Hierarchical structure-and-motion recovery from uncalibrated images

This paper addresses the structure-and-motion problem, that requires to find camera motion and 3D struc- ture from point matches. A new pipeline, dubbed Samantha, is presented, that departs from the prevailing sequential paradigm and embraces instead a hierarchical approach. This method has several advantages, like a provably lower computational complexity, which is necessary to achieve true scalability, and better error containment, leading to more stability and less drift. Moreover, a practical autocalibration procedure allows to process images without ancillary information. Experiments with real data assess the accuracy and the computational efficiency of the method.Comment: Accepted for publication in CVI

Confidence-based cost modulation for stereo matching

We present a novel operator to be applied at raw matching costs in the context of low level vision tasks such as stereo matching or optical \ufb02ow. It aims at im- proving matching reliability by ef\ufb01ciently modulating pixel-wise pairing costs, injecting a con\ufb01dence backed bias before the aggregation step. It works analyzing a noisy estimate of the correspondances in order to fa- vor or prune potential matches. We test the operator by developing a local, realtime stereo matching algorithm and showing that our solution can drastically clean the resulting depth map while also reducing border bleed- ing. Its good performance is also evaluated quanti- tavely by testing the algorithm against the popular Mid- dlebury benchmark where our local greedy implemen- tation is able to obtain results comparable to those of n\ua8 aive global approaches

Advances in 3D reconstruction

La tesi affronta il problema della ricostruzione di scene tridimensionali a partire da insiemi non strutturati di fotografie delle stesse. Lo stato dell'arte viene avanzato su diversi fronti: il primo contributo consiste in una formulazione robusta del problema di struttura e moto basata su di un approccio gerarchico, contrariamente a quello sequenziale prevalente in letteratura. Questa metodologia abbatte di un ordine di grandezza il costo computazionale complessivo, risulta inerentemente parallelizzabile, minimizza il progressivo accumulo degli errori e elimina la cruciale dipendenza dalla scelta della coppia di viste iniziale comune a tutte le formulazioni concorrenti. Un secondo contributo consiste nello sviluppo di una nuova procedura di autocalibrazione, particolarmente robusta e adatta al contesto del problema di moto e struttura. La soluzione proposta consiste in una procedura in forma chiusa per il recupero del piano all'infinito data una stima dei parametri intrinseci di almeno due camere. Questo metodo viene utilizzato per la ricerca esaustiva dei parametri interni, il cui spazio di ricerca Š strutturalmente limitato dalla finitezza dei dispositivi di acquisizione. Si Š indagato infine come visualizzare in maniera efficiente e gradevole i risultati di ricostruzione ottenuti: a tale scopo sono stati sviluppati algoritmi per il calcolo della disparit… stereo e procedure per la visualizzazione delle ricostruzione come insiemi di piani tessiturati automaticamente estratti, ottenendo una rappresentazione fedele, compatta e semanticamente significativa. Ogni risultato Š stato corredato da una validazione sperimentale rigorosa, con verifiche sia qualitative che quantitative.The thesis tackles the problem of 3D reconstruction of scenes from unstructured picture datasets. State of the art is advanced on several aspects: the first contribute consists in a robust formulation of the structure and motion problem based on a hierarchical approach, as opposed to the sequential one prevalent in literature. This methodology reduces the total computational complexity by one order of magnitude, is inherently parallelizable, minimizes the error accumulation causing drift and eliminates the crucial dependency from the choice of the initial couple of views which is common to all competing approaches. A second contribute consists in the discovery of a novel slef-calibration procedure, very robust and tailored to the structure and motion task. The proposed solution is a closed-form procedure for the recovery of the plane at infinity given a rough estimate of focal parameters of at least two cameras. This method is employed for the exaustive search of internal parameters, whise space is inherently bounded from the finiteness of acquisition devices. Finally, we inevstigated how to visualize in a efficient and compelling way the obtained reconstruction results: to this effect several algorithms for the computation of stereo disparity are presented. Along with procedures for the automatic extraction of support planes, they have been employed to obtain a faithful, compact and semantically significant representation of the scene as a collection of textured planes, eventually augmented by depth information encoded in relief maps. Every result has been verified by a rigorous experimental validation, comprising both qualitative and quantitative comparisons

