Cette thèse avait pour objectif d'analyser l'influence de certains facteurs (expertise, difficulté de la tâche) sur le traitement dimages en 2D et 3D. Le terrain choisi pour étudier cette question est le domaine de la chirurgie minimale invasive, qui, par les nouvelles technologies quelle utilise, permet de recueillir des données écologiques dans une situation réelle avec de vrais experts. Nous avons donc comparé la performance de sujets novices et experts dans des tâches de complexités diverses avec différentes technologies chirurgicales (laparoscopie classique en 2D et 3D et laparoscopie robotique en 2D et 3D). Nos plans expérimentaux nous ont permis de mettre en évidence deux dimensions distinctes : une perceptive (différence 2D-3D) et une instrumentale (différence laparoscopie classique-robotique). Nos résultats montrent dans lensemble que les différences entre le 2D et le 3D se marquent particulièrement pour les sujets novices et dans les tâches de complexité moyenne. En effet, peu de différence entre le 2D et 3D est mise en évidence chez les chirurgiens experts qui ont développé des mécanismes de compensation très efficaces quand ils sont dans un environnement en 2D. En ce qui concerne la complexité des tâches, la différence entre le 2D et 3D est minime quand la tâche est simple et augmente avec la difficulté de la tâche. Elle atteint cependant un sommet à partir duquel elle napparaît plus, la différence se marquant pour les tâches très complexes à un niveau instrumental et non plus perceptif. Enfin, nous montrons chez nos sujets novices très peu de transfert dhabiletés dune technologie à lautre, ce qui encourage la poursuite des formations avec les diverses techniques afin déviter tout risque lors dune reconversion au cours dune intervention chirurgicale. This thesis aimed to analyse the influence of some factors (expertise, task complexity) on the processing of 2D and 3D images. The field of these studies was the minimal invasive surgery which uses new technologies and allows to obtain ecological data from real experts. We compared the performance of novices (medical students) and experts (surgeons) in tasks of varied complexities with different surgical techniques (classical laparoscopy in 2D and 3d and robotic laparoscopy in 2D and 3D). Our experimental plans allowed us to differentiate two dimensions: one perceptive (2D-3D difference) and one instrumental (classical and robotic laparoscopy difference). Our main results showed that difference between 2D and 3D particularly occurs in novice performance and in tasks of middle complexity. Indeed, we observed very few differences between 2D and 3D in expert performance, surgeons have developed very efficient compensatory mechanisms when they act in 2D vision. Concerning the task complexity, the difference between 2D and 3D was really minor when the task is easy and increased with the complexity of the task. However, this difference reached a top after which the difference between 2D and 3D disappeared and thus only the instrumental difference remained for very complex tasks. Finally, we showed very switch of skills between the techniques by novice subjects. This finding stresses the necessity to pursue training with the different techniques in order to prevent gaps in performance and thus operating risk if a conversion procedure occurs.

Thesis (M.P.H.)--University of Texas Health Science Center at Houston, School of Public Health, 2008. / Source: Masters Abstracts International, Volume: 46-06, page: 3262. Adviser: John R. Herbold. Includes bibliographical references.

