Dissertations / Theses on the topic 'Depth perception'

A fingerprint can identify an individual, yet it tells us nothing specific about the person it belongs to. It is almost invisible, yet it can be traced. Hair can be both beautiful and repulsive, depending on its context--It is an element of the body that lingers, amazingly, after decay.I am inspired by my observations of natural occurring phenomena. The impermanence of all things speaks to me in a whisper. I am captivated by the traces and residue of life that lingers and will eventually dissolve. Using glass, paper, wax, and film I make objects and installations that give physical form to something fleeting. My work is a record of my process. I use imprints and textures of my body to leave a trace or mark on my surroundings--You are here. A pushpin on a giant map represents the earth and our location on it. Working with magnification and systems that generate form, my work embodies a preservation of the ephemeral with all of its unimaginable residual effects.

The focus of this thesis is to investigate if diffusedaylight affects human depth perception. It is builtupon previous knowledge and methods of observingand perceiving light brought into a research thatexperiment with different spatial contexts throughscale models. The central position of perceptual cueswithin the human visual field is discussed in relationto perceptual depth and visual elementsThe result of the performed experiement showed apossibility for diffuse daylight to have an effect on theperception of depth.Having the knowledge of building with daylightwill lead to a better understanding of how daylightis affecting our perception of spaces, which potentiallycan improve the ability of creating sustainableperceptual spatial experiences when designing andbuilding with daylight as an integrated part of the design

Thesis (M. S.)--Psychology, Georgia Institute of Technology, 2005.
Randall W. Engle, Ph.D., Committee Member ; Paul M. Corballis, Ph.D., Committee Chair ; Daniel H. Spieler, Ph.D., Committee Member. Includes bibliographical references.

Tele-presence refers to technologies enabling the remote presence of an observer or operator of robotics machines - through the use of monitoring and display devices. This involves the facilitation of 3D space perception on the basis of 2D pictures, a problem which is of interest to engineers, and psychologists who study space and picture perception. From a functional perspective the issue requires the specification of the necessary characteristics of a tele-presence system for effective task performance by a human observer. Since the central problem in picture perception is the conflict between the 3D re-presentation of the scene and the 2D surface of the picture, one possibility for tele-presence systems to reduce this conflict consists in the use of a camera which is slaved to observer movement. Thus the video picture is yoked to the head movement of the observer: changes in the video picture viewed by the observer emulate the changes that would have occurred in the visual field if the observer was viewing the scene directly. The explanation for reduced cue conflict and improved depth perception in pictures lies in the availability of motion parallax information. The main aim of this research was to see whether tele-presence which provides motion parallax information on a video picture improves depth perception compared to static tele-presence. While theoretical claims concerning the usefulness of motion parallax have a long history, the empirical findings are more equivocal. The basic design compared depth perception of a moving observer with that of a stationary observer. Two initial experiments showed that the movement condition leads to more accurate depth perception than the stationary condition, both under tele-presence and direct viewing conditions. Experiments 4 to 7 showed that active observation leads only to non- significantly better accuracy than passive observation. Interrupting the natural link between action and perception by reversing the picture tends to reduce the difference between the movement and the stationary condition. However, combining the analysis of the active, passive and reverse picture conditions did not lead to significant differences. A further experiment using an adjustment task supported the finding that reverse viewing does not reduce accuracy. In general the differences between the movement and the static condition while significant were not very strong which suggested that other sources of information such as visual angle information may have specified depth to a considerable extent. Simulation of fully remote tele-presence was expected to provide stronger differences. However, the differences were small and explainable in terms of short term learning processes resulting in perceptual fixity, i.e. an inability to take advantage of the information available. It was concluded that motion parallax is probably only a weak cue to depth under practical circumstances, and that learning effects in tele-presence systems require further attention. Future attention should be directed at learning processes and at the complexity of the stimulus displays. The study of learning processes may help to understand the consistent finding of large individual differences in using motion parallax information. And the study of more complex stimulus displays would enable a more adequate assessment of the ecological emphasis on the role of motion parallax.

How do we know where objects are in the environment and how do we use this information to guide our actions? Recovering the three-dimensional (3D) structure of our surroundings from the two-dimensional retinal input received from the eyes is a computationally challenging task and depends on the brain processing and combining ambiguous sources of sensory information (cues) to depth. This thesis combines psychophysical and computational techniques to gain further insight into (i) which cues the brain uses for perceptual judgments of depth and motion-in-depth; and (ii) the processes underlying the combination of the information from these cues into a single percept of depth. The first chapter deals with the question which sources of information the visual system uses to estimate the time remaining until an approaching object will hit us; a problem that is complicated by the fact that the variable of interest (time) is highly correlated to other perceptual variables that may be used (e.g. distance). Despite these high correlations we show that the visual system recovers a temporal estimate, rather than using one or more of its covariates. In the second chapter I ask how extra-retinal signals (changes in the convergence angles of the eyes) contribute to estimates of 3D speed. Traditionally, extra-retinal signals are reputed to be a poor indicator of 3D motion. Using techniques to isolate extra-retinal signals to changes in vergence, we show that judgments of 3D speed are best explained on the basis that the visual system computes a weighted average of retinal and extra-retinal signals. The third and fourth chapters investigate how the visual system combines binocular and monocular cues to depth in judgments of relative depth and the speed of 3D motion. In chapter three I show that differences in retinal size systematically affect the perceived disparityde defined depth between two unfamiliar targets, so that a target with a larger retinal size is seen as closer than a target with a smaller retinal size at the same disparity-defined distance. This perceptual bias increases as the retinal size ratio between the targets is increased but remains constant as the absolute sizes of the targets change concurrently while keeping the retinal size ratio constant. In addition, bias increases as the absolute distance to both targets increases. I propose that these findings can be explained on the basis that the visual system attempts to optimally combine disparity with retinal size cues (or in the case of 3D motion: changing disparity information with looming cues), but assumes that both objects are of equal size while they are not. In chapter 4 these findings are extended to 3D motion: physically larger unfamiliar targets are reported to approach faster than a smaller target moving at the same speed at the same distance. These findings cannot be explained on the basis of observers' use of a biased perceived distance, caused by differences in the retinal size (as found in chapter 3). I conclude that, in line with contemporary theories of visual perception, the brain solves the puzzle of 3D perception by combining all available sources of visual information in an optimal manner, even though this may lead to inaccuracies in the final estimate of depth.

