Blickpunktabhängige Computergraphik

Contemporary digital displays feature multi-million pixels at ever-increasing refresh rates. Reality, on the other hand, provides us with a view of the world that is continuous in space and time. The discrepancy between viewing the physical world and its sampled depiction on digital displays gives rise to perceptual quality degradations. By measuring or estimating where we look, gaze-contingent algorithms aim at exploiting the way we visually perceive to remedy visible artifacts. This dissertation presents a variety of novel gaze-contingent algorithms and respective perceptual studies. Chapter 4 and 5 present methods to boost perceived visual quality of conventional video footage when viewed on commodity monitors or projectors. In Chapter 6 a novel head-mounted display with real-time gaze tracking is described. The device enables a large variety of applications in the context of Virtual Reality and Augmented Reality. Using the gaze-tracking VR headset, a novel gaze-contingent render method is described in Chapter 7. The gaze-aware approach greatly reduces computational efforts for shading virtual worlds. The described methods and studies show that gaze-contingent algorithms are able to improve the quality of displayed images and videos or reduce the computational effort for image generation, while display quality perceived by the user does not change.Moderne digitale Bildschirme ermöglichen immer höhere Auflösungen bei ebenfalls steigenden Bildwiederholraten. Die Realität hingegen ist in Raum und Zeit kontinuierlich. Diese Grundverschiedenheit führt beim Betrachter zu perzeptuellen Unterschieden. Die Verfolgung der Aug-Blickrichtung ermöglicht blickpunktabhängige Darstellungsmethoden, die sichtbare Artefakte verhindern können. Diese Dissertation trägt zu vier Bereichen blickpunktabhängiger und wahrnehmungstreuer Darstellungsmethoden bei. Die Verfahren in Kapitel 4 und 5 haben zum Ziel, die wahrgenommene visuelle Qualität von Videos für den Betrachter zu erhöhen, wobei die Videos auf gewöhnlicher Ausgabehardware wie z.B. einem Fernseher oder Projektor dargestellt werden. Kapitel 6 beschreibt die Entwicklung eines neuartigen Head-mounted Displays mit Unterstützung zur Erfassung der Blickrichtung in Echtzeit. Die Kombination der Funktionen ermöglicht eine Reihe interessanter Anwendungen in Bezug auf Virtuelle Realität (VR) und Erweiterte Realität (AR). Das vierte und abschließende Verfahren in Kapitel 7 dieser Dissertation beschreibt einen neuen Algorithmus, der das entwickelte Eye-Tracking Head-mounted Display zum blickpunktabhängigen Rendern nutzt. Die Qualität des Shadings wird hierbei auf Basis eines Wahrnehmungsmodells für jeden Bildpixel in Echtzeit analysiert und angepasst. Das Verfahren hat das Potenzial den Berechnungsaufwand für das Shading einer virtuellen Szene auf ein Bruchteil zu reduzieren. Die in dieser Dissertation beschriebenen Verfahren und Untersuchungen zeigen, dass blickpunktabhängige Algorithmen die Darstellungsqualität von Bildern und Videos wirksam verbessern können, beziehungsweise sich bei gleichbleibender Bildqualität der Berechnungsaufwand des bildgebenden Verfahrens erheblich verringern lässt

Un modelo de atención visual para la detección de regiones de interés en imágenes radiológicas

La detección, segmentación y cuantificación de lesiones de esclerosis múltiple (MS) en imágenes de resonancia magnética (MRI) ha sido un área de estudio muy activa en las ´últimas dos décadas. Esto es debido la necesidad de correlacionar estas medidas con la efectividad de los tratamientos farmacológicos. Muchos métodos han sido desarrollados y la mayoría no son específicos para los diferentes tipos de lesiones, es decir que no pueden distinguir entre lesiones agudas y crónicas. Los médicos radiólogos por su parte son capaces de distinguir entre diferentes niveles de la enfermedad haciendo uso de las imágenes de resonancia magnética de diferentes tipos. La principal motivación de este trabajo es la de emular mediante un modelo computacional la percepción visual del radiólogo, haciendo uso de los principios fisiológicos del sistema visual. De esta manera logramos detectar satisfactoriamente las lesiones de esclerosis múltiple en imágenes de resonancia magnética del cerebro. Este tipo de análisis nos permite estudiar y mejorar el estudio de las redes neuronales al poder introducir información a priori.Abstract. The detection, segmentation and quantification of multiple sclerosis (MS) lesions on magnetic resonance images (MRI) has been a very active field for the last two decades because of the urge to correlate these measures with the e↵ectiveness of pharmacological treatment. A myriad of methods has been developed and most of these are non specific for the type of lesions, e.g. they do not di↵erentiate between acute and chronic lesions. On the other hand, radiologists are able to distinguish between several stages of the disease on di↵erent types of MRI images. The main motivation of the work presented here is to computationally emulate the visual perception of the radiologist by using modeling principles of the neuronal centers along the visual system. By using this approach we were able to successfully detect multiple sclerosis lesions in brain MRI. This type of approach allows us to study and improve the analysis of brain networks by introducing a priori informationMaestrí