Lice, Flies, Mites, and Ticks on Raptors (Accipitriformes, Falconiformes and Strigiformes) in Rescue Centers in Central Italy

Abstract: This study aims to assess the occurrence of external arthropods on deceased raptors in rescue centers in Tuscany, central Italy. The examined diurnal raptors include 17 common buzzards (Buteo buteo), two European honey buzzards (Pernis apivorus), seven sparrowhawks (Accipiter nisus), six common kestrels (Falco tinnunculus), a western osprey (Pandion haliaetus), and a peregrine falcon (Falco peregrinus). Nocturnal raptors included seven barn owls (Tyto alba), ten tawny owls (Strix aluco), 22 little owls (Athene noctua) and two scops owls (Otus scops). The skin and the feathers of each animal were examined, and arthropods were collected, fixed, and microscopically identified. In 48 out of the 75 examined birds (64%), at least a single arthropod species was found. Identified arthropods included chewing lice (Degeeriella fulva, D. rufa, Colpocephalum turbinatum, C. apivorus, Nosopon lucidum, N. clayae, Craspedorrhyncus platystomus, Laemobothrion tinnunculi, Kurodaia subpachygaster, Strigiphilus cursitans), hippoboscid flies (Ornithomya avicularia), chigger and feather mites (Kramerella lunulata, K. lyra, Kramerella sp., Glaucalges attenuatus, Hieracolichus nisi, Hieracolichus sp., Neotrombicula autumnalis) and ticks (Haemaphysalis sp.). Most of the identified mite, fly and tick species are the first records in raptors in Italy. Moreover, this study presents the first record of Hieracolichus sp. and N. autumnalis mites in P. haliaetus and F. tinnunculus, respectively

HollowNeRF: Pruning Hashgrid-Based NeRFs with Trainable Collision Mitigation

Neural radiance fields (NeRF) have garnered significant attention, with recent works such as Instant-NGP accelerating NeRF training and evaluation through a combination of hashgrid-based positional encoding and neural networks. However, effectively leveraging the spatial sparsity of 3D scenes remains a challenge. To cull away unnecessary regions of the feature grid, existing solutions rely on prior knowledge of object shape or periodically estimate object shape during training by repeated model evaluations, which are costly and wasteful. To address this issue, we propose HollowNeRF, a novel compression solution for hashgrid-based NeRF which automatically sparsifies the feature grid during the training phase. Instead of directly compressing dense features, HollowNeRF trains a coarse 3D saliency mask that guides efficient feature pruning, and employs an alternating direction method of multipliers (ADMM) pruner to sparsify the 3D saliency mask during training. By exploiting the sparsity in the 3D scene to redistribute hash collisions, HollowNeRF improves rendering quality while using a fraction of the parameters of comparable state-of-the-art solutions, leading to a better cost-accuracy trade-off. Our method delivers comparable rendering quality to Instant-NGP, while utilizing just 31% of the parameters. In addition, our solution can achieve a PSNR accuracy gain of up to 1dB using only 56% of the parameters.Comment: Accepted to ICCV 202

Effective Real Image Editing with Accelerated Iterative Diffusion Inversion

Despite all recent progress, it is still challenging to edit and manipulate natural images with modern generative models. When using Generative Adversarial Network (GAN), one major hurdle is in the inversion process mapping a real image to its corresponding noise vector in the latent space, since its necessary to be able to reconstruct an image to edit its contents. Likewise for Denoising Diffusion Implicit Models (DDIM), the linearization assumption in each inversion step makes the whole deterministic inversion process unreliable. Existing approaches that have tackled the problem of inversion stability often incur in significant trade-offs in computational efficiency. In this work we propose an Accelerated Iterative Diffusion Inversion method, dubbed AIDI, that significantly improves reconstruction accuracy with minimal additional overhead in space and time complexity. By using a novel blended guidance technique, we show that effective results can be obtained on a large range of image editing tasks without large classifier-free guidance in inversion. Furthermore, when compared with other diffusion inversion based works, our proposed process is shown to be more robust for fast image editing in the 10 and 20 diffusion steps' regimes.Comment: Accepted to ICCV 2023 (Oral