This thesis has been the product of three projects which are all related to depth perception, within the core discipline of vision science. The first project was collaborative work between the University of Durham and researchers at University of California, Berkeley. These included Prof. Martin S. Banks and Bill Sprague at U.C. Berkeley, and Dr. Jurgen Schmoll and Prof. Gordon Love at the University of Durham. This project built on previous research investigating the ocular adaptations in different land-dwelling vertebrate species. We found that we could strongly predict pupil shape based on the diel activity and trophic strategies of a species, and our simulations showed that multifocal pupils may extend depth of focus. The second project was also in collaboration with U.C. Berkeley; Prof. Martin S. Banks, and Paul Johnson, which involved a study into 3D displays and different approaches to reducing the vergence-accommodation conflict. Our results showed that a focus-correct adaptive system did assist in the vergence-accommodation conflict, but monovision was less efficacious and we believe this was due to a reduction in stereoacuity. The third project considered spherical aberration as a cue to the sign of defocus. We present simulations which show that the spatial frequency content of images on either side of focus differ, and suggest that this could, in principle, drive the accommodative process.

The perception of a three-dimensional world is a challenge for the visual system because the retinal image is only two-dimensional. Stereopsis is the ability to detect depth from small differences in perspective between each eye’s two—dimensional view. In this thesis I examine three aspects of stereoscopic vision in human observers using psychophysical methods. In part 1, the role of stereopsis in image segmentation and ”camouflage breaking” is investigated using a contrast masking paradigm. Binocular disparity is found to reduce contrast masking, and threshold elevation decreases monotonically with increasing disparity until i8 arcmin of disparity between the target and a natural image mask. An orientation discrimination task is used as a control to rule out sensitivity to interocular decorrelation as an alternative explanation for the effect. The results indicate that stereopsis facilitates image segmentation as a target can be seen at a lower contrast when it is in depth defined by disparity. Part 2 examines the reason for the decline in stereoacuity across the visual field using equivalent noise analysis. Stereoacuity thresholds are measured in a depth discrimination task at foveal and peripheral locations (up to 9° eccentricity) under increasing levels of disparity noise. The equivalent noise model reveals that internal noise limits peripheral stereoacuity, with no contribution from a reduction in sampling efficiency. This indicates that a loss of precision of local disparity estimates early in visual processing limits peripheral stereoacuity. Part 3 compares speed sensitivity to motion in depth from two binocular cues: changing disparity over time and interocular velocity difference. Motion discrimination contours in space-time are measured for motion-in-depth stimuli of different speeds, containing ei— ther one or both binocular cue(s). Evidence for speed sensitivity is found only for slow speeds containing both binocular cues. This suggests that interocular velocity difference is the critical cue for speed perception of objects moving in depth. Together, the experimental results are consistent with the high spatial precision and low temporal resolution of stereoscopic vision. In the final chapter, the results of the three sections are discussed together in the context of the role of stereopsis in visual processing. The use of ’natural’ versus ’artificial’ stimuli in vision research is examined in the context of the experimental results, and some novel suggestions for future research in stereopsis are proposed.

How does the human visual system convert two-dimensional projections from our eyes into a three-dimensional percept? One primary method is from binocular disparities, which result from having two horizontally separated eyes and are used to provide a powerful cue to depth in our environment. In this thesis, I use human fMRI to investigate the cortical signals associated with binocular disparity. I address several core issues, including the relationship between cortical activity and perception, the significance of the reference plane on depth configurations, and the topography of disparity signals on the cortical surface. In measuring responses to coarse and fine disparities, researchers typically engage two respective tasks: a signal-in-noise and a feature difference task. In the first chapter, we decouple the disparity magnitude from the perceptual task and examine cortical responses to both of these tasks when using fine disparities. Further, we manipulated performance and identified visual areas whose activity varied in line with perceptual judgments. We reveal that responses in later dorsal regions VIPS and POIPS were closely related to perception for both tasks. In the second chapter, we used a similar manipulation to investigate cortical regions that have solved the correspondence problem and whose responses were consistent with the depth percept of the observer, and reveal that this takes place in V7 and VIPS. The third chapter examines the importance of the reference in disparity calculations. We performed several classifications based on depths that were considered relative to fixation or relative to the surround. We found that early visual areas were most sensitive to disparity edges; dorsal visual areas used both the fixation plane and the surround in computing disparity whereas ventral visual areas processed disparity with reference to the surround. In the fourth chapter, we attempt to identify a topographic organisation of binocular disparity in the visual cortex. We estimate the disparity preferences of each voxel in two distinct ways, and displayed these preferences on a flatmap of the cortical surface. Although we did not observe a topographic map of disparity, we observed a cluster in intermediate dorsal regions (V3A, V3B/KO, V7) that consistently showed a bias towards crossed disparities of a larger magnitude.

Mestrado em Engenharia Mecânica
This thesis is focused on the installation of multiple Light Detection And Ranging and vision-based sensors on a full sized mobile platform, ATLASCAR 2. This vehicle is a Mitsubishi i-MiEV. In the scope of this work it will be equipped with two planar scanners, a 3D scanner and a camera. The sensors will be installed in the vehicle's front supported by an infrastructure built in aluminium pro le and connected to the vehicle's chassis. All sensors are powered by the car's low voltage circuit and controlled by a switched board placed in the trunk alongside with a processing unit. Sensor calibration is accomplished using a calibration package developed at the Laboratory of Automation an Robotics, to which an option to calibrate a new 3D sensor was added, Velodyne Puck VLP-16. After the sensor calibration and to demonstrate the functionalities of the platform, an application was developed that merges the data from the Light Detection And Ranging sensors, properly referenced, in a single frame and computes and represents the space free to navigate around the vehicle.
Este trabalho assenta na instalação de sensores Light Detection And Ranging e de visão numa plataforma movel à escala real, o ATLASCAR 2. Este veículo é um Mitsubishi i-MiEV que, no ambito deste trabalho, será equipado com dois scaners planares, um scaner 3D e uma camara. Estes sensores serão instalados na frente do veículo e suportados por uma infraestrurura desenvolvida em per l da alumínio e xa ao chassis do mesmo. A alimentação dos sensores é feita atravéz do circuito de baixa tensão do veículo e controlada por um quadro elétrico situado no porta bagagens juntamente com a unidade de processamento. A calibração destes sensores realizou-se atravéz um pacote de calibração multisensorial devenvolvido no Laboratorio de Automa ção e Robotica, ao qual foi adicionada a opção de calibrar um novo sensor 3D, Velodyne Puck VLP-16. Após a calibração dos sensores e no sentido de demonstrar as funcionalidades da plataforma, foi desenvolvida uma aplicação que combina os dados dos sensors Light Detection And Ranging devidamente referenciados e calcula e representa o espaço, disponivel para navegar em torno do veiculo.

