2,939 research outputs found

    The Perception of Surface Properties: Translucence and Gloss

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    The human visual system is sensitive to differences in gloss and translucence, two optical properties which are found in conjunction in many natural materials. They are driven by similar underlying physical properties of light transport - the degree to which light is scattered from the surface of a material, or within the material. This thesis aimed to address some fundamental questions about how gloss and translucence are perceived. Two psychophysical methods (maximum likelihood difference scaling, and conjoint measurement) were used throughout, as they provided an appropriate way of investigating how perceptual experiences related to physical variables. In the introduction, I review the literature on the perception of gloss and translucence. Study 1 investigated the relationship between variables controlling light transport in translucent volumes and percepts of translucence. The results show that translucence perception is not based on estimates of light transport properties per se, but probably uses spatially-related statistical pseudocues in conjunction with other cues. Study 2 examined a similar issue, but the translucent material was presented as a layer enveloping a solid object. Behavioural responses were similar for these translucent materials, which were perceived as glossy layers of coating. Study 3 further explored established findings that perceived translucence shows inconstancy under changes in viewing condition. Perceived translucence was dependent in a complex way on both light-scattering in the material and illumination direction in both volumes and layers of translucent materials. Study 4 used similar layers of subsurface light-scattering and -absorbing material and applied them to multiple base materials. Opacity and a lack of mirror-like reflections enabled observers to make the most accurate independent judgements of darkness and cloudiness. Study 5 explored observers' sensitivity to spatial variation of scatter across a surface using similar layers of coating, and the way in which observers might weight cues differently to answer subtly different questions (judgements of 'shininess' vs. 'cleanliness'). Layer thickness and variation of scatter significantly affected perceived shine and cleanliness, with layer thickness influencing decisions more than variation. Scatter variation contributed to decisions significantly more for judgements of cleanliness than shine. Study 6 investigated how tactile surface roughness influenced perceived gloss. Previous findings have shown that tactile compliance and friction influence perceived gloss, and that friction interacts with visual gloss. Our results showed that surface roughness and visual gloss both affected perceived gloss, but there was no interaction, suggesting that different types of haptic information are combined with visual information differently. Finally, study 7 explored the potential cortical basis of perceived translucence. Through testing a neuropsychological patient, we showed that perceived translucence is dependent on cortical areas not responsible for colour or texture discrimination. The thesis concludes with a discussion of additional recent findings, the implications of the research reported in this thesis, and proposals for future research

    Differential processing of binocular and monocular gloss cues in human visual cortex.

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    The visual impression of an object's surface reflectance ("gloss") relies on a range of visual cues, both monocular and binocular. Whereas previous imaging work has identified processing within ventral visual areas as important for monocular cues, little is known about cortical areas involved in processing binocular cues. Here, we used human functional MRI (fMRI) to test for brain areas selectively involved in the processing of binocular cues. We manipulated stereoscopic information to create four conditions that differed in their disparity structure and in the impression of surface gloss that they evoked. We performed multivoxel pattern analysis to find areas whose fMRI responses allow classes of stimuli to be distinguished based on their depth structure vs. material appearance. We show that higher dorsal areas play a role in processing binocular gloss information, in addition to known ventral areas involved in material processing, with ventral area lateral occipital responding to both object shape and surface material properties. Moreover, we tested for similarities between the representation of gloss from binocular cues and monocular cues. Specifically, we tested for transfer in the decoding performance of an algorithm trained on glossy vs. matte objects defined by either binocular or by monocular cues. We found transfer effects from monocular to binocular cues in dorsal visual area V3B/kinetic occipital (KO), suggesting a shared representation of the two cues in this area. These results indicate the involvement of mid- to high-level visual circuitry in the estimation of surface material properties, with V3B/KO potentially playing a role in integrating monocular and binocular cues.This project was supported by fellowships to A.E.W. from the Wellcome Trust (095183/Z/10/Z) and to H.B. from the Japan Society for the Promotion of Science (JSPS KAKENHI (26870911)).This is the final version of the article. It first appeared from the American Physiological Society via https://doi.org/10.1152/jn.00829.201

    Makeup Lifestyles of the Female Youths in Ghana. Evidence from Kumasi and Accra Tertiary Institutions

