detail
(The Eurographics Association, 2007) Levente, Kovács; Tamás, Szirányi; Paolo Cignoni and Jiri Sochor
We present a novel method for automatically creating scalable and portable 2D non-photorealistically rendered (NPR) images with painterly effects, with level of detail control. The novelty of the approach lies both in using optical image analysis for automatic focus region extraction, and in producing the painterly rendered images as vector graphics. The approach is also novel in that we automatically extract the regions of higher interest without the need of any tools, devices, or a priori image information. The method is a combination of automatic relative focus map estimation and simple digital strokes for the foreground, and color image segmentation for the background. The images are rendered into scalable vector graphics (SVG) for easy viewing and editing with a variety of existing applications and use in other designs/graphics.
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.
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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