Stress echocardiography for risk stratification of patients following coronary bypass surgery

Objectives: To assess the prognostic value of stress echocardiography following coronary bypass surgery. Methods: We evaluated 451 patients (360 men; age 65?10 years) who underwent stress echocardiography with exercise (n=33), dipyridamole (n=319) or dobutamine (n=99) after a median of 69 months from coronary bypass surgery. Patients were followed-up for the occurence of hard (death, infarction) and major events (death, infarction, late [>3 months] revascularization). Results: Ischemia at stress echo was assessed in 185 (41%) patients. During a median follow-up of 25 months, there were 119 events (56 deaths, 17 myocardial infarctions, and 46 late revascularizations). Additionally 55 patients underwent early [<3 months] revascularization and were censored. Independent predictors of hard events were age (HR=1.06; 95% CI=1.03-1.10; p<0.0001), and peak wall motion score index (HR=3.36; 95% CI=1.85-6.11; p<0.0001). 4-year major event rate was 26% in patients with and 17% in those without ischemia (p=0.44) (Figure). Independent predictors of major events were age (HR=1.03; 95% CI=1,01-1.06; p=0.002), ischemia at stress echo (HR=1.73; 95% CI=1.20-2.49; p=0.004), and resting wall motion score index (HR=1.82; 95% CI=1.20-2.77; p=0.005). 4-year major event rate was 40% in patients with and 26% in those without ischemia (p=0.02) (Figure). Conclusion: In patients with previous coronary bypass surgery, ischemia at stress echo is a multivariable indicator of future major events. However, it is unable to predict hard events

Visual change detection on tunnel linings

We describe an automated system for detecting, localising, clustering and ranking visual changes on tunnel surfaces. The system is designed to provide assistance to expert human inspectors carrying out structural health monitoring and maintenance on ageing tunnel networks. A three-dimensional tunnel surface model is first recovered from a set of reference images using Structure from Motion techniques. New images are localised accurately within the model and changes are detected versus the reference images and model geometry. We formulate the problem of detecting changes probabilistically and evaluate the use of different feature maps and a novel geometric prior to achieve invariance to noise and nuisance sources such as parallax and lighting changes. A clustering and ranking method is proposed which efficiently presents detected changes and further improves the inspection efficiency. System performance is assessed on a real data set collected using a low-cost prototype capture device and labelled with ground truth. Results demonstrate that our system is a step towards higher frequency visual inspection at a reduced cost.The authors gratefully acknowledge the support by Toshiba Research Europe.This is the accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s00138-014-0648-8

Inquinamento atmosferico e ricoveri ospedalieri urgenti in 25 citt? italiane: risultati del progetto EpiAir2 Air pollution and urgent hospital admissions in 25 Italian cities: results from the EpiAir2 project