It has long been held that luminance acts as a cue for depth perception. But varying the luminance of a stimulus inevitably alters its contrast with its background. Recent research shows that contrast is a depth cue. I have distinguished two kinds of contrast, external contrast, the contrast of a stimulus with its background, and internal contrast, the contrast within the stimulus. I compared the relative apparent depth of two stimuli (both directly and indirectly; stimuli were either sine-wave filled hemifields, sine-wave filled squares, or plain squares), as their luminances and internal contrasts were varied along with the luminance of their background. I found internal and external contrast to be additive effects, whereby the stimulus with either a higher internal or external contrast appeared nearer. When the internal and external contrasts of the stimuli were equated, luminance acted as an ambiguous cue, with the lighter square appearing nearer for the majority of observers, and farther for a minority. Luminance may act as a depth cues from our experience with artificial lighting (artificial light varies ambiguously with depth). Contrast may act as a depth cue from its usual association with the reduction of contrast of objects with distance through the atmosphere. I conclude that luminance and contrast are independent depth-cues that are caused by two different mechanisms.

Motion in depth (MID) can be cued by two binocular sources of information. These are changes in retinal disparity over time (changing disparity, CD), and binocular opponent velocity vectors (inter-ocular velocity difference, IOVD). This thesis presents a series of psychophysical and fMRI experiments investigating the neural pathways supporting the perception of CD and IOVD. The first two experiments investigated how CD and IOVD mechanisms draw on information encoded in the magnocellular, parvocellular and koniocellular pathways. The chromaticity of CD and IOVD-isolating stimuli was manipulated to bias activity in these three pathways. Although all stimulus types and chromaticities supported a MID percept, fMRI revealed an especially dominant koniocellular contribution to the IOVD mechanism. Because IOVD depends on eye-specific velocity signals, experiment three sought to identify an area in the brain that encodes motion direction and eye of origin information. Classification and multivariate pattern analysis techniques were applied to fMRI data, but no area where both types of information were present simultaneously was identified. Results suggested that IOVD mechanisms inherit eye-specific information from V1. Finally, experiment four asked whether activity elicited by CD and IOVD stimuli could also be modulated by an attentional task where participants were asked to detect changes in MID or local contrast. fMRI activity was strongly modulated by attentional state, and activity in motion-selective areas was predictive of whether participants correctly identified the change in CD or IOVD MID. This suggests that these areas contain populations of neurons that are crucial for detecting, and behaviourally responding to, both types of MID. The work presented in this thesis detail a thorough investigation of the neural pathways that underlie the computation of CD and IOVD cues to MID.

