Italian Chapter Conference 2010

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https://diglib.eg.org/handle/10.2312/913

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An Adaptive Video Surveillance Architecture for Behavior Analysis
(The Eurographics Association, 2010) Zini, Luca; Noceti, Nicoletta; Odone, Francesca; Enrico Puppo and Andrea Brogni and Leila De Floriani
Adaptivity to scene changes is a main requirement for video analysis. The interpretation of video streams can be dealt by triggering different techniques depending on the scene properties. We present a work-on-progress for the design of a video surveillance architecture where different tasks in the context of behavior analysis are addressed, depending on the crowd level. A coarse estimation of the scene occupancy allows us to focus on single person or groups, adopting appropriate strategies to model the dynamic information. This paper focuses in particular on the crowd estimation problem: we propose a solution to detect and localize groups of people, able to provide an estimate of the number of people in the scene.
Adaptive Quad Mesh Simplification
(The Eurographics Association, 2010) Bozzo, Agostino; Panozzo, Daniele; Puppo, Enrico; Pietroni, Nico; Rocca, Luigi; Enrico Puppo and Andrea Brogni and Leila De Floriani
We present an improved algorithm for the progressive simplification of quad meshes, which adapts the resolution of the mesh to details of the modeled shape. We extend previous work [TPC*10], by simplifying the approach and combining it with the concept of Fitmaps introduced in [PPT*10]. The new algorithm has several advantages: it is simpler and more robust; it does not need a parametrization of the input shape; it is adaptive; and it preserves projectability of the output mesh to the input shape, thus supporting displacement mapping. We present experimental results on a variety of datasets, showing relevant improvement over previous results under several aspects.
Mixed Reality and Gesture Based Interaction for Medical Imaging Applications
(The Eurographics Association, 2010) Abate, Andrea F.; Nappi, Michele; Ricciardi, Stefano; Tortora, Genoveffa; Enrico Puppo and Andrea Brogni and Leila De Floriani
This paper presents a framework providing a collection of techniques to enhance reliability, accuracy and overall effectiveness of gesture-based interaction applied to the manipulation of virtual objects within a Mixed Reality context. We propose an approach characterized by a floating interface, operated by two-hand gestures, for an enhanced manipulation of 3D objects. Our interaction paradigm, exploits one-hand, twohand and time-dependent gesture patterns to allow the user to perform inherently 3D tasks, like arbitrary object rotation, or measurements of relevant features, in a more intuitive yet accurate way. A real-time adaptation to the user s needs is performed by monitoring hands and fingers motions, in order to allow both direct manipulation of virtual objects and conventional keyboard-like operations. The interface layout, whose details depend on the particular application at hand, is visualized via a stereoscopic see-through Head Mounted Display (HMD). It projects virtual interface elements, as well as application related virtual objects, in the central region of the user s field of view, floating in a close-at-hand volume. The application presented here is targeted to interactive 3D visualization of human anatomy resulting from diagnostic imaging or from virtual models aimed at training activities. The testing conducted so far shows a measurable and user-wise perceptible improvement in performing 3D interactive tasks, like the selection of a particular spot on a complex 3D surface or the distance measurement between two 3D landmarks. This study includes both qualitative and quantitative reports on the system usability.
Developing a Web 3.0 E-learning Portal with X3D Technologies
(The Eurographics Association, 2010) Cerbo, Francesco Di; Dodero, Gabriella; Papaleo, Laura; Enrico Puppo and Andrea Brogni and Leila De Floriani
The paper describes our experience in the development of the DIEL learning management system, and especially its 3D interface, which has been developed using X3D. DIEL allows to structure learning activities along a virtual learning path, composed by a set of virtual rooms. Each room can be represented as a 2D or 3D virtual environment. A first implementation of DIEL s 3D interface had been developed using Flash, recently such an interface was refactored using the new and innovative technologies X3D and X3DOM, with a substantial increase in terms of virtual environment personalization and in the possibility of supporting new features in the future.
Natural Interaction and Computer Graphics Applications
(The Eurographics Association, 2010) Iacolina, Samuel A.; Lai, Alessandro; Soro, Alessandro; Scateni, Riccardo; Enrico Puppo and Andrea Brogni and Leila De Floriani
Natural Interaction with computers has been a challenging topic of research since the very beginning of the digital era and refers to the possibility, on the user s part, of exploiting natural abilities to control the machine and interpret its outputs. If in the infancy of computer graphics this meant using visual representation and pen pointing, nowadays more refined techniques are needed to fit the wide range of applications, from home entertainment to virtual and augmented reality. This paper describes some advances in gesture, tangible and surface computing, showing how such interaction models, if treated as a continuum, improve the usability, accessibility and overall experience of computer graphics applications.