Les technologies de relief tridimensionnel (3D) ont récemment reçu un nouvel attrait. Lesraisons potentielles sont que ces technologies peuvent fournir une expérience visuelle plusriche et plus immersive. En effet, un observateur peut extraire les disparités binoculairesprésentées entre les vues gauche et droite, pour retrouver plus efficacement la profondeur dela scène visuelle observée, et ainsi, trouver une nouvelle dimension dans le contenu.Cependant, tandis que la valeur de la profondeur est plutôt bien appréciée, un certain nombrede problèmes qui impactent la qualité de l’expérience dans les représentations 3D ont étéidentifiés. L’objective de cette thèse est d’étudier les principaux facteurs qui affectent laqualité de l’expérience en stéréoscopie dans le but de fournir des méthodes qui pourraientaméliorer l’utilisation des systèmes stéréoscopiques. Trois aspects majeurs de la qualité del’expérience sont adressés : (1) les sources et causes de la fatigue visuelle, (2) les distorsionsperceptives et (3) l’amélioration de la qualité de l’expérience en 3D au travers de l’adaptationdu contenu visuel. Pour étudier la fatigue visuelle, les mouvements de vergence étaientmesurés à la fois avec un écran 3D et avec un système à double écran qui permettaient laprésentation de stimuli avec les informations de disparité et de flou présentés en congruencecomme en incongruence. L’effet de la stéréoscopie sur les mouvements de vergence a étéétudié dans le but de tester si la mesure oculaire pouvait être utilisée comme indicateur defatigue visuelle. Le sujet suivant étudiait la consistance de la perception des formes 3Dstéréoscopiques en fonction de distances virtuelles induites par la disparité et par le signald’accommodation. Le rôle de la taille de la pupille et de la profondeur de champ enstéréoscopie étaient étudiés par la manipulation de la taille de la pupille avec deux conditionsd’illumination contrôlée. Finalement, l’amélioration de la perception de la forme 3D estquestionnée au travers de l’adaptation du contenu visuel en fonction de la mesure de seuilsperceptifs individuels pour des stimuli se déplaçant en profondeur. / Stereoscopic 3-Dimensional (S3D) technology has recently received growing attraction,potentially because it provides a more informative and more immersive visual experience.Indeed, the viewer may extract the binocular disparities displayed between the left and theright views, more efficiently retrieve the depth of the observed visual scene, and thus, givevisual content another dimension. However, while the additional value of depth is ratherappreciated, a number of problems have been raised that impact the Quality of Experience(QoE) in S3D representations. The objective of this thesis is to investigate the main factorsaffecting QoE in stereopsis in order to provide guidelines towards the improvement andfurther use of stereoscopic systems. Three main aspects of QoE in S3D are addressed: (1) thesources and causes of visual fatigue, (2) the perceptual distortions arising in S3D and, (3) theimprovement of S3D QoE through content adaptation. To study visual fatigue in S3D,vergence eye movements were measured both in S3D display and in dual-screen display thatenables the presentation of matched disparity and defocus stimuli. The effect of stereopsis onvergence movements was studied so as to test whether vergence tracking can be used asindicator of visual fatigue. The next topic investigated the consistency in stereoscopic 3Dshape perception as a function of vergence distance and accommodation distance. The role ofthe pupil size and the depth of focus in S3D were evaluated by manipulating the pupilaperture with two controlled lighting conditions. Finally, the improvement of 3D shapeperception is addressed through content adaptation according to individual perceptionthresholds measurement for motion-in-depth stimuli.

This study investigates different design choices for graphical user interfaces meant to improve depth perception in remote crane operation through measuring efficiency and user experience. To achieve this, three different graphical user interface designs were created and implemented into a cargo port simulator within the game engine Unity. These GUIs consists of a top-down shadow overlay, a guideline overlay and one overlay that would display held containers as see-through, called X-ray overlay. The three GUIs were then tested in a user study along a blank interface which had no overlay, in order to compare task efficiency, accuracy and usability among the four interfaces. In total, 15 participants took part in the user study in which none had any previous experience in using heavy machinery such as cargo cranes. These 15 participants were of various ages between 22-59 and of various genders. The results from the user study shows that the shadow overlay and the guideline overlay were more favoured among the participants who took part in the experiment, as well as more usable in comparison towards the X-ray overlay and having no overlay. The participants were also more accurate and efficient in placing containers while using the shadow overlay and the guideline overlay.

PURPOSE: Gait during obstacle negotiation is adapted in visually normal subjects whose vision is temporarily and unilaterally blurred or occluded. This study was conducted to examine whether gait parameters in individuals with long-standing deficient stereopsis are similarly adapted. METHODS: Twelve visually normal subjects and 16 individuals with deficient stereopsis due to amblyopia and/or its associated conditions negotiated floor-based obstacles of different heights (7-22 cm). Trials were conducted during binocular viewing and monocular occlusion. Analyses focused on foot placement before the obstacle and toe clearance over it. RESULTS: Across all viewing conditions, there were significant group-by-obstacle height interactions for toe clearance (P < 0.001), walking velocity (P = 0.003), and penultimate step length (P = 0.022). Toe clearance decreased (approximately 0.7 cm) with increasing obstacle height in visually normal subjects, but it increased (approximately 1.5 cm) with increasing obstacle height in the stereo-deficient group. Walking velocity and penultimate step length decreased with increasing obstacle height in both groups, but the reduction was more pronounced in stereo-deficient individuals. Post hoc analyses indicated group differences in toe clearance and penultimate step length when negotiating the highest obstacle (P < 0.05). CONCLUSIONS: Occlusion of either eye caused significant and similar gait changes in both groups, suggesting that in stereo-deficient individuals, as in visually normal subjects, both eyes contribute usefully to the execution of adaptive gait. Under monocular and binocular viewing, obstacle-crossing performance in stereo-deficient individuals was more cautious when compared with that of visually normal subjects, but this difference became evident only when the subjects were negotiating higher obstacles; suggesting that such individuals may be at greater risk of tripping or falling during everyday locomotion.