Model Simplification for Efficient Collision Detection in Robotics

Motion planning for industrial robots is a computationally intensive task due to the massive number of potential motions between any two configurations. Calculating all possibilities is generally not feasible. Instead, many motion planners sample a sub-set of the available space until a viable solution is found. Simplifying models to improve collision detection performance, a significant component of motion planning, results in faster and more capable motion planners. Several approaches for simplifying models to improve collision detection performance have been presented in the literature. However, many of them are sub-optimal for an industrial robotics application due to input model limitations, accuracy sacrifices, or the probability of increasing false negatives during collision queries. This thesis focuses on the development of model simplification approaches optimised for industrial robotics applications. Firstly, a new simplification approach, the Bounding Sphere Simplification (BSS), is presented that converts triangle-mesh inputs to a collection of spheres for efficient collision and distance queries. Additionally, BSS removes small features and generates an output model less prone to false negatives

High-level perceptual contours from a variety of low-level physical features

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (p. 87-90).by Brian M. Scassellati.M.Eng

Visual recognition of objects : behavioral, computational, and neurobiological aspects

I surveyed work on visual object recognition and perception. In animals, vision has been studied mainly on the behavioral and neurobiological levels. Behavioral data typically show what the visual system, by itself or together with the rest of the organism, is capable of. They show, for example, that humans can recognie objects regardless of size and position, but that rotated objects pose problems. Important insights into the organization of behavior have also been provided by people who suffered localized brain damage. We have learned that the brain is divided into areas subserving different and relatively well-defined behaviors. The visual system itself is also organized in different subsystems; the visual cortex alone contains nearly twenty maps of the visual field. And individual neurons respond selectively to visual stimuli, e.g., the orientation of line segments, color, direction of motion, and, most intriguingly, faces. The question is how the actions of all these neurons produce the behavior we observe. How do neurons represent the shape of objects such that they can be recognized? Before we can answer the question, we have to understand the computational aspect of shape representation, the nature of the problem as it were. Many methods for representing shape have been explored, mainly by computer scientists, but so far no satisfactory answers have been found

Cognitive architecture for an Attention-based and Bidirectional Loop-closing Domain (CABILDO)

This Ph. D. Thesis presents a novel attention-based cognitive architecture for social robots. The architecture aims to join perception and reasoning considering a double and simultaneous imbrication: the ongoing task biases the perceptual process to obtain only useful elements whereas perceived items determine the behaviours to be accomplished. Therefore, the proposed architecture represents a bidirectional solution to the perception-reasoning-action loop closing problem. The basis of the architecture is an Object-Based Visual Attention model. This perception system draws attention over perceptual units of visual information, called proto-objects. In order to highlight relevant elements, not only several intrinsic basic features (such as colour, location or shape) but also the constraints provided by the ongoing behaviour and context are considered. The proposed architecture is divided into two levels of performance. The lower level is concerned with quantitative models of execution, namely tasks that are suitable for the current work conditions, whereas a qualitative framework that describes and defines tasks relationships and coverages is placed at the top level. Perceived items determine the tasks that can be executed in each moment, following a need-based approach. Thereby, the tasks that better fit the perceived environment are more likely to be executed. Finally, the cognitive architecture has been tested using a real and unrestricted scenario that involves a real robot, time-varying tasks and daily life situations, in order to demonstrate that the proposal is able to efficiently address time- and behaviour-varying environments, overcoming the main drawbacks of already existing models

A Science Education Study Using Visual Cognition and Eye Tracking to Explore Medication Selection in the Novice Versus Expert Nurse Anesthetist

The purpose of this science education study is to explore visual cognition and eye tracking during medication selection in the student nurse anesthetist (first year and second year students) and the expert nurse anesthetist. The first phase of this study consisted of the selection of a specific medication (target) from an array of medications via computer simulation. Various dependent variables were recorded to examine performance (reaction time and accuracy), and the allocation of visual attention was measured with eye tracking (dwell proportion, verification, and guidance). The second phase of this study included the administration of a demographic and post experiment questionnaire to capture additional quantitative and qualitative data. Results demonstrate that similar distractors attract attention during search as evidenced by longer reaction times when similar distractors are present, most significantly in expert participants. Additionally, all participants spent a greater amount of time looking at the similar distractor as compared to randomly chosen non-similar distractors when a similar distractor was present. However, the presence of similar distractors in target present trials increased performance in experts, decreased performance in second year students, and had no effect on first year students’ performance. Expertise effects were further demonstrated, as expert participants were significantly slower than both first and second years during target verification. The post experiment questionnaire included both open-ended and close-ended questions, to allow for themes to emerge related the participants’ beliefs related to visual search and medication selection. The results reinforced the eye tracking results reported above, with most participants identifying “color” and “medication label” as the most difficult medication features to distinguish during visual search. Additionally, the majority of participants who responded they had committed a medication error, identified “similarity” as the most common factor that led to the medication error