La evolución de la tecnología de Realidad Virtual (RV) ha contribuido en todos los campos, incluyendo la psicología. Esta evolución implica mejoras tanto en hardware como en software, que permiten experiencias más inmersivas. En un entorno de RV los usuarios pueden percibir la sensación de "presencia" y sentirse "inmersos". Estas sensaciones son posibles utilizando HMDs. Hoy en día, el desarrollo de los HMDs se ha centrado en mejorar sus características técnicas para ofrecer inmersión total. En psicología, los entornos de RV son una herramienta de investigación. Hay algunas aplicaciones para evaluar la memoria espacial que utilizan métodos básicos de interacción. Sin embargo, sistemas de RV que incorporen estereoscopía y movimiento físico todavía no se han explotado en psicología. En esta tesis, se ha desarrollado un nuevo sistema de RV que combina características inmersivas, interactivas y de movimiento. El sistema de RV (tarea en un laberinto virtual) se ha utilizado para evaluar la memoria espacial y la percepción de profundidad. Se han integrado dos tipos diferentes de interacción: una basada en locomoción que consistió en pedalear en una bicicleta fija (condición1) y otra estacionaria usando un gamepad (condición2). El sistema integró dos tipos de visualización: 1) Oculus Rift (OR); 2) Una gran pantalla estéreo. Se diseñaron dos estudios. El primer estudio (N=89) evaluó la memoria espacial a corto plazo usando el OR y los dos tipos de interacción. Los resultados indican que existían diferencias significativas entre ambas condiciones. Los participantes que utilizaron la condición2 obtuvieron mejor rendimiento que los que utilizaron la tarea en la condición1. Sin embargo, no se encontraron diferencias significativas en las puntuaciones de satisfacción e interacción entre ambas condiciones. El desempeño en la tarea correlacionó con el desempeño en las pruebas neuropsicológicas clásicas, revelando la verosimilitud entre ellas. El segundo estudio (N=59) incluyó participantes con y sin estereopsis. Este estudio evaluó la percepción de profundidad comparando los dos sistemas de visualización. Los participantes realizaron la tarea usando la condición2. Los resultados mostraron que las diferentes características del sistema de visualización no influyeron en el rendimiento en la tarea entre los participantes con y sin estereopsis. Se encontraron diferencias significativas a favor del HMD entre las dos condiciones y entre los dos grupos de participantes respecto a la percepción de profundidad. Los participantes que no tenían estereopsis y no podían percibir la profundidad cuando utilizaban otros sistemas de visualización, tuvieron la ilusión de percepción de profundidad cuando utilizaron el OR. El estudio sugiere que para las personas que no tienen estereopsis, el seguimiento de la cabeza influye en gran medida en la experiencia 3D. Los resultados estadísticos de ambos estudios han demostrado que el sistema de RV desarrollado es una herramienta apropiada para evaluar la memoria espacial a corto plazo y la percepción de profundidad. Por lo tanto, los sistemas de RV que combinan inmersión total, interacción y movimiento pueden ser una herramienta útil para la evaluación de procesos cognitivos humanos como la memoria. De estos estudios se han extraído las siguientes conclusiones generales: 1) La tecnología de RV y la inmersión proporcionada por los actuales HMDs son herramientas adecuadas para aplicaciones psicológicas, en particular, la evaluación de la memoria espacial a corto plazo; 2) Un sistema de RV como el presentado podría ser utilizado como herramienta para evaluar o entrenar adultos en habilidades relacionadas con la memoria espacial a corto plazo; 3) Los dos tipos de interacción utilizados para la navegación en el laberinto virtual podrían ser útiles para su uso con diferentes colectivos; 4) El OR permite que los usuarios sin estereopsis puedan percibir l
The evolution of Virtual Reality (VR) technology has contributed in all fields, including psychology. This evolution involves improvements in hardware and software allowing more immersive experiences. In a VR environment users can perceive the sensation of "presence" and feel "immersed". These sensations are possible using VR devices as HMDs. Nowadays, the development of the HMDs has focused on improving their technical features to offer full immersion. In psychology, VR environments are research tools because they allow the use of new paradigms that are not possible to employ in a real environment. There are some applications for assessing spatial memory that use basic methods of HCI. However, VR systems that incorporate stereoscopy and physical movement have not yet been exploited in psychology. In this thesis, a novel VR system combining immersive, interactive and motion features was developed. This system was used for the assessment of the spatial memory and the evaluation of depth perception. For this system, a virtual maze task was designed and implemented. In this system, two different types of interaction were integrated: a locomotion-based interaction pedaling a fixed bicycle (condition1), and a stationary interaction using a gamepad (condition2). This system integrated two types of display systems: 1) The Oculus Rift; 2) A large stereo screen. Two studies were designed to determine the efficacy of the VR system using physical movement and immersion. The first study (N=89) assessed the spatial short term memory using the Oculus Rift and the two types of interaction The results showed that there were statistically significant differences between both conditions. The participants who performed the condition2 got better performance than participants who performed the condition1. However, there were no statistically significant differences in satisfaction and interaction scores between both conditions. The performance on the task correlated with the performance on other classical neuropsychological tests, revealing a verisimilitude between them. The second study (N=59) involved participants who had and who had not stereopsis. This study assessed the depth perception by comparing the two display systems. The participants performed the task using the condition2. The results showed that the different features of the display system did not influence the performance on the task between the participants with and without stereopsis. Statistically significant differences were found in favor of the HMD between the two conditions and between the two groups of participants regard to depth perception. The participants who did not have stereopsis and could not perceive the depth when they used other display systems (e.g. CAVE); however, they had the illusion of depth perception when they used the Oculus Rift. The study suggests that for the people who did not have stereopsis, the head tracking largely influences the 3D experience. The statistical results of both studies have proven that the VR system developed for this research is an appropriate tool to assess the spatial short-term memory and the depth perception. Therefore, the VR systems that combine full immersion, interaction and movement can be a helpful tool for the assessment of human cognitive processes as the memory. General conclusions from these studies are: 1) The VR technology and immersion provided by current HMDs are appropriate tools for psychological applications, in particular, the assessment of spatial short-term memory; 2) A VR system like the one presented in this thesis could be used as a tool to assess or train adults in skills related to spatial short-term memory; 3) The two types of interaction (condition1 and condition2) used for navigation within the virtual maze could be helpful to use with different collectives; 4) The Oculus Rift allows that the users without stereopsis can perceive the depth perception of 3D objects and have rich 3D experiences.
L'evolució de la tecnologia de Realitat Virtual (RV) ha contribuït en tots els camps, incloent la psicologia. Aquesta evolució implica millores en el maquinari i el programari que permeten experiències més immersives. En un entorn de RV, els usuaris poden percebre la sensació de "presència" i sentir-se "immersos". Aquestes sensacions són possibles utilitzant HMDs. Avui dia, el desenvolupament dels HMDs s'ha centrat a millorar les seves característiques tècniques per oferir immersió plena. En la psicologia, els entorns de RV són eines de recerca. Hi ha algunes aplicacions per avaluar la memòria espacial que utilitzen mètodes bàsics d'interacció. Tanmateix, sistemes de RV que incorporen estereoscòpia i moviment físic no s'han explotat en psicologia. En aquesta tesi, s'ha desenvolupat un sistema de RV novell que combina immersió, interacció i moviment. El sistema (tasca en un laberint virtual) s'ha utilitzat per a l'avaluació de la memòria espacial i la percepció de profunditat. S'han integrat dos tipus d'interacció: una interacció basada en locomoció pedalejant una bicicleta fixa (condició1), i l'altra una interacció estacionària usant un gamepad (condició2). S'han integrat dos tipus de sistemes de pantalla: 1) L'Oculus Rift; 2) Una gran pantalla estereoscòpica. Dos estudis van ser dissenyats. El primer estudi (N=89) va avaluar la memòria a curt termini i espacial utilitzant l'Oculus Rift i els dos tipus d'interacció. Els resultats indiquen que hi havia diferències significatives entre les dues condicions. Els participants que van utilitzar la condició2 van obtenir millor rendiment que els participants que van utilitzar la condició1. Tanmateix, no hi havia diferències significatives dins satisfacció i puntuacions d'interacció entre les dues condicions. El rendiment de la tasca va correlacionar amb el rendiment en les proves neuropsicològiques clàssiques, revelant versemblança entre elles. El segon estudi (N=59) va implicar participants que van tenir i que van haver-hi no estereopsis. Aquest estudi va avaluar la percepció de profunditat comparant els dos sistemes de pantalla. Els participants realitzen la tasca utilitzant la condició2. Els resultats van mostrar que les diferents característiques del sistema de pantalla no va influir en el rendiment en la tasca entre els participants qui tenien i els qui no tenien estereopsis. Diferències significatives van ser trobades a favor del HMD entre les dues condicions i entre els dos grups de participants. Els participants que no van tenir estereopsis i no podien percebre la profunditat quan van utilitzar altres sistemes de pantalla (per exemple, CAVE), van tenir la il.lusió de percepció de profunditat quan van utilitzar l'Oculus Rift. L'estudi suggereix que per les persones que no van tenir estereopsis, el seguiment del cap influeix en gran mesura en l'experiència 3D. Els resultats estadístics dels dos estudis han provat que el sistema de RV desenvolupat per aquesta recerca és una eina apropiada per avaluar la memòria espacial a curt termini i la percepció de profunditat. Per això, els sistemes de RV que combinen immersió plena, interacció i moviment poden ser una eina útil per la avaluació de processos cognitius humans com la memòria Les conclusions generals que s'han extret d'aquests estudis, són les següents: 1) La tecnologia de RV i la immersió proporcionada pels HMDs són eines apropiades per aplicacions psicològiques, en particular, la avaluació de memòria espacial a curt termini; 2) Un sistema de RV com el presentat podria ser utilitzat com a eina per avaluar o entrenar adults en habilitats relacionades amb la memòria espacial a curt termini; 3) Els dos tipus d'interacció utilitzats per navegació dins del laberint virtual podrien ser útils per al seu ús amb diferent col.lectius; 3) L'Oculus Rift permet que els usuaris que no tenen estereopsis puguen percebre la percepció de profunditat dels objectes 3D i tenir
Cárdenas Delgado, SE. (2017). VR systems for memory assessment and depth perception [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/94629
TESIS