PURPOSE: A recent study suggested that updated spectacles could increase fall rate in frail older people. The authors hypothesized that the increased risk may be due to changes in spectacle magnification. The present study was conducted to assess the effects of spectacle magnification on step negotiation. METHODS: Adaptive gait and visual function were measured in 10 older adults (mean age, 77.1 +/- 4.3 years) with the participants' optimal refractive correction and when blurred with +1.00, +2.00, -1.00, and -2.00 DS lenses. Adaptive gait measurements for the leading and trailing foot included foot position before the step, toe clearance of the step edge, and foot position on the step. Vision measurements included visual acuity, contrast sensitivity, and stereoacuity. RESULTS: The blur lenses led to equal decrements in visual acuity and stereoacuity for the +1.00 and -1.00 DS and the +2.00 and -2.00 DS lenses. However, they had very different effects on step negotiation compared with the optimal correction. Positive-blur lenses led to an increased distance of the feet from the step, increased vertical toe clearance and reduced distance of the leading heel position on the step. Negative lenses led to the opposite of these changes. CONCLUSIONS: The step negotiation changes did not mirror the effects of blur on vision, but were driven by the magnification changes of the lenses. Steps appear closer and larger with positive lenses and farther away and smaller with negative ones. Magnification is a likely explanation of the mobility problems some older adults have with updated spectacles and after cataract surgery.

PURPOSE. Gait during obstacle negotiation is adapted in visually normal subjects whose vision is temporarily and unilaterally blurred or occluded. This study was conducted to examine whether gait parameters in individuals with long-standing deficient stereopsis are similarly adapted. METHODS. Twelve visually normal subjects and 16 individuals with deficient stereopsis due to amblyopia and/or its associated conditions negotiated floor-based obstacles of different heights (7-22 cm). Trials were conducted during binocular viewing and monocular occlusion. Analyses focused on foot placement before the obstacle and toe clearance over it. RESULTS. Across all viewing conditions, there were significant group-by-obstacle height interactions for toe clearance (P < 0.001), walking velocity (P = 0.003), and penultimate step length (P = 0.022). Toe clearance decreased (similar to 0.7 cm) with increasing obstacle height in visually normal subjects, but it increased (similar to 1.5 cm) with increasing obstacle height in the stereo-deficient group. Walking velocity and penultimate step length decreased with increasing obstacle height in both groups, but the reduction was more pronounced in stereo-deficient individuals. Post hoc analyses indicated group differences in toe clearance and penultimate step length when negotiating the highest obstacle (P < 0.05). CONCLUSIONS. Occlusion of either eye caused significant and similar gait changes in both groups, suggesting that in stereo-deficient individuals, as in visually normal subjects, both eyes contribute usefully to the execution of adaptive gait. Under monocular and binocular viewing, obstacle-crossing performance in stereo-deficient individuals was more cautious when compared with that of visually normal subjects, but this difference became evident only when the subjects were negotiating higher obstacles; suggesting that such individuals may be at greater risk of tripping or falling during everyday locomotion. / RCUK (Research Councils, UK)

