Italian Chapter Conference 2016 - Smart Tools and Apps in computer Graphics

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https://diglib.eg.org/handle/10.2312/2630930

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3D Digital Imaging for Knowledge Dissemination of Greek Archaic Statuary
(The Eurographics Association, 2016) Stanco, Filippo; Tanasi, Davide; Allegra, Dario; Milotta, Filippo L. M.; Giovanni Pintore and Filippo Stanco
This paper aims, using a research exercise, to verify the association between two Greek sculptures collected at different times: the head of a boy collected in the Chalcidian colony of Leontinoi in southeastern Sicily, acquired in the 18th century and later kept in the collection of the Museum of Castello Ursino in Catania, and a torso, retrieved in 1904 and since then displayed in the Archaeological Museum of Sicily. The two pieces share similar stylistic features and represent the most significant example of Greek sculpture in Sicily at the end of the 6th century BC. Their association is an open problem still debated by scholars, who have based their studies on comparisons between pictures as a reassembly of two artefacts was never attempted. This critical issue has conditioned curators of the two museums, who could not develop a proper communication policy for the two objects, resulting in a limited cognitive accessibility for the public. By means of 3D scanning techniques, this contribution showcases how virtual restoration can not only improve interpretations of the scholars, but also boost the communication plans of museums, giving back to the public via a web platform a masterpiece of Greek sculpture known just by specialists.
Anisotropic MatCap: Easy Capture and Reproduction of Anisotropic Materials
(The Eurographics Association, 2016) Magri, Dario; Cignoni, Paolo; Tarini, Marco; Giovanni Pintore and Filippo Stanco
We propose Anisotropic MatCap, a simple data structure based on a small volumetric texture that is able to represent, under a fixed lighting, the behavior of anisotropic materials. The data structure is designed to allow fast and practical capture of real-world anisotropic materials (like for example fabrics) and to be used in real-time renderings, requiring only negligible time and texture memory overheads. The resulting technique is suited for application scenarios where digital objects must be inspected by an end user, recreating the look of an object made of a captured anisotropic material and seen under the predetermined lighting conditions. The technique proved particularly useful for garments and cloth visualization and design.
Automating Large 3D Dataset Publication in a Web-Based Multimedia Repository
(The Eurographics Association, 2016) Potenziani, Marco; Fritsch, Bernhard; Dellepiane, Matteo; Scopigno, Roberto; Giovanni Pintore and Filippo Stanco
Online publishing of almost every type of 3D data has become a quasi-standard routine. Nevertheless, the integration in a web page of a single 3D model, or of a predefined restricted set of models, raises different issues compared to an efficient and effective integration of thousands of them in an online repository. In this case it is mandatory to have an automatized pipeline to prepare and homogenize the dataset. The pipeline should be able to automatically wrap 3D data in all conditions, and display every single model with the best scene setup without any (or with a minimal) interaction by the database maintainers. This paper, retracing the steps of a recent real application case, aims at showing all the faced issues (and the adopted solutions) to publish a large and heterogeneous three-dimensional dataset in a web specialized repository. We want to introduce a valid and reusable strategy, starting from the description of the pipeline adopted for data pre-processing and moving to the choices made in the 3D viewer implementation. The paper concludes with a discussion on the actual state of the integration of 3D data with the other multimedia informative layers.
Design and Fabrication of Grid-shells Mockups
(The Eurographics Association, 2016) Tonelli, Davide; Pietroni, Nico; Cignoni, Paolo; Scopigno, Roberto; Giovanni Pintore and Filippo Stanco
Statics Aware Voronoi Grid-shells have been recently introduced in the Architectural Geometry field. These are innovative gridshells endowed with a polygonal topology, whose geometry is structurally optimized by means of a novel algorithm [PTP+15]. Although being structurally effective as proved in [TPP+16] and arguably aesthetically charming, so far these grid-shells have struggled to attract architects' interest. We propose a method to fabricate a mockup of the grid shell by using modern additive 3D printing and laser cutting technologies. We also show how the realised mockup can be used to perform a preliminary validation of the simulated static performances of the grid-shell structure.
