Many Object recognition techniques perform some flavour of point pattern matching between a model... more Many Object recognition techniques perform some flavour of point pattern matching between a model and a scene. Such points are usually selected through a feature detection algorithm that is robust to a class of image transformations and a suitable descriptor is computed over them in order to get a reliable matching. Moreover, some approaches take an additional step by casting the correspondence problem into a matching between graphs defined over feature points. The motivation is that the relational model would add more discriminative power, however the overall effectiveness strongly depends on the ability to build a graph that is stable with respect to both changes in the object appearance and spatial distribution of interest points. In fact, widely used graph-based representations, have shown to suffer some limitations, especially with respect to changes in the Euclidean organization of the feature points. In this paper we introduce a technique to build relational structures over c...
Proceedings of the 2014 International Working Conference on Advanced Visual Interfaces - AVI '14, 2014
ABSTRACT In many visual interaction applications the user needs to explore a scene by moving with... more ABSTRACT In many visual interaction applications the user needs to explore a scene by moving with respect to the virtual environment. Using a fixed camera viewpoint leads to visual inconsistencies, which can be avoided only if the exact pose of the user head is known and can be used to produce a perspective correct rendering. To this end, tracking devices are often used, however many of them are relatively expensive or require the user to wear special apparel. With this paper we present a tracking system that can be implemented with a simple and very low cost modification of standard shutter glasses. The accuracy of such approach has been evaluated quantitatively with a specially crafted experimental setup.
Proceedings of the 2014 International Working Conference on Advanced Visual Interfaces - AVI '14, 2014
ABSTRACT We evaluate the accuracy of perception of a viewer-dependent system that has been implem... more ABSTRACT We evaluate the accuracy of perception of a viewer-dependent system that has been implemented through a simple augmentation of basic shutter glasses for stereoscopic setups. The evaluation is based on length measures performed by a group of users on two different scenes, rendered through different perspectives computed from the dynamic user position and from a fixed point of view.
Proceedings of the 2014 International Working Conference on Advanced Visual Interfaces - AVI '14, 2014
ABSTRACT A simple and natural interaction is considered the most important feature of an interfac... more ABSTRACT A simple and natural interaction is considered the most important feature of an interface for multiple impromptu users in public spaces. Intuitiveness and forthright feedback are key factors to enable a steep learning curve for untrained users that need to grasp the interaction model in a short time span. The lack of proper constraints, designed to restrict and guide the user actions, might hinder such intuitiveness, mainly when the number of users grows or their behavior is exceedingly unrestrained. In this paper we introduce the idea of sandboxed interaction, a general concept that groups many flavors of physical and software-based measures aiming at guaranteeing a smooth and fitting interaction. To this end, we propose different types of sandboxes, suitable to handle different kind of interaction problems, and discuss a case study where several sandboxing measures have been put into use and evaluated within a real-world application scenario.
Finding the most relevant symmetry planes for an object is a key step in many computer vision and... more Finding the most relevant symmetry planes for an object is a key step in many computer vision and object recognition tasks. In fact such information can be effectively used as a starting point for object segmentation, noise reduction, alignment and recognition. Some of these applications are strongly affected by the accuracy of symmetry planes estimation, thus the use of a
ABSTRACT Interactive whiteboards are nowadays rather common equipments in classrooms as they prov... more ABSTRACT Interactive whiteboards are nowadays rather common equipments in classrooms as they provide large advantages in terms of expressive power. Despite the radical paradigm shift, their interaction model is firmly tied to the archetypal concept of strokes and gestures over a whiteboard. In this paper we introduce a novel pointing device that enables one to escape the surface-based interaction, by means of a robust and occlusion-resilient multi-camera 3D tracking. More precisely, we designed a frequency-based active pen. By means of a camera network such pen can be localized in a 3D frame featuring the same 5 degrees of freedom exposed by a real whiteboard marker. Our approach allows for using many pointers at the same time, by reliably assigning an unique and permanent identity to each one. By levering on these capabilities, interaction designers can conceive new and inventive interaction models. A few of them have been implemented within this study and are described in the experimental part of this work.
ABSTRACT Surface registration is often performed as a two step process. A feature matching scheme... more ABSTRACT Surface registration is often performed as a two step process. A feature matching scheme is first adopted to find a coarse initial alignment between two meshes. Subsequently, a refinement step, which usually operates in the space of rigid motions, is applied to reach an optimal registration with respect to pointwise distances between overlapping areas. In this paper we propose a novel technique that allows to obtain an accurate surface registration in a single step, without the need for an initial motion estimation. The main idea of our approach is to cast the selection of correspondences between points on the surfaces in a game-theoretic framework, where a natural selection process allows matching points that satisfy a mutual rigidity constraint to thrive, eliminating all the other correspondences. This process yields a very robust inlier selection scheme that does not depend on any particular technique for selecting the initial strategies as it relies only on the global geometric compatibility between correspondences. The practical effectiveness of the approach is confirmed by an extensive set of experiments and comparisons with state-of-the-art techniques.