Constructing the space of visual attention

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Architecture, 2012.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Page 180 blank. Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 168-171).This thesis explores the nature of a human experience in space through a primary inquiry into vision. This inquiry begins by questioning the existing methods and instruments employed to capture and represent a human experience of space. While existing qualitative and quantitative methods and instruments -- from "subjective" interviews to "objective" photographic documentation -- may lead to insight in the study of a human experience in space, we argue that they are inherently limited with respect to physiological realities. As one moves about the world, one believes to see the world as continuous and fully resolved. However, this is not how human vision is currently understood to function on a physiological level. If we want to understand how humans visually construct a space, then we must examine patterns of visual attention on a physiological level. In order to inquire into patterns of visual attention in three dimensional space, we need to develop new instruments and new methods of representation. The instruments we require, directly address the physiological realities of vision, and the methods of representation seek to situate the human subject within a space of their own construction. In order to achieve this goal we have developed PUPIL, a custom set of hardware and software instruments, that capture the subject's eye movements. Using PUPIL, we have conducted a series of trials from proof of concept -- demonstrating the capabilities of our instruments -- to critical inquiry of the relationship between a human subject and a space. We have developed software to visualize this unique spatial experience, and have posed open questions based on the initial findings of our trials. This thesis aims to contribute to spatial design disciplines, by providing a new way to capture and represent a human experience of space.by Moritz Philipp Kassner [and] William Rhoades Patera.S.M

The effect of aberrations and light scatter on visual performance at photopic and mesopic light levels

The Contrast Acuity Assessment (CAA) test was developed to assess the minimum spatial vision requirements for commercial pilots. The goal of the CAA test was for it to be sensitive to retinal image degradation in subjects who had undergone excimer laser refractive surgery. Increased aberrations and scattered light or abnormal processing of visual information in the retina and/or the visual pathway are the main causes of retinal image degradation. The purpose of this study was to further investigate the effect of aberrations, scatter and other parameters on the CAA test under photopic and mesopic conditions. This could help to provide explanations for previous CAA test results. The effect of contrast, stimulus onset time, pupil size and crowding on the CAA test was examined. This was in order to try to provide explanations for the decline in Landolt ring gap acuity over the central 5 degrees, as observed in previous CAA test results, which had shown a foveal dip to occur under photopic and mesopic conditions. Contrast Sensitivity was measured on eight subjects using 6 and 3 mm artificial pupils using the City University Contrast Sensitivity Test. A significant trend of decreasing contrast sensitivity with increased pupil size occurred for the middle and lower spatial frequencies (1.2 and 6.1 cpd), but not for the highest 19.1 cpd spatial frequency. The effects of using high contrast (125%) rather than low contrast (24%) CAA test targets were investigated, in combination with the use of artificial pupils of 6 mm and 3 mm. We concluded that low contrast could play a role in producing a foveal dip under photopic and mesopic conditions. The effect of crowding and stimulus onset time on the CAA Test was examined on 3 subjects, by reducing the contrast of the fixation guides under mesopic and photopic conditions and increasing stimulus onset time. This gave inconclusive results. No significant conclusions were drawn concerning the effect of crowding or stimulus onset time on the CAA foveal dip. The effect of aberrations on normal subjects on the photopic and mesopic CAA test was examined, to determine whether they may have influenced the foveal dip. 14 subjects were tested with natural pupils, under photopic conditions and 10 subjects, were tested under mesopic conditions. A Shack Hartmann aberrometer was used to take wavefront aberration measurements. No significant regressions were found between aberrations and foveal dip. We concluded that aberrations were probably not the cause of the foveal dip. Q value lenses consisting of Q = -2, Q = -1, Q = 0, Q = +1 and Q = +1.5 contact lenses were tested on subjects with natural pupils, to determine whether the CAA test could pick up larger non-physiological changes in aberrations. Large changes in visual performance were observed. Z (4,0) spherical aberration versus central CAA gap acuity was found to produce a significant quadratic regression under mesopic conditions. Seidel coma and Seidel astigmatism were also found to produce significant linear regressions. under photopic conditions. Scatter was measured in 4 subjects, using 6 mm and 3 mm artificial pupils, to determine whether scatter would increase with the larger pupil size. Linear regressions of scatter k’ versus foveal dip gave results which were not statistically significant. Scatter was measured for 3 subjects using the 5 different Q value contact lenses, to see if the Q values affected the scatter. The results were not statistically significant. The differences in scatter produced were found to be far less than the increase of scatter found in two subjects with pathological conditions. We concluded that scatter played an insignificant role in producing the foveal dip or changing visual performance with the use of Q value contact lenses. The project produced a systematic investigation of the parameters affecting the CAA test. A statistically significant association, described by a quadratic regression curve, exists between CAA mesopic gap acuity and Z (4,0) spherical aberration