Generalized Trackball for Surfing Over Surfaces
(The Eurographics Association, 2016) Malomo, Luigi; Cignoni, Paolo; Scopigno, Roberto; Giovanni Pintore and Filippo Stanco
We present an efficient 3D interaction technique: generalizing the well known trackball approach, this technique unifies and blends the two common interaction mechanisms known as panning and orbiting. The approach allows to inspect a virtual object by navigating over its surrounding space, remaining at a chosen distance and performing an automatic panning over its surface. This generalized trackball allows an intuitive navigation of topologically complex shapes, enabling unexperienced users to visit hard-to-reach parts better and faster than with standard GUI components. The approach is based on the construction of multiple smooth approximations of the model under inspection; at rendering time, it constrains the camera to stay at a given distance to these approximations. The approach requires negligible preprocessing and memory overhead and works well for both mousebased and touch interfaces. An informal user study confirms the impact of the proposed technique.
Interactive Analytical Treemaps for Visualisation of Call Centre Data
(The Eurographics Association, 2016) Roberts, Richard C.; Tong, Chao; Laramee, Robert S.; Smith, Gary A.; Brookes, Paul; D'Cruze, Tony; Giovanni Pintore and Filippo Stanco
In the United Kingdom alone, there are over one million employees working at over 5,000 call centres. Some estimates claim approximately four million call centre employees in Europe. In this unique application paper we present methods for visualising the vast amount of data generated and collected by call centres. We design the application to address the challenges of exploration, analysis and visualisation of complex, time-dependant call centre data, and aim to maximise the utility the software contributes to the business stakeholders in the industry. The application implements a custom, interactive analytical treemap view that presents an overview and details of the data on demand. We implement a smooth temporal navigation system to allow the user to zoom the visualisation to a higher resolution of data. Then an interactive multivariate focus and context analytic filtering interface provides the user control over caller subsets they are interested in for analysis. The software is designed in close collaboration with industry experts. This application reveals new insight into call centre events and behaviour that traditional forms of analysis do not as quickly, nor as easily. We also report the positive reaction of domain experts to our visualisations.
Kernel-Reflection Sequences
(The Eurographics Association, 2016) Szécsi, László; Bendefy, Zoltán; Kacsó, Ágota; Giovanni Pintore and Filippo Stanco
Complex geometries, like those of plants, rocks, terrain, or even clouds are challenging to model in a way that allows for real-time rendering but does not make concessions in terms of visible detail. In this paper we propose a procedural modeling approach, called KRS, or kernel-reflection sequences, inspired by iterated function systems. The model is composed of kernel geometries defined by signed distance functions, and reflection transformations that multiply them. We show that a global distance function can be evaluated over this structure without recursion, allowing for the implementation of real-time sphere tracing on parallel hardware. We also show how the algorithm readily delivers continuous level-of-detail and minification filtering. We propose several techniques to enhance modeling freedom and avoid conspicuous symmetries. Most importantly, we extend sphere tracing to conformally transformed geometries. We also propose a GPU load balancing scheme for best utilization of computing power. To prove that the model can be used to realize various natural phenomena in uncompromising detail and extents, without obvious clues of symmetry, we render aquatic and terrestrial surface formations and vegetation in real-time.
Low Cost Handheld 3D Scanning for Architectural Elements Acquisition
(The Eurographics Association, 2016) Allegra, Dario; Gallo, Giovanni; Inzerillo, Laura; Lombardo, Marcella; Milotta, Filippo L. M.; Santagati, Cettina; Stanco, Filippo; Giovanni Pintore and Filippo Stanco
3D scanning has gone a long way since its first appearance in cultural heritage digitization and modeling. In the recent years some new low cost, fast, accurate emerging technologies are flooding the market. Envisioning the massive use of these cheap and easy to use devices in the next years, it is crucial to explore the possible fields of application and to test their effectiveness in terms of easiness of 3D data collection, processing, mesh resolution and metric accuracy against the size and features of the objects. In this study we focus the attention on one emerging technology, the Structure Sensor device, in order to verify a 3D pipeline acquisition on an architectural element and its details. The methodological approach is thought to define a pipeline of 3D acquisition exploiting low cost and open source technologies and foresees the assessment of this procedure in comparison with data obtained by a Time of Flight device.
Manipulating Topological Decompositions of Non-Manifold Shapes
(The Eurographics Association, 2016) Canino, David; Giovanni Pintore and Filippo Stanco
Decomposing a non-manifold shape into its almost manifold components is a powerful tool for analyzing its complex structure. Many techniques for decomposing a non-manifold shape are available in the current literature, and provide a structural model, which exposes its non-manifold singularities, as well as the connectivity of its relevant subcomponents, connected through the singularities. However, the majority of the decompositions are static, and are not automatically updated, if the corresponding non-manifold shape is modified by an editing operator. In many cases, the resulting decomposition is recomputed from scratch without reusing the unchanged portions of the existing decomposition. In this paper, we describe how updating automatically a specific decomposition of a non-manifold shape. Here, we show that our approach may be useful for adapting many geometry processing techniques also to non-manifold shapes, where several problems may arise. One of the most promising applications consists of defining a multiresolution version for the specific structural model of interest, due to its good topological properties.