Suite à l’amélioration des outils de capture et de stockage des données, ces dernières années ont vu les quantités de données à traiter croître énormément. De nombreux travaux, allant du traitement automatique à la visualisation d’information, ont alors été mis en place, mais certains domaines sont encore trop spécifiques pour en profiter. C’est le cas du Renseignement d’Origine ÉlectroMagnétique (ROEM). Ce domaine ne fait pas uniquement face à de grandes quantités de données mais doit aussi gérer des données et des usages complexes ainsi que des populations d’utilisateurs ayant de moins en moins d’expérience. Dans cette thèse nous nous sommes intéressés à l’usage de l’existant et des nouvelles technologies appliquées à la visualisation pour proposer des solutions à la combinaison de problématiques comme les données en grandes quantité et les données complexes. Nous commençons par présenter une analyse du domaine du ROEM qui a permis d’extraire les problématiques auxquelles il doit faire face. Nous nous intéressons ensuite aux solutions gérant les combinaisons de telles problématiques. L’existant ne contenant pas directement de telles solutions, nous nous intéressons alors à la description des problématiques de visualisation et proposons une caractérisation de ces problématiques. Cette caractérisation nous permet de décrire les représentations existantes et de mettre en place un outil de recommandation des représentations basé sur la façon dont l’existant résout les problématiques. Enfin nous nous intéressons à identifier de nouvelles métaphores pour compléter l’existant et proposons une représentation immersive permettant de résoudre les problématiques du ROEM. Ces contributions permettent d’analyser et d’utiliser l’existant et approfondissent l’usage des représentations immersives pour la visualisation d’information. / As a result of the improvement of data capture and storage, recent years have seen the amount of data to be processed increase dramatically. Many studies, ranging from automatic processing to information visualization, have been performed, but some areas are still too specific to take advantage of. This is the case of ELectromagnetic INTelligence(ELINT). This domain does not only deal with a huge amount of data but also has to handle complex data and usage as well as populations of users with less and less experience. In this thesis we focus on the use of existing and new technologies applied to visualization to propose solutions to the combination of issues such as huge amount and complex data. We begin by presenting an analysis of the ELINT field which made it possible to extract the issues that it must faces. Then, we focus on the visual solutions handling the combinations of such issues but the existing work do not contain directly such solutions. Therefore, we focus on the description of visual issues and propose a characterization of these issues. This characterization allows us to describe the existing representations and to build a recommendation tool based on how the existing work solves the issues. Finally, we focus on identifying new metaphors to complete the existing work and propose an immersive representation to solve the issues of ELINT. These contributions make it possible to analyze and use the existing and deepen the use of immersive representations for the visualization of information.

The recent emergence of time-of-flight cameras has opened up new possibilities in the world of computer vision. These compact sensors, capable of recording the depth of a scene in real-time, are very advantageous in many applications, such as scene or object reconstruction. This thesis first addresses the problem of fusing depth data with color images. A complete process to combine a time-of-flight camera with a color camera is described and its accuracy is evaluated. The results show that a satisfying precision is reached and that the step of calibration is very important. The second part of the work consists of applying super-resolution techniques to the time-of-flight camera in order to improve its low resolution. Different types of super-resolution algorithms exist but this thesis focuses on the combination of multiple shifted depth maps. The proposed framework is made of two steps: registration and reconstruction. Different methods for each step are tested and compared according to the improvements reached in term of level of details, sharpness and noise reduction. The results obtained show that Lucas-Kanade performs the best for the registration and that a non-uniform interpolation gives the best results in term of reconstruction. Finally, a few suggestions are made about future work and extensions for our solutions.

The challenges found in three-dimensional platformer games heavily rely on the player’s ability to perceive depth and it is therefore crucial for them to feature shadows as they are an important depth cue for the human visual system. In this paper, we compare two different kinds of shadowing solutions, blob shadows and shadow-maps. Subjects split into two groups each played a differently shadowed version of a 3D platformer game prototype as well as a common, unshadowed version. The first group’s prototype featured blob shadows while the second group’s used shadowmaps. The players were asked to input their own proficiency level from one to five into the program. The data collected through in-prototype logging to a file hinted at shadowmaps being more desirable as the shadowmap group’s delta from shadowed to unshadowed playthrough was lower than the blob shadow group’s. However, this data featured a number of problems, such as low sample size, subjective evaluation of player proficiency in 3D platformer games and different distribution of proficiency in and across groups. / Utmaningarna funna i tredimensionella platformsspel beror starkt på spelarens förmåga att uppfatta djup och det är därför avgörande för spelaren att ha skuggor eftersom de är en viktig antydan till djup för det mänskliga visuella systemet. I detta examensarbete jämför vi två olika typer av skuggningslösningar, “blob shadows” och “shadowmaps”. Försökspersonerna delades upp i två grupper, var och en spelade en annorlunda skuggad version av en prototyp för ett 3D-plattformsspel samt en ordinär, version utan skugga. Den första gruppens skuggor gjordes med “blob shadows” medan för den andra gruppen användes “shadowmaps”. Spelarna ombads att mata in sin egen kompetensnivå från ett till fem i programmet. Uppgifterna som samlats in via loggning i prototypen skrevs till en fil som antydde att “shadowmaps” var mer önskvärda eftersom “shadowmap”-gruppens delta från skuggad till icke-skuggad igenomspelning var lägre än skugga-gruppens. Dessa data innehöll emellertid ett antal problem, såsom låg provstorlek, subjektiv utvärdering av spelarens kunskaper i 3D-plattformsspel och olika spridning av kunskaper i och över grupper. Insikter för framtida forskning inkluderar skapandet av en objektiv ram för utvärdering för kunskaperna för spelarna såväl som förminskningen av prototypens omfattning.