Building Morphological Representations for 2D and 3D Scalar Fields
(The Eurographics Association, 2010) Comic, Lidija; Floriani, Leila De; Iuricich, Federico; Enrico Puppo and Andrea Brogni and Leila De Floriani
Ascending and descending Morse complexes, defined by the critical points and integral lines of a scalar field f defined on a manifold domain D, induce a subdivision of D into regions of uniform gradient flow, and thus provide a compact description of the morphology of f on D. We propose a dimension-independent representation for the ascending and descending Morse complexes, and we describe a data structure which assumes a discrete representation of the field as a simplicial mesh, that we call the incidence-based data structure. We present algorithms for building such data structure for 2D and 3D scalar fields, which make use of a watershed approach to compute the cells of the Morse decompositions.
A Dimension-Independent and Extensible Framework for Huge Geometric Models
(The Eurographics Association, 2010) Canino, David; Enrico Puppo and Andrea Brogni and Leila De Floriani
Nowadays, gigantic models can be easily produced in many applications and their dimension often exceeds the RAM size in a common workstation. Thus, using an external memory technique is mandatory in this case. In this paper, we define a dimension-independent and extensible framework, called Objects Management in Secondary Memory (OMSM), for managing huge models. The OMSM framework can be easily adapted to the users needs through dynamic plugins, providing many techniques to be integrated in a storing architecture.
Towards a Voting Scheme for Calculating Light Source Positions from a given Target Illumination
(The Eurographics Association, 2010) Zmugg, René; Havemann, Sven; Fellner, Dieter W.; Enrico Puppo and Andrea Brogni and Leila De Floriani
Lighting conditions can make the difference between success or failure of an architectural space. The vision of space-light co-design is that architects can control the impression of an illuminated space already at an early design stage, instead of first designing spaces and then searching for a good lighting setup. As a first step towards this vision we propose a novel method to calculate potential light source positions from a given user defined target illumination. The method is independent of the tessellation of the scene and assumes a homogeneous diffuse Lambertian material. This allows using a voting system that determines potential positions for standard light sources with chosen size and brightness. Votes are cast from an illuminated surface point to all potential positions of a light source that would yield this illumination. Vote clusters consequently indicate a more probable light source position. With a slight extension the method can also identify mid-air light source positions.
Edge Adaptive and Energy Preserving Volume Upscaling for High Quality Volume Rendering
(The Eurographics Association, 2010) Giachetti, Andrea; Guitián, J. A. Iglesias; Gobbetti, Enrico; Enrico Puppo and Andrea Brogni and Leila De Floriani
We describe an edge-directed optimization-based method for volumetric data supersampling. The method is based on voxel splitting and iterative refinement performed with a greedy optimization driven by the smoothing of second order gray level derivatives and the assumption that the average gray level in the original voxels region cannot change. Due to these assumptions, the method, which is the 3D extension of a recently proposed technique, is particularly suitable for upscaling medical imaging data creating physically reasonable voxel values and overcoming the so-called partial volume effect. The good quality of the results obtained is demonstrated through experimental tests. Furthermore, we show how offline 3D upscaling of volumes can be coupled with recent techniques to perform high quality volume rendering of large datasets, obtaining a better inspection of medical volumetric data
Toward Wide-Area Camera Localization for Mixed Reality
(The Eurographics Association, 2010) Garro, Valeria; Fusiello, Andrea; Enrico Puppo and Andrea Brogni and Leila De Floriani
This paper describes a work in progress towards the implementation of a complete system that provides tourists with relevant visual information related to cultural heritage sites. Thanks to the diffusion of high-end mobile devices and the recent improvement in computer vision research on 3D Structure and Motion reconstruction, it is now possible to develop mobile mixed reality applications that can interact with spots of historical interest in the city. In particular we present an accurate localization of the mobile device that leverages on a pre-computed 3D structure to obtain image-model correspondences. Preliminary experiments with a calibrated camera indoor and outdoor demonstrate sufficient accuracy to support mixed reality.
Facile: a System for Artificial Face Dataset Generation
(The Eurographics Association, 2010) Brambilla, Andrea; Colombo, Alessandro; Enrico Puppo and Andrea Brogni and Leila De Floriani
We present Facile, a system for the generation of artificial face datasets aimed to assist the training and evaluation phases of face related algorithms. Facile is able to generate, starting from a set of textured 3D faces with neutral expressions, a new dataset containing synthesized facial expressions, multiple viewpoint positions and lighting conditions. The system is featured by a facial animation algorithm based on a mass-spring system. Muscles, defined on a reference face, modify springs contractions when activated. Dense correspondence with the reference face is computed for each input face: in this way muscles are automatically positioned and the desired facial expression is generated through physical simulation. Output images can be rendered with different lighting conditions and viewpoint positions depending on the task requirements.
