Gaze-based text entry is undoubtedly one of the most useful applications of eye-tracking technology for human-machine interaction, both in the assistive context (users with severe motor disabilities can exploit such writing modalities to communicate with the world) and as a way to allow touchless text input in everyday life. Different eye-driven text entry methods have been developed to date, and almost all of them require preliminary calibration procedures to work correctly. When a short text, such as a password or a PIN, needs to be entered without using hands or voice, calibration may be perceived as an unnecessary nuisance (and may not be properly maintained in public places due to “ambient noise,” caused, for example, by nearby people). Inadequate calibration may also be a problem in case of assistive uses. In this article we presentSPEye, a calibration-free eye-controlled writing technique based on smooth pursuit. Although its writing speed is significantly lower than that of ordinary calibrated methods, the absence of an initial calibration makes it suitable for short text entry. The technique has been tested through several experiments, obtaining good performances in terms of key strokes per character and total error rate metrics, and receiving positive feedback from the participants in the tests.

The technological revolution which has completely transformed social relations and which has enabled communication and sharing of multimedia formats is also rapidly transforming the field of art and cultural heritage management. This contribution focuses on the innovative use of interactive digital technologies in digital humanities practices. In the last recent years, we experienced different approaches exploiting advanced technological innovation in the field of cultural heritage promotion and conservation. In 2015, for the exhibition “1525-2015. Pavia, the Battle, the Future. Nothing was the same again”, we applied multimodal interaction modalities. Visitors could look at and examine seven ancient tapestries through 3D reconstructions, virtual simulations, eye interaction and gesture navigation. Moreover, a transposition of the tapestries into tactile images enabled exploration by partially sighted and blind people. Motivated by this successful exhibition, in 2018, a more ambitious project, the 3D reconstruction of Pavia in the Renaissance, was undertaken. Advanced techniques and innovative applications have led to a resource useful for the promotion of the history of the city and its architectural richness through videos offering virtual tours of the city. Later, in 2019, a “Digital Anastylosis of Frescoes challeNgE (DAFNE)” has been proposed, to provide virtual solutions that ultimately add to the fresco restorer's toolkit, with digital re-composition of `puzzles' formed by the artwork fragments, often mixed with spurious elements.

Mixed reality has been proposed for industrial applications such as AR-assisted manteinance and repair in which real equipment are augmented by visual aids. A possible complementary use of this technology for the same context can be achieved by performing virtual training in a “mixed reality environment” enabling to observe actual-size virtual replicas of real equipment within the physical space, providing an advantage in terms of perceptual impact and learning efficacy compared to traditional computer-based-training techniques. To this aim we present an effective hybrid tracking approach, exploiting both optical markers and inertial sensors to measure user's head position and rotation, providing both accuracy and robustness to fast head movements. A field-deployable tridimensionally-arranged marker-set, specifically designed for this kind of application, represents a further contribute of this paper, providing reliable close-to-medium distance optical tracking capabilities and increased robustness to challenging lighting conditions. First experiments confirm the potential of the proposed solution for this context and for many other applications as well.

Provides an overview of the technical articles and features presented in this issue.

In recent years, there have been several proposals for the realization of models inspired to biological solutions for pattern recognition. In this work we propose a new approach, based on a hierarchical modular structure, to realize a system capable to learn by examples and recognize objects in digital images. The adopted techniques are based on multiresolution image analysis and neural networks. Performance on two different data sets and experimental timings on a single instruction multiple data (SIMD) machine are also reported.

The availability of more and more powerful computers and the widespread diffusion of multimedia technology calls for a work force with expertise in ISE (Image System Engineering). This work details our teaching experience with Pacco, an object-oriented data processing environment.

The method proposed in this paper for two-dimensional object recognition relies on the idea of a structural coding of an object at varying levels of resolution. A tree structure describes the evolution of the contour at increasing levels of detail. Each tree node represents a contour segment through a set of attributes to provide a richer description of the image shape. In addition to the attributes, a weight is associated to each descriptor indicating the significance of the corresponding primitives. An approach for 2D object recognition based on a matching of the attributed tree representation of the candidates with that of the model is proposed.

Among the various proposal advanced to build massive parallel systems in which the number of computing units ranges in the thousands, hierarchical topologies share a number of interesting properties. The authors review these architectures and their applicability and reliability, with particular attention to connections complexity and the ability to exchange messages. The usual assumption of the multiple instruction multiple data (MIMD) computational paradigm is as follows: autonomous but cooperating tasks execute on different processing units in the system. The overall complexity of the systems is measured with the analysis of the diameter and of the increasing law that states the number of interconnections against the number of nodes in the system. The various architectures are compared in terms of links load and average internode distance.>

Hierarchical multi-microcomputer systems are reviewed, with particular attention given to the complexity of the interconnection structure and to the ability to exchange messages. The assumption of the multiple-instruction multiple-data (MIMD) computational paradigm is followed; autonomous but cooperating tasks execute on different processing units in the system. The overall complexity of the systems is measured with the analysis of the diameter and of the increasing law, which states the number of interconnections against the number of nodes in the system. The various architectures are compared in terms of links load and average internode distance under the uniform reference model of message distribution and of request independence assumption.>

An approach to object recognition in an industrial environment is described. With the hypothesis that the universe of objects is limited and that the attitudes in space of any object are constrained by the working environment to a few possibilities, a method is obtained that determines minimal descriptions for each model/object pair. These descriptions, which are discriminant of each model, are used by the recognition strategy planner. It automatically determines which descriptions can be conveniently used to identify the object(s) looked for and in what order. Uncertainties due to overlapping are signaled and tentative classifications listed.>

A review of image-processing systems developed until now is given, highlighting the weak points of such systems and the trends that have dictated their evolution through the years producing different generations of machines. Each generation may be characterized by the hardware architecture, the programmability features and the relative application areas. The need for multiprocessing hierarchical systems is discussed, focusing on pyramidal architectures. Their computational paradigms, their virtual and physical implementation, their programming and languages, are discussed.>

In 1981 a national research program for the design, simulation and construction of a multiprocessor image processing system was started. After a first phase devoted to the comparison of suggested and existing systems and to the definition of a set of benchmarks and to the evaluation of the performances of the major classes of machines, a new system has been defined. The structure of the new system is based on a pyramid of processors and many applications in which this machine may be exploited are highlighted. The multiprocessor architecture has been fully designed and the chip will be built by an Italian silicon. foundry, the SGS company, within the framework of the multichip national project.