Many Object recognition techniques perform some flavour of point pattern matching between a model... more Many Object recognition techniques perform some flavour of point pattern matching between a model and a scene. Such points are usually selected through a feature detection algorithm that is robust to a class of image transformations and a suitable descriptor is computed over them in order to get a reliable matching. Moreover, some approaches take an additional step by casting the correspondence problem into a matching between graphs defined over feature points. The motivation is that the relational model would add more discriminative power, however the overall effectiveness strongly depends on the ability to build a graph that is stable with respect to both changes in the object appearance and spatial distribution of interest points. In fact, widely used graph-based representations, have shown to suffer some limitations, especially with respect to changes in the Euclidean organization of the feature points. In this paper we introduce a technique to build relational structures over c...
Proceedings of the 2014 International Working Conference on Advanced Visual Interfaces - AVI '14, 2014
ABSTRACT In many visual interaction applications the user needs to explore a scene by moving with... more ABSTRACT In many visual interaction applications the user needs to explore a scene by moving with respect to the virtual environment. Using a fixed camera viewpoint leads to visual inconsistencies, which can be avoided only if the exact pose of the user head is known and can be used to produce a perspective correct rendering. To this end, tracking devices are often used, however many of them are relatively expensive or require the user to wear special apparel. With this paper we present a tracking system that can be implemented with a simple and very low cost modification of standard shutter glasses. The accuracy of such approach has been evaluated quantitatively with a specially crafted experimental setup.
Proceedings of the 2014 International Working Conference on Advanced Visual Interfaces - AVI '14, 2014
ABSTRACT We evaluate the accuracy of perception of a viewer-dependent system that has been implem... more ABSTRACT We evaluate the accuracy of perception of a viewer-dependent system that has been implemented through a simple augmentation of basic shutter glasses for stereoscopic setups. The evaluation is based on length measures performed by a group of users on two different scenes, rendered through different perspectives computed from the dynamic user position and from a fixed point of view.
Proceedings of the 2014 International Working Conference on Advanced Visual Interfaces - AVI '14, 2014
ABSTRACT A simple and natural interaction is considered the most important feature of an interfac... more ABSTRACT A simple and natural interaction is considered the most important feature of an interface for multiple impromptu users in public spaces. Intuitiveness and forthright feedback are key factors to enable a steep learning curve for untrained users that need to grasp the interaction model in a short time span. The lack of proper constraints, designed to restrict and guide the user actions, might hinder such intuitiveness, mainly when the number of users grows or their behavior is exceedingly unrestrained. In this paper we introduce the idea of sandboxed interaction, a general concept that groups many flavors of physical and software-based measures aiming at guaranteeing a smooth and fitting interaction. To this end, we propose different types of sandboxes, suitable to handle different kind of interaction problems, and discuss a case study where several sandboxing measures have been put into use and evaluated within a real-world application scenario.
Finding the most relevant symmetry planes for an object is a key step in many computer vision and... more Finding the most relevant symmetry planes for an object is a key step in many computer vision and object recognition tasks. In fact such information can be effectively used as a starting point for object segmentation, noise reduction, alignment and recognition. Some of these applications are strongly affected by the accuracy of symmetry planes estimation, thus the use of a
ABSTRACT Interactive whiteboards are nowadays rather common equipments in classrooms as they prov... more ABSTRACT Interactive whiteboards are nowadays rather common equipments in classrooms as they provide large advantages in terms of expressive power. Despite the radical paradigm shift, their interaction model is firmly tied to the archetypal concept of strokes and gestures over a whiteboard. In this paper we introduce a novel pointing device that enables one to escape the surface-based interaction, by means of a robust and occlusion-resilient multi-camera 3D tracking. More precisely, we designed a frequency-based active pen. By means of a camera network such pen can be localized in a 3D frame featuring the same 5 degrees of freedom exposed by a real whiteboard marker. Our approach allows for using many pointers at the same time, by reliably assigning an unique and permanent identity to each one. By levering on these capabilities, interaction designers can conceive new and inventive interaction models. A few of them have been implemented within this study and are described in the experimental part of this work.
ABSTRACT Surface registration is often performed as a two step process. A feature matching scheme... more ABSTRACT Surface registration is often performed as a two step process. A feature matching scheme is first adopted to find a coarse initial alignment between two meshes. Subsequently, a refinement step, which usually operates in the space of rigid motions, is applied to reach an optimal registration with respect to pointwise distances between overlapping areas. In this paper we propose a novel technique that allows to obtain an accurate surface registration in a single step, without the need for an initial motion estimation. The main idea of our approach is to cast the selection of correspondences between points on the surfaces in a game-theoretic framework, where a natural selection process allows matching points that satisfy a mutual rigidity constraint to thrive, eliminating all the other correspondences. This process yields a very robust inlier selection scheme that does not depend on any particular technique for selecting the initial strategies as it relies only on the global geometric compatibility between correspondences. The practical effectiveness of the approach is confirmed by an extensive set of experiments and comparisons with state-of-the-art techniques.
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Papers by Andrea Albarelli