Tools and Applications for Teaching and Research in Computer Graphics
(The Eurographics Association, 2010) Guggeri, Fabio; Livesu, Marco; Scateni, Riccardo; Enrico Puppo and Andrea Brogni and Leila De Floriani
In this paper we present the work in progress along with some preliminary research results in the field of Computational Geometry and Mesh Processing obtained by the Computer Graphics Group of the University of Cagliari, Italy. We focus on the work in mesh analysis by introducing the development of a lightweight visualization and processing tool that helped expanding the aims of the group by letting the students from the University move their first steps in Computer Graphics. We show some results obtained by the group with the focus on the usefulness of a common framework of reference.
Modeling Liquidus Hypersurfaces through Simplicial Complexes
(The Eurographics Association, 2010) Natali, Mattia; Attene, Marco; Ottonello, Giulio; Enrico Puppo and Andrea Brogni and Leila De Floriani
This paper describes an operational pipeline that exploits computational geometry to derive useful knowledge about the crystallization behaviour of materials composed of varying amounts of pure components. Starting from existing knowledge related to the pure components, we compute the Gibbs free energy of all their possible compositions in a given range of temperatures, both in liquid and solid phases. Then, we exploit the convex hull method to derive the coexistence of solid and liquid phases, and model the resulting liquidus hypersurface as a simplicial complex. On such a complex, we propose novel tools to robustly compute descent lines describing the crystallization path induced by heat loss for any initial composition in the system.
Two Examples of GPGPU Acceleration of Memory-intensive Algorithms
(The Eurographics Association, 2010) Marras, Stefano; Mura, Claudio; Gobbetti, Enrico; Scateni, Riccardo; Scopigno, Roberto; Enrico Puppo and Andrea Brogni and Leila De Floriani
The advent of GPGPU technologies has allowed for sensible speed-ups in many high-dimension, memory-intensive computational problems. In this paper we demonstrate the e ectiveness of such techniques by describing two applications of GPGPU computing to two di erent subfields of computer graphics, namely computer vision and mesh processing. In the first case, CUDA technology is employed to accelerate the computation of approximation of motion between two images, known also as optical flow. As for mesh processing, we exploit the massivelyparallel architecture of CUDA devices to accelerate the face clustering procedure that is employed in many recent mesh segmentation algorithms. In both cases, the results obtained so far are presented and thoroughly discussed, along with the expected future development of the work.
Composition of Texture Atlases for 3D Mesh Multi-texturing
(The Eurographics Association, 2010) Pagés, Rafael; Arnaldo, Sergio; Morán, Francisco; Berjón, Daniel; Enrico Puppo and Andrea Brogni and Leila De Floriani
We introduce an automatic technique for mapping onto a 3D triangle mesh, approximating the shape of a real 3D object, a high resolution texture synthesized from several pictures taken simultaneously by real cameras surrounding the object. We create a texture atlas by first unwrapping the 3D mesh to form a set of 2D patches with no distortion (i.e., the angles and relative sizes of the 3D triangles are preserved in the atlas), and then mixing the color information from the input images, through another three steps: step no. 2 packs the 2D patches so that the bounding canvas of the set is as small as possible; step no. 3 assigns at most one triangle to each canvas pixel; finally, in step no. 4, the color of each pixel is calculated as a smoothly varying weighted average of the corresponding pixels from several input photographs. Our method is especially good for the creation of realistic 3D models without the need of having graphic artists retouch the texture.
Monitor-Based tracking system for Wide Augmented Reality Environments
(The Eurographics Association, 2010) Re, Guido Maria; Caruso, Giandomenico; Belluco, Paolo; Bordegoni, Monica; Enrico Puppo and Andrea Brogni and Leila De Floriani
In Augmented Reality (AR) applications, the technological solutions used for tracking objects in the real environment are generally related to the conditions of the environment and to the application purposes. The selection of the most suitable tracking technology satisfies the best compromise among several issues including performance, accuracy and easiness of use. This paper describes an AR tracking approach based on a marker-based tracking and its development for wide environment by displaying itself on a monitor. This solution allows us to improve the visibility of the marker and the tracking, thanks to a dynamic control of marker s dimensions. The technical features and performances of our approach have been assessed by several testing sessions focused on comparative analyses.
