Une vidéo est une source particulièrement riche en informations. Parmi tous les objets que nous pouvons y trouver, les visages humains sont assurément les plus saillants, ceux qui attirent le plus l’attention des spectateurs. Considérons une séquence vidéo dont chaque trame contient un ou plusieurs visages en mouvement. Ils peuvent appartenir à des personnes connues ou qui apparaissent de manière récurrente dans la vidéo Cette thèse a pour but de créer une méthodologie afin d’extraire une ou plusieurs images de visage en vue d’appliquer, par la suite, un algorithme de reconnaissance du visage. La principale hypothèse de cette thèse réside dans le fait que certains exemplaires d’un visage sont meilleurs que d’autres en vue de sa reconnaissance. Un visage est un objet 3D non rigide projeté sur un plan pour obtenir une image. Ainsi, en fonction de la position relative de l’objectif par rapport au visage, l’apparence de ce dernier change. Considérant les études sur la reconnaissance de visages, on peut supposer que les exemplaires d’un visage, les mieux reconnus sont ceux de face. Afin d’extraire les exemplaires les plus frontaux possibles, nous devons d’une part estimer la pose de ce visage. D’autre part, il est essentiel de pouvoir suivre le visage tout au long de la séquence. Faute de quoi, extraire des exemplaires représentatifs d’un visage perd tout son sens. Les travaux de cette thèse présentent trois parties majeures. Dans un premier temps, lorsqu’un visage est détecté dans une séquence, nous cherchons à extraire position et taille des yeux, du nez et de la bouche. Notre approche se base sur la création de cartes d’énergie locale principalement à direction horizontale. Dans un second temps, nous estimons la pose du visage en utilisant notamment les positions relatives des éléments que nous avons extraits. Un visage 3D a trois degrés de liberté : le roulis, le lacet et le tangage. Le roulis est estimé grâce à la maximisation d’une fonction d’énergie horizontale globale au visage. Il correspond à la rotation qui s’effectue parallèlement au plan de l’image. Il est donc possible de le corriger pour qu’il soit nul, contrairement aux autres rotations. Enfin, nous proposons un algorithme de suivi de visage basé sur le suivi des yeux dans une séquence vidéo. Ce suivi repose sur la maximisation de la corrélation des cartes d’énergie binarisées ainsi que sur le suivi des éléments connexes de cette carte binaire. L’ensemble de ces trois méthodes permet alors tout d’abord d’évaluer la pose d’un visage qui se trouve dans une trame donnée puis de lier tous les visages d’une même personne dans une séquence vidéo, pour finalement extraire plusieurs exemplaires de ce visage afin de les soumettre à un algorithme de reconnaissance du visage. / The aim of this thesis is to create a methodology in order to extract one or a few representative face images of a video sequence with a view to apply a face recognition algorithm. A video is a media particularly rich. Among all the objects present in the video, human faces are, for sure, the most salient objects. Let us consider a video sequence where each frame contains a face of the same person. The primary assumption of this thesis is that some samples of this face are better than the others in terms of face recognition. A face is a non-rigid 3D object that is projected on a plan to form an image. Hence, the face appearance changes according to the relative positions of the camera and the face. Many works in the field of face recognition require faces as frontal as possible. To extract the most frontal face samples, on the one hand, we have to estimate the head pose. On the other hand, tracking the face is also essential. Otherwise, extraction representative face samples are senseless. This thesis contains three main parts. First, once a face has been detected in a sequence, we try to extract the positions and sizes of the eyes, the nose and the mouth. Our approach is based on local energy maps mainly with a horizontal direction. In the second part, we estimate the head pose using the relative positions and sizes of the salient elements detected in the first part. A 3D face has 3 degrees of freedom: the roll, the yaw and the pitch. The roll is estimated by the maximization of a global energy function computed on the whole face. Since this roll corresponds to the rotation which is parallel to the image plan, it is possible to correct it to have a null roll value face, contrary to other rotations. In the last part, we propose a face tracking algorithm based on the tracking of the region containing both eyes. This tracking is based on the maximization of a similarity measure between two consecutive frames. Therefore, we are able to estimate the pose of the face present in a video frame, then we are also able to link all the faces of the same person in a video sequence. Finally, we can extract several samples of this face in order to apply a face recognition algorithm on them.

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<p>When users begin to experience virtual reality (VR) for the first time, they can be met with some degree of motion sickness and nausea, especially if continuous joystick locomotion is used. The symptoms that are induced during these VR experiences fall under the umbrella term cybersickness, and due to these uncomfortable experiences, these users can get a bad first impression and abandon the innovative technology, not able to fully appreciate the convenience and fascinating adventures VR has to offer. As such, this project compares the effects of two cybersickness mitigation methods (Dynamic Field of View (FOV) and Virtual Reference Frame), both against each other and combined, on user-reported cybersickness symptoms to determine the best combination to implement in commercial applications to help create more user-friendly VR experiences. The hypothesis is that combining the FOV reduction and the resting frame methods can mitigate VR cybersickness more effectively without hindering the user’s experience and the virtual nose method is more potent at mitigating cybersickness compared to dynamic FOV. To test these hypotheses, an experimental game was developed for the Meta Quest 2 with five levels: a tutorial level and four maze levels (one for each scenario). The participants were asked to complete the tutorial level until they got used to the virtual reality controls, and then they were instructed to complete the maze level twice with one of the following conditions for each run: no method, dynamic field of view only, virtual nose only, and dynamic field of view and virtual nose combined. After completing each maze trial, the participants were asked to complete a simulator sickness questionnaire to get their thoughts on how much sickness they felt during the test. Upon concluding the testing phase with 36 participants and compiling the data, the results showed that while the subjects preferred the dynamic FOV method even though they were able to complete the trials significantly faster with the virtual nose method, it is inconclusive regarding which method is truly more effective. Furthermore, the results showed that it is also inconclusive if the scenario with both methods enabled is significantly better or worse than either method used separately.</p>

The thesis tries to grasp the meaning of lexeme nos "the nose" in cognitively-linguistic perspective, namely in particular through colocation and idioms, which contains the lexeme nos. The goal of this thesis is to define so-called semantic profiles of concept NOSE and to formulate cognitively cultural definition of nose consequential from its location in the Czech linguistic picture of the world. For this purpose nose first will be subjected to analysis from two different perspectives - from medical perspective, which represent the scientific view on the world, and from the perspective of a common user of the language, which represent so- called naive picture of the world. Data relating to the lexeme nos will be excerpted from Czech monolingual, synonymous, etymological and phraseological dictionaries, the semic analysis will be done and the lexeme nos will be included to systemic relationships in Czech vocabulary. Nose also will be introduced in a ligth of an additional perspectives of an alternative medicine and a pseudoscientific disciplines: the phrenology and the physiognomy. Their knowledges play some role in a formation of a naive picture of a nose. The questionnaire research is too a part of the thesis. The questionnaire research search for which association a common user of the Czech language have...