Persistent Homology: a Step-by-step Introduction for Newcomers
(The Eurographics Association, 2016) Fugacci, Ulderico; Scaramuccia, Sara; Iuricich, Federico; Floriani, Leila De; Giovanni Pintore and Filippo Stanco
Persistent homology is a powerful notion rooted in topological data analysis which allows for retrieving the essential topological features of an object. The attention on persistent homology is constantly growing in a large number of application domains, such as biology and chemistry, astrophysics, automatic classification of images, sensor and social network analysis. Thus, an increasing number of researchers is now approaching to persistent homology as a tool to be used in their research activity. At the same time, the literature lacks of tools for introducing beginners to this topic, especially if they do not have a strong mathematical background in algebraic topology. We propose here two complementary tools which meet this requirement. The first one is a web-based user-guide equipped with interactive examples to facilitate the comprehension of the notions at the basis of persistent homology. The second one is an interactive tool, with a specific focus on shape analysis, developed for studying persistence pairs by visualizing them directly on the input complex.
Practical Free-form RTI Acquisition with Local Spot Lights
(The Eurographics Association, 2016) Pintus, Ruggero; Ciortan, Irina Mihaela; Giachetti, Andrea; Gobbetti, Enrico; Giovanni Pintore and Filippo Stanco
We present an automated light calibration pipeline for free-form acquisition of shape and reflectance of objects using common off-the-shelf illuminators, such as LED lights, that can be placed arbitrarily close to the objects. We acquire multiple digital photographs of the studied object shot from a stationary camera. In each photograph, a light is freely positioned around the object in order to cover a wide variety of illumination directions. While common free-form acquisition approaches are based on the simplifying assumptions that the light sources are either sufficiently far from the object that all incoming light can be modeled using parallel rays, or that lights are local points emitting uniformly in space, we use the more realistic model of a scene lit by a moving local spot light with exponential fall-off depending on the cosine of the angle between the spot light optical axis and the illumination direction, raised to the power of the spot exponent. We recover all spot light parameters using a multipass numerical method. First, light positions are determined using standard methods used in photometric stereo approaches. Then, we exploit measures taken on a Lambertian reference planar object to recover the spot light exponent and the per-image spot light optical axis; we minimize the difference between the observed reflectance and the reflectance synthesized by using the near-field Lambertian equation. The optimization is performed in two passes, first generating a starting solution and then refining it using a Levenberg-Marquardt iterative minimizer. We demonstrate the effectiveness of the method based on an error analysis performed on analytical datasets, as well as on real-world experiments.
Practical Offline Rendering of Woven Cloth
(The Eurographics Association, 2016) Nelson, Vidar; McEvoy, Peter M.; Fratarcangeli, Marco; Giovanni Pintore and Filippo Stanco
The techniques for rendering woven cloth employed in a production environment often neglect many of the structural features of the fabric, as well as light-scattering processes that occur in the yarn. Research in this area has progressed, and new promising methods have recently been proposed; however, many of these are not applied in practice due to their inherent complexities. In this paper, we develop and implement a shader for woven cloth that fulfills some of the needs of a production environment using an existing model for simulating the interaction with light. The shader delivers highly realistic results that are comparable, and in some cases superior, to current methods used in a real production environment. We enriched and validated the proposed framework by using direct feedback from a large company that produces images of furniture using computer graphics. The results demonstrate that our shader accurately simulates the appearance of certain types of woven cloth, showing reflections that are not present in other methods in current use. Our shader is easy to integrate in existing pipelines, flexible because it provides the artist with enough parameters to recreate many different types of fabric, and generic for the domain of woven cloth because it is able to accept as input widely used WIF files, which describe weave patterns as well as yarn specific parameters.
Retinal Image Analysis with Shearlets
(The Eurographics Association, 2016) Levet, Francesco; Duval-Poo, Miguel A.; Vito, Ernesto De; Odone, Francesca; Giovanni Pintore and Filippo Stanco
In this paper we propose a method for segmenting blood vessels in retinal images based on the shearlet transform. Shearlets are a relatively new directional multi-scale framework for signal analysis, which have been shown effective to enhance signal discontinuities such as edges and corners at multiple scales. The algorithm we propose builds on the idea of enhancing ridgelike structures at different scales by computing the shearlet transform with an appropriate mother function, the mexican hat wavelet. This allows us to detect precisely structures of different widths. We provide an experimental analysis of our approach on a benchmark dataset and we show very good performances in comparison with other multi-resolution methods from the state of the art.