Mutual Correspondences: An Hybrid Method for Image-to-geometry Registration
(The Eurographics Association, 2010) Sottile, Michele; Dellepiane, Matteo; Cignoni, Paolo; Scopigno, Roberto; Enrico Puppo and Andrea Brogni and Leila De Floriani
Image registration is an important task in several applications of Computer Graphics and Computer Vision. Among the large number of proposed approaches, currently there is no solution which is automatic and robust enough to handle any general case. The most robust methods usually require a significant intervention by the user to specify many 2D-3D correspondences, while automatic techniques often rely on strong assumptions about the quality of 2D and 3D data. In this paper we present Mutual Correspondences, which is based on a minimization function which combines correspondences based and Mutual Information based approaches, and takes advantage of the strong points of both. Mutual Correspondences give the user the possibility to "guide" Mutual Information with only a few 2D- 3D correspondences. The proposed approach results in a wider convergence range and in higher registration accuracy, regardless of the quality of both the image and the 3D model. Mutual Correspondences were applied on some practical cases, where state-of-the-art approaches tended to fail, and they provided a mean to obtain accurate results. This led to a simple, robust and practical approach that can provide a way to register images in a few seconds.
A Framework for Virtual Restoration of Ancient Documents by Combination of Multispectral and 3D Imaging
(The Eurographics Association, 2010) Bianco, Gianfranco; Bruno, Fabio; Tonazzini, A.; Salerno, E.; Savino, P.; Zitova, B.; Sroubek, F.; Console, E.; Enrico Puppo and Andrea Brogni and Leila De Floriani
Historical documents often undergo various changes over time, that alter their original state and reduce their legibility. Digital techniques are widely applied for document preservation, archiving, analysis and dissemination over the Internet. The goal of restoration is to improve the document legibility for both human and automatic operators, to extract patterns and enhance colour reproduction. Our paper presents a framework for virtual restoration of ancient documents based on a combination of multispectral acquisition, 3D imaging and digital image analysis. The proposed framework consists of several steps. First, digital representations of the documents are acquired as multispectral images and 3D surface maps, the latter reconstructed by a structured light technique. A multispectral camera and a digital projector are used in triangular configuration for 2D and 3D data acquisition. Then the multispectral images are registered against possible misalignments, and the 3D surface representation is used to correct geometrical distortions. Document flattening is then performed by 3D surface parameterization and texture mapping. Statistical techniques of decorrelation are applied to extract individual context parts of the document patterns (stamp, text, etc.) and to attenuate interferences. The processed data are then binarized by the proper segmentation technique. The entire digital object history - all the acquisition and processing steps, with the corresponding parameters - is stored in metadata files. These data can be exploited in a future evaluation of the restoration process and can be used for either the creation of an expert knowledge database or the extraction of cross-document observations and conclusions.
An Application of Multiresolution Massive Surface Representations to the Simulation of Asteroid Missions
(The Eurographics Association, 2010) Pintore, Giovanni; Combet, Roberto; Gobbetti, Enrico; Marton, Fabio; Turner, Russell; Enrico Puppo and Andrea Brogni and Leila De Floriani
We report on a real-time application supporting fast, realistic real-time rendering of asteroid datasets, as well as collision detection and response between the asteroid and prototype robotic surface exploration vehicles. The system organizes the asteroid surface into a two-level multiresolution structure, which embeds a fine-grained perpatch spatial index within a coarse-grained patch-based structure. The coarse-grained structure, maintained out-of-core, is used for fast batched I/O and GPU accelerated rendering, while the per-patch fine-grained structure is used to accelerate raycasting and collision queries. The resulting system has been tested with a simple robot lander and surface exploration simulator. The system models gravity using mass particles uniformly distributed within the asteroid bodies. Real-time performance is achieved on a commodity platform with giga triangle representations of asteroids 25143 Itokawa and 433 Eros.
3D Body Model Construction and Matching for Real Time People Re-Identification
(The Eurographics Association, 2010) Baltieri, Davide; Vezzani, Roberto; Cucchiara, Rita; Enrico Puppo and Andrea Brogni and Leila De Floriani
Wide area video surveillance always requires to extract and integrate information coming from different cameras and views. Re-identification of people captured from different cameras or different views is one of most challenging problems. In this paper, we present a novel approach for people matching with vertices-based 3D human models. People are detected and tracked in each calibrated camera, and their silhouette, appearance, position and orientation are extracted and used to place, scale and orientate a 3D body model. Colour features are computed from the 2D appearance images and mapped to the 3D model vertices, generating the 3D model for each tracked person. A distance function between 3D models is defined in order to find matches among models belonging to the same person. This approach achieves robustness against partial occlusions, pose and viewpoint changes. A first experimental evaluation is conducted using images extracted from a real camera set-up.

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