This thesis contains an investigation of the way in which children and adults depict depth when drawing a table. Research on development in depiction is reviewed (Chapters 1 and 2), with particular reference to the use of pictorial depth cues and projection systems. A series of studies on the use of projection systems in the drawing of a table is reported (Chapters 3 to 5) which shows that development in the depiction of depth is not directly related to development in the use of projection systems. It is also shown that the use of projection systems 1s task dependent, and is not closely related to the subject's formal understanding of them. A formal system of classification of table drawings is introduced (Chapter 6), which demonstrates clear developmental trends in the way in which depth is depicted in the drawing of a table, and connects these trends with development in the use of pictorial depth cues. The roots of development in the depiction of depth are examined more closely by further experimental work (Chapters 7 to 9). It is shown that subjects have a very strong preference for oblique projection, and that inaccuracy in the copying of line drawings is largely dependent upon the knowledge of what these drawings represent. It is concluded that the results give support to an information processing view of development, in which the majority of subjects appear to work from a form of canonical model of a table which has implicit depth and is best depicted by oblique projection (Chapter 10). It is also suggested that development in the depiction of depth is linked to the increasing use of pictorial depth cues. These conclusions are presented more explicitly in the form of a possible process model of the way in which we depict depth (Chapter 11).

A key challenge facing 3D interface designers, and operators who teleoperate remote environments is to develop effective techniques to depict objects in 3D space on a 2-dimensional physical medium; a flat computer screen. Spatial relationships among objects, their sizes and locations are of high importance for users in order to be able to locate and manipulate these objects. In particular, depth perception (z dimension) is a main challenge for researchers who have designed many depth cues in order to overcome it. The main trend of providing depth perception is stereoscopy; other approaches utilize shading and shadow, motion, reference frames, size, perspective and others. These visual cues, including stereoscopy, have certain limitations. In this work, we propose to exploit human sensory modality for perceiving depth in teleoperated 3D environments where complex visual information - which may distract the operator - is presented. We exploit the funneling illusion phenomenon to provide a high resolution tactile depth display on the forearm. It utilizes stimulus location perception rather than stimulus intensity perception. One psychophysical experiment is conducted to study the resolution of the funneling illusion method on the forearm, and another experiment to evaluate its performance in a Telepresence and teleaction (TPTA) system scenario where a fragile dangerous object is being manipulated. Experiments show that our approach can replace the visual feedback methods and outperforms the stimulus intensity perception method.

In order to navigate and interact within their environment, animals must process and interpret sensory information to generate a representation or ‘percept’ of that environment. However, sensory information is invariably noisy, ambiguous, or incomplete due to the constraints of sensory apparatus, and this leads to uncertainty in perceptual interpretation. To overcome these problems, sensory systems have evolved multiple strategies for reducing perceptual uncertainty in the face of uncertain visual input, thus optimizing goal-oriented behaviours. Two available strategies have been observed even in the simplest of neural systems, and are represented in Bayesian formulations of perceptual inference: sensory integration and prior experience. In this thesis, I present a series of studies that examine these processes and the neural mechanisms underlying them in the primate visual system, by studying depth perception in human observers. Chapters 2 & 3 used functional brain imaging to localize cortical areas involved in integrating multiple visual depth cues, which enhance observers’ ability to judge depth. Specifically, we tested which of two possible computational methods the brain uses to combine depth cues. Based on the results we applied disruption techniques to examine whether these select brain regions are critical for depth cue integration. Chapters 4 & 5 addressed the question of how memory systems operating over different time scales interact to resolve perceptual ambiguity when the retinal signal is compatible with more than one 3D interpretation of the world. Finally, we examined the role of higher cortical regions (parietal cortex) in depth perception and the resolution of ambiguous visual input by testing patients with brain lesions.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.
Includes bibliographical references (leaves 119-130).
by Jonathan D. Pfautz.
M.Eng.

Stereopsis is a par excellence demonstration of the computational power that neural systems can encapsulate. How is the brain capable of swiftly transforming a stream of binocular two-dimensional signals into a cohesive three-dimensional percept? Many brain regions have been implicated in stereoscopic processing, but their roles remain poorly understood. This dissertation focuses on the contributions of primary and dorsomedial visual cortex. Using convolutional neural networks, we found that disparity encoding in primary visual cortex can be explained by shallow, feed-forward networks optimized to extract absolute depth from naturalistic images. These networks develop physiologically plausible receptive fields, and predict neural responses to highly unnatural stimuli commonly used in the laboratory. They do not necessarily relate to our experience of depth, but seem to act as a bottleneck for depth perception. Conversely, neural activity in downstream specialized areas is likely to be a more faithful correlate of depth perception. Using ultra-high field functional magnetic resonance imaging in humans, we revealed systematic and reproducible cortical organization for stereoscopic depth in dorsal visual areas V3A and V3B/KO. Within these regions, depth selectivity was inversely related to depth magnitude — a key characteristic of stereoscopic perception. Finally, we report evidence for a differential contribution of cortical layers in stereoscopic depth perception.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2008.
Title from PDF title page (viewed Mar. 30, 2010). Additional advisors: Franklin R. Amthor, James E. Cox, Timothy J. Gawne, Rosalyn E. Weller. Includes bibliographical references (p. 104-114).

