2,899 research outputs found
Uncalibrated view synthesis from Relative Affine Structure based on planes parallelism
No full textThis paper focuses on the generation of physically valid views
from two or more uncalibrated images acquired by standard
cameras. The problem is faced without trying to yield a three
dimensional reconstruction of the imaged scene, which would
be unfeasible without the exact knowledge of the positions
of the cameras in the Euclidean frame where the scene is to
be described. Instead, starting from the previous works of
Shashua and Navab on Relative Affine Structure [1] and the
article of Fusiello on views synthesis from uncalibrated views
[2] we propose a novel approach that does not require the
presence of a plane at infinity to define the homography between two views but merely the parallelism between couples
of planes. This allows our approach to be applied to numerous scenes where two parallel planes can be defined (indoor
scenes, straight streets and avenues). Experiments with synthetic images illustrate the approach
Who is the author of the 1876 Stefano manuscript?
No full textFor over one hundred years the Stefano manuscript was a private document in the possession of the Baccich family and descendants. It told a story of the 1875 Stefano shipwreck as narrated by the shipwreck survivor and the founding family patriarch Miho Baccich. In these circumstances the question of authorship of the manuscript was immaterial and did not arise as an issue. However, with the publication of the manuscript the author‟s name, or names, need to be formally attributed to it. It turns out that this is not such a clear-cut matter.
As we shall see, all informed sources attributed the authorship, and the ownership, of the manuscript to Miho Baccich. But the manuscript itself was written by Canon Stjepan Skurla – a priest from Miho‟s hometown of Dubrovnik. The question then arises: should Skurla also be considered as an author of the manuscript, or, even as the sole author (as some would have it)
Improving action classification with volumetric data using 3D morphological operators
No full textThis work deals with the definition of a framework for interpreting, modeling and classifying sequences of body movements into a pre-defined vocabulary of actions. Starting from sequences of volumetric reconstructions of the actor pose in each frame, we split action recognition into three separated tasks. The first task is the representation of the four-dimensional patterns reconstructed from each sequence, the second task is the extraction of motion descriptors, and the third task is the classification into action classes. In particular, we extract the curve skeleton from the reconstructed volumes in order to underly the actor movements and to reduce the system dependence from the actor gender and the body shape. The proposed method increases the action recognition rate
Geometric and radiometric modeling of 3D scenes
No full textModeling of 3D scenes is a hot topic in computer vision from more that thirty years, and probably its history is longer than a century considering also photogrammetry. In the recent years the rapid technological improvements that characterized the acquisition devices (photo-cameras, video-cameras, ..), illumination devices (lasers, structured light sources) and computational units allowed the application of 3D shape estimation methods, based on image analysis techniques, in a wide set of applications. Furthermore real-time 3D analysis is becoming a common tool in virtual and augmented reality contexts. Aim of this presentation is a rapid description of recent major advances on geometric and radiometric modeling of 3D scenes based on image analysis
Multicamera rig calibration by double-sided thick checkerboard
No full textA multi-camera rig calibration algorithm based on a double sided planar target is proposed. Due to their inherently simple realisation, low cost and accuracy, planar calibration targets came out as one of the most largely adopted calibration tools both for intrinsic and extrinsic camera parameters. However, concerning the estimation of extrinsic parameters, one of the major drawbacks of these targets is their requirement for distinct target visibility from both cameras. This prevents many configurations from being adopted where, e.g. two cameras are facing each other. An inexpensive solution could be based on printing/pasting a planar pattern on both target sides, however, the relative misalignment between the patterns on the two sides and the target thickness could be unknown. The authors propose a solution where double-sided target displacement error is estimated together with the extrinsic parameters allowing the reuse of all the available planar calibration tools in less constrained configurations. To assess their approach the authors tested the system in two scenarios, one using two professional 4K cameras and one using two smartphones
Toothbrush motion analysis to help children learn proper tooth brushing
No full textToothbrush training is a complex and not fun task for the child nor for the parents or for the dental stuff. Parents and hygienists often report that they are frustrated by poor responses to the training and in most of cases children go home and resume wrong brushing habits, if any. In this paper we present a novel approach where the tooth brushing procedure can become a fun and enjoyable task for kids using a cheap toothbrush accessory and a tablet or a smartphone. The main idea is to apply a simple and cheap 3D colored target at the end of the toothbrush and to track and analyze its motion, imparted by the child. In particular, from the tablet camera it is possible to track both the toothbrush target and the child’s facial parts in order to estimate the brushed dental side. The proposed approach has been tested on seven kids showing good results both in propensity and accuracy after a 20 days period
Lowest order stabilization free Virtual Element Method for the 2D Poisson equation
No full textWe introduce and analyse the first order Enlarged Enhancement Virtual Element
Method (EVEM) for the Poisson problem. The method allows the definition of
bilinear forms that do not require a stabilization term, thanks to the
exploitation of higher order polynomial projections that are made computable by
suitably enlarging the enhancement (from which comes the prefix of the name
E) property of local virtual spaces. The polynomial degree of local
projections is chosen based on the number of vertices of each polygon. We
provide a proof of well-posedness and optimal order a priori error estimates.
Numerical tests on convex and non-convex polygonal meshes confirm the criterium
for well-posedness and the theoretical convergence rates.Comment: 35 pages, 8 figure
A stabilization-free Virtual Element Method based on divergence-free projections
No full textIn this paper, we propose and analyze a Stabilization Free Virtual Element Method (SFVEM), that allows the definition of bilinear forms that do not require an arbitrary stabilization term, thanks to the exploitation of higher-order polynomial projections on divergence free vectors of polynomials. The method is introduced in the lowest order formulation for the Poisson problem. We provide a sufficient condition on the polynomial projection space that implies the well-posedness, proved on particular classes of polygons, and optimal order a priori error estimates. Numerical tests on convex and non-convex polygonal meshes confirm the theoretical convergence rates and show that the method is suitable for solving problems characterized by anisotropies
Correction Method for Non-Ideal Iris Recognition
No full textThe use of iris as biometric trait has emerged as one of the most preferred method because of its uniqueness, lifetime stability and regular shape. Moreover it shows public acceptance and new user-friendly capture devices are developed and used in a broadened range of applications. Currently, iris recognition systems work well with frontal iris images from cooperative users. Nonideal iris images are still a challenge for iris recognition and can significantly affect the accuracy of iris recognition systems. In this paper, we propose a method to correct off-angle iris image. Taking into account the eye morphology and the reflectance properties of the external transparent layers, we can evaluate the distorting effect that is present in the acquired image. The correction algorithm proposed includes a first modeling phase of the human eye, a segmentation of the acquired image, and a simulation phase where the acquisition geometry is reproduced and the distortions are evaluated. Finally we obtain an image which does not contain the distorting effects due to jumps in the refractive index. We show how this correction process reduce the intra-class variations for off-angle iris images
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