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    Women would want to appear more attractive and feminine to enjoy the benefits that accompany it. It is against this background that they predominate in makeup usage. The study fundamentally determined the makeup lifestyles of the female youths in selected tertiary institutions in Ghana. Employing descriptive research through cross sectional survey and using convenience sampling techniques, data was collected from female students, mainly in Accra and Kumasi tertiary institutions and 260 questionnaires analysed. Findings revealed that respondents generally used makeup for glamour, attractiveness, supporting their career, creativity, feeling confident and empowerment. More respondents applied makeup only on special occasions and mostly considered the complexion, skin tone, skin type, clothing, occasion and quality of the product before using it. Generally, respondents used makeup whilst going to ‘lectures’, ‘on a date’, ‘to church’, and ‘to work’. Some did not use make on all and more makeup users spent less than 15 minutes on all situations especially to ‘lectures’, ‘job interviews’, ‘church’ and ‘visit to friends’. Greater respondents ‘sometimes’ or ‘once daily’ touched up their makeups and many ‘seldom’ carried makeup item(s) for touch-ups mostly being lipstick, powder, and lip-gloss. More respondents started makeup between 16 and 19 years and more viewed makeup to social situations as ‘important’ and that makeup enhances their self-appearance, and boost their consciousness. Respondents were satisfied without makeup than with makeup and majority were aware of the negative effects of makeup on human skin. The study recommends that makeup users be educated on the negative effects of colour cosmetics so that they would be better informed in their application. This study is the first to have been conducted in Ghana and could be useful for the cosmetic industry, researchers and the academia. Keywords: Attractiveness, makeup cosmetics, female youths, tertiary institutions, makeup lifestyle, Ghana. Definition of Terms In this paper, makeup refers to cosmetic makeup and makeup cosmetics means coloured cosmetics, makeup items, cosmetics and are thus used interchangeably. DOI: 10.7176/ADS/75-01 Publication date: August 31st 201

    Science of Facial Attractiveness

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    Varieties of Attractiveness and their Brain Responses

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    The neural basis of visual material properties in the human brain

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    Three independent studies with human functional magnetic resonance imaging (fMRI) measurements were designed to investigate the neural basis of visual glossiness processing in the human brain. The first study is to localize brain areas preferentially responding to glossy objects defined by specular reflectance. We found activations related to gloss in the posterior fusiform (pFs) and in area V3B/KO. The second study is to investigate how the visual-induced haptic sensation is achieved in our brain. We found that in secondary somatosensory area (S2) was distinguishable between glossy and rough surfaces, suggesting that visual information about object surfaces may be transformed into tactile information in S2. In the third study we investigate how the brain processes surface gloss information conveyed by disparity of specular reflections on stereo mirror objects and compared it with the processing of specular reflectance. We found that both dorsal and ventral areas were involving in this processing. The result implicates that in this region the processing of stereoscopic gloss information has a pattern of activation that is additional to the representation of specular reflectance. Overall, the three studies contribute to our understanding about the neural basis of visual glossiness and material processing in the human brain

    Material perception for philosophers

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    Philosophy Compass, EarlyView

    Computer vision methods for unconstrained gesture recognition in the context of sign language annotation