In normal image coding the image quality is the same in all parts of the image. When it is known where in the image a single viewer is focusing it is possible to lower the image quality in other parts of the image without lowering the perceived image quality. This master's thesis introduces a coding scheme based on depth perception where the quality of the parts of the image that correspond to out-of-focus scene objects is lowered to obtain data reduction. To obtain further data reduction the method is combined with angular perception coding where the quality is lowered in parts of the image corresponding to the peripheral visual field. It is concluded that depth perception coding can be done without lowering the perceived image quality and that the coding gain increases as the two methods are combined.

Relative retinal image motion from active observer movement in the environment, often called motion parallax, provides an important source of information both for segmentation and depth perception. Two distinct boundary types occur as a result of such movement: boundaries that are parallel to the direction of movement give rise to a shearing motion, whereas boundaries orthogonal to the direction of movement create dynamic occlusion. This dissertation examines the role and importance of such types of motion boundaries in motion parallax, and how head and eye movements influence them. We psychophysically measured segmentation and depth performance from shear and dynamic occlusion-based motion parallax across different conditions, accompanied by head and eye movement recordings. Segmentation was measured with an orientation judgment, whereas depth ordering was measured using a 2AFC task. Perceived depth magnitude was assessed with a task in which observers matched the amount of perceived depth in the stimulus to a number, using a series of rendered images as a guide. We found that depth perception largely benefits from active observer movement, whereas segmentation performance seemed to be unaffected or even somewhat negatively affected. Shear and dynamic occlusion yielded similar performance for segmentation, whereas dynamic occlusion provided superior depth perception. Perceived depth magnitude was linearly correlated with rendered depth for small values of depth, but did not grow with further increase in rendered depth for both shear and dynamic occlusion. We also measured eye movements during segmentation and depth tasks with motion parallax. Eye movements only partially compensated to maintain fixation during translational head movements. Furthermore, eye movements were independent of the actual stimulus motion for shear, whereas they showed some dependence in dynamic occlusion. Psychophysical performance was significantly correlated with the accuracy of eye movements, primarily in the mid-range values of rendered depth. Taken together, these studies demonstrated distinct patterns of results for segmentation and depth performance across different ranges of rendered depth. These findings suggest that motion parallax information might be processed by distinct mechanisms, perhaps in separate areas of the visual cortex, depending upon the amount of depth in the visual stimulus.
Le mouvement relatif d'une image sur la rétine dû au mouvement actif de l'observateur dans son environnement, souvent appelé mouvement de parallaxe, fournit une importante source d'informations pour la segmentation et la perception de la profondeur. Deux types de contours peuvent résulter d'un tel mouvement : les contours parallèles à la direction du mouvement génèrent un mouvement de cisaillement, alors que les contours orthogonaux à la direction du mouvement créent une occlusion dynamique. Cette dissertation étudie le rôle et l'importance de ces contours définis par le mouvement de parallaxe, et comment les mouvements de la tête et des yeux les influencent. Nous avons effectué des mesures psychophysiques de la segmentation et de la détection de profondeur issues du mouvement de parallaxe par cisaillement et par occlusion dynamique dans différentes conditions, tout en enregistrant les mouvements des yeux et de la tête. La segmentation a été mesurée par jugement d'orientation, alors que l'ordre de profondeur a été mesuré en utilisant une tâche de choix forcé d'alternative. L'amplitude de la profondeur perçue a été étudiée avec une tâche dans laquelle les observateurs jugeaient la profondeur du stimulus en lui attribuant un nombre choisi grâce à un guide d'images de références.Nous avons observé que la perception de la profondeur bénéficie énormément du mouvement actif de l'observateur alors que la performance de segmentation semble peu affectée, voire même réduite. Le mouvement de cisaillement et l'occlusion dynamique induisent la même performance pour la segmentation, alors que l'occlusion dynamique fournit une meilleure perception de la profondeur. Pour les faibles valeurs, l'amplitude de la profondeur perçue est linéairement corrélée avec la profondeur rendue, mais m'augmente plus après un certain point, pour à la fois le cisaillement et l'occlusion dynamique.Nous avons également mesuré les mouvements des yeux pendant les tâches de profondeur et de segmentation par mouvement de parallaxe. Les mouvements des yeux ne compensent que partiellement le maintient de la fixation pendant les mouvements de tête translationnels. De plus, les mouvements des yeux sont indépendants du mouvement du stimulus pour le cisaillement alors qu'ils montrent une certaine dépendance pour l'occlusion dynamique. La performance psychophysique est significativement corrélée avec la précision du mouvement des yeux, particulièrement pour les valeurs moyennes de profondeur rendue. Ces résultats suggèrent que l'information du mouvement de parallaxe pourrait être traitée par des mécanismes distincts, peut-être dans des aires différentes du cortex visuel, selon la quantité de profondeur dans le stimulus visuel.

The purpose of this thesis is to identify new methods of improving the delivery and assessment of minimally invasive surgery (MIS), particularly under the constraint of monoscopic MIS visualisation. In this thesis, the role of visual spatial ability in the acquisition of surgical skills is first investigated. A psychometric test is used to elucidate the correlation between spatial ability and complex tasks, and highlight the need for more quantitative assessment of visuomotor behaviours in laparoscopic procedures. To this end, a wavelet-based analysis framework for instrument trajectory analysis is developed for extracting intrinsic motion behaviours. This is used to provide an insight into subconscious integration of the visual and motor axes in a depthless operative field. The issue of monoscopic visualisation of the operative field in MIS is also addressed and a method of improving depth perception by digitally enhancing a "weak" shadow cast by a secondary light source is proposed. By performing experiments on MIS novices, significant improvements in depth perception by the use of the proposed technique are demonstrated. Finally, eye tracking is used to study the difference in visual behaviour between laparoscopic novices and experts. A distinct visual behaviour of instrument tool-tip tracking during instrument manoeuvring is observed among the novices but not the experts, and this behaviour is shown to be repeatable in both groups. These results provide an important insight into how the cognitive, motor and visual stimuli are integrated during MIS surgery, as well as how the surgeons compensate for the depthless operative field. These findings can be used for the development of more focussed training curricula and the development of improved MIS instruments for its safe practice.