OBJECTIVE: to evaluate the relationship between air pollution and hospital admissions in 25 Italian cities that took part in the EpiAir (Epidemiological surveillance of air pollution effects among Italian cities) project. DESIGN: study of time series with case-crossover methodology, with adjustment for meteorological and time-dependent variables. The association air pollution hospitalisation was analyzed in each of the 25 cities involved in the study; the overall estimates of effect were obtained subsequently by means of a meta-analysis. The pollutants considered were PM10, PM2.5 (in 13 cities only), NO2 and ozone (O3); this last pollutant restricted to the summer season (April-September). SETTING AND PARTICIPANTS: the study has analyzed 2,246,448 urgent hospital admissions for non-accidental diseases in 25 Italian cities during the period 2006- 2010; 10 out of 25 cities took part also in the first phase of the project (2001-2005). MAIN OUTCOME MEASURES: urgent hospital admissions for cardiac, cerebrovascular and respiratory diseases, for all age groups, were considered. The respiratory hospital admissions were analysed also for the 0-14-year subgroup. Percentage increases risk of hospitalization associated with increments of 10 &#956;g/m3 and interquartile range (IQR) of the concentration of each pollutant were calculated. RESULTS: reported results were related to an increment of 10 &#956;g/m3 of air pollutant. The percent increase for PM10 for cardiac causes was 0.34% at lag 0 (95%CI 0.04-0.63), for respiratory causes 0.75%at lag 0-5 (95%CI 0.25-1.25). For PM2.5, the percent increase for respiratory causes was 1.23% at lag 0- 5 (95%CI 0.58-1.88). For NO2, the percent increase for cardiac causes was 0.57%at lag 0 (95%CI 0.13-1.02); 1.29% at lag 0-5 (95%CI 0.52-2.06) for respiratory causes. Ozone (O3) did not turned out to be positively associated neither with cardiac nor with respiratory causes as noted in the previous period (2001-2005). CONCLUSION: the results of the study confirm an association between PM10, PM2.5, and NO2 on hospital admissions among 25 Italian cities. No positive associations for ozone was noted in this period.OBIETTIVO: valutare la relazione tra inquinamento atmosferico e ricoveri ospedalieri nelle citt? italiane partecipanti alla seconda fase del progetto EpiAir (Sorveglianza epidemiologica dell\u27inquinamento atmosferico: valutazione dei rischi e degli impatti nelle citt? italiane). DISEGNO: studio di serie temporali con metodologia case-crossover, con aggiustamento per i fattori temporali e meteorologici rilevanti. L\u27associazione inquinamento atmosferico- ospedalizzazioni ? stata analizzata in ciascuna delle 25 citt? in studio, le stime complessive di effetto sono state ottenute successivamente mediante una metanalisi. Gli inquinanti considerati sono stati il particolato (PM10), il biossido di azoto (NO2) e l\u27ozono (O3), quest\u27ultimo limitatamente al semestre estivo (da aprile a settembre). In 13 citt? in cui i dati erano disponibili ? stata analizzata anche la frazione fine del particolato (PM2.5). SETTING E PARTECIPANTI: lo studio ha esaminato 2.246.448 ricoveri ospedalieri urgenti per cause naturali di pazienti residenti e ricoverati, nel periodo 2006-2010, in 25 citt? italiane, di cui 10 gi? partecipanti alla prima fase del progetto EpiAir (2001-2005). PRINCIPALIMISURE DI OUTCOME: sono stati considerati i ricoveri ospedalieri urgenti per malattie cardiache, cerebrovascolari e respiratorie per tutte le fasce di et?. I ricoveri per cause respiratorie sono stati analizzati separatamente anche per la fascia di et? 0-14 anni. L\u27esposizione ? stata valutata per incremento sia di 10 &#956;g/m3 sia pari all\u27intervallo interquartile (IQR) della concentrazione di ciascun inquinante. RISULTATI: considerando un incremento di 10 &#956;g/m3 per inquinante, per il PM10 ? stato osservato un incremento percentuale di rischio per patologie cardiache dello 0,34%a lag 0 (IC95% 0,04-0,63), e per patologie respiratorie dello 0,75% a lag 0-5 (IC95% 0,25-1,25). Per il PM2.5 l\u27incremento percentuale di rischio per patologie respiratorie ? risultato dell\u271,23%a lag 0-5 (IC95%0,58-1,88). Per l\u27NO2 la stima di effetto per patologie cardiache ? risultata dello 0,57% a lag 0 (IC95% 0,13-1,02), e per patologie respiratorie dell\u271,29% a lag 0-5 (IC95% 0,52-2,06). L\u27ozono non ? risultato positivamente associato n? alle patologie cardiache n? a quelle respiratorie (a differenza del periodo 2001-2005). CONCLUSIONE: i risultati dello studio confermano l\u27effetto a breve termine dell\u27inquinamento atmosferico da PM10, PM2.5 e NO2 sulla morbosit?, in particolare respiratoria, nelle citt? italiane. Non sono state rilevate associazioni positive per l\u27O3