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    Cette thèse porte sur l'étude des méthodes de vision par ordinateur pour la reconnaissance de gestes naturels dans le contexte de l'annotation de la Langue des Signes. La langue des signes (LS) est une langue gestuelle développée par les sourds pour communiquer. Un énoncé en LS consiste en une séquence de signes réalisés par les mains, accompagnés d'expressions du visage et de mouvements du haut du corps, permettant de transmettre des informations en parallèles dans le discours. Même si les signes sont définis dans des dictionnaires, on trouve une très grande variabilité liée au contexte lors de leur réalisation. De plus, les signes sont souvent séparés par des mouvements de co-articulation. Cette extrême variabilité et l'effet de co-articulation représentent un problème important dans les recherches en traitement automatique de la LS. Il est donc nécessaire d'avoir de nombreuses vidéos annotées en LS, si l'on veut étudier cette langue et utiliser des méthodes d'apprentissage automatique. Les annotations de vidéo en LS sont réalisées manuellement par des linguistes ou experts en LS, ce qui est source d'erreur, non reproductible et extrêmement chronophage. De plus, la qualité des annotations dépend des connaissances en LS de l'annotateur. L'association de l'expertise de l'annotateur aux traitements automatiques facilite cette tâche et représente un gain de temps et de robustesse. Le but de nos recherches est d'étudier des méthodes de traitement d'images afin d'assister l'annotation des corpus vidéo: suivi des composantes corporelles, segmentation des mains, segmentation temporelle, reconnaissance de gloses. Au cours de cette thèse nous avons étudié un ensemble de méthodes permettant de réaliser l'annotation en glose. Dans un premier temps, nous cherchons à détecter les limites de début et fin de signe. Cette méthode d'annotation nécessite plusieurs traitements de bas niveau afin de segmenter les signes et d'extraire les caractéristiques de mouvement et de forme de la main. D'abord nous proposons une méthode de suivi des composantes corporelles robuste aux occultations basée sur le filtrage particulaire. Ensuite, un algorithme de segmentation des mains est développé afin d'extraire la région des mains même quand elles se trouvent devant le visage. Puis, les caractéristiques de mouvement sont utilisées pour réaliser une première segmentation temporelle des signes qui est par la suite améliorée grâce à l'utilisation de caractéristiques de forme. En effet celles-ci permettent de supprimer les limites de segmentation détectées en milieu des signes. Une fois les signes segmentés, on procède à l'extraction de caractéristiques visuelles pour leur reconnaissance en termes de gloses à l'aide de modèles phonologiques. Nous avons évalué nos algorithmes à l'aide de corpus internationaux, afin de montrer leur avantages et limitations. L'évaluation montre la robustesse de nos méthodes par rapport à la dynamique et le grand nombre d'occultations entre les différents membres. L'annotation résultante est indépendante de l'annotateur et représente un gain de robustese important.This PhD thesis concerns the study of computer vision methods for the automatic recognition of unconstrained gestures in the context of sign language annotation. Sign Language (SL) is a visual-gestural language developed by deaf communities. Continuous SL consists on a sequence of signs performed one after another involving manual and non-manual features conveying simultaneous information. Even though standard signs are defined in dictionaries, we find a huge variability caused by the context-dependency of signs. In addition signs are often linked by movement epenthesis which consists on the meaningless gesture between signs. The huge variability and the co-articulation effect represent a challenging problem during automatic SL processing. It is necessary to have numerous annotated video corpus in order to train statistical machine translators and study this language. Generally the annotation of SL video corpus is manually performed by linguists or computer scientists experienced in SL. However manual annotation is error-prone, unreproducible and time consuming. In addition de quality of the results depends on the SL annotators knowledge. Associating annotator knowledge to image processing techniques facilitates the annotation task increasing robustness and speeding up the required time. The goal of this research concerns on the study and development of image processing technique in order to assist the annotation of SL video corpus: body tracking, hand segmentation, temporal segmentation, gloss recognition. Along this PhD thesis we address the problem of gloss annotation of SL video corpus. First of all we intend to detect the limits corresponding to the beginning and end of a sign. This annotation method requires several low level approaches for performing temporal segmentation and for extracting motion and hand shape features. First we propose a particle filter based approach for robustly tracking hand and face robust to occlusions. Then a segmentation method for extracting hand when it is in front of the face has been developed. Motion is used for segmenting signs and later hand shape is used to improve the results. Indeed hand shape allows to delete limits detected in the middle of a sign. Once signs have been segmented we proceed to the gloss recognition using lexical description of signs. We have evaluated our algorithms using international corpus, in order to show their advantages and limitations. The evaluation has shown the robustness of the proposed methods with respect to high dynamics and numerous occlusions between body parts. Resulting annotation is independent on the annotator and represents a gain on annotation consistency

    Intuitive and Accurate Material Appearance Design and Editing

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    Creating and editing high-quality materials for photorealistic rendering can be a difficult task due to the diversity and complexity of material appearance. Material design is the process by which artists specify the reflectance properties of a surface, such as its diffuse color and specular roughness. Even with the support of commercial software packages, material design can be a time-consuming trial-and-error task due to the counter-intuitive nature of the complex reflectance models. Moreover, many material design tasks require the physical realization of virtually designed materials as the final step, which makes the process even more challenging due to rendering artifacts and the limitations of fabrication. In this dissertation, we propose a series of studies and novel techniques to improve the intuitiveness and accuracy of material design and editing. Our goal is to understand how humans visually perceive materials, simplify user interaction in the design process and, and improve the accuracy of the physical fabrication of designs. Our first work focuses on understanding the perceptual dimensions for measured material data. We build a perceptual space based on a low-dimensional reflectance manifold that is computed from crowd-sourced data using a multi-dimensional scaling model. Our analysis shows the proposed perceptual space is consistent with the physical interpretation of the measured data. We also put forward a new material editing interface that takes advantage of the proposed perceptual space. We visualize each dimension of the manifold to help users understand how it changes the material appearance. Our second work investigates the relationship between translucency and glossiness in material perception. We conduct two human subject studies to test if subsurface scattering impacts gloss perception and examine how the shape of an object influences this perception. Based on our results, we discuss why it is necessary to include transparent and translucent media for future research in gloss perception and material design. Our third work addresses user interaction in the material design system. We present a novel Augmented Reality (AR) material design prototype, which allows users to visualize their designs against a real environment and lighting. We believe introducing AR technology can make the design process more intuitive and improve the authenticity of the results for both novice and experienced users. To test this assumption, we conduct a user study to compare our prototype with the traditional material design system with gray-scale background and synthetic lighting. The results demonstrate that with the help of AR techniques, users perform better in terms of objectively measured accuracy and time and they are subjectively more satisfied with their results. Finally, our last work turns to the challenge presented by the physical realization of designed materials. We propose a learning-based solution to map the virtually designed appearance to a meso-scale geometry that can be easily fabricated. Essentially, this is a fitting problem, but compared with previous solutions, our method can provide the fabrication recipe with higher reconstruction accuracy for a large fitting gamut. We demonstrate the efficacy of our solution by comparing the reconstructions with existing solutions and comparing fabrication results with the original design. We also provide an application of bi-scale material editing using the proposed method
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