Selective Rasterized Ray-traced Reflections on the GPU
(The Eurographics Association, 2016) Kastrati, Mattias Frid; Goswami, Prashant; Giovanni Pintore and Filippo Stanco
Ray-tracing achieves impressive effects such as realistic reflections on complex surfaces but is also more computationally expensive than classic rasterization. Rasterized ray-tracing methods can accelerate ray-tracing by taking advantage of the massive parallelization available in the rasterization pipeline on the GPU. In this paper, we propose a selective rasterized raytracing method that optimizes the rasterized ray-tracing by selectively allocating computational resources to reflective regions in the image. Our experiments suggest that the method can speed-up the computation by up to 4 times and also reduce the memory footprint by almost 66% without affecting the image quality. We demonstrate the effectiveness of our method using complex scenes and animations.
STAG 2016: Frontmatter
(Eurographics Association, 2016) Gianni Pintore; Filippo Stanco;
Surface Reconstruction from Range Images
(The Eurographics Association, 2016) Mariosa, Gianfranco; Fioraio, Nicola; Franchi, Alessandro; Stefano, Luigi Di; Giovanni Pintore and Filippo Stanco
In this work we propose an algorithm for fast and detailed surface reconstruction from range images. Our method extends the well-known Ball Pivoting Algorithm (BPA) so to exploit the inherent structure of range images, outperforming the state-of-theart both in terms of reconstruction quality and computation time. Moreover, we have investigated on automatic estimation of the algorithm's parameters and, in particular, we propose a novel robust approach to estimate the sequence of radii required by BPA, thus demanding less effort by the user compared to existing solutions.
Tonal Art Maps with Image Space Strokes
(The Eurographics Association, 2016) Szécsi, László; Szirányi, Marcell; Kacsó, Ágota; Giovanni Pintore and Filippo Stanco
This paper presents a hybrid hatching solution that uses robust and fast texture space hatching to gather stroke fragments, but fits stylized brush strokes over those fragments in image space. Thus we obtain a real-time solution that avoids the challenges associated with hidden stroke removal in image space approaches, but allows for the artistic stylization of strokes exceeding the limitations of texture space methods. This includes strokes running over outlines or behind occluders, uniquely random strokes, and adherence to image space brush properties.
Tracking the Evolution of Rainfall Precipitation Fields Using Persistent Maxima
(The Eurographics Association, 2016) Biasotti, Silvia; Cerri, Andrea; Pittaluga, Simone; Sobrero, Davide; Spagnuolo, Michela; Giovanni Pintore and Filippo Stanco
In this paper we propose a novel methodology for tracking the maxima of rainfall precipitation fields, whose changes in time may give interesting insights on the evolution of storm. Our approach is based on a topological analysis of rainfall data allowing for the extraction of the most prominent, and hence meaningful, rainfall field maxima. Then, an ad-hoc bottleneck matching is used to track the evolution of maxima along multiple time instances. The potential of our method is exhibited through a set of experiments carried out on a collection of observed punctual rainfall data and radar measurements provided by Genova municipality and Regione Liguria.
Vocal One Switch (VOS) Selection Interfaces for Virtual and Augmented Reality Hands-free Tasks
(The Eurographics Association, 2016) Manuri, Federico; Sanna, Andrea; Lamberti, Fabrizio; Paravati, Gianluca; Giovanni Pintore and Filippo Stanco
Several virtual and augmented reality tasks involve users in hands-free interactions; in this case, speech-based systems are often preferred for their intuitiveness and naturalness. On the other hand, the robustness of this kind of interfaces can be an issue, thus affecting both the usability and the user experience, when they are used in noisy environments. This paper proposes a comparison of a traditional multiword interface with a one switch interface triggered by vocal commands: three different scanning algorithms are tested. With one switch scanning interfaces users can sequentially select the desired command, thus improving the robustness of traditional multiword speech recognition-based interfaces. Latency time is an issue for one switch interfaces, but it is shown how a bidirectional scanning algorithm based on a non binary switch can strongly mitigate this problem. The comparison considered both objectively (robustness and efficiency) and subjectively (user feedback) parameters.

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