This thesis has reviewed how increased depth perception can be used to increase the understanding of hydrographic data First visual cues and various visual displays and techniques were investigated. From this investigation 3D stereoscopic techniques prove to be superior in improving the depth perception and understanding of spatially related data and a further investigation on current 3D stereoscopic visualisation techniques was carried out. After reviewing how hydrographic data is currently visualised it was decided that the chromo stereoscopic visualisation technique is preferred to be used for further research on selected hydrographic data models. A novel chromo stereoscopic application was developed and the results from the evaluation on selected hydrographic data models clearly show an improved depth perception and understanding of the data models.

Motion parallax is often considered to be an inherently ambiguous cue to depth. Despite the theoretical ambiguity associated with the pattern of retinal image motion, motion parallax generally evokes compelling three-dimensional (3-D) percepts and for this reason is regarded as an important source of 3-D information. Certain studies have indicated, however, that a parallax surface that contains a given amount of simulated depth is often perceived to rotate, rather than simply remain stationary, as the observer moves. This thesis provides an experimental investigation of the factors which influence perceived rotation and shearing in motion parallax surfaces. In a series of psychophysical experiments, the cue of self-produced motion parallax was manipulated in order to provide insights into the mechanisms underlying the perception of 3-D surfaces. Since larger parallax motions often produce the impression of rotation, the "transition point" between stationarity and rotation was measured as a function of several factors. The maximum motion gradient was shown to be the principal determinant of this transition point surfaces with a steep motion gradient were perceived to rotate at lower relative motion amplitudes than surfaces with shallow motion gradients. Vertical perspective information played a smaller role. The transition point also fell with increasing viewing distance. At even higher amplitudes, parallax surfaces can appear nonrigid or even lacking in all 3-D structure, and the experiments reported have measured the transition points between each of the different perceptual zones. A model was introduced in order to determine whether the perceived magnitudes of depth and rotation of sinusoidal parallax surfaces were in accordance with geometric constraints. Qualitative support was found for a trade-off between depth and rotation when corrugation frequency or stimulus size was manipulated. Results were less conclusive when a dynamic vertical perspective cue was varied. A similar model was applied to the perceived magnitudes of depth and shearing in square wave surfaces. The relationship between these attributes was less clear-cut. The perceived rotation of sinusoidal surfaces increased with increasing viewing distance; possibly due to a decreasing propensity of the observer, with increasing viewing distance, to attribute the vertical perspective changes to self-motion. In sum, these experiments demonstrate the importance of motion gradients and vertical perspective information in the perception of motion parallax surfaces, and suggest that the surfaces are generally perceived in qualitative accord with the totality of visual information present (Helmholtz, 1909).

This research by practice into the visual and aesthetic qualities of ceramic glaze investigates its ability to create an impression of depth. Because perspectival depth alone can not fully account for my artistic concerns, and the requirements of perspectival illusion are at odds with some of my major artistic preoccupations, such as an interest in accidents and imprecision in material rendering, I raised the hypothesis of a poetic dimension of depth, posing the research question for this project: “What is poetic depth in a ceramic glaze?” Traditionally, research into glazes focuses on aspects of material science, craftsmanship, archaeology or art history, and optical depth has been the subject of investigations into the microstructure of glaze. By seeking to address the aesthetic dimension of glaze I am moving away from such concerns. While the aesthetics of ceramic glaze is a new field of research, with little existing material, I am seeking to find parallels with practice, theories and research from the field of literary poetry, even though by ‘poetic’ I am referring to a quality that is not only mediated by language and goes beyond the field of literature. Further, I am also referring to Gaston Bachelard’s approach to material imagination through his poetics of the natural elements and to the concept of transitional space developed by psychoanalysts of the British Independent Group, Donald Winnicott and Marion Milner. My thesis consists of a threefold dialogue between my artistic practice of glaze, theories and practices of literary poetry and the concept of the transitional phenomenon. My findings are at the intersection of those three elements, and they are the results of my investigations through both making and writing: • ‘Poetic tension’ is a paradoxical and conflicting process between authority – the ability to control – and subjectivity on the one hand and factors of dissent, questioning the very possibility of authorship, on the other: among these are the unconscious and the materiality of the glaze. • The concern for interiority is a central element of poetry, the transitional phenomenon and my works. • My practice of glaze is an attempt to re-enact and objectify the fusion between the self and the world, addressing the issues of the illusion of all-encompassing subjectivity and the disillusion of objectivity, both key elements of the transitional phenomenon. • Play has been a natural development of my practice of glaze and I further established parallels with the literary poetic in a shared aspiration for subversion, dissent and laughter. • The concept of the formless permeates Bachelard’s material imagination and my practice of glaze. Moreover it is often a prerequisite for Winnicott’s and Milner’s approach to creativity and play. • Failure is the essence of a certain form of poetry, which Georges Bataille summed up as the ‘Impossible’. It is also a key aspect of my practice of glaze: an essence of flux or a further element of play whose irresolution or unlikely balance can create yet another dimension of the poetic. • Flux is a necessary element of glazes but it also summarizes the dynamics and dialectics of the transitional phenomenon and of the Bataillean ‘Impossible’ and the playful poetic. All three strands: my practice of glaze, the literary poetic and the transitional phenomenon intertwine, cross-fertilize and develop in parallel. Together, they have helped articulate the concepts and the artistic vocabulary through which the poetic and the transitional phenomenon have become operative categories of aesthetics, artistic practice, and of research processes.

Successful navigation in the world requires effective visuospatial processing. Unfortunately, older adults have many visuospatial deficits, which can have severe real-world consequences. It is therefore crucial to understand and try to alleviate these deficits whenever possible. One visuospatial process, depth from motion parallax, has been largely unexplored in older adults. Depth from motion parallax requires retinal image motion processing and pursuit eye movements, both of which are affected by age. Given these deficits, it follows logically that sensitivity to motion parallax may be affected in older adults, but no one has yet investigated this possibility. The goals of the current study were to characterize depth from motion parallax in older adults, to explore the mechanisms by which age might affect depth from motion parallax, and to develop training programs that might alleviate the effects of age on motion parallax. In Experiment One, older and younger adults’ motion parallax depth thresholds were characterized. Motion thresholds and pursuit accuracies were also measured. The results of Experiment One revealed that older adults had higher MP depth thresholds than younger adults, and that these age changes were primarily driven by age changes in pursuit eye movements. In Experiment Two, older adults were provided with motion and pursuit training programs to use at home, following the logic that training in motion and pursuit would improve older adults’ depth thresholds. Improvements of performance at these training tasks were assessed. Depth thresholds, motion thresholds, and pursuit accuracy pre- and post-training were evaluated as well, using the same methods as in Experiment One. The results of Experiment Two revealed that motion and pursuit training did not affect observers’ performance throughout the course of training, and there were no effects of training on depth or motion thresholds or pursuit eye movements. The current study is the first to examine age changes in motion parallax depth thresholds, and to investigate the mechanisms of age changes in the perception of depth from motion parallax. Though the training programs in Experiment Two did not produce improvements of perceptual performance, this study was successful in implementing an easy-to-use, at-home training technique.
Graduate School Doctoral Dissertation Fellowship

L’estimation de la profondeur consiste à calculer la distance entre différents points de la scène et la caméra. Savoir à quelle distance un objet donné est de la caméra permettrait de comprendre sa représentation spatiale. Les anciennes méthodes ont utilisé des paires d’images stéréo pour extraire la profondeur. Pour avoir une paire d’images stéréo, nous avons besoin d’une paire de caméras calibrées. Cependant, il est plus simple d’avoir une seule image étant donnée qu’aucun calibrage de caméra n’est alors nécessaire. C’est pour cette raison que les méthodes basées sur l’apprentissage sont apparues. Ils estiment la profondeur à partir d’une seule image. Les premières solutions des méthodes basées sur l’apprentissage ont utilisé la vérité terrain de la profondeur durant l’apprentissage. Cette vérité terrain est généralement acquise à partir de capteurs tels que Kinect ou Lidar. L’acquisition de profondeur est coûteuse et difficile, c’est pourquoi des méthodes auto-supervisées se sont apparues naturellement comme une solution. Ces méthodes ont montré de bons résultats pour l’estimation de la profondeur d’une seule image. Dans ce travail, nous proposons d’estimer des cartes de profondeur d’images prises du point de vue des conducteurs de train. Pour ce faire, nous avons proposé d’utiliser les contraintes géométriques et les paramètres standards des rails pour extraire la carte de profondeur à entre les rails, afin de la fournir comme signal de supervision au réseau. Il a été démontré que la carte de profondeur fournie au réseau résout le problème de la profondeur des voies ferrées qui apparaissent généralement comme des objets verticaux devant la caméra. Cela a également amélioré les résultats de l’estimation de la profondeur des séquences des trains. Au cours de ce projet, nous avons d’abord choisi certaines séquences de trains et déterminé leurs distances focales pour calculer la carte de profondeur de la voie ferrée. Nous avons utilisé ce jeu de données et les distances focales calculées pour affiner un modèle existant « Monodepth2 » pré-entrainé précédemment sur le jeu de données Kitti.
Depth prediction is the task of computing the distance of different points in the scene from the camera. Knowing how far away a given object is from the camera would make it possible to understand its spatial representation. Early methods have used stereo pairs of images to extract depth. To have a stereo pair of images, we need a calibrated pair of cameras. However, it is simpler to have a single image as no calibration or synchronization is needed. For this reason, learning-based methods, which estimate depth from monocular images, have been introduced. Early solutions of learning-based problems have used ground truth depth for training, usually acquired from sensors such as Kinect or Lidar. Acquiring depth ground truth is expensive and difficult which is why self-supervised methods, which do not acquire such ground truth for fine-tuning, has appeared and have shown promising results for single image depth estimation. In this work, we propose to estimate depth maps for images taken from the train driver viewpoint. To do so, we propose to use geometry constraints and rails standard parameters to extract the depth map inside the rails, to provide it as a supervisory signal to the network. To this end, we first gathered a train sequences dataset and determined their focal lengths to compute the depth map inside the rails. Then we used this dataset and the computed focal lengths to finetune an existing model “Monodepth2” trained previously on the Kitti dataset. We show that the ground truth depth map provided to the network solves the problem of depth of the rail tracks which otherwise appear as standing objects in front of the camera. It also improves the results of depth estimation of train sequences.

Thesis (Master of Architecture)--University of Cincinnati, 2006.
Title from electronic thesis title page (viewed July 24, 2006). Includes abstract. Keywords: spatial limitations; spatial perception; spatial depth; spatial definition; reflection; representation; transparency; visual fluctuation; spatial fluctuation; movement. Includes bibliographical references.

Previous investigations of the perception of 3-D shape from deforming boundary contours have focused on judgments of global shape (Cortese & Anderson, 1991), judgments of rigid vs. nonrigid motion (Norman & Todd, 1994), and object recognition (Norman, Dawson, & Raines, 2000). Raines and Norman (1999) provided the first study demonstrating that deforming boundary contours could support the accurate perception of local 3-D surface structure. The present set of experiments extend the Raines and Norman study by further investigating whether the distance from the boundary contour or the amount of overall boundary deformation affect the human ability to make local judgments about 3-D shape. In these experiments, the observers viewed either static or moving silhouettes of randomly shaped, smoothly curved objects (see Raines & Norman, 1999; Norman & Todd, 1996, 1998) before making ordinal depth judgments about two highlighted regions on the object's surface. Two local regions on the objects' surface were highlighted, and the observers were required to judge which of the two regions was closer to them in depth. In Experiment 1, the proximity of the highlighted regions to the objects' occlusion boundary was manipulated as well as the presence or absence of binocularly disparate views. Viewing regions closer to the boundary contour led to more precise judgments of ordinal depth than those regions further away. The results also showed that the presence of disparate views had a different effect on the two motion types. While stereoscopic views improved performance dramatically in the stationary conditions, the same disparities had little effect on performance in the motion conditions. In Experiment 2, the observers viewed apparent motion sequences that presented varying degrees of boundary deformation. Although performance decreased as the amount of deformation decreased, the observers' judgments remained relatively precise even at the smallest angles of oscillation. In summary, these results confirm previous findings showing that boundary contours, especially deforming contours, are an important source of information about 3-D shape. These results also show that information from the boundary contour propagates inward to regions far from the boundary and that even small amounts of deformation can support the accurate perception of ordinal depth.